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Why are there so many species of large predator on the African savanna?

Why are there so many species of large predator on the African savanna?


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On the tropical grasslands of Africa, there are loads of large carnivores. Lions, cheetahs, leopards, hyenas and wild dogs are all found, sometimes, in the same place. I was wondering, why is it that there are so many species of large predator in the same place? Wouldn't competition drive all but one species to extinction?

Obviously, this means that each of the predators fills a special niche. So, could anyone tell me what these ecological niches are? What makes the position in the food web of lions, leopards, cheetahs, hyenas and wild dogs different to eachother?


Are there any natural African elephant predators?

It’s difficult to describe how enormous and imposing an African elephant is, especially to someone who has never seen one in person. A bull elephant can stand more than three meters tall, and weigh up to six tonnes. Cow elephants aren’t much smaller.

They are also incredibly powerful and can overturn cars, destroy large patches of land and deal decisively with any trouble from other animals and people. We don’t generally think of elephants as prey.


The Race to Save African Vultures

While they may not have the same inherent majesty of a pride of lions or a racing cheetah, a scrum of vultures feeding at a carcass on the African savanna is every bit as iconic of that continent as the graceful, swaying gait of a giraffe. What’s more, vultures play an incred­ibly important ecological role—hence the reason for deep alarm among conservationists about the growing col­lapse of Africa’s once-abundant vulture populations.

Vultures are already the most threatened group of raptors in the world, which is why, in some respects, the unfolding crisis in Africa feels like the repeat of a bad dream that played out in South Asia in the 1990s. There, vulture populations—especially in India, Pakistan, and Nepal—rapidly crumbled after farmers began treating their livestock with a cheap nonste­roidal anti-inflammatory pain reliever (NSAID) called diclofenac, which eases aches and increases milk yields. It’s also, however, astoundingly toxic to many Old World vultures that feed on the carcasses of livestock treated with it. By 2007, vulture populations in India had dropped by as much as 99.9%, and by only slightly less apocalyptic rates else­where in the region—almost all because of diclofenac.

Frantic, last-ditch efforts like cap­tive-breeding programs and campaigns to stop the veterinary use of NSAIDs have stabilized the vulture population in Asia today, at least somewhat. But now a similar collapse is playing out across Africa—with different driving forces that make the situation at once more challenging, and perhaps more hopeful, for those trying to stave off another vulture disaster.

The White-backed Vulture is listed as Critically Endangered by the International Union for the Conservation of Nature (IUCN). Image by André Botha.

The Egyptian Vulture is listed as Endangered by the IUCN. Image by by André Botha.

The Hooded Vulture is listed as Critically Endangered by the IUCN. Image by Nathalie Santa Maria/Macaulay Library.

Rüppell’s Griffon is listed as Critically Endangered by the IUCN. Image by Markus Lilje/Macaulay Library.

Seventy percent of African Vulture Species Are Endangered

Seven of Africa’s ten vulture species are now listed as endangered or critically endangered, with some populations falling by as much as 97% in the last few years. The steepest declines have occurred in West and East Africa and have even hit protected areas such as parks, with White-headed and Egyptian Vulture, and Rüppell’s and Cape Griffon populations dropping fastest.

The list of threats to vultures in Africa is long and complex: NSAID poi­soning (which is still a relatively minor issue compared to Asia) habitat loss electrocution and collision with a rap­idly growing power grid infrastructure ingestion of lead ammunition from feeding on animals killed by hunters and human disturbance at breeding col­onies, including egg-collecting and rec­reational rock-climbing. Food scarcity is also a problem for vultures, especially in West Africa, where large-mammal populations have fallen 60% since 1970. And vultures are frequently the unintended victims of livestock growers who illegally use pesticide-laced car­casses to kill off predators that threaten their herds, such as lions, jackals, and hyenas. Poisoning accounts for more than 60% of the vulture deaths in Africa every year.

“A lot of the things that affect vultures are not aimed at vultures,” says Darcy Ogada, assistant director of Africa pro­grams for the Peregrine Fund and lead author of a 2016 paper in the journal Conservation Letters that thrust Africa’s vulture problem into the global limelight.

More on Vulture Conservation in this Issue

But, Ogada says, the biggest threats to African vultures come when poisons are aimed directly at them. In particular, a burgeoning trade in vulture body parts for traditional belief-based use (mostly as good-luck charms) uses poisons like carbamate pesticides as the preferred method of killing.

“In southern Africa and parts of West Africa, people believe the use of vulture parts provides you with a degree of clairvoyance,” explains André Botha, the Vultures for Africa program man­ager at the Endangered Wildlife Trust and cochair of the vulture specialist group for the International Union for the Conservation of Nature. The myth that vultures use clairvoyance to find faraway carcasses has led to the belief that consuming vulture parts can con­vey ESP to humans.

“People tend to use it for betting and gambling, but we also know examples where people used it to predict the outcome of exams,” he says.

Although there is a modest food market for smoked vulture meat, most buyers simply want to possess part of a vulture, especially the head, believing it will improve success in business, raise the IQ of children, cure a variety of illnesses, and generally bring good luck and ward off evil.

Some of the illegal trade in vulture heads is marketed to students in northern Tanzania to help with their exams. Photo by Allan Baino.

Parts of vultures are sold as good-luck charms and are said to provide clairvoyance. Photo by Allan Baino.

The decline and likely extirpation of White-backed Vultures from Nigeria has been blamed on belief-based trade in that country. The most shocking examples of poisoning for trade, though, have occurred in Guinea-Bissau, where more than 2,000 Hooded Vultures—a species already listed as critically endangered—have been killed since 2019. Hundreds of poisoned vultures have been found at a single site, many without their heads. Given that this small West African country holds about 43,000 Hooded Vultures—more than a fifth of the world’s population—the losses have seriously alarmed conser­vationists, who see trade connections to larger, more populous countries like Nigeria as driving the demand. Botha notes that the use of vulture parts as charms has a long history, with hunters using traditional means to kill vultures.

“But now, using modern pesticides, single incidents can kill hundreds and, as in the case of Guinea-Bissau, even thousands of birds,” he says.

While belief uses are strongest in West Africa, the practice has a sizable foothold in southern Africa, Botha says. Experts see a disturbing rise in East Africa as well.

“The sort of good [vulture] pop­ulations remaining in West Africa probably won’t stay that way for very long,” Ogada warns, with the economic turmoil and job losses of the COVID-19 pandemic adding fresh incentives for people to monetize vultures.

Dead vultures at a poisoned elephant carcass. Photo by André Botha.

Poachers poisoned more than 100 vultures at a single elephant carcass in southern Mozambique in 2018. Photo by André Botha.

Ogada says African vultures are also targeted in so-called sentinel poisoning, a common practice in which elephant or rhino poachers dose a carcass with toxins to preemptively kill off vultures so there are no gathering flocks of wheeling, gangly birds circling above an illegal kill to tip off the authorities.

The explosion in elephant poaching in the early 2000s drew international attention and condemnation, but ele­phant poachers also killed enormous numbers of vultures. Most notable among numerous incidents, as many as 500 vultures died at a single poisoned carcass at a national park in Namibia, and more than 150 vultures were killed at a dosed elephant body at Kruger National Park in South Africa. (In most cases, rapid decomposition meant that conservationists were unable to deter­mine exactly which species of vultures were involved.)

Sentinel poisoning is an issue that’s largely beyond vulture conservationists’ control, says the Peregrine Fund’s Ogada. But thankfully for elephants and vultures, it may be on a downward trend. Whereas sentinel poisoning accounted for about a third of the vultures killed in Africa each year in the early 2010s, Ogada says sentinel poisoning has decreased significantly in some countries, thanks to international pressure and stronger enforcement on elephant poaching.

Cape Griffons gather in Limpopo, South Africa, Photo by Angus Fitton/Macaulay Library.

A Reason for Hope

For all the bad news, conservationists have taken heart from the fact that the decline in African vultures has been slower than the extraordinarily rapid collapse that occurred in Asia, which has given them time to mobilize and respond. But they recognize the task of saving the continent’s great scavengers will not be easy. Some Africans view vultures with superstitious dread, and few understand their ecological importance, which is why vulture specialists are fighting back with education and training.

Through the Endangered Wildlife Trust’s poisoning intervention pro­gram, which Botha started, he and his colleagues have trained more than 2,500 conservation rangers, law enforcement officers, and veterinarians in southern Africa to detect, prevent, and prose­cute wildlife poisoning events. He has worked with Ogada to begin similar training in Kenya, where the Peregrine Fund has joined forces with a nonprofit group called Lion Landscapes to provide a two-part education program for communities. Participants spend one day learning about the dangers of poisons and the importance of vultures, and the second day on how to build better, more secure livestock corrals, known locally as bomas, out of chain-link fence and sturdy gates. Improved bomas means fewer instances of wan­dering livestock lost to predators, and thus a reduced incentive for communi­ties to poison lions or hyenas—and also vultures that feed on poisoned bait or secondarily poisoned predators. In the year and a half before the pandemic hit, the partnership had facilitated the building of 350 such corrals.

The Peregrine Fund and Lion Landscapes trained women from the Samburu community in Kenya to construct predator-proof bomas (livestock corrals), reducing the need to poison predators and, secondarily, vultures. Photo by Martin Odino.

“Communities generally just want the boma training, but we won’t do the boma training with a community without doing the poisoning [segment] with it, because we know that if a boma fails or they don’t build it, the first thing they usually do is poison,” Ogada says.

There have been other significant signs of progress. In 2017, a multi-species action plan drafted under the auspices of the U.N. Convention on Migratory Species—and covering all 16 species of African and Eurasian vultures—was approved by 128 countries in Europe, Asia, and Africa. Botha is serving as the coordinator for the plan, which sets targets for reducing and eventually eliminating various kinds of poisoning, focusing first on protected areas and nearby buffers. The plan also focuses on international efforts to eliminate the veterinary use of NSAIDs and calls for the identification of areas where electrical infrastructure, including proposed wind farms, poses the greatest risk to vultures. In February 2020, the 131 nations that are party to the U.N. Convention on the Conservation of Migratory Species of Wild Animals came to an agreement for testing of all NSAIDs for vulture toxicity, the withdrawal from veterinary use of NSAIDs that are toxic, and vulture-safety testing for new drugs.

Another approach that shows promise is the creation of vulture safe zones, or VSZs, a technique pioneered in Asia in which a buffer is created around a vulture population strong­hold. Within VSZs, diclofenac use is aggressively combatted and drug-free carcasses are provided at artificial vulture feeding stations.

Before the pandemic hit, the Peregrine Fund and Lion Landscapes had facilitated the building of 350 bomas in Kenya. Local participants in the program also attended an educational program on the importance of vultures. Photo by Coexistence Co-op.

However, Botha says the situation in Africa calls for thinking on a bigger scale.

“In Asia, they’re looking at about a 150-kilometer radius around a breeding site or feeding location, but we know from tracking that [African vultures] are so incredibly mobile,” Botha says. Many African vulture species roam over immense areas every day, and with more than 50 countries on the conti­nent, a single vulture may cross three or four international boundaries on a single daily foraging trip. “In Africa, because of the far more complex suite of threats the birds face, you need to think in much wider terms than that.”

For that reason, African conserva­tionists are turning to the creation of multinational VSZs, like one announced in September overlapping the borders of Zimbabwe, South Africa, and Botswana.

“In this area we find the largest breeding colony of Cape Griffons on the planet, about 1,400 pairs of birds nesting at the single colony in the zone,” Botha says. “There are also significant popula­tions of tree-nesting vultures, like about 300 pairs of White-backed Vultures that nest in the riparian vegetation along the Limpopo River,” which forms the border between the three countries.

About the Author

Scott Weidensaul’s latest book.

Scott Weidensaul is an author and field researcher specializing in migration. He lives in New Hampshire.

Twenty years after his Pulitzer-nominated book Living on the Wind, he recently completed a follow-up that circles the globe: A World on the Wing: The Global Odyssey of Migratory Birds.

Across 10 chapters, Weidensaul’s new book tells exhilarating stories of bird migration from the Yellow Sea of China to the dusty hills of southern Cyprus to the Americas. His anecdotes often dive into scientific explanations, such as how sandpipers fly nonstop from Canada to Venezuela and avoid dehydration by “drinking” moisture from their own muscles. Some chapters are updated and expanded versions of stories previously published in Living Bird, such as Weidensaul’s travels to encounter Spoon-billed Sandpipers and Amur Falcons.

Of the 11,500 square miles that the safe zone would encompass, 80% is private land, including several immense private game reserves. Botha says con­servationists will work with the private landowners within the VSZ (which include corporations like the DeBeers diamond company), as well as national, provincial, and local governments to bolster existing legal protection for vul­tures, and energy companies to reduce the chance of electrocution and power­line collisions. Conservationists are also exploring antipoisoning interventions and the use of supplementary feeding stations to provide vultures with a safe supply of food. If successful, Botha says, it will serve as a model for similar trans­national zones elsewhere in Africa, like the Maasai Mara in East Africa, where vultures follow migrating game herds across boundaries.

“There are promising signs, but if you think of Africa as a whole, there’s a lot that needs doing,” Botha says. “The scale of the challenge is massive. We try to box clever and work in those key areas we have identified, build these strongholds so that we have populations that are maintained there.

“Then we start looking at expanding that work and maybe gain areas and habitat for the birds in the longer run,” Botha says. “But that’s some way down the road.


African Elephants Really Two Wildly Different Species?

"Big surprise": They're as different as Asian elephants are from mammoths.

The African elephant is actually two different species, according to a new DNA study that may settle a long-simmering debate.

"The big surprise of this paper," though, is just how genetically different the African savanna elephant and the African forest elephant are, co-author David Reich said.

(See African forest elephant pictures from National Geographic magazine.)

According to the new research, the two major types of African elephants are about as genetically distinct from each other as the Asian elephant is from the extinct woolly mammoth.

And that difference has deep roots in the elephant family tree, the DNA evidence suggests.

The two apparent African elephant species appear to have evolved from a common ancestor between two and a half million and five million years ago—nearly as long ago as the human and chimpanzee lineages diverged, according to some genetic studies.

For Species Designation, Size Doesn't Matter

Traditionally, the forest and savanna elephants have been classified as subspecies of the same species. But numerous distinctions have been noted. For example, forest elephants live in family groups of just a few animals, whereas savanna elephant family groups number about ten and often congregate in groups of 70 or so.

And—perhaps unsurprisingly, given its wide-open habitat—the African savanna elephant (Loxodonta africana) has evolved to be about twice as big as the forest elephant (Loxodonta cyclotis).

The savanna elephant tips the scales at up to seven tons and stands a full meter (3.3 feet) taller at the shoulder than the African forest elephant, which lives in equatorial forests of central and western Africa.

But even plainly visible morphological, or physical, differences don't necessarily indicate that animals are of separate species.

"Animals have an amazing capacity to change in morphology over short periods of time," said Reich, a population geneticist at Harvard Medical School.

Without pressures from predators and competitors, for example, species isolated on islands can shrink in just tens of thousands of years—a blink of the eye in evolutionary time.

Elephants have experienced such transitions before, producing animals like the "pygmy" Asian elephant of Borneo, which isn't considered a separate species, despite its relatively short, round shape.

Interspecies Elephant Sex?

Debate over the species status of African elephants has been simmering for at least a decade.

But then other studies showed that at least a small number of savanna elephants shared mitochondrial DNA—genetic information passed down from only mothers—with forest elephants.

This "proved there was some interbreeding within at least the past 500,000 years," Reich explained.

But that limited interbreeding isn't evidence that the two elephant types are from the same species, he said. It's just an example of interspecies hybridization, relatively common in the animal world, ha added.

Mammoth DNA Called Into Play

The key to the new discovery was some "cold case" genetics work on ancient, extinct elephant relatives: the woolly mammoth and the mastodon. The mastodon's nuclear genome, in particular, was sequenced for the first time for the study.

The genomes of five distinct animals—the Asian elephant, African savanna elephant, African forest elephant, woolly mammoth, and American mastodon—were then compared and contrasted.

The results showed that "in fact these [African elephant] populations diverged long ago and are at least as different as Asian elephants and mammoths—and those two are not only different species but entirely different genera," Reich said.

The apparent new species discovery is more than just cocktail party fodder for geneticists—it may have important conservation and management implications.

If Africa's elephants are from two distinct species, then each has a smaller population than previously believed. In this case, forest elephants may be of particular concern, because far less is known about their population status. Their numbers may prove small enough to garner additional protections.


Contents

The martial eagle can be found in most of sub-Saharan Africa, wherever food is abundant and the environment favourable. With a total estimated distribution of about 26,000 km 2 (10,000 sq mi), it has a substantial distribution across Africa, giving it a somewhat broader range than other species there like the crowned eagle (Stephanoaetus coronatus) and the Verreaux's eagle (Aquila verreauxii). [6] Although never common, greater population densities do exist in southern Africa and in some parts of east Africa. Martial eagles tend to be rare and irregular in west Africa but are known to reside in Senegal, The Gambia and northern Guinea-Bissau, southern Mali and the northern portions of Ivory Coast and Ghana. From southern Niger and eastern Nigeria the species is distributed spottily through Chad, Sudan and the Central African Republic as well as the northern, eastern, and southern portions of the Democratic Republic of the Congo. In east Africa, they range from Somaliland and Ethiopia more or less continuously south through Kenya, Uganda, Tanzania and in southern Africa from Angola, Zambia, Malawi and southern Mozambique to South Africa. [2] Some of the larger remaining populations are known to persist in Zimbabwe and South Africa. Generally, these birds are more abundant in protected areas such as Kruger National Park and Kgalagadi Transfrontier Park in South Africa, or Etosha National Park in Namibia. [7]

The Accipitridae (hereafter accipitrids) family is by far the most diverse family of diurnal raptors in the world with more than 230 currently accepted species. [8] As a member of the booted eagle subfamily, Aquilinae, it is one of the roughly 15% extant species of the family to have feathers covering its legs. [2] This may be a useful feature for distinguishing these species from other eagles and raptors, as they are present even in tropical species such as the martial eagle. [9] Under current classifications, booted eagles consist of approximately 38 living species that are distributed in every continent inhabited by the accipitrids, which excludes only the continent of Antarctica. Just under half of the living species of booted eagle are found in Africa. [10] [11] Studies have been conducted on the mitochondrial DNA of most booted eagle species, including the martial eagle, in order to gain insight on how the subfamily is ordered and which species bear relation to one another. DNA testing in the 1980s indicated the martial eagle was a specialized off-shoot of the small-bodied Hieraaetus eagles and one study went so far as to advocate that the martial eagle be included in the genus. [10] However, more modern and comprehensive genetic testing has shown that the martial eagle is extremely distinct from other living booted eagles and diverged from other existing genera several million years ago. [11] [12] Genetically, the martial eagle fell between two other species in monotypical genera, the African long-crested eagle (Lophaetus occipitalis) and the Asian rufous-bellied eagle (Lophotriorchis kienerii), that similarly diverged long ago from other modern species. Given the disparity of this species’ unique morphology and that the two aforementioned most closely related living species are only about as large as the bigger buzzards, the unique heritage of the martial eagle is considered even superficially evident. [11] [12] There are no subspecies of martial eagle and the species varies little in appearance and genetic diversity across its distribution. [2] [5]

The martial eagle is a very large eagle. In total length, it can range from 78 to 96 cm (31 to 38 in), with an average of approximately 85.5 cm (33.7 in). [2] [13] Its total length – in comparison to its wingspan – is restricted by its relatively short tail. Nonetheless, it appears to be the sixth or seventh longest extant eagle species. [2] The wingspan of martial eagles can range from 188 to 240 cm (6 ft 2 in to 7 ft 10 in). [2] [8] [14] [15] Wingspans of as much as 260 cm (8 ft 6 in) have been reported but may be unsubstantiated. [16] [17] Average wingspans have been claimed of 205 cm (6 ft 9 in) and 207.5 cm (6 ft 10 in) for the species, however ten measured martial eagles in the wild were found to average 211.9 cm (6 ft 11 in) in wingspan. Thus, the martial eagle appears to average fourth in wingspan among living eagles, behind only the Steller's sea-eagle (Haliaeetus pelagicus), the white-tailed eagle (Haliaeetus albicilla) and the wedge-tailed eagle (Aquila audax), in roughly that order. [2] [13] [18] [19] [20] For a species that is fairly homogeneous in its genetic make-up, the body mass of martial eagles is surprisingly variable. To some extent, the variation of body masses in the species is attributable to considerable reverse sexual dimorphism as well as varying environmental conditions of various eagle populations. [21] Unsexed martial eagles from various studies have been found to have weighed an average of 3.93 kg (8.7 lb) in 17 birds, 3.97 kg (8.8 lb) in 20 birds and 4.23 kg (9.3 lb) in 20 birds while the average weight of martial eagles shot by game wardens in the early 20th century in South Africa was listed as 4.71 kg (10.4 lb). [18] [21] [22] [23] [24] In weight range, the martial eagle broadly overlaps in size with the golden eagle (Aquila chrysaetos) and Verreaux's eagle (and is even exceeded by them in maximum known body mass). Based on numerous studies, the martial eagle appear to average mildly heavier than the Verreaux's eagle but (derived from the globally combined body mass of its various races), the mean body masses of golden and martial eagles are identical at approximately 4.17 kg (9.2 lb). The renders the golden and martial eagles as tied as the largest African eagles (by body mass but not in total length or wingspan, in which the martial bests the golden), as well as the heaviest two species of booted eagle in the world and as tied as the sixth heaviest eagles in the world, after the three largest species of sea eagle (Steller's being the heaviest extant, the others ranking 4th and 5th), the harpy eagle (Harpia harpyja) and the Philippine eagle (Pithecophaga jefferyi). [2] [18] [21] [23] [25] [26] The longest African eagle (and second longest booted eagle after the wedge-tailed eagle (Aquila audax)) is the crowned eagle by virtue of its relatively longer tail, as its body weight is slightly less than these three heaviest booted eagle species. [2] [23]

Sexual dimorphism Edit

Martial eagles are highly sexually dimorphic. While females average about 10% larger in linear dimension, in body mass, the sexual dimorphism of martial eagles is more pronounced. Males reportedly can weigh from 2.2 to 3.8 kg (4.9 to 8.4 lb). Seven males in southern Africa averaged 3.17 kg (7.0 lb) and five in another dataset averaged 3.3 kg (7.3 lb). [25] [27] [28] Twelve adult males in Maasai Mara, Kenya averaged 3.45 kg (7.6 lb). [29] Meanwhile, females can weigh from 4.45 to 6.5 kg (9.8 to 14.3 lb). In southern Africa, seven females averaging 4.95 kg (10.9 lb). [25] Elsewhere, a claim was made of an average of 5.2 kg (11 lb) almost certainly describes a sample entirely of female specimens. [30] In Maasai Mara, 7 females averaged 4.67 kg (10.3 lb). [29] Reports of males weighing as much as 5.1 kg (11 lb) and females weighing as little as 3.9 kg (8.6 lb) are known but may possibly represent individual eagles misidentified by sex, which is reportedly not infrequent due to mistakes in the field. [28] [31] [32] Thus the dimorphism by weight is roughly 36% in favor of the female, which is unusually out-of-sync with the linear differences between the sexes. For example, the greater spotted eagle (Clanga clanga), the most sexually dimorphic booted eagle overall with a linear difference between the sexes of 20%, has around the same level of sexual dimorphism by body mass as the martial eagle which show about half as much linear dimorphism. [2] [27] In standard measurements, male martial eagles measure 560 to 610 mm (22 to 24 in) in wing chord size, 273 to 280 mm (10.7 to 11.0 in) in tail length and 97 to 118 mm (3.8 to 4.6 in) in tarsus length. Meanwhile, females measure 605 to 675 mm (23.8 to 26.6 in) in wing chord, 280 to 320 mm (11 to 13 in) in tail length and 114 to 130 mm (4.5 to 5.1 in) tarsal length. [2] Overall, the bulk and much more massive proportions of females, which include more robust feet and longer tarsi, may at times allow experienced observers to sex lone birds in the wild. [3] [28]

Colouring and field identification Edit

The adult's plumage consists of dark brown coloration on the upperparts, head and upper chest, with an occasional slightly lighter edging to these feathers. The dark feathers can appear grayish, blackish or even plum-colored depending on lighting conditions. The body underparts are feathered white with sparse but conspicuous blackish-brown spotting. The underwing coverts are dark brown, with the remiges being pale streaked with black, overall imparting the wings of adults a dark look. The underside of the tail has similar barring as the remiges while the upperside is the same uniform brown as the back and upperwing coverts. The eyes of mature martial eagles are rich yellow, while the cere and large feet pale greenish and the talons black. Martial eagles have a short erectile crest, which is typically neither prominent nor flared (unlike that of the crowned eagle) and generally appears as an angular back to a seemingly flat head. This species often perches in a quite upright position, with its long wings completely covering the tail, causing it be described as “standing” rather than “sitting” on a branch when perched. In flight, martial eagles bear long broad wings with relatively narrow rounded tips that can appear pointed at times depending on how the eagle is holding its wings. It is capable of flexible beats with gliding on flattish wings, or slightly raised in a dihedral. This species often spends a large portion of the day on the wing, more so than probably any other African eagles, and often at a great height. [2] [3] [8] Juvenile martial eagles are conspicuously distinct in plumage with a pearly gray colour above with considerable white edging, as well as a speckled grey effect on crown and hind neck. The entire underside is conspicuously white. The wing coverts of juveniles are mottled grey-brown and white, with patterns of bars on primaries and tail that are similar to adult but lighter and greyer. In the 4th or 5th years, a very gradual increase to brownish feather speckling is noted but the back and crown remain a fairly pale grey. At this age, there may be increasing spots on throat and chest which coalesce into a gorget and some spots on abdomen may variably manifest as well. The eyes of juveniles are dark brown. This species reaches adult plumage by its seventh year with the transition to adult plumage happening quite rapidly after many years in a little-changing juvenile plumage. [2] [3] [33]

There are few serious identification challenges for the species. The black-chested snake eagle (Circaetus pectoralis) is similar in overall colouring (despite its name it is brown on the chest and the back, being no darker than the adult martial eagle) to martial eagles but is markedly smaller, with a relatively more prominent, rounded head with large eyes, plain, spotless abdomen, bare and whitish legs. In flight, the profile of the snake eagle is quite different with nearly white (rather than dark brown) flight feathers and much smaller, narrower wings and a relatively larger tail. For juveniles, the main source for potential confusion is the juvenile crowned eagle, which also regularly perches in an erect position. The proportions of crowned eagles are quite distinct from martial eagles as they have much shorter wings and a distinctly longer tail. The juvenile crowned eagle has a whiter head, more scaled back, and spotted thighs and legs lacking in the martial eagle. Beyond their distinct flight profile by wing and tail proportions, crowned eagles have whiter and more obviously banded flight-feathers and tail. Other large immature eagles in Africa tend to be much darker and more heavily marked both above and below than martial eagles. [2] [3]

Predatory Physiology Edit

Martial eagles have been noted as remarkable for their extremely keen eyesight (3.0–3.6 times human acuity), partly due to their eye being nearly as large as a human's eye. Due to this power, they can spot potential prey from a very great distance, having been known to be able to spot prey from as far as 5 to 6 km (3.1 to 3.7 mi) away. [2] [34] Their visual acuity may rival some eagles from the genus Aquila and some of the larger falcons as the greatest of all diurnal raptors. [35] [36] The talons of martial eagles are impressive and can approach the size, especially in mature females, of those of the crowned eagle despite their slenderer metatarsus and toes compared to the crowned species. [37] Accipitrids usually kill their prey with an elongated, sharp hind toe-claw, which is referred to as the hallux-claw and is reliably the largest talon in members of the accipitrid family. [38] The average length of the hallux-claw in unsexed martial eagles from Tsavo East National Park, Kenya was found to be 51.1 mm (2.01 in). [32] In comparison, the average hallux-claw of a large sample of golden eagles was similar at 51.7 mm (2.04 in). Meanwhile, the three largest clawed modern eagles were found to measure as such: in small samples, the Philippine eagle and crowned eagle had an average hallux-claw length of 55.7 mm (2.19 in) and 55.8 mm (2.20 in), respectively, and harpy eagles have an average hallux-claw length of approximately 63.3 mm (2.49 in). [39] [40] [41] [42] The inner-claw on the front of the foot of the martial eagle is especially sizeable proportional to other extremities and unusually can approach, if not reach, the same size as the hallux-claw. This inner-claw was found to average 46.1 mm (1.81 in), in comparison to that of the crowned eagle which measures 47.4 mm (1.87 in). [32] [43] The tarsus is quite long in martial eagles, the fourth longest of any living eagle and the longest of any booted eagle species, seemingly an adaptation to prey capture in long grass, including potentially dangerous prey. [2] [11] The bill is of medium-size relative to other large eagles, with a mean culmen length from Tsavo East of 43.7 mm (1.72 in). Their bill is larger than the average bill size of the large members of the genus Aquila but is notably smaller than those of the large species of sea eagle and the Philippine eagle. [32] [27] [41] [39] [44] The gape size of martial eagles is relatively large however, being proportionally larger than in other booted eagle species behind (albeit considerably behind) the Indian spotted eagle (Clanga hastata) and the steppe eagle (Aquila nipalensis) in relative gape size, indicating a relative specialization towards swallowing large prey whole. [45] [46]

Voice Edit

The martial eagle is a weak and infrequent vocaliser. Little vocal activity has been reported even during the breeding season. The recorded contact call between pair-members consists of the birds, usually when perched, letting out a low mellow whistle, ko-wee-oh. More or less the same vocalisation is known to have been uttered by females when male brings food and repeated mildly by large begging young. During territorial aerial display and sometimes when perched, adults may utter a loud, trilling klee-klee-klooeee-klooeee-kulee. The territorial call may be heard from some distance. Recent fledglings also at times make this call. A soft quolp may be heard, made by pairs around their nest, perhaps being a mutual contact call. [2] [3] [9] In comparison, the crowned eagle is highly vocal especially in the context of breeding. [9]

The martial eagle is to some degree adaptable to varied habitats but shows an overall preference for open woods and woodland edges, wooded savannah and thornbush habitats. The martial eagle has been recorded at elevations of up to 3,000 m (9,800 ft) but is not a true mountain dwelling species and resident eagles do not usually exceed an elevation of 1,500 m (4,900 ft). [2] [3] These eagles also avoid closed-canopy forests and hyper-arid desert. [7] As such it is mostly absent from Guinean and Congolian forests, despite the species’ requirement for large trees for nesting purposes. It is shown that martial eagles can inhabit forests locally in areas where openings occur. [9] For example, in a bird atlas for the country of Kenya, perhaps surprisingly, 88% of martial eagles were found to reside in well-wooded areas and they occurred in areas where annual rainfall exceeded 250 mm (9.8 in). [47] In southern Africa, they have adapted to seemingly more open habitats than elsewhere in their range, such as semi-desert and open savanna with scattered trees, wooded hillocks and, as a recent adaptation, around pylons. In the desert areas of Namibia, they utilize ephemeral rivers that flow occasionally and allow large trees to grow. [2] [7] They usually seem to prefer desolate or protected areas. In the Karoo of South Africa, they consistently avoid areas with moderate to heavy cultivation or with heavier or more consistent winter rainfall. [48] One study on the occurrence of diurnal raptors in protected areas against unprotected areas, found that martial eagle detection was nearly twice as frequent in protected areas during the dry season and more than three times as frequent during the wet season than in unprotected areas. Some assorted diurnal raptors were even relatively rarer outside of protected areas such as hooded vultures (Necrosyrtes monachus). [49]

The martial eagle spends an exceptional amount of the time in the air, often soaring about hill slopes high enough that binoculars are often needed to perceive them. When not breeding, both mature eagles from a breeding pair may be found roosting on their own in some prominent tree up to several miles from their nesting haunt, probably hunting for several days in one area, until viable prey resources are exhausted, and then moving on to another area. [9] [50] However, martial eagles, especially adult birds, are typically devoted to less disturbed areas, both due to these typically offering more extensive prey selection and their apparent dislike for a considerable human presence. [48] Martial eagles tend to be very solitary and are not known to tolerate others of the own species in the area outside of the pair during the breeding season. [51] In general this species is more shy towards humans than other big eagles of Africa, but may be seen passing over populated country at times. [9] The most frequently seen type of martial eagle away from traditional habitats are presumed nomadic subadults. One individual that was ringed as subadult was recovered 5.5 years later 130 km (81 mi) away from the initial banding site. Another martial eagle ringed as a nestling was found to have moved 180 km (110 mi) in 11 months. [2]

The martial eagle is one of the world's most powerful avian predators. Due to both its underside spotting and ferocious efficiency as a predator it is sometimes nicknamed “the leopard of the air”. [52] The martial eagle is an apex predator, being at the top of the avian food chain in its environment. [28] In its common, scientific and most regional African names, this species name means “war-like” and indicates the force, brashness and indefatigable nature of their hunting habits. The aggressiveness of the hunting martial eagle, which may rival that of the overall behaviorally bolder crowned eagle, can seem incongruous with their other behaviours, as it otherwise is considered a shy, wary and evasive bird. [3] [53] [54] Martial eagles have been seen to charge at much larger adult ungulates and rake at their heads and flanks, at times presumably to separate the mammals from their young so they can take the latter with more ease. [55] [56] At other times, these eagles will set down upon a wide range of potentially dangerous prey including other aggressive predators in broad daylight, such as monitor lizards, venomous snakes, jackals and medium-sized wild cats. [3] Adult eagles tend to hunt larger, potentially dangerous prey more often than immature ones, presumably as they refine their hunting skills with maturity. [3] The martial eagle hunts mostly in flight, circling at a great height anywhere in its home range. When prey is perceived with their superb vision, the hunting eagle then stoops sharply to catch its prey by surprise with the prey often being unable to perceive the eagle at nearly as far as the eagle can perceive them despite often being in the open. [2] [9] The martial eagle tends to hunt in a long, shallow stoop, however when the quarry is seen in a more enclosed space, it parachutes down at a relatively steeper angle. The speed of descent is controlled by the angle at which the wings are held above the back. At the point of impact, it shoots its long legs forward, often killing victims on impact somewhat like large falcons often dispatch their prey. [3] [9] Prey may often be spotted from 3 to 5 km (1.9 to 3.1 mi) away with a record of about 6 km (3.7 mi). [2] On occasion, they may still-hunt from a high perch or concealed in vegetation near watering holes. If the initial attempt fails, they may swoop around to attempt again, especially if the intended victim is not dangerous. If the quarry is potentially hazardous, such as mammalian carnivores, venomous snakes or large ungulates, and becomes aware of the eagle too soon, the hunt tends to be abandoned. [2] [3] Unusually for a bird of its size, it may rarely hover while hunting. This hunting method may be employed particularly if the quarry is any of the aforementioned potentially dangerous prey items such as venomous snakes or carnivores. Other large eagles may hunt similarly (if infrequently) hover over prey such as canids and then quickly drop onto if the quarry makes the mistake of pointing its dangerous mouth downwards, then gripping its victim on the back while controlling the neck with the other foot until blood-loss is sufficient to cause the prey to expire. [57] [26] Prey, including birds, are generally killed on the ground, with infrequent reports of prey taken from trees. Some larger (and presumably slower-flying) avian prey may be taken while in flight, victims of successful hunts as such have consisted of water birds such as herons, storks and geese. [3] If kills are too large and heavy to carry in flight, both members of a pair may return to the kill over several days, probably roosting nearby. If nesting, the pair tends to dismember pieces of large kills such as limbs to bring to the nest. Much of the large prey, perhaps most, that is left on the ground is lost to scavengers, however. [2] [3]

The diet of the martial eagle varies greatly with prey availability and can be dictated largely by opportunity. Remarkably, mammals, birds and reptiles can in turn dominate the prey selection of martial eagles in a given area with no one prey type globally dominating their prey spectrum. [3] [9] In some areas, both mammals and birds can each comprise more than 80% of the prey selection. [9] [58] Over 170 prey species have been reported for the martial eagle which is a much higher number than the full prey spectrum of other larger African booted eagles, and even this may neglect some of the prey they take in the little studied populations from west and central Africa and the northern part of east Africa. [3] [59] Prey may vary considerably in size but for the most part, prey weighing less than 0.5 kg (1.1 lb) are ignored by hunting martial eagles, with only about 15% of the known prey species averaging less than this. A majority of studies report the average size of prey for martial eagles being between 1 and 5 kg (2.2 and 11.0 lb). [3] [60] Average weight of prey taken has been reported at as low as 1.2 kg (2.6 lb). [61] A food study largely based in data from the Great Rift Valley, Kenya, as well as from Maasai Mara, did reinforce a mean prey mass of just over 1.2 kg (2.6 lb) for the species. [62] However, the mean prey body mass is considerably higher in known dietary studies. In by far the largest dietary study thus far conducted for the martial eagle species (in the Cape Province, South Africa) the estimated mean prey body mass was approximately 2.26 kg (5.0 lb). [60] In Tsavo East National Park of Kenya, the mean estimated body mass of prey was quite similar at approximately 2.31 kg (5.1 lb). [32] Average prey weights in a study of the Maasai Mara was seemingly even higher. [29] Despite perhaps a majority of prey for this species weighing less than 5 kg (11 lb), martial eagles regular prey size range is claimed at up to 12 to 15 kg (26 to 33 lb). [5] [63] [64] There is some evidence of prey partitioning (which can be potentially delineated both by prey species and body size of prey items taken) between the sexes. This is typical of raptors with pronounced size sexual dimorphism, as is the case in martial eagles. For instance, in populations where large adult monitor lizards are significant as prey, they only start to appear in prey remains at nests only after the female resumes hunting in the latter part of the breeding season. [3] The species was the focus for a study using web sourced photography to explore the species' diet across its African range, this study revealed new insight into difference in prey composition between regions, and also revealed differences in prey composition between adult and sub-adult birds, with adults found to prey more frequently on bird prey than sub-adults. [65] The sexual dimorphism of kills was verified in studies from the Great Rift Valley and Maasai Mara. One study stated that the mean weight of male kills was 744 g (1.640 lb) and that of females was 1.375 kg (3.03 lb). [62] In Maasai Mara, the mean prey was significantly higher for both males, at about 1.98 kg (4.4 lb), and for females, at about 3.74 kg (8.2 lb). [29]

Mammals Edit

The most diverse class of prey in the diet as known are mammals, with over 90 mammalian prey species reported. [3] In the Cape Province, the 2.1 kg (4.6 lb) cape hare (Lepus capensis) reportedly dominates the prey selection, comprising about 53% of the foods selected. [60] Other lagomorphs, namely the slightly smaller Smith's red rock hare (Pronolagus rupestris), mildly larger African savanna hare (Lepus microtis) and the much larger 3.6 kg (7.9 lb) scrub hare (Lepus saxatilis), are not infrequently taken both in and outside of the Cape area. [3] [60] [66] In Maasai Mara, the most regularly identified food, at 17.3% of 191 prey items (and particularly for male martial eagles at 23.9% of their kills), was found to be comprised by a mixture of cape and scrub hares, these in total weighing an estimated mean of 2.54 kg (5.6 lb). [29] For the most part rodents are ignored as prey as they are probably too small despite martial eagles taking at times appreciable numbers of Cape (Xerus inauris) and unstriped ground squirrels (Xerus rutilus). [60] [67] [68] However, rodents selected as prey have ranged in size from the 0.14 kg (4.9 oz) Southern African vlei rat (Otomys irroratus) to the 3.04 kg (6.7 lb) South African springhare (Pedetes capensis) and the 4 kg (8.8 lb) greater cane rat (Thryonomys swinderianus). [3] [69] [70] There are records of predation on 0.28 kg (9.9 oz) (the second largest African bat) straw-coloured fruit bats (Eidolon helvum) and galagos of various sizes (usually weighing a kilo or less) but otherwise mammalian prey they pursue tends to be relatively larger. [71] [72] [73]

Locally, large numbers are taken of any species of hyrax. The attractiveness of hyraxes as a prey resource may encourage martial eagles to vary their hunting techniques to potentially more time-consuming perch hunting so that they may capture rock hyraxes from rock formations and tree hyraxes from trees, contrary to their usual preference for capturing prey on the ground in the open after soaring high. Ranging in average mass from 2.2 to 3.14 kg (4.9 to 6.9 lb), hyraxes can comprise a healthy meal for a family of martial eagle and are probably among the larger items that male eagles will regularly deliver to nests. [60] [74] [75] [76] Another miscellaneous mammal known to fall prey to martial eagles is the ground pangolin (Smutsia temminckii), although it is not clear the age pangolins that are preyed on and how they are dispatched, considering that adults weigh some 11.6 kg (26 lb) and have a hard keratin shell that is capable of withstanding lion (Panthera leo) jaws when in its rolled-up defensive posture. [3] [4] [77] Although far less accomplished and prolific as a predator of monkeys than the crowned eagle, the martial eagle has been known to prey on at least 14 species of monkey. The monkeys to turn up most often as martial eagle prey are grivets (Chlorocebus aethiops), vervet monkeys (Chlorocebus pygerythrus) and malbroucks (Chlorocebus cynosuros), with mean body masses of 2.8 kg (6.2 lb), 4.12 kg (9.1 lb) and 4.53 kg (10.0 lb), respectively, because of their savanna-woods dwelling habits, tendencies to forage on the ground and their primarily diurnal activity. [3] [32] [75] [78] Similarly, the larger Patas monkey (Erythrocebus patas), at 8.13 kg (17.9 lb), also dwells in similar habitats and so may be subject to occasional predaceous attacks. [79] [80] [81] There's evidence that these monkey species have special alarm calls, distinct from those uttered in response to the presence of a leopard (Panthera pardus) for example, specifically for martial eagles. [82] [83] Martial eagles are also known to prey on mangabeys, Cercopithecus sp., colobus monkeys and guerezas, presumably around forest clearings, but these are probably quantitatively rare as prey given their forest-dwelling habits. [75] [84] [85] [86] Predatory attacks by martial eagles have been reported as well for every species of baboon, although either mostly or entirely on young ones, and even on young chimpanzees (Pan troglodytes). [4] [60] [75] [87] [88] It has been claimed that juvenile monkeys are the most often selected as prey by martial eagles, even for species as small as vervet monkeys but little comprehensive analysis is known on this (the most accomplished modern avian primate predator, the crowned eagle, in Uganda, selects adult monkeys 52% of the time, juveniles 48% of the time). [61] [89] On the hand, at times, martial eagles may at times be able to dispatch adult male monkeys weighing 9 kg (20 lb) or more, such as patas monkeys and Tana River mangabeys (Cercocebus galeritus), in seldom cases. [75] [79] On at least one occasion, this species has been known to attack humans with apparently predatory intent, making it one of the only birds of prey to do so. In 2019 a young boy was killed, and two other children injured, by an immature martial eagle in the Ethiopian town of Gaashaamo. [90] Carnivores are exceptionally important prey for martial eagles. Among these many mongoose tend to be well represented in their diet. Most mongoose native to savanna tend to be highly social burrowers. Most of these types of mongoose are also relatively small (probably the second smallest important martial eagle food source after korhaans) and can effectively escape quickly to the safety of their underground home, so the lighter, more nimble male martial eagle is more likely to habitually pursue them. In southern Africa, the 0.72 kg (1.6 lb) meerkat (Suricata suricatta) comprises up to at least 9.6% of prey remains (as in the Cape Province) and the 0.75 kg (1.7 lb) Cape grey mongoose (Galerella pulverulenta) comprising an average of 7.2% of prey remains in the Cape area. [60] [91] [92] The largest of the social savanna-dwelling mongoose is the banded mongoose at 2.12 kg (4.7 lb). In pooled data from the Great Rift Valley and Maasai Mara, the banded mongoose fell third behind only francolins and hares as the most regularly selected prey for martial eagles. [62] Despite often being successful in capturing banded mongoose, in one case when a (presumably inexperienced) immature martial eagle took one to a tree, the dominant male banded mongoose of the group scaled the tree and pulled away from the eagle the still-living mongoose prey to safety. [93] [94] The martial eagle is a known predator of the full size range of mongoose species, from the smallest species, the 0.27 kg (9.5 oz) common dwarf mongoose (Helogale parvula), to the largest, the 3.38 kg (7.5 lb) white-tailed mongoose (Ichneumia albicauda). [75] [95] Other moderate-sized carnivores known to fall prey to martial eagles include 0.83 kg (1.8 lb) striped polecat (Ictonyx striatus) and a few species of genet, which are about twice as heavy on average as the polecat. [4] [60] [75] The martial eagle, however, can be a surprisingly effective predator of carnivorans close to their own size or larger. In the Cape Province, 72 bat-eared foxes (Otocyon megalotis), which average about 4.1 kg (9.0 lb), were found in the prey remains, 85% of which were adults. [60] [75] Other foxes have also been hunted, as well as both Black-backed jackals (Canis mesomelas) and the African golden wolf (Canis anthus). [60] [96] Some of the black-backed jackals that martial eagles have captured and flown off with have included “half-grown” individuals and a rare adult, averaging some 8.9 kg (20 lb), may also be killed but is usually grounded prey. Despite being marginally the smallest of the 3 jackals, the black-backed is the most aggressive and predatory species, so are probably taken only in surprise blitzes. [60] [75] [97] Adult domestic dogs (Canis lupus familiaris) of up to a modest size may occasionally be killed by martial eagles. [98] Martial eagles are also known to opportunistically grab pups of African wild dogs (Lycaon pictus) as they emerge from their dens. [99] A similarly impressive range of felids have been included in their prey spectrum. Adults of both domestic cats and their ancestors, the 4.65 kg (10.3 lb) African wildcat (Felis silvestris lybica), are known to fall prey to this species. [60] [98] Arguably their most impressive mammalian carnivore prey though are adults of much larger cat species such as the 10.1 kg (22 lb) serval (Leptailurus serval) and even the 12.7 kg (28 lb) caracal (Caracal caracal). [3] [60] [75] Apparent predatory attacks are even attempted on big cat cubs as they are considered potential predators of lion and leopard (Panthera pardus) cubs and confirmed predators of cheetah (Acinonyx jubatus) cubs. Evidence shows, however, they rapidly abandon hunting attempts if the formidable mother lion or leopard are present. [100] [101] [102] [103] Successful predatory attacks on other relatively large carnivores have included adults of the 12.4 kg (27 lb) African civet (Civettictis civetta) and the 8.16 kg (18.0 lb) aardwolf (Proteles cristata). [60] [104]

While large accipitrids from around the world are credited with attacks on (almost always young) ungulates, perhaps no other species is as accomplished in this regard as this martial eagle. Over 30 species of ungulate have been identified as prey for this species, more species than are attributed to the perhaps more powerful crowned eagles and all the world's golden eagles, although in all 3 seldom more than 30% of the diet are comprised by ungulates in a given region. [3] [32] [26] [60] In Kruger National Park, the martial eagle is mentioned as the only bird considered as a major predator of ungulate species. [105] A majority of the ungulate diet of martial eagles are comprised by small antelope species or the young of larger antelopes. Locally favored prey are the dik-diks, one of the smallest kind of antelope, and every known species may be vulnerable to this eagle. [106] In Tsavo East National Park, Kirk's dik-dik (Madoqua kirkii) were the second most numerous prey species and it was estimated that at least 86 dik-diks are taken in the park over the course of the year by two pairs of martial eagles. At an average of 5 kg (11 lb), these can provide a very fulfilling meal for an eagle family. [32] In Maasai Mara, young ungulates appeared particularly significant in the diet of adult female martial eagles, with impala fawns averaging an estimated 7.5 kg (17 lb) comprising 34.2% of female kills (and 13.6% of the species' overall foods) and Thomson's gazelle fawns at about 3.75 kg (8.3 lb) comprising a further 15.1% of female kills (and 10.5% of the overall diet here). Furthermore, young Grant's gazelles, weighing a mean of 9.02 kg (19.9 lb), were sometimes taken by females in Maasai Mara. [29] Adults of other smaller antelope such as 4.95 kg (10.9 lb) suni (Neotragus moschatus) and 4.93 kg (10.9 lb) blue duikers (Philantomba monticola) are probably also taken with relative ease. [3] [60] [75] In general, the young of other antelope are usually attacked, including newborns. Occasional ambush attacks or successful predations are reported on adults of much larger species despite young ones being rather more vulnerable, including 12.1 kg (27 lb) klipspringers (Oreotragus oreotragus), 11.1 kg (24 lb) steenboks (Raphicerus campestris), both species of grysbok (7.6 to 10.6 kg (17 to 23 lb) on average), 14.6 kg (32 lb) oribis (Ourebia ourebi) and perhaps up to half a dozen larger duikers, potentially weighing from 7.7 to 25 kg (17 to 55 lb). [3] [60] [105] [106] [107] [108] [109] One duiker dispatched via strangulation weighed an estimated 37 kg (82 lb), one of the largest known raptorial kill for any species on the African continent. [2] [3] [110] Among extant birds of prey, only wedge-tailed eagles, reportedly capable of killing sheep and female red kangaroos (Macropus rufus) weighing up to 50 kg (110 lb), crowned eagles taking antelope of the same estimated weight and golden eagles, credited with taking adult female deer of several species with weights estimated at 50 to 70 kg (110 to 150 lb), and capable of apparently dispatching domestic calves weighing up to 114 kg (251 lb), have larger kills attributed to them. [111] [112] [113] [114] [115] Calves, including neonatal young, of the following antelope may also be included in their prey spectrum: impala (Aepyceros melampus), hartebeest (Alcelaphus buselaphus), bontebok (Damaliscus pygargus), common tsessebe (Damaliscus lunatus), springbok (Antidorcas marsupialis), Eudorcas gazelles, gerenuk (Litocranius walleri), bushbuck (Tragelaphus sylvaticus), grey rhebok (Pelea capreolus), kob (Kobus kob) and mountain reedbuck (Redunca arundinum). These species can vary in weight from 2.6 kg (5.7 lb) (i.e. gazelles) to 11 kg (24 lb) (i.e. tsessebe) in newborns. [3] [32] [60] [116] [117] [118] [119] [120] For the newborn impala, weighing already 5.55 kg (12.2 lb), the martial eagle is the only bird considered to be a significant predator. [63] [121] Additionally, piglets of warthogs (Phacochoerus africanus) (of which only the martial eagle among accipitrids is similarly mentioned as a significant predator) and bushpigs (Potamochoerus larvatus) are taken. [4] [60] [122]

Birds Edit

Compared to the range and sizes of mammals included in their prey spectrum, birds taken by martial eagles may seem less impressive as a whole but the morphology of the martial eagle, including large wing surface areas, pronounced sexual dimorphism and relatively long toes, shows that the species is at least partially specialized to hunt avian prey. Birds are universally considered by biologists more difficult to capture than mammals of the same size. In all, more than 50 bird species have been identified as the prey of martial eagles. [2] [3] [123] The most significant portion of the avian diet is comprised by medium-sized terrestrial upland birds such as guineafowl, spurfowl and bustards. In total more than a dozen species of the galliform order and the bustard family each have been identified as their prey. [3] [4] [60] When attacking these ground-loving birds, which are understandably quite easily spooked and usually react to potential danger by flying off, martial eagles almost always try to take them on the ground much like they do mammalian prey. If the birds take flight, the hunting attempt will fail, although a hunting eagle may try to surprise the same birds again. [3] In Niger, the most numerous prey species is apparently the 1.29 kg (2.8 lb) helmeted guineafowl (Numida meleagris). [124] Other guineafowl such as the vulturine (Acryllium vulturinum) and crested guineafowl (Guttera edouardi) are also readily taken elsewhere. [125] [126] Guineafowl and spurfowl were stated as the most numerous prey for martial eagles in Kruger National Park. [127] In Tsavo East National Park, the 0.67 kg (1.5 lb) red-crested korhaan (Lophotis ruficrista), perhaps the smallest bustard the eagle hunts, is the most numerous prey taken, comprising about 39% of the prey remains. [32] In the Great Rift Valley and Maasai Mara data, the Coqui francolin (Peliperdix coqui) was reportedly the most regularly identified prey and, in separate studies, helmeted guineafowl averaging 1.48 kg (3.3 lb) made up 12% of the foods in Maasai Mara. [29] [62] Medium-sized bustards such as the 1.2 kg (2.6 lb) Hartlaub's bustard (Lissotis hartlaubii) and the 1.7 kg (3.7 lb) karoo korhaan (Eupodotis vigorsii) were oft-taken supplemental prey in Tsavo East and the Cape Province, respectively. [32] [25] [60] Although these are not usually taken in large numbers, martial eagles are one of the main predators of larger bustards. These may include (averaged between the extremely size dimorphic sexes) the 3.44 kg (7.6 lb) Ludwig's bustard (Neotis ludwigii), the 5.07 kg (11.2 lb) Denham's bustard (Neotis denhami) and even the kori bustard (Ardeotis kori), seemingly the heaviest bustard in the world on average at 8.43 kg (18.6 lb), the average estimated weight of 13 kori bustard kills being 8 kg (18 lb). [4] [25] [60] [65] Attacks on adult male kori bustards, which are certain to be the largest avian prey attacked by martial eagles and are twice as heavy as females, averaging some 11.1 kg (24 lb), can be extremely prolonged. One protracted battle resulted in an injured leg for the eagle and massive, fatal blood loss for the male bustard, which was ultimately scavenged by a jackal by the following morning. [25] [128]

Despite its preference for ground-dwelling avian prey, a surprisingly considerable number of water birds may also be attacked. Waterfowl known to be attacked include the 1.18 kg (2.6 lb) South African shelduck (Tadorna cana), 1 kg (2.2 lb) yellow-billed duck (Anas undulata), the 4.43 kg (9.8 lb) spur-winged goose (Plectropterus gambensis) (Africa's largest waterfowl species) and especially the peculiar, overly bold and aggressive 1.76 kg (3.9 lb) Egyptian goose (Alopochen aegyptiaca), which is one of the main prey species for martial eagles in Kruger National Park. [3] [4] [25] [60] [127] [129] Based on the high estimated weight when taken of Egyptian goose of 3.5 kg (7.7 lb), male geese may be targeted over females. [65] Larger wading birds are also fairly frequently attacked including herons and egrets, flamingoes storks, ibises, spoonbills and cranes. [3] [4] [60] [130] [131] The diversity and number of storks taken is particularly impressive. They are known to take 8 species of stork, ranging from the smallest known species, the 1.08 kg (2.4 lb) African openbill (Anastomus lamelligerus), to the tallest species in the world, the 6.16 kg (13.6 lb), 1.5 m (4 ft 11 in)-tall saddle-billed stork (Ephippiorhynchus senegalensis). One naturalists observed up to a half dozen attacks in different parts of Africa on 3.45 kg (7.6 lb) white storks (Ciconia ciconia). [3] [132] [133] Short of three attacks on spotted thick-knees (Burhinus capensis), which weigh about 0.42 kg (15 oz), and smaller still crowned lapwings (Vanellus coronatus) so far as is known small waders or shorebirds are ignored as prey. [3] [29] [60] Other assorted avian prey may consists of ostrich (Struthio camelus) chicks weighing an estimated mean of 4.5 kg (9.9 lb), frequently resulting in the immediate ire of protective ostrich parents. Further avian prey may extent to sandgrouse, pigeons and doves, hornbills and crows. [3] [4] [60] [65] [134] Beyond occasional captures of other birds of prey (covered later), one other impressive avian prey species is the southern ground hornbill (Bucorvus leadbeateri), which at 3.77 kg (8.3 lb) is probably the world's largest hornbill. [25] [135] At the other end of the scale, some martial eagles may capture a few small social species of passerine, which are exceptionally small prey (the smallest recorded prey species for the eagle overall), potentially consisting of the 18.6 g (0.66 oz) red-billed queleas (Quelea quelea) and the 27.4 g (0.97 oz) sociable weavers (Philetairus socius), as practically every meat-eating bird in Africa may be attracted to these species’ colonial abundance. [3] [25] [136]

Reptiles Edit

Reptiles can be locally important in the diet, and they are known to take larger numbers of reptiles than other large African booted eagles. Only relatively large reptiles, it seems, are attacked and many of this prey is also potentially dangerous, so a great majority of the time such prey is taken in ambushes. [3] [11] In particular, in the former Transvaal province of northeastern South Africa, reptiles were the main prey, with monitor lizards alone comprising just under half of the prey remains. A small food study in Zimbabwe found 69% of 39 prey items were made up of monitor lizards. The monitors attacked may include the 6.1 kg (13 lb) rock monitor (Varanus albigularis), the 5.25 kg (11.6 lb) nile monitor (Varanus niloticus) and the 1.02 kg (2.2 lb) savannah monitor (Varanus exanthematicus). These monitors, the largest lizards in Africa, are formidable prey and almost all attacks are ambushes on adult monitors by mature female eagles. Sometimes a lengthy struggle will ensue as the eagles try to get a good grip into the tough back skin of the monitors while simultaneously trying to control their necks to avoid the prey's powerful jaws, however the eagles are usually successful in dispatching the large lizards. [3] [4] [32] [60] [137] [138] [139] [140] [141] Overall, monitor prey taken based on photographic analysis is estimated to weigh a mean of 4 kg (8.8 lb). [65] Reptiles as a whole made up 38% of the prey remains from Kruger National Park. These consisted of monitor lizards as well as wide range of venomous snakes, including Cape cobras (Naja nivea), boomslangs (Dispholidus typus), puff adders (Bitis arietans), the eastern (Dendroaspis angusticeps) and western green mambas (Dendroaspis viridis), and even black mambas (Dendroaspis polylepis), these species ranging in size from the 0.3 kg (11 oz) boomslang to the 1.6 kg (3.5 lb) black mamba. Also taken here were the non-venomous but already sizeable youngsters of the African rock python (Python sebae), the largest African snake. [127] [142] The weight estimated for a rock python kill was 12 kg (26 lb). [65] Elsewhere, snouted cobras (Naja annulifera) may added to the list of their prey spectrum. [4] A surprising number of tortoises and turtles are also taken by martial eagles, ranging from one of the smallest tortoises, the 0.23 kg (0.51 lb) greater padloper (Homopus femoralis) to the one of the largest, the 10.8 kg (24 lb) leopard tortoise (Stigmochelys pardalis) (though probably only small specimens of the latter species are taken of this, the second largest tortoise on mainland Africa). [60] [143] [144] [145] [146] [147] In one case, an estimated 90 cm (2 ft 11 in) nile crocodile (Crocodylus niloticus) was captured and flown with by a martial eagle. [148]

Interspecies predatory relationships Edit

For terrestrial predators, including birds of prey, sub-Saharan Africa may be the most competitive environment in the modern world. Due to great diversity of raptors present, each species have shown adaptive specializations, which may consist of various morphological differences that allow them to capitalize on distinct prey selection, hunting methods, habitat and/or nesting habits. [2] [3] [149] [150] The larger booted eagles that dominate the avian food chain in Africa consists of martial eagles, 4 kg (8.8 lb) Verreaux's eagles and 3.64 kg (8.0 lb) crowned eagles, which due to their size and conspicuousness may lend themselves to comparisons. While prey species may overlap in these in southern Africa and some parts of east Africa, where the prey size range of all three eagles averages 1 to 5 kg (2.2 to 11.0 lb), these three powerful eagles differ considerably in habitat preferences, nesting habits and hunting methods. The Verreaux's eagle nests in and hunts around rocky, mountainous kopje to be in close proximity to the much favored prey, rock hyraxes, which they mainly use contour-hunting (hugging the uneven ground to surprise the prey) to capture. The crowned eagle dwells mainly in mature forests, building nests in large interior trees, and is primarily a perch-hunter, watching and listening for monkeys and other prey over a long period. While all three are known to locally favor rock hyraxes, the nesting habitat differences where they overlap are sufficient to allow these birds not to effect one another. [2] [3] [18] [23] [25] [151] The average prey mass of Verreaux's eagle was similar to that martial eagles, with a pair of studies showing it ranges from 1.82 to 2.6 kg (4.0 to 5.7 lb). [26] [152] The mean prey mass of crowned eagles in southern Africa also appears to be similar to that of martial eagles but in west Africa (i.e. Ivory Coast) it was considerably heavier at 5.67 kg (12.5 lb) (which may well be the highest mean prey mass for any of the world's raptors). [137] [153] Elsewhere, mean prey masses for the larger booted eagles appears to be considerably smaller than in the larger African species, i.e. single studies for the Spanish imperial eagle (Aquila adalberti) and wedge-tailed eagles showed means of 0.45 kg (0.99 lb) and 1.3 kg (2.9 lb), respectively, while a large number of extensive dietary studies for the golden eagle show its global mean prey mass is around 1.61 kg (3.5 lb). [26] [154] [155]

More similar in habitat and, locally, prey selection to martial eagles are three medium-sized eagles, the 1.47 kg (3.2 lb) African hawk-eagle (Aquila spilogaster), the 2.25 kg (5.0 lb) tawny eagle (Aquila rapax) and the 2.2 kg (4.9 lb) bateleur (Terathopius ecaudatus). [3] [32] [25] The biology of martial eagles was compared extensively with that of these species in Tsavo East National Park, Kenya, where all four were known to prey on large numbers of Kirk's dik-diks (albeit none of these took as many as did the martial eagles and some eaten by bateleurs and tawny eagles are probably scavenged). It was found that the bateleur and tawny eagle are even broader in their prey composition and take live prey more often of a smaller size, also often coming to and feeding on carrion (which is seldom seen in martial eagles) and pirating from other raptors, especially the tawny eagles. The African hawk-eagle takes fairly similar prey to the martial eagle but does not conflict with martial eagles considering its much smaller size and preference for slightly denser wooded areas. In Tsavo East, 29% of prey of tawny eagle and 21% of bateleur foods were the same as that of martial eagles. In east Africa, the breeding season differs mildly between these eagles with bateleurs nesting much earlier than the others and African hawk-eagles breeding peaking slightly later. Thus pressure on shared prey types such as dik-diks are exerted at different times of the year. While the bateleur and tawny eagle can kill prey weighing up to 4 kg (8.8 lb) and the African hawk-eagle (being relatively large footed and clawed despite its smaller size) can kill prey of up to 5 kg (11 lb), these raptors are too small to regularly go after live prey as large in the prey spectrum of martial eagles, with the bateleur and tawny having talons relatively smaller even adjusted for their body size (the hawk-eagle's talons were relatively similar in proportion to their body size). [2] [3] [32] Due to its large size and broad wings, martial eagles are not highly maneuverable in flight and are not infrequently robbed of their catches by these more agile and swift smaller eagles, particularly bold tawny eagles. Other raptors known to steal food from martial eagles include bateleurs and even other big species such as Verreaux's eagles and lappet-faced vultures (Torgos tracheliotos). Considering their potential for aggressiveness in regards to prey pursuits, martial eagles often appear to be surprisingly passive in response to kleptoparasitism, especially if they are able to first fill their crop. This may be because they try to avoid unnecessary expenditures of energy in contention over food. [3] [156] Leopards also rarely steal kills from martial eagles but may also be robbed of small kills by martial eagles as have cheetahs. [157] [158] In another case, a martial eagle stole a rock hyrax from a bearded vulture (Gypaetus barbatus). [3] Prey species are shared by a wide range of birds of prey, both other eagles and other, usually, larger raptors, and mammalian carnivores of many sizes that are too numerous to mention. Some mammalian carnivores such as caracals have superficially similar diets to martial eagles. [159] [160] One other species worth noting is the Verreaux's eagle owl (Bubo lacteus), as it is similarly the largest African owl, weighing about 2.1 kg (4.6 lb), with almost identical habitat preferences and distributional range as the martial eagle. [3] [25] [27] Therefore, some consider the eagle owl to be the martial eagle's nocturnal ecological equivalent. [161] While there is considerable overlap in their diets, there are discrepancies as the eagle owl tends to hunt large numbers of hedgehogs (not known in the eagle's diet) and occasionally high quantities of mole-rats. When considered this in combination with their different times of activity and the fact that the eagle owl weighs about half as much as the martial eagle, direct competition probably does not affect either predator in any considerable way. [3] [162]

The martial eagle infrequently hunts other birds of prey, perhaps doing so only slightly more often than do crowned eagles and Verreaux's eagles. [3] [60] In comparison, the temperate-zone-dwelling golden eagle is a frequent predator of other birds of prey. This may be due to more scarce prey resources in colder regions forcing eagles to pursue difficult prey such as this more frequently, whereas booted eagles in rich Africa biospheres may not need to do so as much. [26] [163] [164] Nonetheless, a somewhat diverse range of raptorial birds have been identified as prey for martial eagles: the 0.61 kg (1.3 lb) lanner falcon (Falco biarmicus), the 0.72 kg (1.6 lb) peregrine falcon (Falco peregrinus), the 0.65 kg (1.4 lb) spotted eagle owl (Bubo africanus) (with a surprisingly large number of 6 found at one nest in Tsavo East), the 0.67 kg (1.5 lb) pale chanting goshawk (Melierax canorus), the 2.04 kg (4.5 lb) hooded vulture (Necrosyrtes monachus) (in one case after a protracted aerial battle), the 4.17 kg (9.2 lb) white-headed vulture (Trigonoceps occipitalis) and even Africa's largest bird of prey, the 9.28 kg (20.5 lb) Cape vulture (Gyps coprotheres). [32] [18] [60] [165] [166] [167] As apex predators, martial eagles are themselves largely invulnerable to predation. A video exists that purportedly depicts a leopard killing a martial eagle but this eagle was misidentified as it actually features a leopard preying on an immature African fish eagle (Haliaeetus vociferus) (and, at that, one that was possibly grounded for unknown reasons). [168] There are, however, verified (if rare) cases of caracals preying on sleeping martial eagles at night, by climbing trees and pouncing in an ambush. [169] [170] [171] Additionally a case was reported where a honey badger killed an incubating adult martial eagle. [172] It is possible that leopards may too ambush sleeping eagles but post-fledgling martial eagles are known to be highly wary and healthy individuals a great majority of the time will successfully evade potential dangers by day. [3] Predation on nests of martial eagles, beyond those by humans, are little-known, with no verified depredations known in the literature, but are likely to occur. [173]

Despite their rather aerial existence, the territorial display of adult martial eagles is considered relatively unspectacular. Their display often consists of nothing more than the adult male or both members of a pair circling and calling over their home range area or perching and calling near nestlings. Compared to other large African booted eagles, this species infrequently “sky-dances” (i.e. undulation and dramatic movements high in the sky), but some are known with presumably the male martial eagle only engaging in shallow undulations. [2] [9] [174] During mutual circling, the adult female may turn and present talons. Martial eagles are not known to “cartwheel” which is when two eagles lock feet and circle down, falling almost to the ground, an action that was once thought to be part of breeding displays but is now generally considered territorial in nature. [2] [175] The territory of martial eagles can vary greatly in size. The average home range is estimated to be 125 to 150 km 2 (48 to 58 sq mi) in east Africa and southern Africa, with mean distances between nests of approximately 11 to 12 km (6.8 to 7.5 mi). [2] In Kruger National Park, the average home range of pairs is 144 km 2 (56 sq mi) with an average nest-spacing of 11.2 km (7.0 mi). In Namib-Naukluft National Park, Namibia, the home range size was 250 km 2 (97 sq mi) per pair. [3] Within Kalahari Gemsbok National Park, South Africa, nest spacing ranged from 15.1 km (9.4 mi) in the Auob river basin to 31.3 km (19.4 mi) in the interior dunes area. [173] In the Nyika Plateau of northern Malawi, the average nest spacing was 32 km (20 mi), with only one martial eagle nest recorded in an area that contained four crowned eagle nests. [176] In protected areas of west Africa, the average home range size of martial eagles is about 150 to 300 km 2 (58 to 116 sq mi). [177] Somewhat surprisingly, considering their relative scarcity in west Africa overall in comparison in east and southern Africa, home ranges may be just as large in some parts of Kenya, at up to 300 km 2 (120 sq mi), and the largest known home ranges sizes known come from southern Africa. These are from Zimbabwe’s Hwange National Park where the home ranges may be anywhere from 225 to 990 km 2 (87 to 382 sq mi), with average spacing between nests of 37 km (23 mi). By the 1990s, approximately 100 pairs were estimated to breed in Hwange. [2] [178] This disparity in territory sizes are likely due to regional differences in food supply, persecution rates and habitat disturbance. [2] [8]

Martial eagles may breed in various months in the different parts of their range. They are considered a fairly early breeder compared to the average for sub-Saharan Africa birds of prey but breed much less early than bateleurs. [32] [179] [180] The mating season is in November through April in Senegal, January to June in Sudan, August to July in northeast Africa and almost any month in east Africa and southern Africa, though mostly in April–November. The breeding season may thus begin in various parts of the range in a wet season or the earlier or later part of the local dry season so that no part of the brooding stage will occur during heavy rains. [2] [9] They build their nests in large trees, often larger than other trees in the woodlot. The nest is usually placed them in the main fork of tree at 6–20 m (20–66 ft) off the ground, though nests have been recorded at anywhere from 5 to 70 m (16 to 230 ft) high, in the highest cases on top of the tree canopy. Tree species is unimportant with the eagles seeming to prefer any type that is difficult to climb, such as those that have thorny branches, few lower branches or smoother bark. [2] [9] [108] In Kalahari Gemsbok National Park of South Africa, almost all nests were in the highly thorny, Acacia-like tree, Vachellia erioloba, in savanna areas. [173] Most nests in southern Africa often are at a height of less than 15 m (49 ft). [3] Often trees used are on the sides of cliffs, ridges, valley or hilltop, with one nest having been found within a cave. [2] [181] In the karoo of South Africa, they have also nested on electric-power pylons. Locally, with the sometimes epidemic levels of clear-cutting of old-growth trees, such pylons may provide a fairly suitable alternative that the eagles can utilize in absence of woodlands. [182] [183] [184] The nest of the martial eagle is a large and conspicuous construction of sticks. In the first year of construction, the nest will average 1.2 to 1.5 m (3.9 to 4.9 ft) in diameter and measure about 0.6 m (2.0 ft) deep. After regular use over several years, the nests can regularly measure in excess of 2 m (6.6 ft) in both diameter and depth. The nest may be lightly lined with green leaves. [2] The central depression of the nest averages about 0.4 to 0.5 m (1.3 to 1.6 ft) across. [3] The nest of martial eagles average slightly smaller than those of crowned eagles and, compared to other large eagle tree nests, are much broader than they are deep, relatively, especially when newly constructed. [9] The construction of new nests can take several months and, in some cases, pairs can take up to two months where they appear to return to the nests daily but contribute only green leaves to line the nest. The repair of an existing nest takes on average two to three weeks. Most pairs will usually just use one nest (as opposed to temperate-zone eagles which may have several alternate nests), with up to 21 years of continuous use for one nest recorded, but pairs constructing a second nest are not infrequent either. One exceptionally prolific pair built or repaired 7 nests during 17 years in Zimbabwe, although they only nested 5 of the 17 years. [3] [185]

Martial eagles have a slow breeding rate, laying usually one egg (rarely two) every two years. Clutches of two have only been reported only in South Africa and once in Zambia and the younger sibling probably never survives or possibly ever even hatches unless the first egg or hatchling dies. [9] [186] Martial eagle eggs are rounded oval and are white to pale greenish-blue, variously. Sometimes they may be handsomely marked with brown and grey blotches. The eggs of martial eagles measure 79.9 mm × 63.4 mm (3.15 in × 2.50 in) on average among 57 eggs, with ranges of 72 to 87.5 mm (2.83 to 3.44 in) in egg length by 60 to 69 mm (2.4 to 2.7 in) in width. Their eggs are the largest of any booted eagle, slightly larger on average than those of golden or Verreaux's eagle and considerably larger than those of crowned eagles. [3] [9] [187] [188] The egg is incubated for 45 to 53 days. The female does a great majority of the incubation, as is typical, but the male may relieve her and incubate for a maximum of three hours in a day. [2] [3] If the nest is approached by humans, the female tends to sit tight, often only flying off once the nest is reached. Unlike the crowned eagle, the martial eagle is not known to protectively attack animals such as humans who come too close to the nest, usually just unobtrusively abandoning the nest until the person leaves the area, in a similar fashion to Aquila eagles. However, if maimed or grounded themselves, martial eagles are known to viciously turn on their human tormentors until they are finished off, in some anecdotal claims of early hunting journals, an occasion hunting accident have resulted in martial eagles tearing the flesh down to the bone on the legs of game wardens and even broken arms with their powerful grip. Although these accounts are quite possibly exaggerated, the ferocity of cornered martial eagles may have some influence on its name. [3] [24] [189] [190] Once the eggs hatch, the male of a pair may rarely brood the young but has never been seen to the feed the chick and, for the most part, the male just brings prey for the female to distribute between herself and the nestling. The female attendance at the nest drops considerably at seven weeks after hatching, at which point she resumes hunting. Then, the female may become main food provider but males will also make deliveries. Despite her lower attendance, she still roosts on or near the nest until the nestling stage is done. Despite the occasional capture of food, the male usually is rarely seen near the nest after the female resumes hunting. [3] [9] In one unusual case, a first or second year plumaged male martial eagle was seen assisting an adult female in the way that an adult male would but it was not known if he had merely replaced a deceased male that had sired the young or had actually bred with the female, the following year the young male was verified to mate with the female. Cases of immature plumaged eagles breeding are often considered indicative of stress on a species’ regional population. [3]

The newly hatched chick tends to have a two-tone down pattern which is dark grey above and white below, which lightens at about four weeks of age, with the down becoming pale-grey. At 7 weeks, the feathers mostly cover the down and do so completely by 10 weeks except that at that stage the flight feathers are underdeveloped. [3] The new chick is usually quite weak and feeble, becoming more active only after they are 20 days old. [9] The nestlings usually first feeds itself at 9 to 11 weeks old, while it tends to engage in vigorous wing exercises performed from 10 weeks on. Like crowned eagles, males seem to be more active than female youngsters and probably fly sooner too. In one case, a male fledged prematurely at 75 days, however it is possible that male fledging can occur at less than 90 days. [3] Most estimations place fledging as occurring at 96 to 109 days, on average at about 99 days of age. However, after making their first flight, the fledgling usually return to roost in the nest for several days, before gradually moving away from it. [2] [3] [9] Despite increasing signs of independence (such as flight and beginning to practice hunting), in extreme cases, juvenile birds may remain in the care of their parents for a further 6 to 12 months. A typical post-fledgling care stage will continue for about 3 months after fledging. Despite its ability to fly, it will continue to beg for food from both parents as they are seen. Sometimes, the young eagle from the prior mating season may still be present at the onset of the next breeding season. Evidence exist of juvenile eagles returning to their nest site at as old as 3 years of age but are likely to be no longer fed. [3] [9] On the other hand, juvenile martial eagle soar much more readily than crowned eagles and, unlike that species, have been recorded traveling up to several miles from the nest 3 to 4 months after making their first flight. [9] Due to this long dependence period, these eagles can usually only mate in alternate years.


Materials and methods

Study area

We conducted our study in the W-Arly-Pendjari (WAP) protected area complex that spans 26,515 km 2 in the transboundary region of Burkina Faso, Niger, and Benin (0°E-3° E, 10°N-13°N Figure 2a). The complex contains 5 national parks (54% of total area), 14 hunting concessions (40%), and 1 faunal reserve (6%). Our study area within WAP comprised three national parks and 11 hunting concessions in Burkina Faso and Niger across ca. 13,100 km 2 (Figure 2a). Trophy hunting of many ungulate species and African lions (Panthera leo) is permitted in hunting concessions, while all hunting is illegal in the national parks and reserves in the complex. Other human activities in the park include livestock herding, resource extraction, recreation, and poaching (Sogbohossou et al., 2011 Miller et al., 2015 Harris et al., 2019). Recently, Harris et al., 2019 reported 4 large carnivore species (African lion, African leopard Panthera pardus, spotted hyena Crocuta crocuta, and cheetah Acinonyx jubatus) and 17 ungulate species belonging to the superorder Ungulata in the three national parks included in our study area from an extensive camera trap survey. Cheetahs were detected only once, while wild dogs (Lycaon pictus) were not reported in the survey area. WAP has an arid climate and consists predominantly of Sudanian and Sahel savannas, with savanna accounting for ca. 90% of the habitat cover in the study area (Lamarque, 2004 Mills et al., 2020). We conducted our survey in the drier northern portion of WAP during the dry season with average monthly rainfall ranging from 0 to 1 mm in February to 42–91 mm in June (Fick and Hijmans, 2017). Although our study design may limit inferences to dry season conditions, evidence suggests that large African herbivores show similar overall temporal activity distributions as seasons change (Owen-Smith et al., 2010).

Camera survey

We systematically deployed 238 white-flash and infrared motion-sensor cameras (Reconyx [Holmen, WI] PC800, PC850, PC900) within 10 × 10 km grid cells across our study area to assess effects of human presence on diel activity within the wildlife community. A single unbaited camera was placed within 2 km of the centroid in a total of 204 sampled grid cells over three survey seasons from January to June in 2016–2018 (Figure 2—figure supplement 1). Camera stations within cells that were surveyed in multiple years were not necessarily placed in the same location both years, but they were placed within the same 2 km buffer and are considered representative of the grid cell each year. Species identifications from camera images were validated by two members of the Applied Wildlife Ecology (AWE) Lab at the University of Michigan. We excluded false triggers, unidentifiable images, research team, and park staff from analyses. To ensure robustness in our analyses, we combined all remaining human images into a single ‘Human’ categorization representing a variety of human activities observed in WAP (e.g. livestock herding, resource gathering, recreation, poaching, and hunting). Our work is not human subjects research requiring IRB review, although we remain grateful to authorities granting permission for our research and their efforts to manage coupled human-natural ecosystems. (see Figure 2—figure supplement 1, Mills et al., 2020 and Harris et al., 2019 for additional methods on camera deployment and image processing). Due to limited detections for some species, we aggregated survey data from all 3 years into a single dataset. We accounted for temporal variation in human space use during the subsequent modeling process, and previous work suggests little annual variation in wildlife activity (Mills et al., 2020). We created independence of species triggers using a 30-min quiet period between detection events using the ‘camtrapR’ package in R 3.5.1 (http://www.r-project.org) (Niedballa et al., 2016), and we assumed detections to be a random sample of each species’ underlying activity distribution (Linkie and Ridout, 2011).

Human occupancy models

We constructed single-season, single-species occupancy models to designate WAP into areas of low and high human use. We chose to use single-season models to assess the overall distribution of human space use across the study area, as opposed to multi-season occupancy models which also estimate extinction/colonization rates that is not necessary for our objectives. Instead, we included the year as covariate in single-species models to assess temporal variation in human occupancy patterns. Occupancy models account for spatial heterogeneity in human presence across the study area, facilitating investigation into the behavioral responses of sympatric wildlife. We separated detection/non-detection data for humans into 2-week observation periods, which were modeled as independent surveys to account for imperfect detection. Our occupancy models first modeled the detection process (p) using covariates expected to influence detection while holding occupancy (Ψ) constant, and then modeled human occupancy by incorporating grouping variables among which Ψ may vary.

The global detection model included covariates related to survey design and the environment that we expected to influence the detection of humans: % savanna habitat (SAV), survey year (YR), trap-nights (TN), camera type (CAM), management type (MGMT), and site (i.e. one of 14 individual parks or concessions SITE). MGMT was a binary variable that distinguished national parks from hunting concessions. Human occupancy was modeled with only grouping variables: MGMT, YR, and SITE. We included YR as a covariate to account for temporal variation in site use or detection, as cells surveyed in multiple years were considered separate sites for our single-season model. A grid cell surveyed in multiple years could, therefore, have different levels of occupancy between surveys. Variables included in the top performing occupancy and detection model(s) are considered those which best described the spatial variation in human detection and site use. We evaluated the support for all combinations of detection and occupancy covariates using the Akaike information criterion corrected for small sample sizes (AICc). We selected the top-performing detection and occupancy models as those with ΔAICc <2 compared to the lowest AICc model. We assessed goodness-of-fit of the top-performing models using 1000 parametric bootstraps of a χ 2 test statistic appropriate for binary data and estimated the ĉ statistic to ensure the data were not over-dispersed (Fiske and Chandler, 2017). We created all detection and occupancy models using the ‘unmarked’ package and conducted model selection using the ‘MuMIn’ package in R (Fiske and Chandler, 2011 Bartoń, 2019).

We extracted cell-specific latent occupancy probabilities, representing probabilities of site use by humans because the 10-km 2 grid cells do not meet the assumption of closure, from the top-performing (lowest AICc) occupancy model corrected for imperfect detection (MacKenzie et al., 2016). From those estimates, we categorized grid cells as either low or high human use. We delineated the threshold for human use using the mean value of human occupancy. We chose to use the mean occupancy as the threshold value because of the bimodal distribution of occupancy values and to facilitate comparisons between similar sample sizes of low and high human use grid cells (Figure 2b). We also conducted a sensitivity analysis to evaluate the selected threshold by repeating our analyses using thresholds ± 0.1, as described in the following section.

Temporal analyses

Using detection timestamps from our camera survey, we compared the temporal activity patterns for apex predators (lions, leopards, and spotted hyenas) and sympatric ungulates between areas of low and high human use. We included 12 ungulate species: savanna buffalo (Syncerus caffer brachyceros), roan antelope (Hippotragus equinus koba), western hartebeest (Alcelaphus buselaphus major), waterbuck (Kobus ellipsiprymnus defassa), Buffon’s kob (Kobus kob kob), Bohor reedbuck (Redunca redunca), bushbuck (Tragelaphus sylvaticus), aardvark (Orycteropus afer), warthog (Phacochoerus africanus), oribi (Ourebia ourebi), red-flanked duiker (Cephalophus rufilatus), and common duiker (Sylvicapra grimmia). We excluded four ungulate species from analysis in our study: topi (Damaliscus korrigum jimela) and red-fronted gazelle (Eudorcas rufifrons) due to few detections (<50), and elephant (Loxodonta africana) and hippopotamus (Hippopotamus amphibius) due to large body sizes that make them uncommon prey items for large carnivores. Duiker species were aggregated due to difficulty distinguishing the two in camera trap images, resulting in 11 total ungulate species in our analyses. Previous work in this system supports estimation of prey availability from camera trap data in that predator space use is heavily influenced by prey availability as estimated from camera trap detections (Mills et al., 2020). Further, temporal activity overlap between species directly influences the strength of interspecific interactions (Kronfeld-Schor et al., 2017).

We used kernel density estimation to produce diel activity curves representing a species’ realized temporal niche in both human use zones for each of the 14 species. We first tested for differences in these activity distributions between low and high human use areas for all individual species and for each guild (representing the overall available prey base and predation pressures) by calculating the probability that two sets of circular observations come from the same distribution with a bootstrapped randomization test (Ridout and Linkie, 2009). Significant differences in temporal activities were evaluated as p-value<0.05. We conducted a sensitivity analysis by adjusting the human occupancy threshold ±0.1 and repeating this test for all species and both guilds to ensure robustness of our results (Supplementary file 3).

Using 10,000 parametric bootstraps of the temporal distribution models, we then calculated the area under the diel activity curves to determine the proportion of each species’ activity that occurred during nocturnal hours (2 hr after sunset to 2 hr before sunrise). We used the sunrise (05:41) and sunset (18:06) times from the median date of our surveys (April 4, 2018) at the survey area centroid to define nocturnal hours. To test if wildlife nocturnality differed in response to human presence, we compared the bootstrapped 95% confidence intervals (CIs) of the difference in nocturnality for each species and overall guilds between low and high human areas where a significant difference was observed when the CI did not overlap 0.

We used the coefficient of overlap (Δ) to quantify the total temporal overlap between each apex predator and their associated prey from circular activity distributions. Buffalo were excluded from the prey list of African leopards due to large body size. All other prey species were aggregated to produce a single diel activity curve of all prey for comparison to predator activity. We chose the specific estimator based on the minimum sample size of detections for both guilds to contrast human use levels (Δ1 if N < 75, Δ4 if N > 75). Values of Δ range from 0 to 1 where 0 represents no temporal overlap and 1 represents complete overlap or identical temporal niche between predators and their prey. We used 10,000 bootstrapped estimates to extract the bias-corrected 95% CIs of Δ. We compared CIs of Δ between human use levels for each species to assess differences in predator-prey overlap in response to human occurrence. Non-overlapping CIs between human use levels indicated that the overall temporal overlap of predators with their prey was significantly altered by human presence. Temporal analyses were conducted using the ‘activity’ and ‘overlap’ packages in R (Ridout and Linkie, 2009 Rowcliffe, 2019).

Predator access to prey

After determining overlap between predators and their prey as well as shifts induced by humans, we determined the implications for predator access to prey. To our knowledge, we developed a new method to assess species-specific prey access for predators that is temporally explicit over the diel period, enabling assessment of differences in the composition and diversity of accessible prey for predators resulting from responses to humans in both guilds. We first combined (i.e. stacked) the bootstrapped temporal kernel density curves for individual prey to produce a total diel activity curve for prey, but this time maintaining each species’ contributions to overall prey activity. We then multiplied each prey species’ proportional contribution to prey activity at a given point in the diel cycle by the corresponding kernel density activity value of each respective apex predator. This method produced a discrete area under the predator temporal activity curve for each prey species of a given apex predator (percent area under curve, PAUC), where each prey species’ value represents the relative temporal overlap between the apex predator and that prey species throughout the day. We used these PAUC values to assess whether predator access to individual prey species, relative to all available prey, were different between low and high human areas by calculating the difference in prey access (ΔPAUC) for each predator/prey combination between areas of low and high human use. To determine if prey access significantly differed between human presence levels, we compared bootstrapped estimates and 95% CIs of ΔPAUC. Finally, we used a Fligner-Killeen test for homogeneity of variance to determine how the diversity of each predator’s accessible prey differed in association with human presence based on PAUC values. Lower variance in prey access represents more evenness (i.e. more diversity) in access across prey items, while higher variance indicates prey access is higher for a subset of species compared to others.


African mammals, foodwebs, and coexistence

In the 65 million years since a mass extinction led to the demise of dinosaurs, evolution has generated amazingly diverse and complex foodwebs on each continent (1). These foodwebs contain hundreds to thousands of interacting species, each linked to other species either by feeding on them or by being fed on by them. However, it has been difficult to determine consumer diets across seasons, individuals, and space, and especially hard to quantify the strengths of these linkages in all but the simplest foodwebs. These issues have limited the ability of ecologists to understand how foodwebs are structured, how so many interacting species can coexist, and how the patterning and strengths of these linkages determine the stability of foodwebs (2). The use of next-generation sequencing is emerging as a key tool for quantifying, with fine resolution, the diet composition of consumers (3). By using these high-throughput techniques on fecal samples from large African herbivore species to quantify their diets, Kartzinel et al. (4) provide important insights into foodweb structure and coexistence in one of the few remaining terrestrial foodwebs that still has its full complement of large mammals.

In particular, Kartzinel et al. (4) extracted DNA from the feces of seven large African herbivores—the African elephant, impala, two species of zebra, buffalo, Boran cattle, and dik-dik—within a 150 km 2 portion of Kenyan savanna ( Fig. 1 ). To determine diets of each species, they obtained from 27 to 52 fecal samples per species during a single season. DNA metabarcoding allowed them to quantify the relative dietary abundances of about 100 different plant species or genera, thus demonstrating the efficacy of this approach for coexisting mammals. They found surprisingly strong dietary differences among these herbivore species. This dietary niche differentiation can explain the stable coexistence of these competing species.

African mammals studied range in size from elephants (Top), to Grevy’s zebra (Middle), to the dik-dik (Bottom). Images courtesy of Andrew Dobson (Department of Ecology and Evolutionary Biology, Princeton University).

An earlier study that used carbon isotopes in feces was able to quantify abundances of two major groups of plants, grasses, and browse, and showed that many (but not all) herbivore species were separated along a gradient defined by the ratio of these two plant groups (5). Kartzinel et al. (4) have provided the finest-resolution evidence to date demonstrating that each large African herbivore species consumes a suite of plant species different from the suite consumed by other cooccurring herbivore species.

Why is this so important? The work of Kartzinel et al. (4) suggests that the performance of a given herbivore species depends not on how much 𠇏orage” a grassland or savanna may contain but on the actual abundances of those particular plant species on which that herbivore specializes. For example, the plains zebra and Grevy’s zebra both mainly eat grass and thus would seem to be strong competitors. However, Kartzinel et al. found that there were 14 grass species and a forb species upon which these two competitors were niche differentiated, with 10 of these plant species mainly eaten by Grevy’s zebra and 5 mainly eaten by the plains zebra.

Why does this dietary differentiation lead to coexistence? Clearly, by eating different plant species, each herbivore species reduces the abundances of its own preferred food plant species more than it reduces the abundances of the preferred food for the other species. This dietary differentiation meets the classic ecological criterion for the coexistence of competing species: that each species inhibits itself more than it inhibits the other species. However, because of the multiple linkages and potential feedback paths in foodwebs, cause and effect relations are rarely so simple (6 𠄹). These 15 plant species likely compete with each other. When Grevy’s zebras are at high abundance, they will cause their 10 favored plant species to be rarer. The five plant species preferentially consumed by the plains zebra might then increase in abundance because of reduced competition, which would benefit the plains zebra. A similar process could cause high densities of plains zebras to benefit Grevy’s zebras. These indirect effects, mediated by competitive interactions among plants for their own limiting resources (water, nitrogen, phosphorus, light, etc.), would enhance the ability of two seemingly close competitors to stably coexist. Indeed, the net effect of each of the zebra species on the other might actually become positive and form an “indirect mutualism” if the competitive interactions among the 15 plant species were strong (7).

Achieving a more mechanistic and predictive understanding of foodwebs is one of the major challenges facing ecology. A foodweb is a complex network influenced by the intensity of species interactions, which themselves quantitatively depend on the tradeoffs each species faces in dealing with top-down forces (e.g., from its predators or disease), bottom-up forces (from competition for growth-limiting resources), and feedback effects that propagate through the network. Generalist consumers, such as large herbivores, can affect distant parts of a food web, yet a detailed understanding of the interactions between generalist consumers and their food species was generally out of reach until the development of next-generation sequencing tools.

Dietary differentiation, should it prove to be of general importance in other mammalian foodwebs, could shed light not just on the present-day ecology of these foodwebs but also on the ecological constraints that may have structured the evolution of large mammalian herbivores and that perhaps determined which species were successful migrants between continents during the last 20+ million years.

Earth’s large terrestrial mammals evolved on five continents but now mainly survive in Africa. Africa’s high diversity resulted from land bridges that periodically allowed mammalian herbivores and predators that evolved on one continent to move to another. A variety of mammals that evolved in North America migrated to Asia and Africa, including camels, horses, and other grazing or browsing herbivore species and several scavengers and predators. Other mammals of African or Asian origin similarly migrated into North America. Despite apparent similarities among species, the resident and invading species coexisted (1, 10, 11). Such coexistence is also common following migration by mollusks, plants, and other taxonomic lines to new geographic regions (12 �).

The work of Kartzinel et al. (4) raises the interesting possibility that the species that were successful invaders had dietary preferences different from the established species on their new continent, and that such differences allowed both their invasion and their coexistence. After all, an invading species must be able to survive and reproduce on the resources left unconsumed by the species established in the shared habitat. There will generally be notable levels of unconsumed resources if an invading species has dietary preferences that are significantly different from those of the established species. Although we cannot go back in time, comparative studies of current diets of both herbivores and predators might

Kartzinel et al. provide important insights into foodweb structure and coexistence in one of the few remaining terrestrial foodwebs that still has its full complement of large mammals.

shed considerable light on why some species were able to invade and coexist with, but not displace, the established species, and why other species were not able to invade, and yet also were not displaced by species that did invade their habitat.

The work of Kartzinel et al. (4) also raises many questions. For instance, what constraints and tradeoffs limit the breadth of diets and lead to specialization by herbivores? Are dietary choices mainly the result of how plant species meet the nutritional needs of an herbivore? Or do diets reflect spatial patterns of cooccurrence of various plant species? Or might the dietary choices of large herbivores be determined by the plant species that tend to cooccur in the sites that provide a given species of herbivore with its greatest protection from its predators?

Each terrestrial foodweb is a 1,000+ piece puzzle containing some subset of Earth’s 𾌀,000 species of vascular plants, 㸥,000 species of vertebrate herbivores, omnivores, and predators, and ϡ,000,000 species of herbivorous, predatory, parasitoid, and pollinating insects and arthropods (15). All organisms evolved in, and live in, such foodwebs, where, to survive, they must successfully compete for limiting resources and defend themselves from predators, parasites, and diseases. The next-generation sequencing approaches used by Kartzinel et al. (4) may finally allow us learn, at the level of individual species, how the constraints, tradeoffs, and feedback effects species experience in foodwebs interact to determine the diversity, functioning, and stability of Earth’s most complex, and most threatened, terrestrial ecosystems.


Big Cats

As recently as 1900, more than 100,000 cheetahs roamed the African savanna. In 2011, only 9,000 to 12,000 remain. With a top speed of 70 miles per hour, these black-spotted cats hold the record as the fastest land mammal. Cheetahs, which grow to 3 1/2 feet tall and weigh about 140 pounds, eat mostly small, hoofed species such as gazelles, impalas and young wildebeests. The greatest threat to diminishing cheetah populations lies in a dwindling habitat.

At time of publication, only 21,000 African lions remain on the savanna -- a reduction by half since the 1950s. These huge cats weigh up to 500 pounds and prey on a range of other mammals, from buffaloes and giraffes to hippos they will even attack elephants in times of hunger. Lion populations are most threatened by habitat loss and diseases related to climate change.


Why are there so many species of large predator on the African savanna? - Biology

How much do we really know about African lions? What is their current conservation status? Why are these lions significant? Once we know about these lions, how can we help them?

General facts about the African Lion…

Lions are the “King of the Jungle” — they dominate their environment as strong and brave creatures. Male lions are larger than their female counterparts. A male lion weighs in the range of 330 to 500 pounds, and has an average lifespan of 10 to 14 years. The African lion’s diet consists of animals such as zebra, giraffe, buffalo and rhino. According to Defenders of Wildlife, there are fewer than 21,000 African lions remaining on the entire African continent today. Lions are now only found in the south Sahara desert, and southern and eastern Africa.

Their current conservation status…

The African lion’s current conservation and protection status is ‘vulnerable’ under CITES. According to the Scientific American blog, they will be near extinction by the year 2050 — which is not too far in the future, when we stop and think about it. In March 2011, Born Free USA (among others) petitioned the U.S. Fish and Wildlife Service to reclassify the African lion as “endangered” under the U.S. Endangered Species Act. With the tragic trophy hunting of Cecil the lion in Zimbabwe in July 2015, the hope is this will be considered more seriously.

African Lion’s role in the ecosystem…

Population Control

Lions play a key role in the food chain by helping to control the herbivore population. If the herbivore population is not regulated, the increase of competition among them would cause some to go extinct and thus reduce biodiversity. The lions have a reputation of being the ‘chief’ predator of their habitat as they are known to even kill large herbivores such as elephants and giraffes.

Disease Control

Lions prey mainly on herd animals. Nature comes to play as lions take down the weakest of the herd. This keeps the herd population resilient and healthy. If lions did not exist, there would be a symbiotic relationship between parasites and herd animals. This way, parasites could increase and spread throughout the herd, resulting in fewer healthy animals.

Smaller Carnivores: Olive Baboons

Where predators like lions do not exist, smaller carnivores tend to increase. Smaller carnivores such as olive baboons will reproduce more and cause complications for farmers by destroying their crops and livestock, and spreading diseases.

Current news about the African Lion…

Human-Wildlife Conflict

As the human population increases, the lion’s habitat is more and more threatened. As humans encroach on what was once the lion’s territory, human-wildlife conflicts increase. When farmers’ livestock push out antelopes, lions begin killing cattle. In turn farmers will poison lions. However, some have found solutions to stop the killing with something as simple as lights. [Update January 2019: Marnus is working on an amazing project… saving the lions and their home]

Trophy Hunting

Dentist Walter James Palmer recently made news for killing “Cecil the Lion” in Zimbabwe, Africa. Palmer not only killed the lion, but skinned, beheaded, and left him on the outskirts of the national park. The hunters who did it tried to remove and destroy Cecil’s collar to cover their tracks. The media, celebrities and activist groups such as PETA reacted by sending hate emails and letters to Palmer for killing a well-known, protected lion loved by the locals. He allegedly paid someone USD$55,000 to kill and mutilate “Cecil the Lion” and is now faced with poaching charges. Because of men like Palmer, African lions are closer to extinction than we expected. The moral of the story is that locals, activists, and conservation groups need to be more cautious of their protected lions from big trophy hunters like Palmer.

How you can help to protect African Lions…

There are different ways to help protect these majestic creatures:

First, one can inform others about the conservation status of the African lion.

Second, help organizations by signing petitions for gaining approval of the U.S law that would make it against the law to sell lions or their parts across states and international borders.

Third, one can look for organizations — either national or global — that specialize in conserving lions.

Fourth, learn how to appreciate African lions and their habitats.

Contributed by Nikela Volunteer Monserrat Gomez


Blue Wildebeest (Connochaetes taurinus)

Characteristics
Dark grey bovid with pronounced shoulders which in males are up to 1,5m high males weigh up to 290kg approximately 17 000 in Kruger

Behaviour
Average herd size in Kruger is between four and six individuals lead by a dominant bull clans often join in larger groupings social grazer often with impala and zebra very keen nose for water.

Food
Exclusively grazers, preferring short grass.

Where best to see them in Kruger
Grazer open grassland and lightly wooded savanna throughout Kruger.



Comments:

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  2. Mikarr

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  3. Portier

    Perhaps I agree with your opinion

  4. Mull

    In my opinion it is obvious. I will refrain from comments.

  5. Coyan

    This magnificent idea, by the way, just falls



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