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African Elephant - Change Over Time - Biology

African Elephant - Change Over Time - Biology


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Early estimates of elephants on the continent of Africa suggest that there were as many as 26 million elephants living there in the 1500s. By 1913, the African elephant population had dropped to an estimated 10 million.

Elephant slaughter increased in the 1950s, where it is estimated that 250 elephants were killed per day. In 1978, the elephant is listed as threatened under the United States’ Endangered Species Act. This limited the trade of some ivory. Still, ivory trade continued across the world. By 1979, there were only 1.3 million elephants left.

A ban on the international trade of ivory goes into effect in 1990, though the population of elephants is now fewer than a million. Despite the bans, there is still a demand for ivory in countries like Japan and China. This drives the illegal trade of ivory. Illegal hunting of elephants, or poaching, occurs at alarming levels. It is unknown how many elephants survive in African, many herds are protected in preserved areas, like Gorongosa National Park in Mozambique.


Elephant specialists that study the elephants in this preserved area have collected data on the herds in the park. They noticed that while all the males have tusks, about 50% of the females in the park that are over the age of 20 years do not have tusks. When compared to the elephant populations across Africa, the frequency of tuskless elephants is only 6%.

  1. Why are elephants killed in Africa?
  2. Why do bans on ivory trade not stop elephants from being slaughtered?
  3. How do countries in Africa protect elephant herds?
  4. How are the elephants at Gorongosa National Park differ from other elephant populations?
  5. Suggest a reason for this difference.

Watch “Selection for Tuskless Elephants”

  1. What happened in Mozambique between 1977 and 1992?
  2. Why did soldiers kill elephants?
  3. What is unusual about the elephant populations found in Gorongosa now?
  4. What are tusks?
  5. How do elephants use their tusks?
  6. How does a MALE elephant use his tusks?
  7. What would probably happen to a male elephant that doesn’t have tusks?
    Therefore, tusklessness in male elephants is a ___________ (rare/common) trait.
  8. What percentage of females are typically tuskless in an elephant population less affected by poaching? __________________
  9. Tusklessness is an ___________________________ (inherited/acquired) trait.
    Tuskless females tend to have _________________________ (tusked/tuskless) offspring.
  10. Use the theory of evolution to explain the observation that there are no tuskless males in the park. WHY do males retain their tusks, when 50% of females lost them.
  11. Complete the following table.
ConditionDescriptionEvidence from Species Studied
VariationIndividuals in a population differ in some trait. Variations can be physical features, behaviors, bodily functions, or resistance to disease.
Inheritance

The trait is inherited (passed from parents to offspring). The variation comes from random mutations and the recombination during sexual reproduction.

Differential Survival and Reproduction

Some individuals with a trait are more likely to survive and reproduce than those without the trait.

Selection depends on the environment. Traits that are beneficial in one environment may not be beneficial in another.

AdaptationThe frequency of the trait that helps individuals survive or leave more offspring will increase in the population over time.

African elephant

The African elephant (Loxodonta) is a genus comprising two living elephant species, the African bush elephant (L. africana) and the smaller African forest elephant (L. cyclotis). Both are social herbivores with grey skin, but differ in the size and color of their tusks and in the shape and size of their ears and skulls.

Both species are considered at heavy risk of extinction on the IUCN Red List as of 2021, the bush elephant is considered endangered and the forest elephant is considered critically endangered. They are threatened by habitat loss and fragmentation, and poaching for the illegal ivory trade is a threat in several range countries as well.

Loxodonta is one of two extant genera of the family Elephantidae. The name refers to the lozenge-shaped enamel of their molar teeth. Fossil remains of Loxodonta species have been excavated in Africa, dating to the Middle Pliocene.


Elephant Trunk

The trunk of elephants has evolved from the fused muscles of their nose and upper lips, and contains up to 150,000 separate muscles. These muscles provides flexibility and motion for such functions as feeding and grasping objects. It also provides strength to the trunk, allowing it to lift substances that weigh up to 350kg. The trunk is also capable of holding up to 10L of water. The trunk is useful for spraying water all over the body of the elephant as a means to cool down, or to spray sand over the skin after a bath so as to protect the skin.

The trunk is covered with fine sensory hairs. This provides a sense of smell that is four times as sensitive as that of a bloodhound. This allows elephants to locate water sources and to sense the reproductive state of other elephants over long distances. Thus, elephants are able to locate prospective mating partners in the vicinity.

African elephants have two finger-like extensions at the tips of their trunks to grasp objects, while Asian elephants only have one finger-like extension and can therefore only use their trunk to scoop objects up by wrapping it around the object.


Ivory from a 16th century shipwreck reveals new details about African elephants

In 1533, a Portuguese trading ship dubbed the Bom Jesus went missing. Today, its recovered ivory cargo is answering questions about African elephants (one pictured).

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December 17, 2020 at 11:00 am

In 2008, miners off the coast of Namibia stumbled upon buried treasure: a sunken Portuguese ship known as the Bom Jesus, which went missing on its way to India in 1533. The trading ship bore a trove of gold and silver coins and other valuable materials. But to a team of archaeologists and biologists, the Bom Jesus’ most precious cargo was a haul of more than 100 elephant tusks — the largest archaeological cargo of African ivory ever discovered.

Genetic and chemical analyses have now traced those tusks back to several distinct herds of forest elephants that once roamed West Africa. “It is by far the most detailed and comprehensive attempt to source [archaeological] elephant ivory,” says Paul Lane, an archaeologist at the University of Cambridge not involved in the work.

The new results, reported in the Feb. 8 Current Biology, give insight into historical African elephant populations and ivory trade networks.

For having been lost at sea for nearly 500 years, the Bom Jesus’ ivory is incredibly well-preserved, says Alida de Flamingh, a molecular biologist at the University of Illinois at Urbana-Champaign. “When the ship sank, the copper and lead ingots [stored above the tusks] kind of pushed the ivory down into the seabed,” protecting the tusks from scattering and erosion. A frigid ocean current also runs through this region of the Atlantic. “That really cold current probably helped preserve the DNA that was in the tusks,” de Flamingh says.

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She and her colleagues extracted DNA from 44 tusks. The genetic material revealed that all of that ivory came from African forest elephants (Loxodonta cyclotis) rather than their African savanna kin (L. africana). By comparing the ivory DNA with that of past and present African elephant populations with known origins, the team determined that the shipwrecked tusks belonged to elephants from at least 17 genetically distinct herds across West Africa — only four of which still exist. The other elephant lineages may have died out as a result of hunting or habitat destruction (SN: 11/7/16).

The types, or isotopes, of carbon and nitrogen in the tusks provided more detail about where these elephants lived. Carbon and nitrogen accumulate in tusks over an elephant’s lifetime through the food the animal eats and the water it drinks. Relative amounts of different carbon and nitrogen isotopes depend on whether an elephant spent most of its time in, say, a rainforest or an arid grassland. The isotopes in the Bom Jesus tusks revealed that these elephants lived in a mix of forests and savannas.

More than 100 elephant tusks (some pictured) ranging from two to 33 kilograms were recovered from the Bom Jesus shipwreck off the coast of Namibia. National Museum of Namibia

“We were quite surprised,” says study coauthor Ashley Coutu, an archaeologist at the University of Oxford. Modern African forest elephants are known to roam forests as well as savannas. But researchers thought that forest elephants first ventured out into grasslands only in the 20th century, as many savanna elephants were wiped out by poachers and the forest elephants’ original habitats were destroyed by human development. The new results suggest that African forest elephants were amenable to both forest and savanna habitats all along.

Better understanding the habitats historically preferred by African forest elephants could inform efforts to conserve this vulnerable species (SN: 9/9/16). More than 60 percent of these elephants have been poached within the last decade, and the ones that remain inhabit only about a quarter of their historical range, according to the African Wildlife Foundation.

The origins of the Bom Jesus’ ivory also paint a clearer picture of the 16th century ivory trade on the African continent, Lane says. The fact that the tusks originated from many different herds hints that multiple communities in West Africa were involved in supplying the ivory. But it’s unclear whether Portuguese traders gathered this diverse ivory from several locally sourced ports along the coast, or from a single port that was linked to extensive trading networks within the continent, Lane says. Future analyses of ivory uncovered at historical port sites could help solve the mystery.

Questions or comments on this article? E-mail us at [email protected]

A version of this article appears in the January 30, 2021 issue of Science News.


Implications

Controversy continues to surround management and trade policies for African elephants. Results of this study bear directly on this controversy. The length of time required to recover from extensive poaching detected in our study suggest that African elephants have had insufficient time to recover from the 60% poaching-related decline of the 1980’s. Thus, the impacts of renewed illegal trade in elephant ivory or culling as a means of population control in this highly intelligent, tightly knit social species may be far more grave than predicted by economic models alone.

Regrettably poaching is once again on the rise.


Altered Elephant Behavior

Poaching is causing alarming changes in the behavior of African elephants.

The Selous Game Reserve in the south of Tanzania is home to 60 percent of Africa&rsquos elephants. Among the largest undisturbed, protected areas in Africa, it has also become one of Africa&rsquos elephant &ldquokilling fields.&rdquo Those on the front lines studying elephant behavior witness the alarming effect poaching has had on the elephants that survive. This clip from the National Geographic film Battle for the Elephants documents the disturbing changes in elephant behavior, including dramatic displays of fear and increased agitation, stress, and aggression in the presence of humans.

Scientists who study elephant behavior agree that survivors of poaching are stressed. Their fears can disrupt the elephants&rsquo complex matriarchal social structure, reduce their success in breeding, and increase their antagonism toward humans. Elephants mourn their deceased companions, demonstrating rituals that include touching the remains and carrying the deceased elephant&rsquos bones or tusks with them.

Where is the Selous Game Reserve, and why is it referred to as Africa's elephant "killing fields?"

The Selous is located in southern Tanzania. DNA testing has confirmed that much of the poached ivory coming into Dar Es Salaam, Tanzania&rsquos largest city, for smuggling to countries around the world originates in the Selous, which is home to sixty percent of Africa&rsquos elephants.

Why is the change in elephant behavior an area of concern for scientists and elephant advocates?

The change in elephant behavior in the Selous Game Reserve signals a critical disruption in the elephants&rsquo complex social structure&mdasha structure that maintains the health and well-being of the elephant families and groups. As the elephants&rsquo social structure breaks down, their chances for successful breeding decrease, further reducing the animals&rsquo chances of survival. Fear replaces the animal&rsquos natural curiosity and sociability. Many feel that poaching, along with the residual effects of poaching on surviving animals, may lead to the extinction of the African elephant.


Elephant Evolution

Forms of the elephant are believed to date back to 2,000 B.C. In these early times they were used to help with building due to their size. Many experts believe that the Mammoth which is now extinct is an early form of the elephant. They believe what we have on Earth now are direct decedents of them and that many of the changes including the loss of the thick hair occurred during the evolution process.

When we think about elephants we tend to always think of very large animals. However, there is also evidence to suggest that in the prehistoric period some of the species were the size of pigs and cows. DNA testing has proven beyond any doubt that they are indeed related to elephants. They are also distantly related to both dugongs, and hyraxes.

Another surprise to many is to find that elephants have some relationship to manatees which are commonly referred to a sea cows. It is believed that early on many species of elephants had two sets of tusks – one in the upper jaw and one in the lower jaw. What is very sad is that many experts believe at one time there were more than 350 species of elephants in the world. Now there are almost none at all left.

Early elephants were very different in their size and their appearance back then compared to what we see of them today. During the Ice Age the elephants likely had very thick hair like the mammoth. However, as the temperatures got warmer they didn’t have a need for it. This is why they got thicker skin and very little hair on it at all. This allowed them to live in regions where the temperatures were extremely hot. They have to be able to reduce their body temperatures and to regulate them. This can also account for the larger size of the ears they use them as fans to cool down.

The length of the trunk as well as the ability to use it for so many different things is also something that happened for elephants through evolution. Their needs to be able to grasp things are one of the main reasons why this likely. While early elephants did have trunks they weren’t as versatile as what these animals have today.

It is believed that the ability adapt to a variety of different environments allowed elephants to evolve about 50 to 60 million years ago. Some of them lived in the rainforests while others resided in the desert. They are still considered to be on of the most adaptable animals in the world. However, with humans taking these areas away from them at an alarming rate there is a limit to what they are able to do and where they are able to survive today.

What has been noted by experts it that this evolution process takes place very slowly. This is why so many other species of elephants weren’t able to survive those necessary changes and they are no longer with us today. With that in mind humans have to understand that we can’t simple continue to do what we want to and expect that elephants are going to be able to change fast enough to adapt to all of it.

As you can see the evolution for elephants is one that is quite amazing. Even though we know quite a bit about these animals and their past, many questions still have to be answered. They have continually fought though for survival and due to the evolution process they have been quite successful for millions of years.

References

Michael Garstang. Elephant Sense and Sensibility. Academic Press, 2015.

Raman Sukumar. The Living Elephants: Evolutionary Ecology, Behaviour, and Conservation. Oxford University Press, 2003.


Prolonged ovarian acyclicity is associated with a higher likelihood of developing hyperprolactinemia in zoo female African elephants

Natalia A. Prado, Department of Reproductive Sciences, Center for Species Survival, Smithsonian Conservation Biology Institute, 1500 Remount Road, 22630 Front Royal, VA.

Department of Reproductive Sciences, Center for Species Survival, Smithsonian Conservation Biology Institute, Front Royal, Virginia

Department of Reproductive Sciences, Center for Species Survival, Smithsonian Conservation Biology Institute, Front Royal, Virginia

Department of Reproductive Sciences, Center for Species Survival, Smithsonian Conservation Biology Institute, Front Royal, Virginia

Natalia A. Prado, Department of Reproductive Sciences, Center for Species Survival, Smithsonian Conservation Biology Institute, 1500 Remount Road, 22630 Front Royal, VA.

Department of Reproductive Sciences, Center for Species Survival, Smithsonian Conservation Biology Institute, Front Royal, Virginia

Department of Reproductive Sciences, Center for Species Survival, Smithsonian Conservation Biology Institute, Front Royal, Virginia

Abstract

Hyperprolactinemia is a common disorder of the hypothalamic-pituitary axis, and a cause of ovarian dysfunction in women. Currently, over half of non-cycling African elephant females in North America also are hyperprolactinemic, suggesting a similar link between these two conditions may exist. The objective of this study was to determine the relationship between acyclicity and prolactin status by comparing mean prolactin concentrations of bi-weekly samples collected over a 1-year period in 2012 with 20 years of historical weekly progestagen data to assess cyclicity. Females were categorized as: 1) non-cycling with an average prolactin concentration of 15 ng/ml or greater (HIGH n = 17) 2) non-cycling with an average prolactin concentration below 15 ng/ml (LOW n = 16) and 3) typical temporal patterns of progestagen and prolactin secretion (NORMAL n = 45), and evaluated based on length of time (in years) they had experienced ovarian inactivity. Results showed that the majority of HIGH prolactin elephants had been acyclic for at least 5 years, and in a number of cases (n = 9) for over 10 years. By contrast, most of the LOW prolactin elephants had experienced acyclicity for less than 5 years. Finally, there was a positive association between duration of acyclicity and mean prolactin concentrations, with an increase in the likelihood of having higher prolactin concentrations the longer an individual was acyclic. This study highlights the importance of longitudinal hormonal datasets to examine temporal changes in biological functioning and better understand the etiology of infertility problems.


Following African elephant trails to approach conservation differently

Elephant trails may lead the way to better conservation approaches.

"Think of elephants as engineers of the forests," said Melissa J. Remis, professor and head of anthropology at Purdue University, who is best known for her work in ecology and behavior of western gorillas and their ecosystems. "Elephants shape the landscape in many ways that benefit humans. We're talking thousands of miles of trails. If we think about the loss of elephants over time, then we will see the forest structure change and human activities also would shift."

These massive creatures trample thick vegetation through dense forests in the Central African Republic's Congo Basin as they move from the forests' fruit trees to more open water sources where they hydrate, bathe and socialize. African forest elephants, highly sociable animals, travel in small family groups to meet others at these muddy water sources, which are full of rich minerals that they can't find in the forests. By clearing routes to these destinations, elephants have created a very complex network of roads that residents, tourists, scientists and loggers still use today. If elephant populations decline, the forest grows over the trails.

"The fabric and way of life of local communities, and even for the industries and conservation organizations that exist in African forests, have largely been shaped by elephant landscape design," said Carolyn A. Jost Robinson, a former Purdue doctoral student and current visiting scholar who also is director of sociocultural research and engagement at the nonprofit Chengeta Wildlife. "People rely on these elephant highways, and they also are invaluable at understanding and explaining the networks."

Remis and Jost Robinson focus on these massive trail networks and the ecosystem and local foraging community, called the BaAka, as they evaluate how biological anthropology plays a role in conservation. Their research is specific to the elephant trails leading to Dzanga Saline, a famous forest clearing with a large water source in the Congo area. Their findings are published online in American Anthropologist.

"Anthropologists are very famous for critiquing conservation but not always for coming up with effective solutions," Remis said. "The area of conservation is dominated by biological sciences, and you can't make change just tending to ecosystems. Conservation messages focus on flagship species, like elephants, and rarely do they consider the knowledge or needs of people relying on or living with those species. Attention on both could help further conservation and human rights issues."

Framing the big picture

More than 30 years ago, Purdue University's Melissa Remis visited the Dzanga-Sangha Protected Areas for the first time as a biological anthropologist to study gorillas. She became known as the gorilla lady as she visited the site dozens of times. Her fieldwork showed her that to know and study the gorillas, she had to learn about the forest and other wildlife from the local residents who share the land for food, shelter and medicines. Now Remis' work focuses on the big picture -- how the effects of conservation affect people, and what role biological anthropology can play.

"We're broadening the conversation about conservation," said Jost Robinson, who became known as the child of the gorilla lady by local residents at their African research site. "When you see a picture in a magazine story about ivory trafficking and elephant hunting, it is unlikely that the article will capture the entire experience of the community, as well as tourists, researchers and companies with local interests. As part of this change -- whether you want to talk about climate change, forest access or wildlife protection -- these relationships have evolved and taken on new shapes. We looked back on years of data and stories and realized there was a story to tell."

By focusing on the local BaAka community, especially the hunters known as tuma, the scientists capture information from local residents about interaction and living with elephants that is usually not a part of conservation plans.

"We want this to be a model for showing how to get additional insights when addressing how to conserve forests in better collaboration with those people who rely on them for cultural and material sustenance," Remis said. "Being able to tell their stories and share their deep knowledge about the area, and what closing off an elephant trail or part of the forest can due to cut off access to food, medicines or social networks, is usually not part of the conservation approach. We need to hear the BaAka in their own words."


Elephant Physiology

The Asian (Elephas maximus) and African (Loxodonta africana) elephant are the largest extant terrestrial vertebrates. At a maximum, the male African elephant is six orders of magnitude larger than the smallest terrestrial mammal, the Etruscan shrew (Suncus etruscus). Across this extreme range of body masses, the fundamentals of mammalian physiology remain the same, yet a simple but key relationship, the surface to volume ratio, dramatically changes. As an animal increases in size, surface area increases to the square while volume increases to the cube. Thus, large animals have a much smaller surface to volume ratio relative to small animals. Because the surface of the animal is the primary site of biophysical exchange (e.g. heat and water) with the environment, this straightforward physical relationship has a cascade of effects. Most important for this work is the impact that a decreased surface to volume ratio has on the thermal and water balance of an elephant and this idea is a central theme of my work. A second major theme is the value of physiological data and methodology in predicting landscape level effects which stem from interactions between whole animal physiological and biophysical processes and the abiotic and biotic environment.

Elephants present a complex management challenge. Although officially listed as vulnerable by the IUCN, historical management practices of African elephants for example, have led to the sequestration of elephant populations into numerous small to medium sized reserves or into otherwise fragmented landscapes. The result is that in many of these areas, high local elephant densities and their resulting impacts are detrimental to biodiversity and lead to increased incidence of human-elephant conflict (Owen-Smith, Kerley, Page et al. 2006). The recognition that elephant distribution is significantly influenced by surface water availability has led to support for surface water management, a more ethically appealing and sustainable form of population regulation relative to culling or translocation. Although surface water management has gained support, its implementation has been challenged by an inability to adequately predict the outcomes and likely success of surface water management plans for particular populations. With this context in mind the overarching objective of my research was to identify and measure the physiological basis for the elephant’s dependence on surface water and then use these data to develop a quantitative and predictive framework with which to examine the influence of surface water and interacting factors on the elephant’s use of landscape.

ADAPTATIONS OF ELEPHANT SKIN FOR NON-EVAPORATIVE AND EVAPORATIVE HEAT LOSS
Collaborators: Drs. Ann Pabst, Heather Koopman, and Richard Dillaman, UNCW

The primary organ system responsible for the biophysical exchange of heat and water is the integument, which lies at the interface between the animal’s internal environment and the outside world. Despite lacking sweat glands, elephants have among the highest rates of cutaneous water loss (CWL) of a variety of arid dwelling herbivores. Our results indicate that elephant integument conducts heat up to 11 times better than mammals with arctic or sub-arctic pelage and loses water at rates that are comparable to some amphibians, allowing elephants to maximize both non-evaporative and evaporative heat loss.

CLIMATE INFLUENCES THERMAL BALANCE AND WATER USE IN AFRICAN AND ASIAN ELEPHANTS: PHYSIOLOGY CAN PREDICT DRIVERS OF ELEPHANT DISTRIBUTION
Collaborators: Dinah Wilson (Wildlife Safari), Nicolas Way (Six Flags Marine World), Kari Johnson (Have Trunk Will Travel), Terrie M. Williams (UCSC)

To predict how surface water and ambient temperature drive elephant movement patterns, I quantified thermal and water budgets of African and Asian elephants across 30oC range of temperatures. This work specifically addresses the whole animal level mechanism of the elephant’s water dependence by quantifying the exchange of heat and water in relation to an environmental variable, thus determining the physiological demand for water at an ecologically relevant temporal scale. Simulated thermal and water budgets using climate data from Port Elizabeth, South Africa and Okaukuejo, Namibia suggested that the 24-hr evaporative cooling water debt incurred in warm climates can be more than 4.5 times that incurred in mesic climates. This study confirms elephants are obligate evaporative coolers but suggests classification of elephants as water dependent is insufficient given the importance of climate in determining the magnitude of this dependence. These data highlight the potential for a physiological modeling approach to predicting the utility of surface water management for specific populations.

A PHYSIOLOGICAL BASED MODEL OF LANDSCAPE USE FOR ELEPHANTS: INTERACTIONS BETWEEN THERMAL CONSTRAINTS, WATER USE, AND ENERGY DEMAND
Collaborators: Dr. Tim Tinker (USGS) and Dr. Terrie Williams (UCSC)

Finally, in chapter 3, the relationships between thermal and water balance and ambient temperature are used to develop a biophysical model coupled with a stochastic dynamic programming model. This modeling framework was used to investigate the separate and combined effects of climate, thermal and water balance, and food availability in determining landscape level patterns of habitat use and habitat impact.

Collaborator Affiliations

Have Trunk Will Travel, Inc.

Publications

Dunkin, R. C., Wilson, D., Way, N., Johnson, K. and Williams, T. M. (2013). Climate influences thermal balance and water use in African and Asian elephants: physiology can predict drivers of elephant distribution. J Exp Biol 216, 2939-2952. Cover article.