Related Resources
Watch a Video of Beth Archie's Zoo Lecture on African Savanna Elephants
Read About Zoo Scientists' Research on African Forest Elephants in Gabon
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The Social Lives of Savanna Elephants
Elizabeth Archie sat in her beat-up four-by-four among the tall grasses in Amboseli National Park in southern Kenya, watching and waiting. After what seemed like forever, the elephants she had been observing finally ambled off toward some trees along the savanna's edge. That was the moment Archie was waiting for. Like a woman possessed, she leaped out of the vehicle, dashed over to where the elephants had been grazing, and donned a pair of latex gloves. Then she reached down and picked up a handful of elephant dung, shoved as much of it as she could into a plastic tube, added some ethanol to remove the water, and shook the resulting glop.
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| Genetic studies are illuminating the stong ties within African savanna elephant herds, especially between mothers, daughters, sisters, aunts, nieces, and first cousins. (Elizabeth Archie) |
Archie, a postdoctoral fellow at the Smithsonian National Zoo's Center for Conservation and Evolutionary Genetics (CCEG), is into elephant dung in a big way. Since 1995, she has filled hundreds of plastic tubes with it. Her goal was not to discover what the elephants eat or which hormones course through their bodies, as it is for most field biologists who collect dung. Rather, she sought to learn which elephants are related to which others, the degree to which different elephants are related, and how that determines their interactions.
For decades, noted elephant experts Cynthia Moss, Iain Douglas-Hamilton, Joyce Poole, and other scientists have used field observations to collect data on the social structure of elephants living in savannas and woodlands of eastern Africa. While the classification of African elephants is still somewhat controversial, many scientists believe these African savanna elephants belong to a separate species—Loxodonta africana—than African forest elephants (Loxodonta cyclotis), which live in the continent's western forests. Because African forest elephants' populations are smaller and they are more difficult to observe in their forested habitat, much less is known about their social and genetic relationships, although National Zoo scientists are working to change that.
At Amboseli, scientists have documented or estimated the birth dates of all elephants born at the park since 1972. From these and other studies, they have learned that African savanna elephants live in family groups of up to 20 adult females and their juvenile offspring. In all, elephant groups may number up to 40 individuals. Daughters tend to stay in the family or core group they were born into, but males usually leave the group when they become teenagers. They may hang out with other males on the outskirts of the family groups, typically joining the females only to mate.
Such information based on observational field studies has long formed the basis of most of what we know of species' behavioral ecology. But observational studies may not always be useful in determining relatedness among elephants or other animals. Scientists may miss seeing a male and female mating, for example, especially if it occurs at night. Thus, they cannot be sure which male fathered a female's offspring. Or they may not know whether or how a new female joining a family group is related to the group's members. And they have no way of knowing for sure how individual elephants born at Amboseli before 1972 are related.
Archie's studies have helped fill in those and other blanks. She extracted mitochondrial DNA, which is inherited exclusively through one's mother, to look at deep maternal relationships. She also analyzed repeating sequences of nuclear DNA called microsatellites to find out which ones in individual elephants were the same or similar to those in other elephants.
Traditionally, scientists conducting genetic studies of wild animals extracted DNA from either blood or tissue. But obtaining these samples from wild animals, especially elephants, is difficult and dangerous. Dung, on the other hand, is easy to collect and does not necessitate tranquilization. Because heat, humidity, and sunlight degrade DNA in dung, Archie had to collect a lot of samples to get enough DNA to carry out her tests.
In so doing, Archie added a new twist to what we know about African savanna elephants. She found that nearly all wild elephants living in family groups whose dung she tested are closely related. That finding corroborates what other researchers have observed in 35 years of field studies at Amboseli and elsewhere in Africa. It also helps further our knowledge of why certain animals choose to live in groups, how group living benefits both the society and individuals within it, and what forces keep individual members within a group. Moreover, Archie's work has demonstrated how the study of genetics can bring new insights to wildlife biology and help promote conservation.
Archie's DNA studies were the first to use genetics as a way of examining how kinship affects social relationships among wild African elephants. "Our studies have shown what an elephant group should look like," Archie says. "Until now, elephant social groups have been defined [by field scientists] based on their behavior. Our study shows they are also genetic units. The most important social relationship is that between close relatives [mothers and daughters, sisters, aunts and nieces, and first cousins]. Such relatives may cooperate in raising calves, defending against predators, and finding food and water."
"Beth has enabled us to better understand the natural world of the African elephant," says Robert Fleischer, head of the CCEG. "We're using genetics to learn more about the social and mating systems of elephants. That may help us better manage and conserve elephants both in the wild and in zoos."
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| Elizabeth Archie at work in Africa. |
Archie's studies are of particular relevance now because African elephants are facing a crisis. Under assault by poachers seeking their ivory tusks in some areas of Africa and culled because they are overpopulating others, the total estimated number of wild savanna and forest elephants has dropped from 1.3 million in 1971 to between 300,000 and 500,000 today. Despite the fact that it is illegal, some 23,000 elephants were killed in Africa for their tusks in 2006. Kenya alone saw its population of savanna elephants plummet by 85 percent from 1972 to 1989. Asian elephants (Elephas maximus) are also declining: Only about 30,000 to 50,000 remain in the wild due to habitat loss.
Scientists have long known that the adult females in a family core group are usually sisters, the mothers or aunts of the youngsters in the group, or the grown daughters of the adult females. They have also learned that several family groups living in the same area may come together from time to time to form what scientists call bond groups. Several bond groups living in the same general area constitute an association.
Elephant societies are known to be very flexible, with a fluidity akin to those of humans. Individual elephants frequently change which other elephants they associate with. Some core groups are very cohesive and remain together for long periods of time, while others are looser and may divide often. When elephant groups divide, usually temporarily, the members split into smaller subgroups. Those subgroups may come back together to re-form the family group later that day or the next, but sometimes stay apart for weeks. Other times they may even join another core group, but usually return to their original family group.
When family groups divide, the adult females remain with their close relatives. When core family groups fuse with other core groups in a bond group, it is because the oldest females in the different family groups are closely related. The link between these maternally related core groups can persist for decades, long after the original female kin have died.
The family and bond groups as well as the associations practice what Archie and other scientists call fission-fusion, denoting a social structure in which elephant groups divide and reunite frequently, often in the space of a few hours or days. Individual elephants may leave their family group and mingle with individuals in another, then return to their own group. Core groups may come together during the wet season in Africa, when food and water are plentiful, then break up again when resources are scarce during the dry months. Although core group fissions are usually temporary and the subgroups later fuse, sometimes fissions are permanent. Core groups have broken up and not come back together a half dozen times or so at Amboseli since 1972, Archie says.
Scientists have also noted that dominance within elephant family groups is based on age and size, Archie says, not nepotism. That distinguishes elephant groups from those of many primates. Among the latter, the offspring of dominant females often get preferred access to food and mates, as well as a leg up in the social hierarchy. Young female elephants, on the other hand, have to wait for such advantages until the older matriarchs die and they become the oldest and largest females in their group.
Archie's studies showed that relatedness and genetic patterns overlay social groups among African elephants, says Susan Alberts, an associate professor of biology at Duke University in Durham, North Carolina, who oversaw Archie's doctoral dissertation. "Elephants do not associate by random. They seek out kin to be with. This study helps us understand why animals care about other individuals in their social group. We had clues about their relationships before, but Beth provided proof."
Archie studied the DNA of elephants living in 52 family groups in and around Amboseli National Park. In all, some 1,200 elephants live in Amboseli and the surrounding area, including Mt. Kilimanjaro. Amboseli is the third most-visited park in Kenya and the one most famous for its elephants.
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| A female savanna elephant in Amboseli. (Elizabeth Archie) |
As expected, Archie found that nearly all the elephants living in family groups she tested are closely related. She also found that members of different family core groups within a bond group are also related, albeit less closely. The older females, in particular, shared the same mitochondrial DNA. Archie found that all the elephants in the core groups except three were what geneticists call "first-order" relatives—mothers and their offspring or full siblings—that shared 50 percent of their nuclear DNA and had the same number of repeat gene forms. The exceptions were single, unrelated females living in three of the 52 family groups. Archie thinks they represent survivors of core groups, most of whose members were killed by poachers. Those survivors may have roamed the wild alone until they were accepted into existing family groups.
Fortunately, because of Amboseli's relatively small size (97,000 acres), the tolerant attitude of the local Masai people toward wildlife, and the near-constant presence of scientists and tourists, elephant poaching there is rare. Where poaching and culling do occur, however, it is often the oldest and most experienced elephants that are killed, due to their large tusks or out-front position when defending their group. Such selective killing can destroy the social and kin relationships within elephant family and bond groups. The survivors may lack the knowledge of where food and water can be found, especially during droughts, or the inclination to defend or care for each other. "How will the new groups [formed by survivors] function without genetic ties?" Alberts asks.
Another unanswered question involves single females and which new family groups they join. Although she could not test that question, Archie thinks the answer may depend on how many relatives the single female has in a new group and how closely related they are. Whatever the reason, Archie says, a new unrelated or distantly related female that joins a new family group brings a different set of DNA into the core group, thus diversifying the latter's future gene pool.
By growing up in a social setting in which members of family and bond groups and associations often interact, young elephants learn to recognize their relatives. How they do that is a little unclear, though. Perhaps, Archie says, young elephants learn over time to recognize their relatives by sight, sound, or smell. Maybe they use behavioral clues. Or maybe a little of each. "Elephants have really good memories for social groups and individuals," she states.
Whatever cues elephants use to identify one another, they seem to prefer to hang out with their relatives, Archie found. The adult females in each family group consistently remain closer to one another, more so than they do with more-distantly related elephants or if social interaction were left to chance. Indeed, closely related females spend up to 90 percent of their time with each other.
But Archie says personality differences among individual elephants can lead to behavioral aberrations. She cites one case in which an adult female preferred the company of another, unrelated adult female to that of her own daughter. The mother had once been speared, the geneticist explains, so she tended to act "kind of crazy." In another case, two not closely related females spent more time together than they did with more closely related females.
Archie's genetic studies have shown that when groups break up and re-form during fission and fusion, the adult females in each group remain with their closest relatives—their sisters and daughters. Similarly, core groups fuse when the oldest females in each family group are closely related. "Individual elephants demonstrate a long-term fidelity to their core and bond groups," she says.
Given the close degree of relatedness among elephants in core and bond groups, another question arises: How do elephants avoid inbreeding? Conservationists and wildlife managers are concerned, because inbreeding can result when wildlife populations decline in numbers and become isolated from one another, leaving individuals within isolated populations with few choices for mates. Poaching and culling, as well as human development that cuts off some populations of elephants from others, can create just such situations. Inbreeding can result in a loss of genetic diversity in the population as well as genetic and physiological abnormalities among individual animals.
Even without poaching or culling, male elephants typically mate with any female that is receptive at any given time, and females mate with different males over their lifetimes. Thus, the offspring of females may have different fathers and half siblings. Some of an elephant's half siblings may live in different core or bond groups. Given that, how do elephants know which possible mates are relatives and which are not?
Again, Archie is not sure, but has learned through her genetic studies that elephants recognize their relatives: "They avoid their maternal and paternal relatives in selecting mates," she says. Rarely do closely related elephants mate. Of 152 pairs of parent elephants Archie identified through her DNA testing, only five were closely related. Although in the long run the problem of potential inbreeding remains, Archie says, in the short term conservationists and wildlife managers "have one less thing to worry about."
Archie's work is part of a larger effort at the National Zoo to study wildlife genetics in order to better manage and conserve species. Fleischer, for example, is studying the genetics of wild Asian elephants. Other scientists around the world are examining DNA taken from the fossils of mammoths, mastodons, and other extinct elephants to help illuminate the evolution of modern African and Asian elephants.
Meanwhile, in a study similar to Archie's, Jesus Maldonado, a research geneticist at the Zoo and Archie's postdoctoral advisor, is using the dung of wild dogs (Lycaon pictus) in South Africa to discern the animals' kinship patterns and how those affect inbreeding and social behavior. And Ben Hirsch, a postdoctoral fellow at the Zoo, has begun looking at the genetics of coatis (Nasua narica)—Central and South American animals that are related to raccoons—that also live in female-led social groups.
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| Female elephants tend to stay in the same herds or groups as their sisters and daughters, according to Archie's work. (Elizabeth Archie) |
And that brings us back to elephant dung. Archie says that working with dung is not as bad as one might think, although several times it has almost gotten her into trouble. Once, she left her car to retrieve some fresh dung, and when she returned a tourist who had been watching the same group of elephants from the safety of a van informed Archie that she had been stalked by a lion. "I was so focused on the elephants that I didn't even see the lion," Archie admits. Another time, an elephant charged Archie's car, but stopped short of ramming it. "The elephants watch you as you watch them," she notes.
Dealing with elephant dung was not what Beth Archie had in mind when she started her graduate studies. She intended to be a marine biologist studying sea snails. After a while, though, snails lost their appeal. Her advisor, Susan Alberts, knew Cynthia Moss and the elephant studies at Amboseli, and suggested Archie switch to pachyderms. "They have a lot of personality and personal differences," Archie says. "They're like chimpanzees or humans in having a really complex social organization. You can't guess what is going on with them by their facial expressions or body postures like you can with primates. I'm hooked on elephants."
—Freelance writer Jeffrey P. Cohn last wrote about grasslands in the U.S. West in the July/August 2006 issue of ZooGoer.
ZooGoer 36(4) 2007. Copyright 2007 Friends of the National Zoo.
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