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Asian Elephants Are Social Networkers
26 July 2011 8:01 pm
Asian elephants have long been considered somewhat antisocial. Instead of living in large, tightly knit herds, as do female elephants on the African savanna, those in Asia were thought to have only small groups of friends and few outside connections. But a new study shows that many female Asian elephants are more like social butterflies, with numerous pals. And they're able to maintain strong friendships even with those they have not seen in a year or more.
The study adds Asian elephants to a short list of other species, including dolphins, that are able to maintain complex social relationships despite not having daily contact, an ability regarded as being cognitively demanding.
"People thought they knew what Asian elephants were doing [socially] based on what they saw them doing in captivity," says Shermin de Silva, a behavioral ecologist with the Elephant, Forest and Environment Conservation Trust in Colombo, Sri Lanka, and the lead author of the new study. Asian elephants are also extremely difficult to study in the wild, she adds. They inhabit dense forests, so researchers are usually able to observe the animals only by climbing tall trees or watching them when they gather at water holes.
But 30 years ago, one population of Asian elephants on Sri Lanka became observable because it lost its forest home. People logged the trees, converted the land into teak plantations, and subsequently dammed the region's main river, creating the large Uda Walawe reservoir. In 1972, 308 square kilometers around the reservoir were made into the Udawalawe National Park. Some 800 to 1200 former forest elephants now live here on grass- and scrublands that resemble an East African savanna, de Silva says.
The open landscape made it possible for de Silva and her team to identify 286 individual adult female Asian elephants, they report in the current issue of BMC Ecology. The researchers then tracked the social relationships of 51 of these elephants over a 2-year period. Almost immediately, de Silva realized that the elephants had larger social networks than previously recognized. Adult females she saw hanging together one day were often not together the next but were with other individuals.
"It was said that Asian elephants usually had only three friends" and loose associations with others, implying an unstable social structure, de Silva says. "But we found they can have 10 or more; some even have 50 friends," de Silva says, adding that these are not random associations. The scientists identified the elephants' "friends" or "companions" as those individuals within 500 meters of one another who were moving, resting, or sharing resources. Those females with the most friends tended to be unfaithful pals, often dropping elephants that the researchers thought were their five "best friends forever" for a new set. Those with the fewest number of friends proved to be the most loyal. How genetically related these adult elephants are is not known but will be investigated in a future study, the researchers say.
Although some Asian elephants may not see certain companions for long stretches of time—more than a year in some cases—they are probably in touch in other ways, de Silva says, because elephants can communicate both chemically and acoustically over long distances. "The 'herd' one sees at any given time is often only a fragment of a much larger social group."
The researchers' statistical analysis of the elephants' relationships shows that female Asian elephants live in a highly dynamic and fluid society, with individuals leaving and rejoining, much as chimpanzees and bottlenose dolphins are known to do. "Elephants showed their tightest bonds during the dry season," de Silva says. When water resources are scarce, some elephant friends would team up to drive others they did not know away from pools.
"It's an intriguing study on two fronts," says George Wittemyer, a wildlife biologist at Colorado State University, Fort Collins. "First, it provides the basic socioecology of a high profile but surprisingly poorly studied species." And second, "it describes a relatively unique social system" that can be understood only by observing it for several years. "It's fascinating," adds Phyllis Lee, a behavioral ecologist at the University of Stirling in the United Kingdom and a member of the Amboseli Elephant Research Project. "The question becomes how do they maintain these relationships," because what the elephants are doing "requires a high level of cognitive capacity," as any social networking maven well knows.
*This article has been corrected. The new research was published in BMC Ecology.