There's good reason why elephants never forget. New research shows that the lifetime experience of the oldest female in an elephant group helps them discriminate friend from foe. Ultimately, groups with wise females produce more offspring. The results may extend to other animals as well, the researchers speculate, and may even explain why some populations of sperm whales have relatively few young.
For the new study, reported in the 20 April issue of Science, animal communication researcher Karen McComb of the University of Sussex in Brighton, United Kingdom, and Sarah Durant of the Institute of Zoology in London studied 20 small family groups of elephants, each typically containing several females and their calves, in Kenya. Each group moves independently, often encountering other clans or individuals while foraging for food.
To test the animals' knowledge of their social environment, McComb, Durant, and their colleagues played recordings of elephant calls and watched the elephants' responses. Typically, calls from complete strangers prompted the mothers to cluster around their young, whereas familiar calls were ignored. But some groups were better than others at picking out the strangers. McComb's analysis showed the older the eldest female was, the better the group's ability to judge calls appropriately. Further analysis showed that the matriarch's storehouse of knowledge helped her clan produce more relatively more calves, McComb's team reports, perhaps because they wasted less time clustering and were less stressed than other clans.
The research sends a strong message to conservationists that elder group members need to be protected, says Hal Whitehead, a marine biologist at Dalhousie University in Halifax, Canada. He wonders whether the low birthrates recorded in sperm whales off the coasts of Peru, Chile, Japan, and northwestern Europe--compared to whales in the Caribbean--are a vestige of whaling practiced until some 18 years ago. If whalers consistently took the larger, older individuals, he suggests, the groups may have "lost their social knowledge and may be less successful."