Thursday April 19 3:15 PM ET
By Will Dunham
WASHINGTON (Reuters) - The grande dames of African elephant society serve as repositories of social knowledge for the pachyderm's female-dominated clans, using that wisdom to guide relations with other elephant groups and ensure reproductive success, researchers said on Thursday.
An innovative, seven-year study conducted by scientists based in Britain and Kenya of elephants in Amboseli National Park in Kenya illustrated the vital role played by elephant matriarchs.
The findings present important implications for conservation of the world's largest land animals because older, larger elephants are more likely to be targets for hunters and poachers, and killing these individuals could weaken entire family units for years, the researchers said.
``The population may be a lot more fragile than it first appears because if you take out a few of those key individuals, you have quite serious effects,"" said Karen McComb of the University of Sussex in Brighton, who led the research appearing in the Journal Science, in a telephone interview.
African elephants are listed as threatened and their numbers have plummeted over the past several decades.
Elephants live in a social hierarchy dominated by older females, McComb said. Females travel in long-lasting social units of about half a dozen adult females and their offspring, with the unit led by a single older female. These units encounter other elephant groups or individuals while forging for food.
Males do not maintain long-term social bonds, remaining in the unit only into their teens. They then live out their lives in loose bachelor groups or wandering on their own.
To test the importance of the age of the female leader of the individual units, McComb, Sarah Durant of the Institute of Zoology in London and scientists with the Amboseli Elephant Research Project in Kenya used high-powered hi-fi equipment to play back the sounds of elephant calls.
To test the clans' response to these calls, they were recorded on digital audio tape and then played back through custom-built loudspeakers on the back of a Land Rover.
Calls from complete elephant strangers prompted the mothers to cluster around their young defensively, while familiar calls were ignored, the researchers said.
The units led by the oldest matriarchs, those with the most experience, were best able to distinguish between friends and those that might present problems by harassing calves or starting disputes, they found.
The researchers showed families with matriarchs aged 55 years or older were several thousand times more likely to bunch together defensively in response to calls from families they rarely encountered than families with which they were in frequent contact.
In contrast, families with matriarchs aged 35 years were only 1.4 times more likely to respond to strangers than acquaintances. In addition, elephant families with experienced matriarchs showed greater discrimination in smelling to confirm the identity of callers than families with younger leaders.
``Elephants live into their 60s,"" McComb said. ``So they have long life spans and they have a long time to build up a memory of other individuals in a population.
``This study provides an indication of the role that this sort of memory can play in social behavior,"" she said. ``One individual in the group, the matriarch, can act as a repository for the group's social knowledge.""
If these key elephant grande dames cannot immediately distinguish potential threats, their families may spend too much time being defensive and not enough time reproducing.
The scientists found the age of the matriarch to be a significant predictor of the number of calves produced by the family per female reproductive year.
Scientists in the Amboseli Elephant Research Project have tracked 1,700 elephants for the past 28 years.
Other large mammals, including killer whales and sperm whales, live in social systems similar to elephants, McComb said. She said she would not be surprised if their findings also applied to these other big-brained, long-living mammals.
The message for conservation is clear, McComb said. ``These key individuals are very important and we have to be careful to protect them.""
SOURCE: Journal Science