A survival advantage
As the Amboseli population has thrived, matriarchs have become older and families larger under their leadership. A family’s propensity to spend time with other families within the network has declined. Analyses of elephant networks by Vicki Fishlock, a resident scientist with the AERP, suggests matriarchs become less gregarious and more conservative in their old age.
When it comes to survival, however, having a wise old matriarch to lead you is just as important as having other elephants to learn from in a wide social network. And the two influences are intertwined, because that matriarch determines who is in your network. “Good matriarch decisions balance the needs of the group, avoiding unnecessary travel while remembering when and where good resources are available,” Fishlock says. Studies in Amboseli have revealed that families with older, larger matriarchs range over larger areas during droughts, apparently because these females better remember the location of food and water resources. “The matriarch has a very strong influence on what everybody does,” she says, though exactly how they communicate their will to the group remains a mystery.
The idea that groups led by older matriarchs might have a survival advantage is supported by a study of elephants in Tangarire National Park in Tanzania. In 1993, infant elephant death rates rose from an annual average of just 2 percent to around 20 percent during a nine-month period of drought. With their dry-season refuge parched, some family groups stayed in the park while others made off for places unknown. Young mothers were far more likely than older ones to stay put and to lose calves, and families that migrated out of the park had lower mortality than those that remained. Since matriarchs lead long-distance group movements, this suggests that older females provide a survival advantage for their extended family.
More recent and direct evidence of the benefits of wise old matriarchs has come from Karen McComb at Britain’s University of Sussex. Using recordings of lions roaring, she tested the responses of Amboseli matriarchs of different ages in the social context of their family group. Elephants encounter lions infrequently, but they are one of the few predators that pose a real threat, especially for young calves. That threat is enhanced if the lion is male, because males, unlike females, are capable of overpowering a young elephant even when hunting alone. McComb found that older elephants — age 60 and older — seemed to listen longer to male than female roars, and their groups huddled together more frequently and closely than did those of younger matriarchs. This suggests that elephants defer to the knowledge of their elders and that matriarchs call the shots in deciding which anti-predator strategy to adopt, she says.
Older matriarchs also seem to be better at judging “stranger danger” from other elephants. At Amboseli, each family group encounters about 25 other families in the course of the year, representing about 175 other adult females. Encounters with less-familiar groups can be antagonistic, and if a family anticipates possible harassment it assumes a defensive formation called bunching. In one experiment, her team found that families led by older matriarchs were less reactive overall but bunched more in response to the sound of less-familiar individuals than did families led by younger females. They suspect this is because older matriarchs have a larger memory catalogue for elephant voices, allowing them to more precisely distinguish between familiar and unfamiliar ones, and respond appropriately.
Built to lead
There may be more to good leadership than just the wisdom that comes with age, though. Elephants appear to have personalities; Moss and Phyllis Lee from Scotland’s University of Stirling wonder whether certain character traits might be associated with effective leadership. They have identified 26 traits possessed by elephants — such things as confidence, fearfulness, opportunism and aggression — that group into four main personality dimensions: playfulness, gentleness, constancy and leadership. So far, they have analyzed just 11 adult females from one Amboseli family, and the matriarch does score highly in the leadership dimension. By assessing more elephant families, the researchers hope to identify the traits shared by the most and least successful matriarchs.
If effective leadership is important in Amboseli, it is even more crucial in parts of Africa where threats are greater. During the 1980s, poaching halved Africa’s elephant population. Things improved after activists and researchers alerted the world and helped bring about an international trade ban on ivory in 1989. However, in recent years poaching has been on the increase again. The oldest animals with the largest tusks are prime targets.
An inkling of the potentially dire consequences of killing matriarchs for ivory comes from Mikumi National Park in Tanzania, where elephants were heavily poached before 1989. In 2008, a team of researchers reported that elephant groups hardest hit by poaching had younger matriarchs, weaker social bonds and lower relatedness. Analysis of their feces revealed high levels of glucocorticoids, indicating chronic stress. And compared with groups with intact social structures, only half as many females had infants younger than 2. The stress of family disruption had clearly reduced their reproductive success.
Losing a leader
We do not yet know the full extent of the damage caused by the killing of wise old matriarchs. Given that they are instrumental in keeping their groups fed, watered, safe and reproducing, their entire social network will feel the loss. But studies suggest that despite disruptions to social structure, the elephants and their networks are resilient over the long term. They can and will recover if poaching pressure can be lifted, but that is a big “if.” Matriarchs may be adept at solving the problems faced by the elephants that look to them for leadership, but at the moment humans are their greatest problem.
This is an edited version of a story that appeared in New Scientist.
~Lesley Evans Ogden and The Scientist
January 27, 2014
The Washington Post
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