Wednesday, May 13, 2009
Age Brings Knowledge
Wayne Grady: Older animals are survivors, and so often the bearers of good genes; they stick around to care for their offspring and grand-offspring, thereby insuring that good genes remain in the pool...
Pilot whales stop having young at around 40 years of age, but females continue producing millk until they are 60 and can babysit their grandchildren while the mothers dive for food... Sperm whales can live into their eighties, and elders actually teach the young the vocal dialects of nearby pods so they can more easily find mates outside the family and thus avoid the dangers of inbreeding.
The more social a species is, the more important its elders are. Among African elephants, elder females remain dominant long after they stop reproducing. This is partly because their growth is indeterminate -- the older they are, the bigger they get -- but also because of their long memories: being able to find water during a drought can be the difference between survival and extirpation. Elephant herds with the oldest matriarch often have the most reproductive success. Older males, too, exert a moderating influence on younger members...
In patriarchies, such as in mountain gorilla troops, males gain leadership by fighting and competition: gorilla leaders are not elders but alphas, and their constant defence of territory and harems can actually render them unfit for breeding. Among pronghorn antelopes, fighting males so often die in their prime than subordinates live longer and have more offspring...
In matriarchies, on the other hand, females become leaders by dint of their experience and superior abilities, and remain leaders long after they pass the peak of their physical strength. In vervet monkeys, subordinate females can acquire leadership simply by living long enough to have more offspring, not only because such females have a small army of defenders, but also because it seems to be understood among vervets that a mother who has a large number of surviving young must be doing something right.
Review of The Social Behavior of Older Animals by Anne Innis Dagg
in the Literary Review of Canada