...and how they save their herds from starvation - Elephants are amazing creatures. The legends say that elephants "never forget," and a new study suggests that old female elephants?and perhaps their memories of distant, life-sustaining sources of food and water?may be the key to the survival of their herds during periods of famine and drought.
Researcher Charles Foley says, "Our findings seem to support the hypothesis that older females with knowledge of distant resources become crucial to the survival of herds during periods of extreme climatic events."
Researcher Nathalie Pettorelli agrees and says, "Climate change is expected to lead to a higher occurrence of severe drought in Africa and our study suggests that such extreme climatic events may act as a selection force on animal populations. As animals battle to cope certain individuals, such as these grand dames of the elephant kingdom, might become increasingly important."
During the 1993 drought in Tanzania's Tarangire National Park (the most severe drought in that region in the past 35 years) sixteen out of 81 elephant calves died, a mortality rate of 20%. The normal mortality rate of calves during non-drought years is only 2%.
The age of the mother elephants was an important predictor for calf survival. The two groups that left the park, presumably in search of food and water, had matriarchs that were ages 45 and 38 years of age, whereas the group that remained had a matriarch that was only 33 years of age, the result of heavy poaching during the 1970's and 1980's that targeted older females with large tusks.
The groups that left the park may have benefited from the specific experiences of their oldest matriarchs, which perhaps were able to draw upon memories of an earlier drought and how they survived it. The case is strengthened by the known life history of the oldest matriarchs in these groups, some of which were five years or older during the drought of 1958-61. The group that remained in Tarangire in 1993 had no individuals old enough to remember the event.
Foley says, "It's enticing to think that these old females and their memories of previous periods of trauma and survival would have meant all the difference. The data seem to support the speculation that the matriarchs with the necessary experience of such events were able to lead their groups to [away from the] drought."
During the 1970s and '80s, many of Eastern Africa's largest elephants fell victim to waves of poachers who were eager to exploit the profitability of the black market for ivory. Foley adds, "Hopefully, this study underlines the importance of how crucial older matriarchs are to the health of elephant populations. Protecting the leaders of elephant herds will be even more important in what may be an increase in droughts due to climate change."
Art credit: gimp-savvy.com
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