Can memory save elephants from climate change?
来源：未知 作者：钟离瘦整 时间：2017-12-22 01:01:07
By Catherine Brahic (Image: Charles Foley) What is the best asset elephants have for resisting climate change? Possibly their legendarily powerful memory, say conservationists. From 1958 to 1961 a drought killed off dozens of elephants in what is now Tanzania’s Tarangire National Park. When another severe dry spell hit the region in 1993, 16 of 81 elephant calves died – a 20% death rate, compared with the usual 2%. Charles Foley of the Wildlife Conservation Society in New York and colleagues wondered if any of the surviving elephants had remembered the previous drought. The researchers looked at how the deaths broke down by sex and clan structure. They found that of three clans, two migrated from the region during the drought, presumably to seek food and water. Their strategy seems to have paid off: the groups that left lost five calves between them, whereas the group that stayed lost 11 of its 27 calves. This could be down to luck, but the team then found that the clan that stayed behind was also the only one to not have any females old enough to have lived through the previous drought. “It is enticing to think that these old females and their memories of previous periods of trauma and survival would have made all the difference,” says Foley. “The data seem to support the speculation that the matriarchs with the necessary experience of such events were able to lead their groups to refuge.” Team member Nathalie Pettorelli of the Zoological Society of London points out that there is nothing to prove that the older matriarchs had previously visited the places they moved their clans to. But she says it is a “strong possibility” that their memories served them well. Numerous studies have shown that elephants have very good memories, allowing them to track their family members and even navigate minefields. The findings may add to the debate over legal elephant culls, such as the one planned to control growing elephant populations in South Africa. “If there is knowledge in old elephants then whenever you kill old elephants you remove all that knowledge,” says Pettorelli. The clan that stayed behind did not have any older matriarchs because they had been killed by poachers in the 1970s and 1980s. Older elephants are more attractive to poachers because of their bigger tusks. Pettorelli says that whether or not their memories helped them out, older females seem to help ensure the survival of the young in their clan: calves with older mothers had a greater chance of survival than those with younger mothers. Climatologists are predicting that droughts will become more frequent as concentrations of greenhouse gases rise. Journal reference: Biology Letters, DOI: 10.1098/rsbl.2008.0370 Climate Change – Want to know more about global warming: the science, impacts and political debate? Visit our continually updated special report. More on these topics: