Elephants of the Namibian desert are genetically the same as their savannah equivalents, but they have a different cultural heritage, according to a paper in Ecology and Evolution, making them as important to preserve as if they were a distinct species.
The heat and limited water of the deserts of Namibia pose challenges for all their inhabitants, leading to some impressive innovations, such as beetles that collect the fog for drinking water. Elephants are no exception, but their adaptations have been behavioral rather than genetic.
"The ability of species such as elephants to learn and change their behavior means that genetic changes are not critical for them to adapt to a new environment," said senior author Professor Alfred Roca of the University of Illinois in a statement. "The behavioral changes can allow species to expand their range to novel marginal habitats that differ sharply from the core habitat."
To keep cool, the desert elephants wet sand, either by urinating on it or using water they carry around in their mouths, before throwing it over themselves. This is uncommon in cooler environments with more accessible water.
These elephants have apparently developed the capacity to recognize the sounds of thunderstorms hundreds of kilometers away, and apply their famously long memories to the location of water resources that might survive droughts. Some of these resources only exist because the elephants dug out larger holes for water to pool in.
Roca tested the nuclear and mitochondrial DNA of elephants from different parts of Africa to show that there are no important genetic differences between those living in deserts and those inhabiting savannas. Instead, the techniques used by desert dwellers are cultural adaptations passed on from mother to child, rather like some dolphins’ use of sponges for hunting.
Elephants from populations in several different environments are “genetically indistinguishable from each other and from desert elephants,” the paper reports. “Given this lack of genetic differentiation, the desert elephants may be more accurately designated ‘desert-dwelling elephants.’”
"Our results and the historical record suggest that a high learning capacity and long distance migrations enabled Namibian elephants to shift their ranges to survive against high variability in climate and in hunting pressure," said the study's lead author, Dr Yasuko Ishida.
The large ranges these elephants cover to cope with sparse food and water could also have contributed to their genetic similarities to their neighbors by bringing them close enough to sometimes interbreed.
Roca said that the understanding of how to cope with desert environments makes the protection of these populations, many of which have been hunted to near extinction, particularly important. "Their knowledge of how to live in the desert is crucial to the survival of future generations of elephants in the arid habitat, and pressure from hunting and climate change may only increase in the coming decades,” he said. Unlike some other populations, these elephants cannot be easily replaced by others should they die out.
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