African elephants are the largest animals on earth. Some males can exceed 6 tons, while females can reach over 4 tons. The energy required to move such a mass across the Savannah in search of nutrient-poor vegetation means making strategic choices to access sufficient food. "The question is how good are they at planning their movements? That is what we are trying to tell thanks to a series of observations," said Fritz Vollrath (Oxford University). His team's latest research was published on March 25 in the Journal of Animal Ecology.

"This time, we were interested in topography. Because if the elephant has to log its weight uphill, when it goes downhill, it doesn't get the energy back," said the researcher. Yet, gaining 100 meters in elevation is equivalent to half an hour of foraging. "Just to stay on level ground, they need to forage about 16 hours a day. They need to drink every day about maybe 100 to 200l." the biologist said.

Vollrath is also a member of Save the Elephants, an NGO based in Nairobi (Kenya), which has been monitoring the movements of adult elephants fitted with GPS collars for more than 30 years. The study analyzed the movements of 157 elephants between 1998 and 2020 in relation to the terrain of the Samburu region in northern Kenya. A model was used to factor in the energy cost of movement based on altitude changes. "The fundamental issue here is that elephants seem to use some economic or ergonomic calculations to balance the cost of going somewhere with benefits," he said.

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