Blame humans, not lions, for cheetah declines
Wild cheetahs have suffered tremendously over the last century—their population has been reduced by an order of magnitude, from some 100,000 one hundred years ago to just 10,000 today. While it’s certain that human activity bears at least some proportion of the responsibility for that decline, many have also pointed fingers at other predators in the cheetahs’ ecosystems. A new study led by biologist David M. Scantlebury of Queen’s University in Belfast finally sets the record straight.
The prevailing idea was that cheetahs suffered from kleptoparasitism. As smaller carnivores, cheetahs tend to be displaced from their carcasses by lions and hyenas. So if the cheetahs do all the work to hunt their food, they would suffer from starvation if too often the lions and hyenas stole their meat. So they have to expend even more energy taking down yet another animal to just be able to eat.
Scantlebury and his team followed fourteen cheetahs in Kgalagadi Transfrontier Park in Botswana’s Kalahari Desert and another five cheetahs in South Africa’s Karongwe Game Reserve, collecting behavioral data as well as estimating the amount of energy they expended each day, thanks to scat samples.
The researchers discovered that the feline hunters weren’t limited by the energy they expended during their high-speed chases. In fact, they didn’t actually use very much energy during their hunts at all. So losing the occasional carcass to another carnivore isn’t actually that big of a deal. In fact, the cheetahs could comfortably survive even if a full one quarter of their meals were stolen, because that would only require an additional 1.1 hours per day of hunting and increase their daily energy expenditure by 12%. They would have to be booted from the cafeteria 50% of the time to worry about long-term survival. In the Kgalagadi Transfrontier Park, where the study was conducted, cheetahs only lose about 9% of their carcasses, which is well below that threshold.
Instead, the main issue was how far they had to travel to find food in the first place. “It seems that the cheetah is able to cope with larger predators and the occasional loss of food without too much difficulty,” said Scantlebury, in an official statement. Indeed, cheetahs evolved to account for the presence of competitors. What they aren’t well-adapted to is the energy costs incurred by looking far and wide to find their prey.
“Human activities that force cheetahs to travel large distances to avoid disturbance and persecution may push [their daily energy expenditure] to the limit,” the researchers write. It’s humans, not lions and hyenas, that threaten the survival of Africa’s cheetahs. North Carolina State University graduate student Johnny Wilson, who co-authored the report, added, “anything that we do to make them move farther to find prey – like depleting their prey stocks or erecting fences or barriers – makes life a lot harder for a cheetah.” – Jason G. Goldman | 08 October 2014
Source: Scantlebury D.M., R. P. Wilson, J. W. Wilson, M. E. J. Mills, S. M. Durant, N. C. Bennett, P. Bradford, N. J. Marks & J. R. Speakman (2014). Flexible energetics of cheetah hunting strategies provide resistance against kleptoparasitism, Science, 346 (6205) 79-81. DOI: http://dx.doi.org/10.1126/science.1256424
Header image: Michael G L Mills, used with permission.
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