In a 4,500 hectare cheetah rehabilitation camp in the middle of Namibia, researchers observe the large, spotted carnivores as they readjust to wild life. This week one such researcher, physiologist Robyn Hetem from the University of the Witwatersrand Medical School, used her observations to disprove a theory about cheetah that has been treated as common knowledge for decades, that a cheetah’s running speed causes its body to overheat while hunting.
Less than 40 percent of cheetah hunts end successfully. Most of the time they stalk and chase but don’t catch, even when the prey is within striking distance. Countless safari guides and animal fact websites state that cheetah give up the hunt because their bodies overheat. But we now know that isn’t true.
After hunting, cheetah lie in the shade, Hetem said, panting, sometimes for more than an hour, and they seem completely exhausted. The overheating “fact” that many safari guides share is based on a 1973 study that showed cheetah stop running when their body temperature reached 40.5º C. The researchers assumed this was the reason cheetah stop chasing prey and lie down for a rest. But that study didn’t simulate natural conditions, it placed cheetah on a treadmill to run for two kilometers at a medium speed, an unrealistic comparison to a real hunt.
“That study was amazing for its time,” Hetem said. “But it didn’t actually answer the question.”
Hetem and her research team implanted two sensors, one for temperature and one to monitor activity, into six cheetah in the Namibian rehabilitation camp. Then, over the course of months, monitored the temperature readings during hunting activities.
It turns out cheetah don’t overheat while stalking and running after prey, in fact, they don’t heat up at all.
“We were definitely surprised,” Hetem said. A cheetah’s body temperature after the chase is the same as its mean daily body temperature, 38.4ºC.
Hetem’s study, published in Biology Letters, states “the supposed thermal limit to exercise of 40.5º C appeared irrelevant in these free-living cheetah.”
If overheating doesn’t explain the failed hunting attempts, what does? Hetem said it is speculation at this point, but one likely culprit is lactic acid build-up in muscles. Just like humans, when cheetah turn on the speed, the muscles tire quickly.
Hetem also noticed something else. Cheetah body temperatures rise in the hour after the hunt, rather than during. In the 40 minutes after unsuccessful hunts, cheetah body temperatures rose about 0.5ºC and after successful hunts, 1.3ºC.
The post-hunt body temperature increase happened gradually over the course of 40 minutes. The increase took place before the cheetah began eating, so it wasn’t a result of consuming its prey. Hetem was also able to rule out several other variables as causing the temperature change, including maximum activity during the hunt, duration of the hunt, air temperature, and size of prey. So what causes a cheetah to heat up after hunting? Stress, Hetem said.
“Cheetah are particularly vulnerable after the kill,” Hetem said. Since they are not at the top of the carnivore hierarchy, there are other animals around, like leopard and lions, that may try to steal the cheetah’s catch. If another carnivore approaches, a hungry cheetah will defend its meat, sometimes to its own peril.
Two of the six cheetah in Hetem’s study were killed by leopards after hunting. Hetem watched as a leopard broke one cheetah’s back while the cheetah tried to defend its fresh kill. She hypothesized that the increased temperature after hunting is likely due to a cheetah’s awareness that other carnivores might be eyeing its dead prey for dinner.
Hetem’s research used cheetah that are cared for by the AfriCat Foundation at the Tusk Trust Cheetah Rehabilitation Camp within Okonjima Nature Reserve.
CITATION: Robyn Hetem et al. (2013). Cheetah do not abandon hunts because they overheat. Biology Letters July 24, 2013.
This article was written by Emily Eggleston, special to mongabay.com