In Botswana, a cheetah explodes into action, and so does its collar. Within seconds, it hits a top speed of 59 miles per hour, driven by leg muscles that generate more power than those of any other runner. Awakened by this phenomenal acceleration, the sensors around its neck record its position and movements, from its first footfalls to the death of its impala prey.
Using these collars, Alan Wilson from the Royal Veterinary College has shown just how extreme a wild cheetah’s movements can be. It’s the culmination of his long-running fascination with an animal that combines two of his great loves—veterinary science and track athletics. “If you’re interesting in running, you very quickly develop an interest in what the cheetah does,” he says.
The cheetah is the world’s fastest land creature, and exists at the very limits of what an animal’s body can accomplish. We know a lot about the adaptations that make them so fast. For example, its flexible spine allows its shoulders and hips to swing through large arcs, greatly extending the length of its stride. In this mind-blowing National Geographic video, watch any foot leaving the ground, and note just how far the cheetah travels before that foot lands again.
But just how fast are they? The published top speed is 64 miles per hour (29 metres per second), which is considerably faster than greyhounds (40 mph), racehorses (42 mph) or Usain Bolt (28 mph). But that figure was based on a single measurement taken in the 1960s. Whenever Wilson clocked captive cheetahs chasing lures on strings, they only performed at greyhound level. “Most of these animals have been reared in a zoo for many generations and have never run for their dinner,” he says. “They’re resting on their evolutionary laurels.”
To really understand what these cats can accomplish, Wilson wanted to study wild ones. He flew to northern Botswana, where a local charity had been studying five cheetahs using tracking collars. Wilson replaced these with new ones of his own design, which could record the animals’ position and acceleration, and were programmed to record more data if the animals were moving quickly. “I’m very proud of the design,” says Wilson. “We made all the hardware and software ourselves.”
“It took substantial imagination to realize how these technologies could be used to investigate these elusive mammals,” says John Bertram at the University of Calgary. “Cheetahs are only highly active for very brief periods, so they’re extremely difficult to observe any other way.”
The data from the collars is astonishing, not least when Wilson overlays it onto maps of the terrain captured through Google Earth. In one hunt, he can see one of the cheetahs using a termite mound to bank! He could even distinguish between runs when cheetahs killed their quarry and those when the prey got away.
Collared cheetah. Credit: Alan Wilson, RVC.
Wilson recorded a total of 367 runs, of which a quarter ended in a kill. There were many surprises. Wildlife documentaries typically show these cats hunting during the day in open grassland. But Wilson’s individuals were hunting day and night. They also made half their runs among shrubs or thick vegetation, and were actually more successful in thicker cover.
The collars cemented the cats’ speedy reputation. The fastest individual, appropriately named Ferrari, hit a top speed of 59 mph, very close to the reported 64 mph maximum. And while that old measurement was taken on a flat, track-like surface, Ferrari was running through vegetation.
But most of the time, the cheetahs didn’t run as fast as they could. Across their hunts, their average top speed was just 33 mph (15 metres per second) and they only hit that for one or two seconds. That’s because speed isn’t the critical factor in a hunt—when the cheetahs killed their prey, they weren’t running any faster than when they flubbed their hunts.
It’s manoeuvrability that matters. To hunt agile prey like impala, cheetahs have to dodge and weave, which becomes much harder at full pelt. Just think about how much harder it is to turn a car at 60 mph than at 20 mph. “If you want to catch something, you don’t want to go faster than you have to,” says Wilson. “Manoeuvring becomes harder if you go quickly.” So, perhaps counter-intuitively, the ability to slow down sharply before a turn is incredibly important.
Cheetahs accomplish this with leg and back muscles that make up half its body weight. These contract at such high speeds that each kilogram of muscle generates 100 watts of power. For comparison, greyhounds produce just 60 watts with the same amount of muscle, horses manage just 30 watts, and Usain Bolt can produce just 25. With these powerful muscles, a cheetah can speed up or slow down by up to 9 mph in a single stride. The cat is like a sports car that always runs on second gear.
The importance of turning also helps to explain some bizarre aspects of the cheetah’s anatomy. People often assume that its limbs should be light and slender so they can move quickly through the air. “However, cheetah limbs are actually quite massive for the animal’s body weight,” says Bertram. “[Wilson’s study] indicates that the extreme forces borne by the skeleton, in manoeuvres such as braking, require a reinforced skeleton.”
Wilson now has bigger plans for his collars. He wants to study other populations of cheetahs, including those that hunt in packs (the collars can be programmed to turn each other on if they sense a hunt has started). The latest collars can also relay their position to cameras on overhead planes, allowing Wilson to film hunts from above.
He has also started to collar other predators, like wild dogs, leopards, lions… and domestic cats. In The Secret Life of the Cat, a documentary airing on BBC2 tomorrow, Wilson’s collars were fixed onto 50 cats in Surrey, England to see what they do when they exit their cat-flaps.
Reference: Wilson, Lowe, Roskilly, Hudson, Golabek & McNutt. 2013. Locomotion dynamics of hunting in wild cheetahs. Nature http://dx.doi.org/10.1038/nature12295
More: Cheetahs do not prosper. Fewer than 10,000 of them survive in the wild, and you can read about their plight in this excellent National Geographic feature.
for more visit http://www.nationalgeographic.com