Animal super-athletes race for life and death on the Serengeti
When a cheetah sprints off in a high-speed pursuit of an impala on the Serengeti plains of Africa, both animals are showing-off almost incomparable athleticism.They race across the grassland, hitting incredible speeds and making explosive turns. These are some of the fastest, most powerful, most agile animals on the planet, engaged in what is literally a life-and-death competition.
Now scientists have dissected that chase in detail using high-tech motion tracking collars. By recording thousands of these chases at resolutions of fractions of a second, they've revealed details of the spectacular athletic performance of these amazing animal athletes, and the tactics they use in a chase.
For Professor Alan Wilson, who heads the Structure and Motion Laboratory at the Royal Veterinary College of the University of London, this is part of a long term labour of love. He's has spent 10 years trapping, collaring and tracking different species of animals on the savannah. "I love Africa, it's a wonderful place to work."
A life and death race
For this study he and his colleagues focused on two predator-prey pairs. They studied cheetahs and impalas, as well as lions and zebras. In both cases the prey are the most frequent targets of the predators, so they've co-evolved to be very similar in athletic performance. "We're looking to see if we could get the extremes of athleticism in these wonderful animals that live on the African savannah. These are animals that do one-on-one chases as a big part of there hunting ecology, so we'd expect them to be the supreme athletes of Africa."
The collars they used contained GPS units, accelerometers and gyroscopes, which recorded data about the animals movements 250 times a second. This gave them a detailed picture of how quickly the animals changed speed and direction in a chase. Wilson says, "It's a bit like a laboratory in the field. So we can tease apart the chases, stride by stride, and examine what the predator does and what the prey does, in each individual stride." They also did tissue biopsies to understand the details of the animals' muscle physiology.
"The remarkable thing is that with the lion chasing the zebra and the cheetah chasing the impala, there are a lot of similarities, despite the fact that the cheetah and the impala are much faster and more athletic," says Wilson. In a typical chase the predator tends to get fairly close to the prey quickly – they're faster in a straight line or else they'd never catch the prey at all. The real chase begins when the predator is within just a couple of steps. The prey then begins to make choices that determine the outcome of the chase. "The prey will make a decision to run in a straight line, or to turn or to accelerate or decelerate. The predator will see that happening and then in the following stride, react to that."
Predators are better athletes, but the prey defines the chase
The data from the collars have shown that there are remarkable parallels between the two predator/prey relationships. Cheetahs and Lions have muscles about 20 per cent more powerful, they're about 40 per cent better in acceleration than their relative prey species. They need that power and agility to make up for the fact that the prey is defining the chase.
This makes for a surprising conclusion in the data. Wilson's found that the prey is better off with a slower speed chase. "The predator is faster so if the prey runs as fast as it can, the predator just has to follow it. And if you're running very fast you can't turn very fast and you can't speed up, so the prey becomes predictable, and what the prey wants to be is unpredictable." In a slower chase, on the other hand, it's possible for the prey to make quicker more unpredictable turns and changes of speed, and the predator, as a result, mostly stays a step or two behind — until someone guesses wrong and the chase ends with an escape or a kill.