In a simple system, there’s a predator and its prey; the predator roams wherever the prey is found. Add in more predator and prey species, and where the predators live should be decided by what they eat. Real life, though, is not that simple. Just look at this new study published online by Ecology of four predator species in South Africa.
An international group of researchers studied an 85-square-kilometer, fenced-in region of South African savanna — the Karongwe Game Reserve. In this area there are four main predator species: lions, cheetahs, leopards, and wild dogs. These predators hunt 12 different ungulate species, mostly impala, blue wildebeest, waterbuck, Burchell’s zebra, warthog, and giraffe.
To figure out where the predators were going and what they were doing, many of the adults of each of the four species were outfitted with VHF transmitters during the study period of 2001 to 2005. The distributions of the prey species were determined by aerial surveys and sampling in the wet and dry seasons (respectively, November to March and April to October).
All that data was then combined. The patterns and interactions of the various species are complex, but there were definite patterns:
Lions: The big cats (above), as might be expected, are the dominant predators in this environment. That power gives them unrestricted access to pretty much anything they want. They go where the best and most vulnerable prey can be found and where they’ve got the best cover for hunting. They don’t worry about where other predator species are. Even the season doesn’t affect them much.
Leopards: These cats overlap in range with lions — the best prey is found where the lions live — but they avoid the much-bigger cats. They also avoid each other. In this area at least, the biggest killer of leopards is other leopards. And during the dry season, when it’s easier to see through parched vegetation and the risk of detection by other cats is higher, leopards find it safest to move towards the smaller wild dogs.
Cheetahs: Like leopards, these spotted cats (above) are also smaller than lions, and it would be expected that they would also avoid the big cats. But, like the leopards, their range overlaps with the lions. And in the wet season, these cats tended to actually move towards locations where lions were recently roaming. The researchers theorize that cheetahs may be using other tactics to avoid lions, such as by choosing habitats, like woodlands, that the bigger cats don’t use, or being active when lions aren’t. Staying near the lions, and their high-quality prey, proved beneficial; some cheetahs were able to take down large prey like wildebeest instead of having to stick with smaller meals. But just because the cheetahs were comfortable venturing into lion territory doesn’t mean that they were entirely fearless; these cats generally stayed away from leopards.
Wild dogs: The African wild dogs — the smallest of the predators — tended to avoid all three of the cat species, but they behaved differently depending on the season. In dry times, when they could be more easily seen, the wild dogs stayed away from the other carnivores’ activity centers. In the wet season, though, when there was more cover available, they took a little more risk and only avoided areas where the other species had been recently. Constrained as they were by the movements of the other predators as well as the boundary fence they could not cross, the wild dogs had to settle for prey species they did not prefer.
The researchers’ take-away message from all these interactions is that for subordinate carnivores like the cheetahs, leopards, and wild dogs, competition with other predators can matter more than what they eat. Because if you have to eat an impala instead of a wildebeest, or even wait another day for a hearty meal, being hungry is better than getting mauled to death by another predator.
Images courtesy of flickr user Jean-Louis A