Predatory Life On The Savanna Is Complicated (Unless You’re A Lion)

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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.

cheetah

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

Got Deer In The Backyard? If You Were In India, You Might Have Leopards

leopard

Here in the U.S., we complain about deer and bunnies munching on our gardens. In some places, people have to worry about more dangerous carnivores like coyotes, wolves, or bears. Where people and nature meet, conflict is often the rule.

In India, they’ve got animals such as leopards and hyenas to worry about. But where one might expect conflict, that isn’t a given, as demonstrated in a study published last month in PLOS One.

The study comes from a group of researchers led by the Wildlife Conservation Society-India who used camera traps to track leopards (Panthera pardus) and striped hyenas (Hyaena hyaena) in western Maharashtra (central India), an area that is rural and where most of the people are farmers growing sugar cane, millet, and vegetables. The cameras captured a number of leopards and hyenas over a one-month period in late 2008, and using those pictures, the researchers were able to calculate that there were about six leopards and five hyenas per 100 square kilometers. (For comparison, there were 100 wolves in Yellowstone National Park in 2011, or about 1.11 wolves per 100 square kilometers.)

Normally leopards in India live off of prey like cheetal and langur, but these smallish animals aren’t found much in this part of the country. Instead, the big cats are surviving on a diet of domestic dog and livestock, the researchers say.

In some places in India, leopards have been found preying on humans, but in western Maharashtra, there have been no fatal conflicts. This is particularly notable because the human population density there is very high — 300 people per square kilometer — and the cats were photographed on human trails, so they are definitely coming near the human population.

Why would there be little conflict?

“The crux of the issue to me is one of tolerance,” study lead author Vidya Athreya writes on the Project Waghoba website. “In many talks in cities, I often ask the public which of them would let be a leopard that is coming to their lane only to get dogs and has never harmed people. I do not think a single hand has ever been raised. However in rural India, tolerating other forms of life is a part of their lifestyle, be it domestic animals or wild.”

But beyond a lesson in tolerance, by showing that what might be considered dangerous wildlife can live near people without harming them, this study calls into question the perceived necessity of moving wildlife like leopards. Leopards that are found near human populations are now often treated as strays and moved to protected areas, the researchers say. But these translocated cats have attacked people near the sites where they are released. If they are less deadly when left in place, perhaps they should be left alone.

But I do wonder how well the local people deal with the loss of their dogs and, especially, their livestock, which is an issue that’s not addressed by the researchers. I imagine that for some poor farmers, losing even one animal can be a devastating financial loss. Any program to protect carnivores really needs to have some sort of scheme to insure people against livestock losses to give the humans less of a reason to kill these wonderful creatures.

Image (camera trap photo of a leopard from the study) credit: Project Waghoba