Dietary Overlap Increases Extinction Risk in Africa’s Carnivores

Imagine you’re sitting down to a family dinner with your siblings, you’re a vegetarian, and your older, bigger, bullying brother just won the fight for the mashed potatoes and ate the last of them, and now the only thing left on the dining table is chicken. Sure you could eat chicken, but it would be difficult for you. Well, that’s sort of how life is for Africa’s large carnivore species, especially for cheetahs and African wild dogs.

African wild dogs and cheetahs, the smallest and most endangered of Africa’s large predators, have the greatest dietary overlap of all African carnivores, as well as the smallest number of prey species to choose from. Both species predominantly dine on Thomson’s gazelle and impala, two small species of ungulate. The risk of extinction increases when a species has fewer food options. Larger carnivores such as lions, spotted hyenas and leopards have more options in their prey, minimizing competition and giving them a more secure status.

Researchers from Nelson Mandela Metropolitan University (NMMU) in South Africa recently conducted a study on prey preferences and dietary overlap amongst Africa’s large predators. The species in the study were leopards, lions, spotted hyenas, cheetahs and African wild dogs. The conservation status of each species into was taken into account during data analysis, which served as a method to estimate the number of surviving individuals within each of the five carnivore species studied.

The researchers found that almost three-quarters of the actual diet for African wild dogs and cheetahs overlapped, the greatest amount of overlap between any of the other large carnivores. The overlap for the preferred diet of these two species was also over 70 percent.

When the scientists looked at the data in comparison to the conservation status of each species, they found that the smaller the dietary options available to a species, the more endangered that species was. Leopards, who have the broadest range of prey to choose from, are of the least conservation concern.

The evolution of Africa’s large predators is now negatively affecting those who evolved to become more specialized. African wild dogs and cheetahs, which have the fewest number of prey options, are also the most threatened, and also suffer from the greatest amount of dietary overlap.

The current theory is that competition with and predation by lions and spotted hyenas forces African wild dogs to exist at low densities. Long-term data shows that the wild dogs were most abundant in the Serengeti during the 1960s and 1970s, when lions and spotted hyenas were more scarce. Over the next two decades, as lion and hyena populations doubled, the African wild dog population declined up until local extinction. The recent findings in the study at NMMU suggest that food limitation may have been a factor in the extinction of the wild dogs in the Serengeti. The decline of the preferred prey species of the wild dogs placed them under greater pressure, and they ultimately went in extinct in that location.

African wild dogs also suffer from human persecution, habitat loss, disease and competition with lions and spotted hyenas. The larger predators interfere with the wild dog’s kills, in addition to lions actually killing the dogs themselves.

Cheetahs suffer from habitat loss, exploitation human interference, disease, predation as well as other predators stealing their food. Habitat loss is their greatest threat, because it reduces the availability of suitable prey species and thus reduces their success in hunting. Competition with other predators also threatens Cheetahs in the Serengeti, where lions kill cheetah cubs.

Cheetah cub mortality depends on the mother’s vigilance and anti-predator behavior. When the mother has to spend more time hunting because of fewer suitable prey options, she has less time to protect her cubs. The same holds true for African wild dogs. The more effort they have to put in to taking down prey, the fewer guard dogs they can leave behind to guard the pups.

Food limitation, and competition for resources between species can now be added to the list of threats for African wild dogs and chetahs, particularly in conservation areas that are free from habitat alteration and human persecution, but where management strategies have led to unnaturally high population densities of all predators found there, which reduces the availability of food.

Conflict with humans restricts large carnivores predominantly to conservation areas. But in clumping the carnivores together in one area, it increases the likelihood that they will have to compete for resources, such as prey, by creating artificially high population densities, and may eventually lead to further extinctions.

The successful management of conservation areas is crucial to ensuring that further extinctions do not take place.  One way to do this is to vary the prey species in the conservation area, and to make sure that the preferred prey species of the more threatened carnivores are available at all times.

By keeping an eye on things and actively engaging in the management of conservation areas, we can ensure that they only serve to booster endangered populations, rather than cause further damage.

Hayward, M., & Kerley, G. (2008). Prey preferences and dietary overlap amongst Africa’s large predators South African Journal of Wildlife Research, 38 (2), 93-108 DOI: 10.3957/0379-4369-38.2.93