GAINESVILLE, Florida – When large carnivores are removed from an African landscape, local farmers need to adopt complex crop management strategies and be more vigilant about crop-raiding baboons, a new modeling study out of the University of Florida finds. In a healthy protected forest ecosystem, apex predators like lions, cheetahs, and hyenas, keep the local baboon population in check. After these large predators are removed through a combination of hunting and forest fragmentation, baboon populations may increase by as much as 500%, putting pressure on farmers growing crops just outside of the protected area. Local farmers, in turn, must spend more resources to manage baboons, and may need to adopt more complex planting schemes, to mitigate the impact of the baboons.
The study, published in the Ecological Society of America’s journal Ecology, uses modeling to explore the dynamics between apex predators (large cats and hyenas), mesopredators (baboons), and ungulates (buffalo, bushbuck, and duikers), and their impact on nearby farmers, using population data from Greater Addo Elephant National Park in South Africa. The study reinforces existing theory on mesopredator release, which states that without a healthy ecosystem mesopredators can experience huge population increases with undesirable side effects like crop-raiding. However, the study contradicts the belief that apex predators can merely be replaced by human predation; instead complex management strategies are required alongside human predation to replicate the success of apex predators. Furthermore, the study builds upon previous work on prey switching by incorporating a new concept of baboon shyness as a factor in determining whether the baboons choose to crop-raid.
Baboons are uniquely diverse omnivores and mesopredators. They can compete directly with ungulates and other small herbivores for forage, but also compete with apex predators (big cats and hyenas) for hunting those same ungulates and mammals. As apex predator populations decline baboon populations increase, due to predator release and increased access to food. As their population expands, baboons are more inclined to opportunistically leave the park to feed on high-quality human crops like maize (yellow corn), which further increases baboon populations.
Crop raiding is a challenge to people both in calories and education. A single successful raid by a troop of baboons can wipe out an entire year’s crop. To address crop-raids farmers must be vigilant in guarding their fields, a burden which falls most heavily on women and children. Hungry children who spend most of their time guarding their family fields can’t prioritize their education.
The model used in this study demonstrates that humans are less effective at controlling baboon population by hunting than apex predators are. Additionally, the model predicted that baboons were unlikely to raid very far from the edge of the protected area. Planting low quality crops (for baboons, like tea) near the park and higher quality crops (like maize) further from the park could be an important part of a larger mitigation strategy.
“By combining predator management, to maintain acceptable levels of apex predators, with baboon control, the extent of crop-raiding could be successfully reduced”, said lead author Dr. Rachel A. Taylor, a postdoctoral research fellow at the University of South Florida.
“In a perfect world, for our conservation goals, all trophic levels would be maintained in protected areas to promote healthy and balanced ecosystems; this would preempt the need to reactively manage spillover impacts” said Dr. Sadie Ryan.
“Mathematical models allow us to explore possible intervention strategies for conservation and control in ways that we can’t in the field, either because of ethical or cost considerations,” says co-author Dr. Leah Johnson.
The collaborative research team includes experts in epidemiology, public health, ecology, mathematical modeling, and geography: lead author Rachel Taylor (University of South Florida), co-author Sadie Ryan (University of Florida), co-author Justin Brashares (University of California, Berkeley), and co-author Leah Johnson (University of South Florida). The work expands upon the team’s prior work at the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara.