Scientists have long known that providing supplemental food for wildlife, or resource provisioning, can sometimes cause more harm than good. UGA ecologists have developed a new mathematical model to tease apart the processes that help explain why. Their research, which has implications for public health and wildlife conservation, was published in the Royal Society journal Biology Letters.
Animals of many kinds increasingly are finding their meals in human environments, gathering at places like backyard bird feeders, landfills or farms that offer an easily accessible year-round source of food. As with people, however, when large numbers of animals congregate they can face a higher risk of contracting disease.
A desire to understand a disparity in disease outcomes motivated the study by Daniel Becker, a doctoral student in the Odum School of Ecology, and co-author Richard Hall, an assistant research scientist in the Odum School and the College of Veterinary Medicine’s infectious diseases department.
Providing food for wildlife—whether intentionally, as with bird feeders or feeding stations for feral cat colonies, or unintentionally as in the case of garbage dumps—can cause changes to an animal’s breeding success, foraging behavior and body condition that, in turn, influence its risk of acquiring harmful infections.
For their model, Becker and Hall used data from studies of feral cats with feline leukemia virus that visited supplemental feeding stations. The model revealed that a key factor in predicting disease outbreaks in wildlife that access supplemental food was how that additional food influenced the strength and speed of the immune response. And more food wasn’t necessarily better.
Under some scenarios, even low levels of supplemental food could increase the risk of outbreaks compared with wild-feeding populations. In other cases, a small amount of supplemental food initially drove down infection levels, but too much led to the population size growing so large that the increased opportunities for infection to spread overcame the animals’ immune defenses, with large outbreaks possible.
The authors said that their results point to the urgent need for more studies to explore the relationship between resource provisioning, immune defense and disease.