The effects of human disturbances on mammal diel activity: Does trophic level matter?
Drew Bruton, Elisa Howanksy
Globally, humans are the most successful predators of terrestrial mammals. Although human exploitation affects all trophic levels, it is more intense for large predators than for mesopredators or herbivores. To avoid the threat posed by humans, mammals may avoid habitats with high human disturbances, but they may also temporally avoid humans by changing their diel activity patterns. We investigated the effect of human disturbance on the diel activity of mammals of different trophic levels. We hypothesized mammals would be more nocturnal in open habitats because they are more visible to humans. We also hypothesized that mammals would be more nocturnal in sites with human disturbance, but the disturbance would affect large predators the most, herbivores the least, and have an intermediate impact on mesopredators. We tested our hypotheses by deploying camera traps at sites across Upstate South Carolina. Each camera was classified by habitat type based on canopy cover and human-disturbance level based on the frequency of images of human activity. Each picture was labeled with species and time of day. We compared the proportion of nocturnal observations at cameras with different disturbance levels and at cameras in different habitats. As hypothesized, we found more nocturnal observations at cameras in more open habitats for all trophic levels. However, we found that while both large predators and herbivores were more nocturnal in areas with higher human disturbance, mesopredators were more diurnal. Our results suggest that when they are more visible to humans, mammals will be more nocturnal. However, members of different trophic levels show different responses to human disturbance. Although large predators and herbivores temporally avoid humans, mesopredators are more tolerant of human disturbances.
Drew Bruton graduated from Highland School of Technology in Gastonia, North Carolina and is a senior environmental science major with a minor in biology. He has also been a member of the men’s lacrosse team at Lander for four years and presented at the USC Upstate research symposium. After graduation, he plans to pursue a job as an ecology field technician.
Elisa Howansky is a senior biology major and a member of the Honors College. Currently, they serve as historian for Lander’s chapter of Tribeta. They have presented their past research at SCURS 2022, and at ASB 2022, where they won honorable mention for the John C. Johnson Award for Excellence in Student Research. At Lander’s 2022 Academic Symposium they were the winner of the Judges’ Choice Award. Post-graduation, they plan to pursue a doctorate in behavioral ecology.