Human infrastructure decreases predator activity, releasing herbivores from a landscape of fear
Kaitlyn Thompson
Human predators affect all animals, but their presence disproportionately harms large predators relative to other trophic levels. In areas with abundant human infrastructure, the density of large predators may be reduced, which could potentially free lower trophic levels from a landscape of fear, allowing them to be more active. Conversely, large predators may change the behavior of lower trophic levels, causing them to be less active in stations where predation risk is high. We hypothesized that in areas with high human infrastructure, large predator activity would decrease while the activity of mesopredators and herbivores would increase. To test these hypotheses, we used our network of 21 camera stations in three counties across South Carolina. The images from the camera traps were collected several times throughout the year and tagged with species and number of individuals present. We calculated the activity level of each trophic level at each station, the intensity of use, by dividing the number of observations of each trophic level by the number of days the camera was active. After this, we used GIS to calculate a human infrastructure score for each camera station based on the density of roads and buildings around the station. To determine whether human infrastructure changes the relationship between trophic levels, we compared the intensity of use for each trophic level between stations with high human infrastructure and stations with low human infrastructure. As hypothesized, the intensity of use by large predators was greater at low-infrastructure stations compared to high-infrastructure stations, and herbivores used high-infrastructure stations more than low-infrastructure stations. In contrast, mesopredators showed no difference between the intensity of use of high and low-infrastructure stations. In conclusion, we observed that large predator activity was reduced by high human infrastructure, releasing herbivores from a landscape of fear, while leaving mesopredators relatively unaffected.
Kaitlyn Thompson is a junior biology major with minors in psychology and chemistry. She is a member of the women’s soccer team and Tribeta Honor Society. She hopes to attend a physician assistant program after graduation with hopes of one day becoming a physician assistant.