Associate Professor University of Maryland: Baltimore County Baltimore, Maryland, United States
Background/Question/Methods:
Trophic cascades generated by the arrival or loss of a top predator typically results in numerical or spatial responses at lower trophic levels. Arrival of a new predator also may initiate trophic cascades by altering the temporal activity of competitors and prey, but there little evidence for this response. In 2020, Eastern coyote (Canis latrans) invaded Baltimore City, bringing them into contact with the urban forest mammal community for the first time. By, 2021 coyotes occurred at 10 of 50 forest patches monitored in the city. I used four years of camera trap data in 2018-2021 to investigate longitudinal change in the time of day of red fox (Vulpes vulpes) occurred before (2018-2019) and following the coyote invasion (2020-2021).
Results/Conclusions:
Prior to the invasion, foxes occurred 14.4 hrs. after sunrise (12.8, 16.0; 95% CI). In contrast, in the presence of coyotes, foxes shifted activity 2.9 hrs. earlier to 11.5 hours after sunrise (9.9,13.0: 95% CI). Camera trap images of fox prey revealed that nocturnally active foxes included eastern cottontail (Sylvilagus floridanus), Virginia opossum(Didelphis virginiana), Peromyscus spp. and anthropogenic items in their diet. More diurnally active fox primarily fed on Eastern grey squirrels (Sciurus carolinensis) and Norway rats (Rattus norvegicus). If the diurnal shift in fox occurrence in response to coyote presence persists, it has the potential to restructure the urban mammal food web.
