Biological invasions disrupt activity patterns of native wildlife: An example from wild pigs

Abstract

Activity patterns are an important behavioral trait linked to animal interactions within food webs. Biological invasions can have impacts on the behavior of native species through predation and competition, but few studies have determined if invasions lead to shifts in activity patterns of native species. Wild pigs (Sus scrofa) are a generalist, invasive vertebrate in North America that may affect activity patterns of native species through competition and predation. We hypothesized native species' activity patterns would differ from their expected activity pattern (i.e., typical hours of daily activity) and be more variable across sites occupied by wild pigs. We used a U.S. nationwide and a regional camera trapping dataset to determine if wild pig presence affected activity patterns of a nocturnal, diurnal, and crepuscular species: northern raccoon (Procyon lotor), eastern gray squirrel (Sciurus carolinensis), and white-tailed deer (Odocoileus virginianus), respectively. We simulated expected activity patterns of each species and overlapped them with observed activity patterns of respective species in populations where wild pigs were present and where they were not detected. Overlap coefficients were used in generalized linear mixed models to determine if wild pig presence explained deviations from the expected activity pattern. When wild pigs were detected, raccoons remained nocturnal, but their activity patterns were less variable, squirrel activity on the ground was less diurnal and their activity patterns were more variable, and deer activity patterns remained similar in both respects. These results highlight how biological invasions may differentially influence native species activity patterns, potentially altering food web-level interactions.