AUTHORS: Nathan J. Proudman, Illinois Natural History Survey at the University of Illinois Urbana-Champaign; Maximilian L. Allen, Illinois Natural History Survey at the University of Illinois Urbana-Champaign
ABSTRACT: The ability of animals to plasticly adjust their diel activity has important implications for their persistence and the structure of food webs. While many studies have examined diel activity in mammals, few have compared multiple abiotic, biotic, and anthropogenic variables to determine what factors have the strongest effects on sympatric species within a system. Understanding the bounds of variation in behavior is vital to accurately determine the effects of environmental stressors on the diel activity of wildlife. We quantified shifts in diel activity among nine sympatric mammal species using camera traps across Illinois. We found biotic variables to be responsible for the greatest average shifts in diel activity across all mammal species (Δ=16.8%). Domestic cats (Felis catus; Δ=25.7%), red foxes (Vulpes vulpes; Δ=25.2%), bobcats (Lynx rufus; Δ=20.7%), and striped skunks (Mephitis mephitis; Δ=19.3%) exhibited the most behavioral plasticity of our focal species, suggesting contrasting behavioral strategies to the variables we tested. Decreased diurnal activity in more open habitat types by multiple species likely reflects the anthropogenic fear effects in the human-dominated landscape of Illinois, while urban environments may act as spatio-temporal refuges from coyotes (Canis latrans) for subordinate mesocarnivores. Our study shows that a broad range of factors contribute to variation in mammal diel activity, which can in turn affect the predatory and competitive pressures among sympatric species, with the potential for cascading effects across multiple trophic levels. Our study provides a robust baseline for the diel variation in mammal activity, allowing for more accurate assessments of their behavior.
