Human Footprint and Human Presence Have Non-Equivalent Effects on Wildlife Habitat Use

Anthropogenic activity can substantially impact wildlife habitat use, altering both the distribution and activity patterns of species across terrestrial mammal communities. Variation in human footprint on the landscape, including commercial and residential development, can decrease habitat quality for mammals, and fear of humans (major sources of wildlife mortality) could drive changes in habitat use if animals avoid human presence spatially and/or temporally. Anthropogenic effects on habitat use are not exclusively negative, however, with many “synanthropic” species exhibiting high use of areas near humans to take advantage of resource subsidies (e.g., food waste). Human footprint and human presence may simultaneously affect habitat use, potentially in opposition, if for instance wildlife avoid interactions with people but take advantage of resources concentrated near development. We used data from a camera trap grid spanning a 1700-km2 mixed-used landscape in central California to compare how human footprint (building density) and human presence (detections of people on camera) affect carnivore and omnivore habitat use. Multi-species occupancy models revealed that, for most species, human footprint and presence differentially affected occupancy and detection probability at camera sites. Synanthropic species (e.g., striped skunks Mephitis mephitis and Virginia opossum Didelphis virginiana) were more likely to occupy sites with higher building density, consistent with use of anthropogenic resources, but were less detectable in areas of high human presence. Larger, highly mobile species (e.g, pumas Puma concolor and bobcats Lynx rufus) were much less detectable with increasing building density, but exhibited greater occupancy at sites with high human presence (potentially due to increased access to trails), avoiding humans temporally at these sites by increasing nocturnality. Our results indicate that, for many species, human footprint and presence have non-equivalent effects on habitat use, thus limiting the value of any single measure as a proxy for all anthropogenic impacts.