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Urbanization often results in biodiversity loss and homogenization, but this result is not universal and there is substantial variability in the spatiotemporal effects of urbanization on wildlife across cities and taxa. Areas with lower population and housing density are some of the fastest-growing regions in the western United States; thus, more research in these areas could offer additional insight into the effects of urbanization on wildlife and the potential importance of wild spaces in maintaining a diverse biotic community surrounding developed areas. To address this need, we conducted a study to identify the effects of urbanization (i.e. housing density) on mammals along a housing density gradient from wilderness to suburbia in Missoula, Montana. We deployed 178 motion-activated trail cameras at random sites within urban/suburban, exurban, rural, and wild regions from May to October 2019 to 2020. We identified all mammals >150 g, then evaluated how housing density influenced: (i) occupancy and (ii) species richness using multispecies occupancy models; (iii) relative abundance using Poisson models; and (iv) diel activity patterns using kernel density estimation and logistic regression. Urbanization was the strongest driver of mammal distribution, with a linear decline in mammal species richness as housing density increased. Urbanization also had strong effects on occupancy and detection rates, with larger-bodied mammals generally having stronger negative associations. Overall, mammal relative abundance was highest in suburban regions; however, this effect was largely driven by White-tailed Deer. Natural environmental factors explained most changes in mammal nocturnal activity; however, urbanization strongly affected nocturnality in some species, with Black Bear and White-tailed Deer becoming more nocturnal and Red Fox and Northern Raccoon becoming less nocturnal as housing density increased. While our study confirms that some mammals can live and thrive in developed areas, it emphasizes the importance of maintaining wild areas for those species that cannot.

Wildlife must adapt to human presence to survive in the Anthropocene, so it is critical to understand species responses to humans in different contexts. We used camera trapping as a lens to view mammal responses to changes in human activity during the COVID-19 pandemic. Across 163 species sampled in 102 projects around the world, changes in the amount and timing of animal activity varied widely. Under higher human activity, mammals were less active in undeveloped areas but unexpectedly more active in developed areas while exhibiting greater nocturnality. Carnivores were most sensitive, showing the strongest decreases in activity and greatest increases in nocturnality. Wildlife managers must consider how habituation and uneven sensitivity across species may cause fundamental differences in human–wildlife interactions along gradients of human influence.

Interspecific interactions can provoke temporal and spatial avoidance, ultimately affecting population densities and spatial distribution patterns. The ability (or inability) of species to coexist has consequences for diversity and ultimately ecosystem stability. Urbanization is predicted to change species interactions but its relative impact is not well known. Urbanization gradients offer the opportunity to evaluate the effect of humans on species interactions by comparing community dynamics across levels of disturbance.

Managing wildlife populations in the face of global change requires regular data on the abundance and distribution of wild animals, but acquiring these over appropriate spatial scales in a sustainable way has proven challenging. Here we present the data from Snapshot USA 2020, a second annual national mammal survey of the USA. This project involved 152 scientists setting camera traps in a standardized protocol at 1485 locations across 103 arrays in 43 states for a total of 52,710 trap‐nights of survey effort. Most (58) of these arrays were also sampled during the same months (September and October) in 2019, providing a direct comparison of animal populations in 2 years that includes data from both during and before the COVID‐19 pandemic. All data were managed by the eMammal system, with all species identifications checked by at least two reviewers. In total, we recorded 117,415 detections of 78 species of wild mammals, 9236 detections of at least 43 species of birds, 15,851 detections of six domestic animals and 23,825 detections of humans or their vehicles. Spatial differences across arrays explained more variation in the relative abundance than temporal variation across years for all 38 species modeled, although there are examples of significant site‐level differences among years for many species. Temporal results show how species allocate their time and can be used to study species interactions, including between humans and wildlife. These data provide a snapshot of the mammal community of the USA for 2020 and will be useful for exploring the drivers of spatial and temporal changes in relative abundance and distribution, and the impacts of species interactions on daily activity patterns. There are no copyright restrictions, and please cite this paper when using these data, or a subset of these data, for publication.