Mammals adjust diel activity across gradients of urbanization

Abstract

Time is a fundamental component of ecological processes. How animal behavior changes over time has been explored through well-known ecological theories like niche partitioning and predator-prey dynamics. Yet, changes in animal behavior within the shorter 24-hr light-dark cycle have largely gone unstudied. Understanding if an animal can adjust their temporal activity to mitigate or adapt to environmental change has become a recent topic of discussion and is important for effective wildlife management and conservation. While spatial habitat is a fundamental consideration in wildlife management and conservation, temporal habitat is often ignored. We formulated a temporal resource selection model to quantify the diel behavior of 8 mammal species across 10 US cities. We found high variability in diel activity patterns within and among species and species-specific correlations between diel activity and human population density, impervious land cover, available greenspace, vegetation cover, and mean daily temperature. We also found that some species may modulate temporal behaviors to manage both natural and anthropogenic risks. Our results highlight the complexity with which temporal activity patterns interact with local environmental characteristics, and suggest that urban mammals may use time along the 24-hr cycle to reduce risk, adapt, and therefore persist, and in some cases thrive, in human-dominated ecosystems.

Keywords: ecology; mammal; temporal resource selection; urban; wildlife cameras.

Figure 1.. City-specific probability of activity for each species.

Gray points are city-specific estimates of the average probability of activity in each time category. The black point indicates the average probability of activity among cities and the horizontal lines are 95% credible interval for the average probability estimates among cities. Wider credible intervals indicate more variation among cities.

Figure 2.. The predicted probability of activity in each time category at each sampling site (x-axis) the species was detected.

Each column on the x-axis is a stacked bar plot representing the probability of activity in each time category at each sampling site. For each bar plot, all categories sum to one. Sampling sites along the x-axis are ordered from the lowest probability of nocturnal activity to the highest.

Figure 3.. Mean (circle) and 95% credible intervals of estimated coefficients from natural and anthropogenic features on temporal selection of deep night, night, dusk, and dawn relative to day.

Figure 4.. Probability of nocturnal activity (night and deep night combined) across each of our natural and anthropogenic characteristics of the urban environment.

Solid line indicates the median predicted line and shaded areas are 95% credible interval. Darker shading represent the relationships whose odds ratios did not overlap 1.

Appendix 1—figure 1.. US cities where remotely triggered wildlife cameras were deployed to assess diel patterns in urban mammals.