Mammal responses to global changes in human activity vary by trophic group and landscape

Abstract

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.

Fig. 1. Camera-trap sampling of contrasts between periods of higher versus lower human activity.

a, Location of camera-trap projects included in the analysis (n = 102). b,c, Examples for two projects: Edmonton, Canada (b) and Danum Valley, Malaysia (c) showing time series of human detections for the two types of comparisons used to assess the effects of higher human activity on animals. b, A between-year comparison with increased human activity during the COVID-19 pandemic (treatment, red shading) relative to the same time period the year before (control, blue shading). c, A within-year comparison with decreased human activity during the pandemic (control, blue shading) relative to the prepandemic period (treatment, red shading).

Fig. 2. Changes in the amount of animal activity in response to increasing human activity.

a, Interpretation of effects. b, Estimated effect sizes (black points) and variances (coloured lines) for all populations included in the analysis (n = 1,065 project–species combinations from 102 independent projects; two example species highlighted) with the global mean (and 95% quantiles) plotted in black to the right. c, Estimated model coefficients (points) and 95% CIs (lines; n = 1,065 project–species combinations from 102 independent projects) for additive factors (with complete data; Methods) hypothesized to influence changes in the amount of animal activity when human activity is higher, where: intercept is diurnal, large herbivore in closed habitat type with a seasonal comparison and all other effects are contrasts. d, Model predictions for the interaction between trophic group and HMI.

Fig. 3. Changes in animal nocturnality in response to increasing human activity.

a, Interpretation of effects. b, Estimated effect sizes (black points) and variances (coloured lines) for all populations included in the analysis (n = 499 project–species combinations from 100 independent projects; two example species highlighted) with the global mean (with 95% quantiles) plotted in black to the right. c, Estimated model coefficients (points) and 95% CIs (lines; n = 499 project–species combinations from 100 independent projects) for additive factors (with complete data; Methods) hypothesized to influence changes in animal nocturnality when human activity is higher, where: intercept is nocturnal, large herbivore in closed habitat type with a seasonal comparison and all other effects are contrasts. d, Model predictions for interaction between trophic group and human modification index. e, Model predictions for interaction between hunting and HMI.