Abstract
Daily activity in herbivores reflects a balance between finding food and safety. The safety‐in‐numbers theory predicts that living in higher population densities increases safety, which should affect this balance. High‐density populations are thus expected to show a more even distribution of activity—that is, spread—and higher activity levels across the day. We tested these predictions for three ungulate species; red deer (Cervus elaphus), roe deer (Capreolus capreolus), and wild boar (Sus scrofa). We used camera traps to measure the level and spread of activity across ten forest sites at the Veluwe, the Netherlands, that widely range in ungulate density. Food availability and hunting levels were included as covariates. Daily activity was more evenly distributed when population density was higher for all three species. Both deer species showed relatively more feeding activity in broad daylight and wild boar during dusk. Activity level increased with population density only for wild boar. Food availability and hunting showed no correlation with activity patterns. These findings indicate that ungulate activity is to some degree density dependent. However, while these patterns might result from larger populations feeling safer as the safety‐in‐numbers theory states, we cannot rule out that they are the outcome of greater intraspecific competition for food, forcing animals to forage during suboptimal times of the day. Overall, this study demonstrates that wild ungulates adjust their activity spread and level based on their population size.
Highlights
Activity patterns—the distribution of activity throughout day and night—are a key feature of animal responses to their environment (Rowcliffe et al, 2014)
We studied whether the temporal spread and level of daily activity varied with population size in three ungulate species—two of which are social: red deer (Cervus elaphus) and wild boar (Sus scrofa), and one of which is a solitary species: roe deer (Capreolus capreolus)
With camera traps deployed in ten temperate forest sites that ranged in ungulate density, we analyzed the relationships between activity and density in three ungulate species: red deer, roe deer, and wild boar
Summary
Activity patterns—the distribution of activity throughout day and night—are a key feature of animal responses to their environment (Rowcliffe et al, 2014). Wild boar (Podgórski et al, 2013) and red brocket deer (Di Bitetti et al, 2008) are more nocturnal in areas with higher human presence, while other animals species are found to respond to proximity to roads and logging (Ngoprasert et al, 2017; Ramesh & Downs, 2013) No such shifts in activity in response to anthropogenic pressure were found by Di Bitetti et al (2008) for two related deer species, suggesting species specificity, or involvement of other factors. Suggests that animals may shift their activity in the spatial and temporal scales depending on the risk of predation or hunting (Cromsigt et al, 2013; Kronfeld-Schor & Dayan, 2003) This body of literature is known as Landscape of Fear (Gaynor et al, 2019). We tested the predictions that activity spread and level increase with ungulate density only for the social species and not for the solitary species, in agreement with the safety-in-numbers theory (Brown, 1988; Brown et al, 1999)
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