Density dependence of daily activity in three ungulate species

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.

Top-down and bottom-up forces explain patch utilization by two deer species and forest recruitment

“…What we did expect and found is that hunting ( β = − 0.34) and landscape abundance of red deer ( β = 0.41) explained patch utilization in opposing ways since this species negatively responds to hunting by human and because this is a social species that benefits from living in groups (Georgii 1981 ; Lone et al 2015 ). In line with our results, a companion study found that population size of red deer indeed positively explained variation in daily activity levels and spread (Ramirez et al 2021c ). Additionally, we expected that distance to forest edge would explain patch utilization as these areas are in the transition between forests and meadows and have therefore, a higher presence of herbaceous plants and a higher production of fresh tree leaves (Murcia 1995 ).…”

“…Studies have partially addressed how patch utilization by wildlife varies with top-down (Kuijper et al 2013 ; Shrader et al 2008 ), bottom-up forces (Rieucau et al 2009 ; Wei et al 2015 ), the landscape matrix (Rieucau et al 2007 ; Bubnicki et al 2019 ) and population size (China et al 2008 ; Ramirez et al 2021c ) but relatively few studies have analysed the relative importance of all these factors in combination. They show in agreement with the Optimal Foraging Theory that animals select patches with high quality food and with low predation risk, and their time in the patch is longer when being as a group (Brown 1988 ).…”

Antelope space‐use and behavior indicate multilevel responses to varying anthropogenic influences in a highly human‐dominated landscape

“…Such a relationship between vigilance and group size has been shown in many species (Isvaran, 2007 ) and is thought to arise from the benefits of shared vigilance in larger groups. This reduction allows animals to allocate more time to other key activities, such as foraging (Roberts, 1996 ), and to increase daily activity levels (Ramirez et al, 2021 ).…”

Insights from a 31‐year study demonstrate an inverse correlation between recreational activities and red deer fecundity, with bodyweight as a mediator

“…(Broekhuizen et al, 2016). Hunting levels in the Veluwe area can be up to 9.48 ungulates km −2 year −1 (Ramirez et al, 2021).…”