Maximising survival by shifting the daily timing of activity

Abstract

Maximising survival requires animals to balance the competing demands of maintaining energy balance and avoiding predation. Here, quantitative modelling shows that optimising the daily timing of activity and rest based on the encountered environmental conditions enables small mammals to maximise survival. Our model shows that nocturnality is typically beneficial when predation risk is higher during the day than during the night, but this is reversed by the energetic benefit of diurnality when food becomes scarce. Empirical testing under semi‐natural conditions revealed that the daily timing of activity and rest in mice exposed to manipulations in energy availability and perceived predation risk is in line with the model’s predictions. Low food availability and decreased perceived daytime predation risk promote diurnal activity patterns. Overall, our results identify temporal niche switching in small mammals as a strategy to maximise survival in response to environmental changes in food availability and perceived predation risk.

Increased Diurnal Activity Is Indicative of Energy Deficit in a Nocturnal Mammal, the Aardvark

“…The shift to diurnality in response to an energy deficit is more pronounced under cold conditions (Van der Vinne et al, 2014), when metabolic costs associated with thermoregulation are highest. Such plasticity of the mammalian circadian system is thought to be an adaptive mechanism that allows nocturnal mammals to conserve their energy (up to 10% in some species, Van der Vinne et al, 2015), thereby enhancing their survival (Van der Vinne et al, 2019). However, if the shift to diurnality occurs when ambient temperatures are high (Van der Vinne et al, 2014), as it did in our aardvark during the summer drought, it would increase their exposure to heat.…”

“…Because the radiant heat sink of the night sky is unlikely to change much with climate change, warmer air temperatures at night are unlikely to offset the energetic cost of reduced resource availability. Instead, as resources become limited, the ability to keep warm at night using metabolic heat might be compromised, such that some nocturnal species may increase their diurnal activity to reduce the energy cost that would have been incurred through being active at night (Van der Vinne et al, 2019). The trade-off then is that they have to acquire sufficient resources while exposed to daytime heat loads, with air temperatures increasing under climate change.…”

Ecological impacts of human‐induced animal behaviour change

“…While changes in species co‐occurrence could potentially impact various ecosystem functions, these ecological consequences have not been documented empirically beyond implications for individual species’ survival (Vinne et al . 2019). Existing studies have largely measured shifts in activity levels, but not in ecologically transferable behaviours (e.g.…”

Humans disrupt access to prey for large African carnivores

“…Wildlife can adaptively respond to their environment by modifying their diel activity and partitioning time to maximize survival and limit exposure to risks, producing a species’ temporal niche ( Bennie et al, 2014 ; Vinne et al, 2019 ). Prey commonly employ predator avoidance strategies along the temporal niche axis ( Kohl et al, 2019 ), which is contrasted by predators selecting for temporal activity patterns that maximize hunting success and minimize competitive encounters ( Cozzi et al, 2012 ; Dröge et al, 2017 ).…”

“…Specifically, human presence engenders shifts in diel activity patterns across guilds, altering their temporal niche to incorporate avoidance of human encounters ( Gaynor et al, 2018 ; Frey et al, 2020 ). Human activities concentrated in the day and predator activity at night reduce the availability of temporal refugia for prey from risky encounters, and can constrain species’ abilities to optimize activity along the temporal niche axis ( Kohl et al, 2019 ; Vinne et al, 2019 ). As predator and prey species alter their diel activity to adaptively respond to human presence, predator-prey temporal overlap and resulting encounter rates are likely to be changed ( Patten et al, 2019 ), thus altering predator access to a suite of prey resources ( Figure 1 ).…”