Balancing food, activity and the dangers of sunlit nights

Abstract

Living in northern latitudes poses challenges to the animals that live in those habitats. The harsh environment provides a short breeding season where the sunlit summer nights provide little reprieve from visibility to predators and increased risk. In this paper, we tested the activity and food choice patterns of bank voles Myodes glareolus in early spring season, categorized by 18 h of daylight and 6 h of dusk in every day cycle. We found that territorial females showed a less predictable pattern of activity than males that were most active during the hours of dusk. The voles also showed preference to forage on high carbohydrate foods at sunset, while switching over to a more protein and fat-based diet towards sunrise. This shift is suggestive of a diet that is a direct adaptation to day-long fasts. Our results suggest a sensitive mechanism between food choice and predator avoidance in a system where light summer nights increase the predation risk considerably. Significance statement Bank voles, Myodes glareolus, are considered a model organism in ecological studies and have been used for studies of population cycles, predator-prey interactions and studies of territoriality with over a century of published records. In this study, we challenge two major preconceptions about these animals using behavioral bio-assays in a controlled environment. (1) We challenge the diurnal activity patterns of these rodents currently accepted to have a bi-modal distribution in summer months and show a unimodular activity pattern. And (2) we show that these animals are not opportunistic foragers but vary their diet to compensate for the stress of an extended daytime fast further supporting a nocturnal pattern of activity even in extreme sunlit nights where night lasts under an hour.

Foraging and Food Selection in a Desert Rodent: Diet Shifts of the Sandy Inland Mouse between Population Booms and Busts

“…Dietary shifts can occur quickly. For example, at high latitudes when days are long (18 h daylight) in summer, bank voles Myodes glareolus switch from selecting high carbohydrate foods at sunset to foods with higher protein and fat content near sunrise to prepare for the day-long fast [53]. Second, during bust periods, sandy inland mice retreat to small and spatially isolated patches of woodland located between the sand dunes and remain confined there until the arrival of drought-breaking rains [37].…”

Voles and weasels in the boreal Fennoscandian small mammal community: what happens if the least weasel disappears due to climate change?

“…In the nocturnal predator-prey interaction, a full moon decreases prey activity as it exposes them more to avian predation, which is documented in desert rodents, with no grass cover allowing shelter during moonlight (Brown et al 2001;Kotler et al 2010). Boreal bank voles have polyphasic activity patterns throughout the day and night (Ylönen 1988, however see Bleicher et al 2019). In a field study where we monitored boreal voles and weasels with radio-tracking in large enclosures, the voles carefully followed the resting times of weasels in their activity and decreased their activity as the weasels in the enclosure started to move again .…”

Landscape of fear in freshwater ecotones: How predation risk and light conditions affect mesopredator activity and foraging in springs

“…Both the diversity of the predator community and the features influencing predator activity and behaviour play major roles in affecting risk exposure and shaping LOF (Gaynor et al, 2019). As an example, predator diel activity patterns may strongly change the features of LOF (Bleicher et al, 2019; Laundre, 2010) with consequent repercussions on prey activity itself. This happens, for example, in streams where fire salamander larvae occur: some of their prey, such as mayfly larvae of the family Baetidae, are drifted more by water flow during the night, when salamanders seem more active, than during the day (Oberrisser & Waringer, 2011).…”