Effects of predation risk on the body mass regulation of growing wood mice

Abstract

Body mass in wild animals has been suggested to be regulated by the opposing fitness consequences of variation in body size (and fat storage) for starvation and predation risk. Many studies of adult mammals and birds have broadly confirmed the predictions of this model. However, relatively few studies have addressed the potential role of such trade-offs during early phases of development when animals are growing. Similarly, studies of the impact of high-fat diets on wild small mammals generally show a resistance to weight gain. But whether growing animals are similarly resistant is unclear. In this study, weaned wood mice (Apodemus sylvaticus) were exposed to a high risk of predation, simulated by the broadcasting of owl calls, for 66 days during which body mass and energy intake were monitored. We hypothesized that if the risk of predation plays a role in regulating body mass during this phase then animals growing under predation risk would grow less. We found female (but not male) mice exposed to the predation risk treatment had lower growth rates and ended the experiment lighter; however, variations in energy intake and resting metabolic rate did not explain the observed differences. Feeding on high-fat diet resulted in individuals with higher body mass. Females reached their adult size earlier than males and were more responsive to the predation risk treatment when feeding on high-fat diet. Our data suggest males body mass to have fitness consequences on social dominance and reproductive success not accounted for in the simple starvation-predation trade-off model.

Predation stress experienced as immature mites extends their lifespan

“…The exposure to the predators, weasels ( Mustela nivalis ) and stoats ( M. erminea ), slowed the maturation rate of bank voles ( Clethrionomys glareolus ) and also delayed their reproduction (Heikkilä et al 1993 ). Weaned females of wood mice ( Apodemus sylvaticus ) had lower growth rates and body mass under predation stress simulated by constant broadcasting of owl calls (Monarca et al 2020 ). Moreover, there was also compensatory effects in the early life of predatory mites ( Phytoseiulus persimilis ) under transient intraguild predation (IGP) risk—the mites exposed to IGP risk during the larval stage delayed larval development but increased foraging activities and accelerated development during the next stage, which is the protonymph (Walzer et al 2015 ).…”

Semi‐intensive shrimp farms as experimental arenas for the study of predation risk from falcons to shorebirds

“…Thus, during periods of high‐energy requirements, prey must trade off between risk of starvation and predation and feed in profitable but dangerous habitats (Houston & McNamara, 1999 ; Lima & Dill, 1990 ). This starvation–predation trade‐off in vertebrates is well known, with most studies measuring energy management in prey exposed to different experimental set‐ups (see recent work in Broggi et al., 2019 ; Monarca et al., 2020 ). However, mainly because of the limitations imposed by the logistics of observing predation events in the wild, particularly in systems involving birds both as predators and prey, the study of predator–prey dynamics would benefit from the identification of opportunities to document both predation events and how prey cope with this trade‐off in environments of predictable food supplies.…”

Larger guts and faster growth in mice selected for high basal metabolic rate

“…Postnatal growth in birds and mammals is the time of highest vulnerability and shapes the organisms' future outcomes [1][2][3]. It is also the period of highest energy demands, relatively much higher than those of the resting state of adults [4].…”