Abstract
BackgroundMany animals live in environments where different types of predators pose a permanent threat and call for predator specific strategies. When foraging, animals have to balance the competing needs of food and safety in order to survive. While animals sometimes can choose between microhabitats that differ in their risk of predation, many habitats are uniform in their risk distribution. So far, little is known about adaptive antipredator behavior under uniform risk. We simulated two predator types, avian and mammalian, each representing a spatially uniform risk in the artificial resource landscapes. Voles served as experimental foragers.ResultsAnimals were exposed to factorial combinations of weasel odour and ground cover to simulate avian and/or mammalian predation. We measured short and long term responses with video analysis and giving-up densities. The results show that previously experienced conditions cause delayed effects. After these effects ceased, the risks of both types of predation caused a reduction in food intake. Avian predation induced a concentration on a smaller number of feeding patches. While higher avian risk caused a delay in activity, the weasel odour shortened the latency until the voles started to be active.ConclusionWe show that the voles differed in risk types and adjusted their feeding strategies accordingly. Responses to avian and mammalian risk differed both in strength and time scales. Uniformity of risk resulted in a concentration of foraging investment and lower foraging efficiency.
Highlights
Many animals live in environments where different types of predators pose a permanent threat and call for predator specific strategies
We show that the voles differed in risk types and adjusted their feeding strategies
Delayed effects as a result of predation risk allocation In the first observation period (1st observation periods (OP)) of a treatment, food intake and the number of trays used were strongly influenced by the relative risk of the previous treatment and interaction between the current and previous treatments (Table 1)
Summary
Many animals live in environments where different types of predators pose a permanent threat and call for predator specific strategies. While animals sometimes can choose between microhabitats that differ in their risk of predation, many habitats are uniform in their risk distribution. Animals can reduce activity, which lowers the energetic reserves of the individual [13]; if high risk is frequent or persistent, animals still need to feed and cannot continually avoid the risky periods [9]. In these cases, they should either posses permanent defences
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