Multitasking and eavesdropping in cotton rats foraging under predation risk

Abstract

Acquiring information regarding resource patchiness can reduce uncertainty in foraging decisions. However, information on patch quality may come at a cost if, when foraging within a risky (micro)environment, foragers allocate more attention to predator detection and consequently allocate less attention to assessing resource patchiness, that is, the cost of multitasking. Foragers may also benefit from alternative means of assessing predation risk that may not entirely conflict with foraging (e.g., vigilance postures are often incompatible with foraging and thus patch assessment). In particular, prey may eavesdrop on the alarm calls of heterospecifics that provide public information about the presence of a potential predator. To investigate these 2 effects, multitasking and eavesdropping, we used giving-up densities (GUDs) to quantify the ability of cotton rats (Sigmodon hispidus) to assess resource heterogeneity (patchiness) under different regimes of predation risk. GUDs were collected over a distance from burrow gradient representing increasing predation risk and provide evidence that risk affected cotton rats' patch assessment abilities in 2 ways. First, under greater risk, cotton rats reduced their foraging time (i.e., higher GUDs) and hence time available for patch assessment. Second, when the effects of foraging time are removed, cotton rats still showed poorer patch assessment (i.e., ability to equalized GUDs between resource patches) in riskier habitats, that is, the cost of multitasking. In the second experiment, we demonstrate that cotton rats eavesdrop on the alarm vocalizations of blue jays and increase their perceived risk of predation during jay alarms, while simultaneously compromising their patch assessment performance. © 2010 The Author.