Rodents in open space adjust their behavioral response to the different risk levels during barn-owl attack

Shahaf Edut,David Eilam

doi:10.1186/1472-6785-3-10

Abstract

BackgroundPrevious studies have revealed that the response of prey species to predatory risk comprised either freezing (when the prey remained immobile), or fleeing (when it ran frantically in order to remove itself from the vicinity of the predator). Other studies, however, have suggested that the prey will adjust its behavior to risk level. The present study was designed to follow the attacks of a barn owl (Tyto alba) on common spiny mice (Acomys cahirinus) and social voles (Microtus socialis guntherei), in order to reveal the correspondence between the behavior of the owl, the risk level at each phase of the owl's attack, and the defensive behavior of the rodents.ResultsSpiny mice dramatically increased the traveled distance upon the appearance of the owl, and kept moving during its attack while taking long trajectories of locomotion. Defensive response in voles dichotomized: in some voles traveled distance dropped when the owl appeared, reaching zero during its attack. In other voles, traveled distance dramatically increased once the owl appeared and further increased under its attack. These defensive responses developed by gradual tuning of normal locomotor behavior in accordance with the level of risk.ConclusionsThe phenotypic difference in defensive behavior between voles and spiny mice probably stems from their different habitats and motor capacities. Agility and running capacity, together with a relatively sheltered natural habitat, make fleeing the most appropriate response for spiny mice during owl attack. Clumsiness and relatively limited motor capacities, together with an open natural habitat, account for the dichotomy to freezing or fleeing in voles. Thus, the apparent species-specific anti-predator response in spiny mice and voles is based on species-specific normal locomotor behavior, which depends on the species-specific ecology and motor capacity, and behaviors like defensive attack or escape jump that are specific to life threat. The latter behaviors are brief, and irregularly inlaid in the ongoing locomotor behavior. Finally, our results show that in both voles and spiny mice there is a gradual transition from normal to defensive behavior in accordance with the increase in risk level.

Highlights

Previous studies have revealed that the response of prey species to predatory risk comprised either freezing, or fleeing
Four sequential phases in owl attack Analysis of the videotaped owl attacks revealed three critical points: i) when the owl was first perceived by the rodent; ii) when the owl initiated its first attack on the rodent; and iii) when the rodent was caught
It should be noted that the change in the behavior of rodents upon owl appearance was abrupt and notable (See 2 and #2 with video-clips of the behavior during the four phases of owl attack in spiny mouse and vole)

Summary

Introduction

Previous studies have revealed that the response of prey species to predatory risk comprised either freezing (when the prey remained immobile), or fleeing (when it ran frantically in order to remove itself from the vicinity of the predator). A caged cat was placed next to a caged rodent, with direct visual and olfactory stimulation but without physical contact [11] This latter study and others on simulating threat were accompanied by adequate controls that unequivocally indicated that a predation risk had been perceived by the prey, they did not include a group with real encounters. This left open the question of when, how, and even whether the defensive patterns observed under simulation of predation occur under actual predation. The behavior of rodents was studied in non-sheltered space, since rodents were attacked and captured by owls more frequently in the open ([12])

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Results

Discussion

Conclusion