Wild Norway Rats Do Not Avoid Predator Scents When Collecting Food in a Familiar Habitat: A Field Study

Rafał Stryjek,Grzegorz R Juszczak,Ewelina Spaltabaka-Gędek,Berenika Mioduszewska

doi:10.1038/s41598-018-27054-4

Abstract

The ability to avoid predators is crucial to wild prey animals’ survival. Potential danger is signalled, among others, by the presence of predator scents. These odors are used in research both to trigger and to study fear reactions in laboratory animals; they are also employed as repellents against pest rodent species. In our study, we assessed nine predator-derived odors for their effectiveness in eliciting avoidance responses in a free-living colony of Norway rats (Rattus norvegicus). The rats were studied in a field setting. Food was put in two compartments inside the experimental pen: in one of them, predator scent was introduced on experimental days. The rats did not avoid boxes with predator odor and did not display an increased latency of food-carrying behavior or any other fear-related behavior, such as freezing or increased grooming. The results confirm the hypothesis that the foraging of rodents in a well-known territory and in relative proximity to burrows and other shelters is not affected by indirect cues of predation risk, such as the presence of predator urine or feces. We have also concluded that in a well-established colony living in a familiar territory, predator scent holds little promise as rodent repellent.

Highlights

It is possible that an aversive response towards predator odors might only occur if the predator and prey share a long evolutionary history and, the prey becomes genetically programmed to avoid the odors of sympatric predators[18]
Other studies demonstrate that even certain pairings of prey and predator species without a shared evolutionary history may result in predator odor avoidance[2,20] and that reduced alien predation pressure after the initial impact might result in the selection for discriminating and avoiding danger in otherwise naïve species[21]
The statistical analysis commenced with a comparative examination of the rats’ behavior in the experimental compartment and in the control compartment, where the cardboard bottom of the bowl was soaked with water instead of predator scent

Summary

Introduction

It is possible that an aversive response towards predator odors might only occur if the predator and prey share a long evolutionary history and, the prey becomes genetically programmed to avoid the odors of sympatric predators[18] (interestingly, a decline in risk-sensitive behavior of prey species seems to be a rapid response to the predator population decline[19]). For these reasons, the negative results obtained in predator odor avoidance studies might reflect the mismatch of predator and prey configurations. Rats’ reactions to predator odors provide insights into the innate fear reactions in animals, as well as into the function of the hypothalamic–pituitary–adrenal axis (HPA axis), which coordinates the function of the sympathetic nervous system[22]

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Conclusion