The effects of predator odors on stress response and reproduction in Norway rats: A review

Norway rat (Rattus norvegicus) is an invaluable laboratory model organism as well as one of the most common rodent pest species. The currently used rodenticides have several significant drawbacks: toxicity to humans and non-target species, environmental harm, the development of avoidance reactions and genetic resistance to the applied substances in rat populations. One of the proposed approaches for rodent pest control is based on natural ways, such as predation, which could be emulated by predator scents. In rodents, olfaction plays a key role in danger recognition, especially in detection of potential predator. Predator odors can activate the hypothalamic-pituitary-adrenal (HPA) axis via central nervous system and thus induce the release of stress hormones. A well-documented suppression of reproduction under psychosocial stress appears to be associated with specific interactions of HPA axis and hypothalamus-pituitary-gonadal (HPG) axis. Hereby we review research on the influences of predator chemical cues on stress response and reproduction in Norway rats with a special focus on long lasting and chronic effects. We describe the effects of predator odors of fox (Vulpes vulpes), ferret (Mustela putorius) and domestic cat (Felis catus) in detail. Assessment of reproductive success in rats may be treated as a robust experimental model to evaluate ecologically relevant stress effects of predator odors. Application of this approach could promote development of environmentally friendly methods to control rat population density.