REVIEW The ethological relevance of predator odors to induce changes in prey species Ibrahim M. Hegab & Shushu Kong & Shengmei Yang & Walaa I. Mohamaden & Wanhong Wei Received: 26 August 2013 /Revised: 19 March 2014 /Accepted: 28 March 2014 # Springer-Verlag Berlin Heidelberg and ISPA 2014 Abstract Predator odors are non-intrusive naturalistic stressors of high ethological relevance. Prey species show specific adaptations that allow recognition, avoidance, and defense against predators. For many mammalian species, this includes sensitivity towards predator-derived odors. The typ- ical sources of such odors include predator skin and fur, urine, feces, and anal gland secretions. Avoidance of predator odors has been observed in many mammalian prey species including rats, mice, and voles. Field and laboratory studies show that predator odors have distinctive behavioral effects which in- clude (1) inhibition of or decreased activity; (2) suppression of non-defensive behaviors such as foraging, feeding, and grooming; and (3) shifts to safe habitats or secured locations where such odors are not present. Chronic exposure to pred- ator odor may elicit one of two controversial processes: sen- sitization and habituation. Some studies have suggested that chronic exposure to predator odors may induce behavioral sensitization while others stated little or even no habituation at all. Finally, prey species respond variably to different de- grees of threats, and the odor intensity is a key factor to determine the “optimal” behavioral response. Future research should aim at linking behavioral and neuroendocrine changes for a better understanding of predator–prey interactions. Keywords Prey . Predator . Behavioral . Responses . Chronic . Odor . Intensity Introduction In nature, animals are exposed to a broad array of threats and dangers. Among these threatening factors, predators are the most intensely investigated. Prey animals exhibit a variety of primary passive adaptations to avoid capture, as well as second- ary mechanisms to actively defend themselves from predators (Luttbeg and Trussell 2013). These defensive mechanisms may be morphological (e.g., spines and armor), physiological (e.g., toxins), related to life histories (e.g., delayed breeding), or behavioral (i.e., predator avoidance and anti-predator behav- iors). Changes in behavior such as reduced activity and shelter seeking reduce the probability of encounters between a predator and prey, whereas morphological defenses reduce the probabil- ity of a successful predatory attack once a prey has been local- ized. Most commonly, species have evolved a suite of behav- ioral anti-predator adaptations that involve tradeoffs and costs. Therefore, one would expect that these behavioral anti-predator responses are used only when an animal has an accurate assess- ment of the current predation risk and, thus, of the benefits of the defense (Dielenberg and McGregor 2001; Kavaliers and Choleris 2001). Predation involves at least five strategies: detec- tion, identification, approach, subjugation, and consumption (Schmitz et al. 2013). Anti-predator defense mechanisms aim at interrupting this sequence. This entails, at minimum, detection and identification of the predator and the initiation and expres- sion of adaptive defensive behaviors. A number of studies have highlighted the changes in the behavioral defenses that facilitate avoidance of potential predators following exposure to predator odors. This includes a large number of field studies, as well as a smaller number of laboratory studies in which a “micro-world” simulation of the field has been constructed (Dielenberg and McGregor 2001). In laboratory studies, acute exposure of rats I. M. Hegab Department of Animal Hygiene, Zoonosis and Animal Behavior and Management, College of Veterinary Medicine, Suez Canal University, Ismailia, Egypt S. Kong : S. Yang : W. Wei (*) Department of Animal Behavior, College of Bioscience and Biotechnology, Yangzhou University, Yangzhou 225009, Jiangsu, China e-mail: whwei@yzu.edu.cn W. I. Mohamaden Department of Animal Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou 225009, Jiangsu, China acta ethol DOI 10.1007/s10211-014-0187-3