Predator odors from various sources (e.g. fur/skin, urine, feces) provide prey animals valuable information that allows them to gage potential environmental threat via the detection of semiochemicals called kairomones. However, studies in rodents have revealed inconsistent and often conflicting results, which may occur from any combination of factors, including source and freshness of the odorant, sex, and genetic strain of the prey animal and/or predator. Regardless of cause, few odorants tested, if any, have lived up to the potent unconditioned predator odor stimuli - cat fur/skin odor - that induces a complete profile of innate unconditioned defensive behaviors (e.g., avoidance, risk assessment and freezing) and produces rapid aversive conditioned responses, both of which are sensitive to standard anxiolytic/anxiogenic drugs. Therefore, the present study investigated the effectiveness of coyote urine and 2-phenylethylamine (PEA), two commercially available predator odor cues, in satisfying the first of these criteria in predator odor naïve, adult male Long-Evans hooded rats. The data revealed that coyote urine, but not PEA, was effective in inducing a complete profile of anti-predator defensive behaviors characterized by avoidance, risk assessment, freezing and a reduction in exploratory behavior. We conclude that commercially available coyote urine satisfies the first criterion of a defense inducing unconditioned predator odor stimulus. In order to fully validate the use of coyote urine as an anxiety- and/or fear-like threat stimulus, future research needs to examine whether it produces aversive conditioning and whether the defensive profile induced by the odorant responds to standard anxiolytic drugs.
Keywords: Anxiety; Defense; Fear; Predation; Predator odor.
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