Avian and rodent responses to the olfactory landscape in a Mediterranean cavity community

Animals rely on cues informing about future predation risk when selecting habitats to breed in. Olfactory information may play a fundamental role in the assessment of predation threats, because predators produce characteristic body odours, but the role of odours in habitat selection has seldom been considered. Here, we test whether fear of predation induced by odour cues may affect the settlement pattern of a Mediterranean cavity-dependent community of rodents and non-excavator hole-nesting birds. To test this hypothesis, we experimentally manipulated the perception of predation risk on a scale of patch by applying either odours of a carnivore predator (risky odour treatment), lemon essence (non-risky odour treatment) and a control non-odorous treatment and studied bird and rodent settlement patterns. Nest-box occupation probability differed across treatments so that species in the community settled in more numbers in control than in non-risky and than in risky odour-treated nest boxes. Concerning settlement patterns, control nest boxes were occupied more rapidly than nest boxes with odour information. Birds and rodents settled earlier in control than in risky odour-treated nest boxes, but their settlement pattern did not significantly vary between risky odour and non-risky odour-treated nest boxes. Our findings demonstrate that olfactory cues may be used to assess habitat quality by settling species in this community, but we cannot pinpoint the exact mechanism that has given rise to the pattern of preference by nest boxes.