Predator avoidance behaviour has been observed in many species and can strongly affect trophic interactions. Animals frequently adjust their response to predators in proportion to risk; however, when they are exposed to chronic predation risk, some animals reduce their antipredator responses in favour of resource acquisition. Animals that are subjected to predation pressure from multiple predator species may have to respond to different spatial and temporal distributions of risk; how they balance these risks will affect their choice of habitat or microhabitat patches. One species that is exposed to a wide range of predators is the pygmy salamander, Desmognathus wrighti. These miniaturized terrestrial plethodontids spend their entire life on the forest floor where they are exposed to a diversity of predators. We examined pygmy salamanders' ability to avoid potential predators based on the presence of substrate-borne chemical cues. The predator species included ground beetles (Carabidae: Pterostichus), Jordan's salamanders, Plethodon jordani, and ring-necked snakes, Diadophis punctatus. The ring-necked snake is a trophic specialist feeding on salamanders while the beetles and Jordan's salamanders are generalist predators. The pygmy salamanders were also exposed to chemical alarm cues from a congeneric salamander (Desmognathus fuscus) and odours from two unfamiliar species: corn snakes (Pantherophis gutattus) and herbivorous desert tortoises (Gopherus agassizii). We used a hierarchical Bayesian beta regression with a repeated measures design to model proportion of time spent in each treatment. Compared to controls, pygmy salamanders exhibited strong aversion to fed ring-necked snakes, a moderate avoidance of unfamiliar odours and a slight attraction to scents from the two common generalist predators. Our results suggest that pygmy salamanders accept modest risk from common generalist predators but avoid less common, specialist predators and unfamiliar species.
- Bayesian beta regression
- predator avoidance
- risk allocation hypothesis
- threat sensitivity hypothesis