Antipredator response of Eurycea nana to a nocturnal and a diurnal predator: avoidance is not affected by circadian cycles of predators

Abstract

Both predators and prey exhibit cyclic shifts in activity throughout the day, which should cause the threat posed by predators to change in a recurrent pattern. If the threat posed by a predator is dependent on their circadian foraging cycle, prey may respond more or less intensely to predators at different times of day, thereby maximizing the effectiveness and efficiency of avoidance behaviors. We examined whether predator-naïveEurycea nana, a federally threatened neotenic salamander, exhibits a different antipredator response to chemical cues of a diurnal predator, the green sunfish (Lepomis cyanellus), and a nocturnal predator, the red swamp crayfish (Procambarus clarkii). We predicted thatE. nanawould show more intense antipredator responses (reduced activity) to a diurnal predator during the day and to a nocturnal predator at night. We found that, although there was significant antipredator behavior ofE. nanatoward sunfish, there was no detectable response to crayfish and no effect of time of day on responses to either predator, suggesting that eitherE. nanadoes not innately exhibit circadian patterns in avoidance of these species or that those patterns were undetectable in this study. Future studies should examine whether experience with predators may cause these salamanders to be more sensitive to the diel variation in threat, as has been found with some other amphibians and fish. Due to the threatened nature of this species, understanding the factors that influence antipredator behavior are crucial for management.