Acute physiological response by the plethodontid salamander Eurycea cirrigera (Southern Two-lined Salamander) to predation stress from alarm chemicals and predator kairomones

Abstract

Plethodontid salamanders may reduce predation risk via behavioral responses to predator kairomones and alarm chemicals from injured salamanders. However, it not known whether such predator cues prompt acute physiological responses, which may enhance arousal and the physical ability to escape from a predator. I examined whether predator chemical cues elicit an acute cardiac response in Eurycea cirrigera (Green, 1831) (Southern Two-lined Salamander). I compared heart rates before and after exposure to the odor of the large predatory Pseudotriton ruber (Sonnini de Manoncourt and Latreille, 1801) (Red Salamander) and exposure to alarm chemicals from homogenized skin of conspecifics. For two controls, I compared heart rates before and after exposure to the odor of live conspecifics and the odor of the large non-predatory Plethodon mississippi Highton in Highton, Maha and Maxson, 1989 (Mississippi Slimy Salamander). Compared with resting values, heart rates significantly increased in response to predator kairomones (mean rate increased 10.9% after 2 min and 12.7% after 5 min) and alarm chemicals from conspecifics (mean rate increased 12.0% after 2 min and 14.5% after 5 min). In contrast, heart rates after exposure to each control odor did not significantly differ from resting values. Results demonstrate an acute cardiac response to chemical cues indicative of either a predator or a predation event.