Meeting Abstract

85.1  Friday, Jan. 7  Invader danger: lizards faced with novel predators exhibit altered behavioral stress responses LANGKILDE, T*; TROMPETER, W. P.; Penn State University; Penn State University tll30@psu.edu

Animals respond to stressors by producing glucocorticoid stress hormones, such as corticosterone (CORT). These hormones are involved in triggering a behavioral response, facilitating an individual’s survival in the face of a threat. To be adaptive, the nature of an animal’s behavioral response to elevated CORT levels should be matched to the particular threats they face. As a result, the behavioral threat response may differ among populations of a single species. Invasive species impose novel pressures on native populations, which may select for a shift in their behavioral response to elevated CORT levels. We tested whether population level exposure to the novel predatory threat imposed by the invasive fire ant (Solenopsis invicta) affects the behavioral response of the native eastern fence lizard (Sceloporus undulatus) to elevated CORT levels. Lizards from a natural site that has not yet been invaded by fire ants responded to experimentally elevated CORT levels by hiding. This threat-response likely provides a survival advantage for lizards faced with native predators (e.g. birds and snakes) within natural populations. Lizards from a fire ant invaded site showed the opposite response; spending more time moving and up on the basking platform when their CORT levels were elevated. Use of basking platform likely reflects a refuge-seeking behavior, rather than thermoregulatory activity, as selected body temperatures were not affected by CORT. Fleeing off the ground may prove more effective than hiding for lizards that regularly encounter small, terrestrially-foraging fire ant predators. This study suggests that invasive species may alter the relationship between the physiological and behavioral threat response of native species.