UC Davis

Animals have always had to deal with a rich array of challenges. Juggling the sometimesconflicting demands of these multiple stressors has only become increasingly challenging as the intensity, pattern, and types of stressors that individuals have to deal with have changed with human induced rapid environmental change. Previous experience with a specific challenge has the potential to prime responses to that same stressor in the future, but experiences may also alter average behavior as well as behavioral variation and correlations in a way that influences responses to a variety of future challenges. I examined how experience with stressors at different life stages influences the behavior of the invasive Western mosquitofish (Gambusia affinis). I first exposed mosquitofish fry to either pulses of warm water, predatory bass cue, both or neither during the first month of their life and examined how these experiences affected responses to known or novel predators at standard or elevated temperatures at five months (Chapter 1). There was evidence for priming both within- and across-stressors in responses to bass cue. Responses to exotic trout cue were more complex and depended on an interaction between developmental treatment and assay temperature. I then assessed how these developmental experiences influenced average activity in the absence of predators and within- and among-individual variance at standard or elevated temperatures (Chapter 2). I found a slight trend for fish to be more active later in life when exposed to alternating predator cue and warm water during development. At standard temperatures, fish exposed to either pulses of warm water or predator cue had lower within-individual variance than control fish. At elevated temperatures, there was a trend for control fish to exhibit lower amongindividual variation than fish exposed to one or both stressors. While exposure to stressors during development tended to influence variance components in such a way as to increase repeatability, results were different for adult exposure to predator cues. I exposed adult mosquitofish to visual and olfactory predator cues for one month and then tested activity, shoaling and exploratory behavior three times per fish (Chapter 3). While average behavior was not affected for any of these measures, fish exposed to predators were less repeatably in terms of activity and shoaling than control fish. Additionally, control fish exhibited correlations between activity and shoaling and activity and exploration that were not present in predator exposed fish. Collectively, these results suggest that exposure to stressors influences behavioral variance but that when that exposure happens may be critically important to determining whether it increases or decreases repeatability. If animals integrate experiences with stressors over the course of their lives to predict whether future environments are likely safe or dangerous, when experiences with stressors occur and whether that experience is consistent over the course of the life may help to explain differences in behavioral variation.