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.