Theses and Dissertations Collection

Boldness is an axis of personality defined by the propensity to take risks. As a personality, behaviors associated with boldness are highly consistent within individu- als across different time scales. Because there is considerable variation within and between populations, behavioral ecologists have long been interested in boldness behaviors and their relationship with fitness. One of the most noticeable examples of boldness variation between populations is between wild and captive-bred stocks. Captive or domesticated individuals tend to show reduced fear and take more risks than wild individuals, and this pattern has been observed repeatedly across a variety of animal species.

My work in this dissertation is focused around the impact that environmental vari- ables have on the evolution of boldness behaviors. Some variables, such as predation pressure, affect the fitness landscape and evolutionary trajectory of behaviors along the bold-shy continuum. Using an agent-based simulation, I show that differences in predation pressure is a likely cause of of the patterns we observe between wild and domestic populations.

Other variables, such as complexity in the environment, can have a plastic effect on the development and expression of boldness behaviors. I test this hypothesis with a zebrafish model and show that early experience to complexity can affect boldness behaviors later in life, but the effect is most pronounced in males over females.

In addition, boldness behaviors display a high degree of sexual dimorphism in zebrafish. I test whether this might affect pharmaceutical responses to the anxiolytic substances nicotine and fluoxetine. While I find no sex-specific effects of each drug, I attribute this to observing no sex differences in the control, suggesting that sex differences in our sample might not have been present.

Because boldness is associated with domestication and adaptation to captivity, these behaviors are of interest to conservation and wildlife management efforts. With captive breeding and rearing programs used to mitigate population loss, care must be taken to ensure that we do not produce individuals that are maladapted for reintroduction to the natural environment.