Kathryn C. S. Yoshida, PhD 2012 Individuals differ in their foraging strategies, responses to predators, reactions to new environments, and daily interactions with conspecifics. When these differences are consistent over time and/or across contexts, they are often called temperament traits or behavior types. Biology has traditionally focused on species-typical adaptations, and either ignored or dismissed these within-species differences as insignificant. Recent research, however, has suggested that this variation between individuals may have significant ecological and evolutionary implications. Spotted hyenas have several distinct life stages and exhibit extremely complex social behavior, making them ideal subjects for temperament studies. First, I hope to determine the dimensions across which hyenas exhibit these individual differences, as well as determine the degree to which differences are domain-specific. I also plan to examine the proximate causes behind temperament traits, including physiological influences such as hormones and genes, as well as environmental effects. Finally, I will examine the effects of certain temperament traits on individual fitness. For example, do more exploratory males experience better success in dispersal? Do more aggressive females enjoy higher reproductive success? By investigating temperament traits in hyenas, I hope to clarify some of the mechanisms behind inter-individual differences, as well as determine the fitness consequences of various temperament traits in animal populations.