The question of how intelligence evolves across the animal kingdom remains unresolved despite more than a century of intensive research. The Social Intelligence Hypothesis (SIH) predicts a primarily social function of intellect whereas the Cognitive Buffer Hypothesis (CBH) suggests that intelligence is most adaptive for dealing with environmental novelty and change. Recently, there has been growing recognition of the value of intraspecific studies of wild, free-ranging populations because they allow researchers to examine the correlates of cognitive variation in an ecologically valid context, and also to examine the fitness consequences of this variation. In my dissertation, I examine the causes and consequences of intraspecific variation in behavioral flexibility in wild, free-ranging spotted hyena (Crocuta crocuta) populations. Behavioral flexibility is the ability to adaptively modify a behavior as current circumstances demand and, akin to fluid intelligence in humans, behavioral flexibility is thought to be an important aspect of intelligence across non-human animals. Spotted hyenas show a great deal of intraspecific variation in behavioral flexibility and persist under a diversity of socio-ecological conditions, making them an ideal model organism for testing hypotheses about the evolution of intelligence with the intraspecific approach. In Chapter One, I review hypotheses for the evolution of intelligence and the methods used to measure intelligence across animal taxa. Next, in Chapters Two and Three, I present evidence for the validity and reliability of apparatus used to measure behavioral flexibility by examining the individual traits that predict high behavioral flexibility and individual consistency in performance. Next, in Chapter Four, I examine the social correlates of behavioral flexibility. My results reveal that socially low-ranking hyenas that live in larger groups have greater behavioral flexibility and that hyenas of any rank that grow up in larger cohorts have greater behavioral flexibility, a result that supports predictions of the SIH. In Chapter Five, I examine the ecological correlates of behavioral flexibility by comparing behavioral flexibility across populations of hyenas experiencing varying degrees of urbanization. Urbanization causes widespread environmental change and introduces a high degree of novelty into habitats; however, my results reveal that the degree of urbanization is negatively correlated with behavioral flexibility, which challenges the CBH. Finally, I examine the fitness consequences of behavioral flexibility in Chapter Six. My results reveal that behaviorally flexible females have lower offspring survivorship but produce significantly more cubs annually than behaviorally inflexible females, which suggests there may be important trade-offs with regards to behavioral flexibility. In sum, my research demonstrates that the intraspecific approach is a powerful tool for understanding how and why behavioral flexibility evolves. My results generally support the SIH and suggest that social living is a key correlate of behavioral flexibility in spotted hyenas. However, it appears that high behavioral flexibility in spotted hyenas may have also been an important factor in facilitating their adaptation to urban environments. Urbanization is putting an increasing number of species at risk globally, and understanding how or why some animals adapt, while others go extinct, is crucial for wildlife conservation.
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