This dissertation describes a series of four studies on cognitive aging, working memory, and cognitive flexibility in dogs (Canis lupus familiaris) and their wild relatives. In Chapters 2 and 3, I designed assessments for age-related cognitive deficits in pet dogs which can be deployed rapidly using inexpensive and accessible materials. These novel tests can be easily implemented by owners, veterinarians, and clinicians and therefore, may improve care for elderly dogs by aiding in the diagnosis of dementia. In addition, these widely deployable tests may facilitate the use of dementia in pet dogs as a naturally occurring model of Alzheimer’s Disease in humans.In Chapters 4 and 5, I modified one of these tests to demonstrate for the first time that coyotes (Canis latrans) and wolves (Canis lupus lupus) develop age-related deficits in cognitive flexibility. This was an important first step towards differentiating between the genetic and environmental components of dementia in dogs and in turn, humans. Unexpectedly, I also detected cognitive deficits in young, adult dogs and wolves but not coyotes. These finding add to a recent shift in understanding cognitive development in dogs which may improve cognitive aging tests as well as training, care, and use of working and pet dogs. These findings also suggest that the ecology of coyotes may select for flexibility earlier in development. In Chapter 5, I piloted the use of the same cognitive flexibility test for red and gray foxes so that future studies may test for lifespan changes in the cognition of small-bodied captive canids. More broadly, this paradigm may accommodate physical and behavioral differences between diverse pet and captive animals. In Chapters 4 and 5, I examined which ecological traits drive the evolution of behavioral flexibility and in turn, species resilience. I found that wolves displayed less flexibility than dogs and coyotes suggesting that species which do not rely heavily on unstable resources may be ill-equipped to cope with human habitat modification. Ultimately, this comparative work may help conservation practitioners to identify and protect species that cannot cope with rapid and unnatural environmental change.

Understanding the evolution of cooperation is a central goal in animal behavior research. In several animal taxa, socioecological environments that promote frequent interaction and social tolerance have favored the evolution of strong, equitable, and enduring social bonds, which facilitate cooperation and confer fitness benefits. Among males, strong bonds are believed to have evolved in the context of long-term alliances that help individuals compete for dominance status and mating access, but it remains unclear in some species what factors predict the strength and quality of bonds and how sociality relates to adaptive outcomes. To fill these gaps, this dissertation presents three studies of male chimpanzees at Gombe National Park, Tanzania, addressing the form, function, and development of male social relationships. Maternal brothers who were close in age formed the strongest bonds, strong bonds were associated with more reciprocal grooming relationships, and the strength of bonds were stable for an average of two years, while lasting up to 13 years. For other males, similarity in age and rank had negligible effects on bond strength, suggesting that bond strength results from a more complex process than a simple accounting of basic characteristics. Additionally, these social bonds, identified using both association in small groups and grooming activity, showed positive relationships with changes in dominance. In combination with prior studies, these results suggest that having strong bonds is a valuable strategy for achieving higher rank and, ultimately, increased reproductive success. Lastly, immature males who associated more with particular adult males while growing up were more likely to both associate and groom with those same males after entering adulthood. By contrast, association rates among immature male peers were not correlated with bond strength as adults. These findings suggest that the persistence of social relationships beyond those between mothers and offspring are more likely to evolve in long-lived species where young males enter adult hierarchies comprised of stronger or more socially experienced competitors. Overall, these studies reinforce the notion that social bonds are a chimpanzee universal, fill in gaps about the relationship between sociality and fitness, and emphasize the utility of a prolonged immature period.

ABSTRACT

Domestic dogs have assisted humans for millennia. However, the extent to which these helpful behaviors are prosocially motivated remains unclear. To assess the propensity of pet dogs to spontaneously and actively rescue distressed humans, this study tested whether sixty pet dogs would release their seemingly trapped owners from a large box. To examine the causal mechanisms that shaped this behavior, the readiness of each dog to open the box was tested in three conditions: 1) the owner sat in the box and called for help (“Distress” test), 2) an experimenter placed high-value food rewards in the box (“Food” test), and 3) the owner sat in the box and calmly read aloud (“Reading” test).

Dogs were as likely to release their distressed owner as to retrieve treats from inside the box, indicating that rescuing an owner may be a highly rewarding action for dogs. After accounting for ability, dogs released the owner more often when the owner called for help than when the owner read aloud calmly. In addition, opening latencies decreased with test number in the Distress test but not the Reading test. Thus, rescuing the owner could not be attributed solely to social facilitation, stimulus enhancement, or social contact-seeking behavior.

Dogs displayed more stress behaviors in the Distress test than in the Reading test, and stress scores decreased with test number in the Reading test but not in the Distress test. This evidence of emotional contagion supports the hypothesis that rescuing the distressed owner was an empathetically-motivated prosocial behavior. Success in the Food task and previous (in-home) experience opening objects were both strong predictors of releasing the owner. Thus, prosocial behavior tests for dogs should control for physical ability and previous experience.