Boldness Behavior and Chronic Stress in Free-Ranging, Urban Coyotes (Canis latrans)
Katie Robertson, PhD
Advisor: Stanley D. Gehrt
Human activity and the development of cities have major impacts on local wildlife. Some populations, however, have adapted their behaviors to successfully live in proximity to people. Within any given species, there is often behavioral variation. Some previous studies have suggested that individual variation is at least partly due to the presence of behavioral syndromes (i.e., suites of correlated behaviors in response to a common stimuli). One commonly studied set of behaviors are those that fall along a bold-to-shy spectrum. Bold individuals are often more risk-prone, more exploratory, and less sensitive to external stressors than their shy counterparts. Behavioral syndromes imply that individuals are have innate, predispositions toward certain responses to external stimuli; behavioral plasticity is therefore limited under the behavioral syndromes paradigm. Limited plasticity can be beneficial in some situations, since it allows individuals to specialize in a particular response. Behavioral tendencies (e.g., boldness) are not necessarily efficient or safe in all situations, however. The environment may help to shape how prevalent certain behavioral syndromes are within a given population. In urban areas, the increased human activity, high level of habitat fragmentation and disturbance, and large quantities of novel resources (e.g., litter) may give bolder individuals multiple advantages. Shy individuals would likely have difficulty coping with the various stressors associated with urban life and would be less likely to find and benefit from novel, anthropogenic resources. In settings where coyotes are actively hunted, trapped, or hazed, however, bold indivdiduals that are more comfortable around people may ultimately be more likely to get involved in a human-coyote conflict. In every environment, there is a tradeoff between potential benefits and potential risks.
To determine if behavioral syndromes are present in free-ranging coyotes and examine the possible relationships between urbanization, behavior, and physiology, coyotes in the Greater Chicago Metropolitan Area were subjected to behavioral tests and tested for chronic stress. In my dissertation, I first provide an overview of some of the impacts of urban areas on wildlife and describe how wildlife sometimes respond to anthropogenic pressures. I also describe the possible link between behavior and physiology and highlight the need for more studies that incorporate both simultaneously.
My second chapter focuses on the results of flight initiation distance (FID) tests I conducted on free-ranging coyotes across Chicagoland’s urbanization gradient. Coyotes in more developed areas tended to have shorter FID, indicating a greater degree of boldness towards human approachers. Additionally, the starting distance from the coyote, the distance from the coyote’s resting place to the nearest road, and the average velocity of the approaching human were significant predictors of coyote FID. Flight initiation distances were consistent over time for individuals that were tested more than once, suggesting that coyote responses may reflect innate, individual variation in responses to risks rather than habituation over time.
In my third chapter, I report on novel object tests that I conducted on urban coyotes. A larger proportion of the coyotes in developed (i.e., urban and suburban) areas tended to be neophilic. A greater degree of neophilia is often associated with increased exploratory and bold behavior. Like FID, coyote responses to novel objects were influenced by the distance from the coyote to the nearest road. Individuals near roads may have been on the bold side of the bold-shy spectrum since, presumably, shyer individuals would have chosen to stay farther away from human activity in the first place. Alternatively, coyotes near roads could have been exposed to human presence and refuse along roadsides more frequently prior to testing and thus reacted less to our behavioral tests due to habituation. Further studies are needed to determine what role, if any, repeated exposures to human activity have on wildlife responses.
The fourth chapter discusses my finding from hair cortisol analyses that were conducted from coyote hair samples collected in the Chicago area. Contrary to our predictions, coyotes at highly urban sites (e.g., downtown Chicago) and coyotes in protected greenspaces outside of city limits (i.e., forest preserves) had similar cortisol levels. Coyotes in suburban areas had higher hair cortisol levels than coyotes in the other groups. It is possible that coyotes in the most urban areas tend to have bolder temperaments and have adapted so well to urban pressures that they exhibit attenuated hypothalamic-pituitary-adrenal (HPA) activity following exposure to each individual stressor. The combination of natural stressors and extra stressors from human presence and activity, however, may lead to urban coyotes being exposed to more stressors than forest preserve individuals. If urban coyotes are exposed to more stressors but respond less to each individual stressor, they may ultimately end up producing similar quantities of stress hormones as coyotes in more natural settings. The suburban animals were exposed to many of the same, or more, stressors as the urban individuals due to the types of human-dominated landscapes they were using. If suburban animals exhibit greater responses to stressors than urban animals and are exposed to more stressors than coyotes in natural areas, it follows that suburban animals may have greater hair cortisol concentrations overall. Other significant predictors of coyote hair cortisol concentrations included the coyote’s age, physical condition (especially if mange was present), and social status.
Lastly, I summarize overall findings of the study, compare and combine results from the different tests, describe possible implications of the study, and suggest some areas to focus on in future research. Collectively, my research provides evidence for the presence of behavioral syndromes in free-ranging coyotes. It also suggests that human activity and urbanization may be altering coyote behavior, and specifically coyote boldness. While increased boldness does not necessarily correlate to aggression, bolder coyotes could still contribute to greater incidences of human-wildlife conflicts. Learning more about the possible mechanisms behind coyote boldness behavior will be imperative for preventing and mitigating future conflicts as coyote behavior continues being shaped by urbanization.