Extreme life histories are associated with altered social behavior and cortisol levels in shelter dogs

High-volume breeders often produce purebred or “designer breeds” to supply the pet industry. Some high-volume commercial breeding facilities (CBEs) include extreme conditions such as overcrowding, little human contact, exposure to harsh weather conditions, inadequate food and water, and untreated medical conditions. Previous research with puppies born in these extreme conditions reports that this early life history of deprivation is associated with multiple behavioral and psychological abnormalities once adopted. Still, few studies to date have examined whether impoverished conditions affect the physiological systems of domestic dogs. The following study examined hormonal and behavioral differences in dogs from adverse early-life environments (i.e., puppy mills, unlicensed commercial breeders, hoarding situations) and a control group of dogs during social interactions with an unfamiliar human while in the shelter environment. Dogs from known early adverse backgrounds displayed significantly higher salivary cortisol levels than other dogs found at the shelter, F(1, 23) = 4.51, p = 0.045. Neither time spent in adverse living conditions nor time spent in the shelter correlated with cortisol output. During social interactions with an unfamiliar human, dogs from adverse backgrounds exhibited more fear behavior (p = 0.022) and displayed lower levels of affiliative behavior (p = 0.039). Dogs from adverse backgrounds spent more time in stationary positions (i.e., sitting, standing, freezing) than other shelter dogs (p = 0.043), and we were unable to complete a food-based social-cognitive task because of this. Using a moderated multiple regression model, we found dogs’ background was a significant moderator of the relationship between total cortisol output and panting during interactions with an unfamiliar human, R² = 0.39, F(1, 11) = 6.94, p = 0.023. In contrast, no relationship between these variables was seen in other shelter dogs. The findings of this study demonstrate that even when residing in the same shelter environment, a history of living in extreme conditions may lead to higher cortisol levels and altered behavior in a novel social context. While studies have examined dogs while still in the CBEs or once they have been adopted, this study examines their behavior and cortisol levels once removed and placed in a shelter environment where the public might interact with them and consider them for adoption. Gaining a better understanding of the behavioral and hormonal outcomes of dogs that have experienced extreme early life deficiencies may assist in the development of effective interventions that will facilitate rehabilitation and enhance the welfare of these dogs as pets.