Glucocorticoid response to naturalistic interactions between children and dogs.

Although research has shown that pets appear to provide certain types of social support to children, little is known about the physiological bases of these effects, especially in naturalistic contexts. In this study, we investigated the effect of free-form interactions between children (ages 8-10 years) and dogs on salivary cortisol concentrations in both species. We further investigated the role of the child-dog relationship by comparing interactions with the child's pet dog to interactions with an unfamiliar dog or a nonsocial control condition, and modeled associations between survey measures of the human-animal bond and children's physiological responses. In both children and dogs, salivary cortisol decreased from pre- to post-interaction; the effect was strongest for children interacting with an unfamiliar dog (compared to their pet dog) and for the pet dogs (compared to the unfamiliar dog). We found minimal evidence for associations between cortisol output and behaviors coded from video, but children scoring higher on survey measures of the human-animal bond exhibited the greatest reductions in cortisol when interacting with dogs. Self-reported loneliness was not related to cortisol or the human-animal bond, but measures of both loneliness and the human-animal bond were higher among children who participated after the onset of the COVID-19 pandemic, relative to those who participated before the pandemic. This study builds on previous work that investigated potential stress-buffering effects of human-animal interaction during explicit stressors and demonstrates important physiological correlates of naturalistic interactions between children and dogs, similar to those that occur in daily life.

Diurnal fecal glucocorticoid metabolite rhythms in a cathemeral primate, the red-bellied lemur (Eulemur rubriventer), and across mammalian species.

Measuring glucocorticoids is one of the most reliable and widely used techniques to monitor stress responses, however invasive techniques to collect plasma samples may not be applicable for wild populations. Monitoring excreted glucocorticoids is an effective noninvasive technique that researchers have used increasingly over the past two decades, and it has allowed the investigation of glucocorticoids in a variety of species with a range of activity patterns. Many species exhibit predictable circadian patterns of glucocorticoid secretion in accordance with their daily activity pattern. There remains a gap in our understanding of how excreted glucocorticoid metabolites vary throughout the day and across species, despite the utility of this information when developing sampling protocols and analyzing data. We investigated circadian patterns of glucocorticoid excretion in a cathemeral primate species, Eulemur rubriventer (red-bellied lemur), in Ranomafana National Park, Madagascar. We collected fecal samples from 10 individuals throughout the day and analyzed fecal glucocorticoid levels across three time points (Early, Midday, and Late), and again across two time points (Morning and Afternoon). We also investigated whether activity pattern, sex (as a control variable), and other traits associated with gut passage rate (diet, body mass) could help predict the presence and timing of circadian patterns of fecal glucocorticoid metabolites across mammal species. We found that fecal glucocorticoid metabolite levels in E. rubriventer fluctuate throughout the day, with lowest levels in the morning and peak levels in the afternoon. None of the variables that we tested predicted whether daily fecal glucocorticoid metabolites changed significantly throughout the day, nor when levels were likely to peak, across species. We stress the importance of controlling for sampling time and reporting these results as standard practice in studies of fecal glucocorticoid metabolites.

Effects of human-animal interaction on salivary and urinary oxytocin in children and dogs.

Oxytocin pathways are hypothesized to play important roles in human-animal interactions and may contribute to some benefits of these interspecific social relationships. We explored the effects of naturalistic interactions between children and dogs on oxytocin release in both species, as well as associations between methylation of the oxytocin receptor gene (OXTRm), social behavior, and oxytocin response in this context. Children (N = 55) participated in a within-subjects design involving a) interaction with their pet dog, b) interaction with an unfamiliar dog, and c) a nonsocial control condition (solitary play). We used immunoassays to measure salivary and urinary oxytocin in both the children and dogs, behavioral coding to characterize dog-child interactions, and bisulfite sequencing to quantify methylation of the oxytocin receptor gene (N = 32 children). Child salivary oxytocin decreased moderately across time in all conditions, but the extent of this effect varied between conditions, with greater oxytocin output during interactions with dogs than the control condition. In the pet dog condition, children's salivary oxytocin response was positively associated with the duration of visual co-orientation between the child and dog. Child urinary oxytocin did not deviate substantially from baseline in any condition. Children with higher levels of OXTRm had greater oxytocin output during interactions with their pet dogs, but lower oxytocin output in the control condition, and engaged in lower levels of affectionate interaction with dogs across conditions. Children's pet dogs exhibited increases in salivary oxytocin, but we observed the opposite pattern in the unfamiliar dog, who exhibited decreases in both urinary and salivary oxytocin on average. Collectively, our results support the hypothesis that oxytocin pathways may shape and respond to social interactions between children and dogs, highlighting an important role for companion animals in child development.