Hennessy, M. B., H. N. Davis, M. T. Williams, C. Mellott and C. W. Douglas. Plasma cortisol levels of dogs in a county animal shelter. Physiol Behav 62(3) 485-490, 1997.--Plasma cortisol levels were examined to assess the stress of dogs in a county animal shelter. Groups of dogs confined in the shelter for their 1st, 2nd, or 3rd day had higher cortisol levels than did a group maintained in the shelter for more than 9 days. Dogs in the shelter for an intermediate period (Day 4-9) had intermediate levels of cortisol. The cortisol concentrations of dogs during their first day in the shelter were greater than either those of the same dogs on Day 4/5 in the shelter or those of a group of pet dogs sampled in their own homes. There was no overall effect of 20 min of social interaction with a human (e.g., petting) on the plasma cortisol levels of dogs in the shelter on Day 1-3. However, the gender of the petter did affect cortisol levels. Those dogs interacting with a female had lower cortisol concentrations at the end of the session than did dogs interacting with a male. The results suggest that confinement in a public animal shelter produces a prolonged activation of the hypothalamic-pituitary-adrenal axis. Further, it appears that some subtle aspect of interaction with a human may be capable of moderating this response. Possible implications for the welfare of confined dogs, and for the development of behavior problems in dogs obtained from shelters, are discussed.