Each year, nearly 4 million dogs will enter one of over 13,000 animal shelters operating in the United States. We review programmes implemented at shelters aimed at increasing the likelihood of adoption. The morphology of shelter dogs plays a large role in in-kennel adopter selection, but their behaviour is also influential in out-of-kennel adopter interactions. Previous studies suggest that dogs have the ability to readily learn new behaviours at the shelter, and programmes designed to improve behaviour of the dogs can increase adoption rates. Whilst human interaction has been well-established to improve behavioural and physiological outcomes of dogs living in shelters, analysis of the effects of sensory, environmental, and social-conspecific enrichment has not resulted in clear conclusions. We also review the literature on the relinquishment of owned dogs and return rates of previously adopted dogs. Whilst owner- and dog-related risks to relinquishment are discussed, we show that there is a notable lack of research into programmes that address issues that may prevent the initial surrender of dogs to shelters, or that could prevent re-relinquishment. It is likely that factors, unrelated to the dog, play a larger role than previously believed. Suggestions for further research include multi-site studies, investigations into the efficacy of in-shelter enrichment programmes, predictive validity of behavioural assessments, understanding of adopter behaviour at the shelter, and programmes within the community focused on keeping dogs in their homes.

Previous research has indicated that certain breeds of dogs stay longer in shelters than others. However, exactly how breed perception and identification influences potential adopters' decisions remains unclear. Current dog breed identification practices in animal shelters are often based upon information supplied by the relinquishing owner, or staff determination based on the dog's phenotype. However, discrepancies have been found between breed identification as typically assessed by welfare agencies and the outcome of DNA analysis. In Study 1, the perceived behavioral and adoptability characteristics of a pit-bull-type dog were compared with those of a Labrador Retriever and Border Collie. How the addition of a human handler influenced those perceptions was also assessed. In Study 2, lengths of stay and perceived attractiveness of dogs that were labeled as pit bull breeds were compared to dogs that were phenotypically similar but were labeled as another breed at an animal shelter. The latter dogs were called "lookalikes." In Study 3, we compared perceived attractiveness in video recordings of pit-bull-type dogs and lookalikes with and without breed labels. Lastly, data from an animal shelter that ceased applying breed labeling on kennels were analyzed, and lengths of stay and outcomes for all dog breeds, including pit bulls, before and after the change in labeling practice were compared. In total, these findings suggest that breed labeling influences potential adopters' perceptions and decision-making. Given the inherent complexity of breed assignment based on morphology coupled with negative breed perceptions, removing breed labels is a relatively low-cost strategy that will likely improve outcomes for dogs in animal shelters.

One of the greatest stressors for dogs living in animal shelters is social isolation. Many studies have demonstrated that human interaction reduces cortisol in shelter dogs, with the possibility that longer periods of interaction may yield greater effects. These types of interventions are contingent upon removing the dog from the kennel and any such reductions in cortisol are often lost when the dog returns to the kennel. More recently, animal shelters are utilizing short-term fostering programs to provide relief from the perceived stresses of kennel life; however the effects of these programs are not well understood. This study assessed the impacts of one- and two-night fostering programs on the urinary cortisol levels, resting pulse rates, longest bout of uninterrupted rest, and proportion of time spent resting of dogs awaiting adoption. Five animal shelters, open and limited-admission facilities, from across the United States participated in the study. During the study, dogs’ urine was collected in the morning before, during, and after fostering stays for cortisol: creatinine analysis. Non-invasive health monitors were worn by the dogs, which collected heart rates and activity levels, in the shelter and in foster homes. In total, 207 dogs participated in the study, and 1,076 cortisol values were used in our analysis. Across all shelters, we found that dogs’ cortisol: creatinine ratios dropped significantly during their fostering stay, but returned to baseline levels after return to the shelter. However, the observed reduction in cortisol varied in magnitude across shelters. We found that dogs of greater weight, age, and average resting pulse rate had higher cortisol levels; and dogs with longer bouts of uninterrupted rest had lower cortisol levels. Dogs had their longest bouts of rest during sleepovers, followed by in the shelter after their sleepovers. Lastly, significant differences were found when comparing in-shelter cortisol values at our five shelters, differences that were in some cases greater than the impact of the fostering intervention itself. Considering the diversity of facilities that participated in this study, it is possible that as yet unstudied, shelter-specific, environmental factors could be contributing to the overall welfare of shelter dogs. Thus while a reprieve from the shelter is impactful for dogs awaiting adoption, mitigating the stressors present in kenneling conditions should also be addressed to improve the lives of shelter dogs.

Previous research in animal shelters has determined the breeds of dogs living in shelters by their visual appearance; however the genetic breed testing of such dogs is seldom conducted, and few studies have compared the breed labels assigned by shelter staff to the results of this testing. In the largest sampling of shelter dogs’ breed identities to-date, 459 dogs at Arizona Animal Welfare League & SPCA (AAWL) in Phoenix, Arizona, and 460 dogs at San Diego Humane Society & SPCA (SDHS) in San Diego, California, were genetically tested using a commercially available product to determine their breed heritage. In our sample, genetic analyses identified 125 distinct breeds with 91 breeds present at both shelters, and 4.9% of the dogs identified as purebreds. The three most common breed signatures, in order of prevalence, American Staffordshire Terrier, Chihuahua, and Poodle, accounted for 42.5% or all breed identifications at the great grandparent level. During their stay at the shelter, dogs with pit bull-type ancestries waited longer to be adopted than other dogs. When we compared shelter breed assignment as determined by visual appearance to that of genetic testing, staff at SDHS was able to successfully match at least one breed in the genetic heritage of 67.7% of dogs tested; however their agreement fell to 10.4% when asked to identify more than one breed. Lastly, we found that as the number of pit bull-type relatives in a dog’s heritage increased, so did the shelter’s ability to match the results of DNA analysis. In total when we consider the complexity of shelter dog breed heritage and the failure to identify multiple breeds based on visual identification coupled with our inability to predict how these breeds then interact within an individual dog, we believe that focusing resources on communicating the physical and behavioral characteristics of shelter dogs would best support adoption efforts.

This study involved examining the ability of a postadoption intervention to reduce returns of newly adopted dogs to shelters by encouraging physical activity between adopters and their dogs. Guardians in the intervention group received emails with dog behavior and human activity advice as well as invitations to join weekly dog walks. Both the intervention and control groups completed surveys regarding outdoor activity with their dogs, their dog-walking habits, and perceptions of their dogs' behaviors. Adopter-dog pairs in the intervention group were not significantly more active than those in the control group, nor did they show a reduced incidence of returning their dogs. Guardians in both groups who reported higher obligation and self-efficacy in their dog walking were more active regardless of experimental condition; however, obligation, dog-walking self-efficacy, and perceptions about their dogs' on-leash behaviors did not predict rates of return to the shelter. These findings add to the understanding of shelter dog re-relinquishment and the effective utilization of resources postadoption, and they indicate further research is needed to address the complexities of this newly forming human-dog relationship.