Enrichment centered on human interaction moderates fear-induced aggression and increases positive expectancy in fearful shelter dogs

Abstract

Some otherwise non-aggressive dogs may display fear-induced aggression under stressful conditions. Admittance to an animal shelter is a stressful experience for dogs, and aggression is often used as a criterion by shelters for precluding opportunities for adoption. We, therefore, examined whether a program of enrichment centered around a form of human interaction known to reduce the stress of shelter dogs would also reduce the aggression of fearful dogs and improve their general welfare. Fearful dogs displaying signs of aggression, as well as dogs displaying neither fear nor aggression, either did or did not receive 30 min a day of human interaction in a secluded room for approximately the first 5 days in a shelter. We then determined the number of enriched and non-enriched fearful and non-fearful dogs that passed a standard test of dog aggression as typically implemented in this shelter to determine eligibility for adoption. We also examined the affective state of dogs in a test of cognitive bias. In two separate experiments, we found that most fearful dogs without enrichment failed the aggression test, whereas most fearful dogs undergoing enrichment completed this assessment successfully (P < 0.001 in each experiment). In contrast, nearly all non-fearful dogs passed the aggression test regardless of enrichment experience. In cognitive bias testing, enrichment reduced the latency at which fearful dogs approached two locations at which the likelihood of reinforcement was ambiguous, a measure of increased positive expectancy (P”s < 0.01). Unexpectedly non-fearful dogs receiving enrichment approached one of the ambiguous locations more slowly than non-enriched controls (P < 0.05), a finding that might be an artifact of the testing procedures used here. While the generality of the results needs to be tested in other populations and shelter environments, the findings: 1) document the vulnerability of dogs exhibiting fear-induced aggression in a shelter environment; 2) demonstrate the ability of an enrichment program focusing on human interaction to reduce aggressiveness in these dogs and thereby increase their chances of being offered for adoption; and, 3) indicate a more-general outcome of the enrichment procedure on the affective state of fearful dogs.