The use of an open-field model to assess sound-induced fear and anxiety-associated behaviors in Labrador retrievers

Previous studies have shown that the playing of thunderstorm recordings during an open-field task elicits fearful or anxious responses in adult beagles. The goal of our study was to apply this open-field test to assess sound-induced behaviors in Labrador retrievers drawn from a pool of candidate-improvised explosive devices (IEDs)-detection dogs. Being robust to fear-inducing sounds and recovering quickly is a critical requirement of these military working dogs. This study presented male and female dogs, with 3 minutes of either ambient noise (days 1, 3, and 5), recorded thunderstorm (day 2), or gunfire (Day 4) sounds in an open-field arena. Behavioral and physiological responses were assessed and compared with control (ambient noise) periods. An observer blinded to sound treatment analyzed video records of the 9-minute daily test sessions. Additional assessments included measurement of distance traveled (activity), heart rate, body temperature, and salivary cortisol concentrations. Overall, there was a decline in distance traveled and heart rate within each day and over the 5-day test period, suggesting that dogs habituated to the open-field arena. Behavioral postures and expressions were assessed using a standardized rubric to score behaviors linked to canine fear and anxiety. These fear/anxiety scores were used to evaluate changes in behaviors after exposure to a sound stressor. Compared with control periods, there was an overall increase in fear/anxiety scores during thunderstorm and gunfire sound stimuli treatment periods. Fear/anxiety scores were correlated with distance traveled and heart rate. Fear/anxiety scores in response to thunderstorm and gunfire were correlated. Dogs showed higher fear/anxiety scores during periods after the sound stimuli compared with control periods. In general, candidate IED-detection Labrador retrievers responded to sound stimuli and recovered quickly, although dogs stratified in their response to sound stimuli. Some dogs were robust to fear/anxiety responses. The results suggest that the open-field sound test may be a useful method to evaluate the suitability of dogs for IED-detection training.