The Use of an Open Field Model to Assess Sound-Induced Fear and Anxiety Associated Behaviors in Labrador Retrievers

Abstract

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 (IED)-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 to 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 five-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 following exposure to a sound stressor. Compared to 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 to 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.

Keywords: Military working dogs; anxiety; fear; gunfire; open field test; thunderstorm.

Figure 1

The open field test arena (3m × 3 m) with “hide.” The schematic representation, not to scale, shows the approximate location of the door, 2 elevated speakers, and 2 cameras. One camera was positioned overhead in the center of the arena, and one camera was laterally positioned, 0.6 m above the floor level, at an opaque window with a port just large enough to accommodate the camera lens.

Figure 2

Mean (± SE) change in heart rate over days (post value – pre value) in the open field test arena

Figure 3

Mean (± SE) change in body temperature over days (post value – pre value) in the open field test arena.

Figure 4

Mean (+/- SE) change in salivary cortisol (post value-baseline value) over days for the open field sessions for males (gray) and females (black).

Figure 5

Mean (+/- SE) distance traveled (in meters) in the open field test arena by Day and Period (A, B, C). Thunderstorm sound was presented on Day 2, Period B; Gunfire sound was presented on Day 4, Period B.

Figure 6

Global fear/anxiety scores (+/- SE) by Day and Period (A, B, C). On Days 2 and 4, global anxiety scores were higher in response to sound stimuli (Period B) compared to periods A and C (p<0.0001). Patterns for inactive and active fear/anxiety scores were similar.