Stress at rest in working dogs assessed with infrared thermography

Abstract

For many years, dogs have been trained to detect objects through smell and help humans to locate different items. These dogs are specially trained to maximize their search capabilities, that this increased concentration could lead to high levels of stress in the animal. The main aim of this study was to assess the stress levels at rest of working police dogs, measured with infrared thermography and by the heart rate (HR).

To achieve this, we evaluated 18 working dogs (13 males and 5 females), half of which had been trained for drug detection and the other half for explosives detection. Eye temperature (ET) assessed with infrared thermography was collected in the kennels (ETK) and inside the police car (ETC), to test differences due to place of location. The mean value between ETK and ETC (MET) and the difference between them (ETD) were also assessed. HR was evaluated inside the police car. The influence of different factors (sex, breed, training type and age) on the stress perceived by these animals was also measured. The results indicated that these animals showed higher ETK (36.8±1.1) than ETC (36.1±1.0), with a similar coefficient of variation (3.0% and 2.8%, respectively). This could be due to the fact that working dogs tend to be calmer when they expect to carry out the assigned job. On the other hand, no statistically significant correlations were found between ET variables and HR, thus supporting previous studies indicating that these parameters differ in their physiological background. The GLM statistical analysis found that females (for sex factor) and dogs trained for explosives detection (for training type factor) showed higher ETK and ETD than males or dogs trained for drug detection. As for breed group, statistical differences between means were found only for ETD, with Shepherd dogs showing higher increases than Retrievers. Thus, the results obtained in this study are the first to show that ET measured using infrared thermography is a suitable tool to assess stress in working dogs; and secondly, that the stress shown by working dogs in the kennel and the magnitude of the stress difference recorded between kennel and police car is influenced by the environment.