Eye Region Surface Temperature and Corticosterone Response to Acute Stress in a High-Arctic Seabird, the Little Auk

SIMPLE SUMMARY: Thermography, which is a method of measuring the heat emitted by various regions of the body, may be useful in detection of a heat increase in response to stress in vertebrates. Using this method, we studied how body surface temperature in eye-region (TEYE) changes in response to short-term stress (capturing and handling) in a wild-living, medium-sized polar seabird, the Little Auk. To this end, we measured TEYE in birds twice: first time—just after their capturing and initial handling and then second—after 30 min of keeping them in a bag. To control birds’ stress response, at the same time we made thermography, and we also collected blood samples from all the individuals, to establish the level of corticosterone (CORT, stress hormone). We found that both TEYE and CORT increased in response to the experimental procedure, although the strength of the TEYE and CORT increase were not related to each other. This indicates that thermography is a good tool for detection of initiation of birds’ reaction to a stress, which may be further useful in other studies, e.g., where there is a need to establish birds’ stress response non-invasively. ABSTRACT: Measuring changes in surface body temperature (specifically in eye-region) in vertebrates using infrared thermography is increasingly applied for detection of the stress reaction. Here we investigated the relationship between the eye-region temperature (TEYE; measured with infrared thermography), the corticosterone level in blood (CORT; stress indicator in birds), and some covariates (ambient temperature, humidity, and sex/body size) in a High-Arctic seabird, the Little Auk Alle alle. The birds responded to the capture-restrain protocol (blood sampling at the moment of capturing, and after 30 min of restrain) by a significant TEYE and CORT increase. However, the strength of the TEYE and CORT response to acute stress were not correlated. It confirms the results of a recent study on other species and all together indicates that infrared thermography is a useful, non-invasive measure of hypothalamic-pituitary-adrenal (HPA) axis reactivity under acute activation, but it might not be a suitable proxy for natural variation of circulating glucocorticoid levels.