The effect of instrument attachment on the surface temperature of juvenile grey seals (Halichoerus grypus) as measured by infrared thermography

Abstract

Previous research has highlighted the importance of minimising hydrodynamic drag from biologging instruments fitted to marine mammals. However, there is a need to investigate other possible impacts of instruments on animals. The aim of this study was to examine the effect of deploying instruments on the surface temperature distribution of grey seals (Halichoerus grypus). Infrared (IR) thermography was used to record the surface temperature of two juveniles that had been fitted with heart rate recorders and mounting straps for the attachment of a time depth recorder. When animals were fully wet and inactive, the surface temperature pattern was unaffected by instruments. However, as animals dried out regions of high temperature were recorded around the edges of attachment sites compared to surrounding fur. This appeared to be due to heat leakage around the sides of instruments and mounting straps that provided an additional layer of insulation. There were no obvious changes in the surface temperature distribution around instruments associated with duration of deployment. This work shows that attachment of relatively small biologging instruments will produce localised effects on heat transfer in air but will not significantly change the total heat exchange of grey seals on land or at sea. IR thermography was also shown to be a useful method of detecting surface temperature patterns associated with epidural anaesthesia and blubber biopsy.