Profiling heat loss in an extreme polar mammal, the Weddell seal

Abstract

A major weakness in predicting habitat change impacts in polar regions is that little is actually known about energetic costs of basic thermoregulation in high‐latitude seals and other apex predators. Characteristics of body size and condition (surface area: volume ratios, insulation) are likely to affect heat loss and manifest as altered thresholds for thermal homeostasis. We monitored the thermal interface between animal‐environment directly via skin surface heat flux sensors (HFS) and indirectly with infrared thermography (IRT) in Weddell seals (n=42) over 2–7d. Utilizing 4 life history categories—pups, juveniles, non‐reproductive adult females (skip breeders) and post‐weaning females—we tested for effect of body size and known insulation patterns (blubber depth via imaging ultrasound). IRT surface temperature maxima and range suggested 4 sites of interest for HFS placement and continued monitoring: axilla (variable hot), head (hot), flank (variable cold) and neck (cold). IRT‐generated surface temperature distribution histograms further permitted the partitioning of body surface area such that an integrated thermal profile could be modeled from HFS data collected at these 4 sites. With this tool we can for the first time examine thermal homeostasis in free‐ranging seals over a range of potentially changing environments. Funded by NSF Polar Programs.