Figure 2.

Graphical depiction of various approaches for understanding the thermal physiology of marine mammals. Both comparative physiology studies performed in the laboratory and ecophysiology studies (i.e. physiology studies conducted in the field where the ecological context is taken into consideration) have contributed to our understanding of marine mammal thermal physiology. However, most have relied heavily on species that are more readily accessible (e.g. seals). The blue box highlights how knowledge gained from ex vivo studies on blubber is relevant to understanding its function in vivo and its influence on other thermal measurements (e.g. skin temperature and heat flux). In vivo studies in the laboratory (yellow box) have provided insights into whole-body thermal dynamics using experimental methods that simulate reality to varying degrees (e.g. forced submersion experiments to trained dives). To understand the ecological relevance of their thermal limits, field studies (green box) using biologgers can record thermal responses during natural behavior and use these baseline measurements to compare those taken under disturbed conditions. Arrows depict efforts to translate findings using different approaches (ex vivo to in vivo, red to yellow) or in different contexts (lab setting to the natural context, blue to green). Skin and blubber biopsy sample from Megaptera novaeangliae and image (courtesy of L. Pallin) collected under scientific research permits NMFS 23095, ACA 2020–016, and UCSC IACUC Friea2004. Ultrasound image from Mirounga angustirostris collected under scientific research permits NMFS 21388 and UCSC IACUC Costad2009-1. Seal outline (© Jessica Kendall-Bar) was modified to depict instrumentation for research conducted under NMFS 19108 and 21388 and UCSC IACUC Costad2009-3. Seal outline depicting body temperature measurements adapted with permission from Miller & Irving 1975. Metabolism and temperature regulation in young harbor seals Phoca vitulina richardi. American Journal of Physiology 229: 506–511. Schematic of an experimental approach reprinted from Gallivan and Ronald, 1979. Temperature regulation in freely diving harp seals (Phoca groenlandica). Canadian Journal of Zoology, 57: 2256–2263. © Canadian Science Publishing. Figure depicting methods used for forced submersion experiments reprinted with permission from Zapol et al. 1979. Regional blood flow during simulated diving in the conscious Weddell seal. Journal of Applied Physiology, 47: 968:973. © American Physiological Society.