The diving physiology of bottlenose dolphins (Tursiops truncatus): III. Thermoregulation at depth

Abstract

During diving, marine mammals initiate a series of cardiovascular changes that include bradycardia and decreased peripheral circulation. Because heat transfer from thermal windows located in peripheral sites of these mammals depends on blood flow, such adjustments may limit their thermoregulatory capabilities during submergence. Here, we demonstrate how the thermoregulatory responses of bottlenose dolphins (Tursiops truncatus) are coordinated with the diving response. Heart rate, skin temperature and heat transfer from the dorsal fin and flank were measured while dolphins rested on the water surface, stationed 5–50 m under water and floated at the surface immediately following a dive. The results showed that heat flow ranged from 42.9+/−7.3 to 126.2+/−23.1 W m(−)(2) and varied with anatomical site and diving activity. Upon submergence, heat flow declined by 35 % from the dorsal fin and by 24 % from the flank. An immediate increase in heat flow to levels exceeding pre-dive values occurred at both sites upon resurfacing. Changes in heart rate during diving paralleled the thermoregulatory responses. Mean pre-dive heart rate (102.0+/−2.6 beats min(−)(1), N=26) decreased by 63.4 % during dives to 50 m and immediately returned to near resting levels upon resurfacing. These studies indicate that heat dissipation by dolphins is attenuated during diving. Rather than challenge the diving response, heat transfer is delayed until post-dive periods when the need for oxygen conservation is reduced.

Diving physiology of marine mammals and birds: the development of biologging techniques

“…Animals in these studies experienced varying degrees of a natural environment, from swimming in narrow flumes to diving in open water. Biologging physiological studies have been undertaken on a variety of such animals, including bottlenose dolphins [101,[136][137][138], Steller and California sea lions [41,52,57,[139][140][141], harbour seals [140], harbour porpoises [102,142], grey seals [143], and tufted ducks, cormorants and Humboldt penguins [33,50,144].…”

Advances in thermal physiology of diving marine mammals: The dual role of peripheral perfusion

“…Some studies have also noted large changes in heat flux associated with small temperature changes between the skin and water. Whether this discrepancy has a physiological underpinning warrants further investigation [ 109 , 110 , 145 ]. Changes in convective heat transfer via blood flow may explain these periodic increases in heat flow at localized skin surface areas [ 15 , 56 , 150 ].…”

Infrared thermography in marine ecology: methods, previous applications and future challenges

“…Portable hand-held infrared cameras were originally used by ecologists to estimate abundances of terrestrial mammals and birds, especially nocturnal species (Hristov et al 2008, Cilulko et al 2013. Within the marine environment, hand-held infrared cameras were first used to count and track the movements of whales, dolphins and seals (Perryman et al 1999, Williams et al 1999, Thomas & Thorne 2001 see Table 2 for a synthesis). Helmuth (2002) was the first to use IRT to measure the body temperatures of marine ectotherms in the field (i.e.…”

“…Thermal physiology studies have been used to assess different aspects of thermoregulation, usually on captive animals. For instance, infrared images have been used to assess diving physiology and blood circulation in bottlenose dolphins (Williams et al 1999, Meagher et al 2002 and thermoregulatory evaporation in captive seals (Mauck et al 2003). More recently, infrared imaging was use as a noninvasive tool to assess body condition in harbour seals and Steller sea lions (Mellish et al 2013).…”