Six minke whales (Balaenoptera acutorostrata) were instrumented with VHF-radio transmitters and four with sonic speed-depth transmitters off the west coast of northern Norway and Svalbard and followed within view for up to 24 h. During such periods their respiratory rate was continuously recorded and their energy expenditure estimated according to Folkow & Blix (1992) at different swimming speeds and types of activity. We found that cost of swimming is remarkably low in these large animals and that their estimated daily energy expenditure on average only amounts to 80 kJ kg-1 day-1.
Body temperature, blubber thickness and lung capacity (Vc) were recorded in newly killed minke whales, while respiratory frequency (f) was determined in free-swimming animals. Mean deep (thoracic) body temperature was 34.7 +/- 0.8 (SD) degrees C (n = 14). Weighted mean core/blubber interface temperature in animals caught in 2.5-5.5 degrees C water was 28.8 +/- 1.7 degrees C (n = 8). The minimum average rate of sensible heat loss (HLs) was 3.81 +/- 0.53 (SD) W kgw-0.75 (n = 8) in animals with body masses (w) in the range of 1840 to 5740 kg, HLs being inversely proportional to w (HLs = -2.98 10(-4) w +4.89 W kgw-0.75 (n = 8, r2 = 0.73, P less than 0.01)). The average rate of respiratory heat loss (HLr) was 0.26 +/- 0.04 (SD) W kgw-0.75, regardless of w, in the same 8 animals. Total rates of heat loss (HL = HLr+HLs) in 2.5-5.5 degrees C water ranged between 3.40 and 4.87 W kgw-0.75, with an average of 4.06 +/- 0.52 (SD) W kgw-0.75 (n = 8). Estimates of oxygen consumption based on records of f and Ve, and data on oxygen extraction from other cetaceans, yielded a range of metabolic rates which compared nicely with the calculated HL values.
Food intake, body weight, serum levels of triiodothyronine (T3) and free thyroxine (FT4), and metabolic rate were measured at intervals in Svalbard (SR) and Norwegian (NR) reindeer. From summer to winter food intake decreased 57 (SR) and 55% (NR), while body weight decreased 8.6 (SR) and 3.8% (NR). In SR T3 and FT4 changed seasonally, whereas this was only evident for T3 in NR. Resting (standing) metabolic rate (RMR) in winter was 1.55 (SR) and 2.05 W X kg-1 (NR), lower critical temperature (TLC) being -50 (SR) and -30 degrees C (NR). RMR in summer was 2.15 (SR) and 2.95 W X kg-1 (NR), TLC being -15 (SR) and 0 degrees C (NR). Seasonal changes in T3 and FT4 did not coincide with changes in food intake or RMR in either SR or NR. RMR did, however, correlate with food intake. This indicates that seasonal changes in RMR are due to the thermic effects of feeding and represent no physiological adaptation aimed at conservation of energy during winter.
Selective cooling of the brain during hyperthermia has been demonstrated in several species of mammals (Baker 1979(Baker , 1982. Such cooling is achieved by heat exchange between the cooled venous blood returning from the nasal mucosa and the warmer arterial blood entering the brain via the carotid rete.Spot measurements of brain temperature (Tbr) and carotid blood temperature (TCar) were made within 1 min. of death in 40 wild reindeer (Rangifer tarandus tarandus). At Tear lower than 40.5°C Tbr was higher than Tcar. With increasing Tear above 40.5°C Tbr remained at approximately 40.5°C, indicating that selective cooling of the brain had occurred.Angiographic examination of the distribution of the venous return from the nasal mucosa during induced hypothalamic or rumen heating and cooling in trained reindeer demonstrated that the angular oculi veins were constricted during cold stress and dilated during heat stress.
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