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- Table 1.
Thermal conductivity k values for blubber from a variety of marine mammals and other substances
Species k (W m-1 deg.-1) (Reported mean) Source Method Cetaceans Balaenoptera acutorostrata 0.20-0.28* Kvadsheim et al., 1996 Standard material Balaenoptera acutorostrata 0.18 Folkow and Blix, 1992 Hot plate Balaenoptera physalus 0.21 Parry, 1949 Hot plate Delphinapterus leucas (blubber) 0.102 Doidge, 1990 Heat flux plate Delphinapterus leucas (epidermis) 0.249 Doidge, 1990 Heat flux plate Phocoena phocoena 0.06 Yasui and Gaskin, 1986 Heat flux disc Phocoena phocoena 0.1 Worthy and Edwards, 1990 Heat flux disc Stenella attenuata 0.2 Worthy and Edwards, 1990 Heat flux disc Pinnipeds Mirounga leonina 0.07 Bryden 1964, in Doidge, 1990 Unknown Phoca groenlandica 0.18 Worthy, 1985 Heat flux disc Phoca groenlandica 0.19 Kvadsheim et al., 1994 Standard material Phoca hispida 0.2 Scholander et al., 1950 Hot plate Phoca vitulina 0.18 Worthy, 1985 Heat flux disc Halichoerus grypus 0.18 Worthy, 1985 Heat flux disc Fatty acids Stearic acid (C18:0) 0.16 CRC 1967 in Doidge, 1990 Unknown Palmitic acid (C16:0) 0.17 CRC 1967 in Doidge, 1990 Unknown Oleic acid (C18:1) 0.23 CRC 1967 in Doidge, 1990 Unknown Miscellaneous materials Air 0.024 Schmidt-Nielsen, 1997 Unknown White pine wood 0.104 Liley, 1996 Unknown Human fat 0.21 Hensel et al., 1973 in Doidge, 1990 Unknown Lead 35 Schmidt-Nielsen, 1997 Unknown Iron 80 Schmidt-Nielsen, 1997 Unknown -
↵* This range of values represent mean thermal conductivity across four body sites.
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- Table 2.
Definitions of life history categories
Life history category Code Defining characters Fetus 1 Position en utero. Neonate 2 Possessed four of the following six characters: presence of rostral hairs, floppy or folded dorsal fin, unhealed umbilicus, prominent fetal folds, floppy or folded dorsal keel, floppy or folded flukes. Juvenile 3 Absence of neonatal characters and estimated to be less than 1 year of age based on total length (≤150 cm). Sub-adult 4 Absence of milk in the stomach, immature reproductive tissues, and total length (>150 cm). Adult 5 Mature reproductive tissues as indicated by obvious ovarian scars in females and the size of the testis and/or presence of sperm in males. Pregnant female 6 Presence of a fetus. Emaciated animal 7 Skeletal elements such as ribs, scapula, vertebral transverse processes, and/or skull prominently visible under blubber layer; atrophy of epaxial musculature and/or the nuchal fat pad. -
Definitions are based on Dearolf et al. (2000) and Struntz et al. (2004).
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- Fig. 1.
A is the blubber sample site used for thermal measurements on an ontogenetic series of Atlantic bottlenose dolphins (T. truncatus).
- Fig. 2.
Heat flux chamber showing placement of thermocouples and heat flux discs. Figure is not drawn to scale and the size of the thermocouples and heat flux discs are exaggerated for clarity.
- Fig. 3.
(A) Example data trace of temperature measurements from one experiment. Probes 1–3 were placed at the interface between the heat source and the standard material, probes 4–6 were placed between the standard material and the deep blubber surface, and probes 7–9 were placed at the interface between the epidermis and air (see Fig. 2). (B) Example data trace of heat flux values from the deep and superficial heat flux discs from the same experiment. For both traces, only data from the final 30 min of the experiment were used in the thermal calculations.
- Table 3.
Thermal data for blubber from each life history category in Atlantic bottlenose dolphins
Fetus Neonate Juvenile Sub-adult Adult Pregnant female Emaciated adult Blubber thickness d (cm) 0.49±0.001c 1.23±0.002b 1.61±0.001a,b 2.0±0.003a 2.13±0.004a 2.05±0.004a 1.57±0.003a,b Lipid mass/wet mass (%) 35.06±6.09b,c 55.82±2.86a,b 69.72±4.08a 62.59±2.31a 54.31±4.88a,b 69.20±5.73a 28.22±9.14c Water mass/wet mass (%) 50.3±3.52a 33.06±1.97b 29.9±0.96b 30.16±2.35b 32.78±1.08b 31.66±1.57b 59.34±6.63a Conductivity k (W m-1 deg.-1) 0.12±0.01c 0.13±0.01c 0.12±0.01c 0.11±0.01c 0.18±0.02b 0.12±0.01c 0.24±0.04a Conductance C (W m-2 deg.-1) 25.69±6.04a 10.44±0.69b,c 7.30±0.61c,d 5.74±0.44d 8.44±1.03c,d 5.73±0.82d 14.79±2.64b Insulation R (m2 deg. W-1) 0.05±0.01d 0.10±0.005b,c,d 0.14±0.01a,b 0.18±0.012a 0.12±0.016b,c 0.18±0.03a 0.07±0.015c,d -
Values are means ± s.e.m.
For all measurements, life history categories with the same letter are not significantly different (P>0.05).
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- Fig. 4.
Fetal blubber (A) thickness and (B) lipid content plotted against total body length in Atlantic bottlenose dolphins (T. truncatus).
- Fig. 5.
Percent lipid content as a function of blubber depth in T. truncatus. Solid trend lines indicate life history categories where there was a significant linear relationship between lipid content and blubber thickness (fetus and adult). Trend lines are not shown for categories where there was not a significant relationship between lipid content and blubber thickness.
- Fig. 6.
Blubber thermal conductivity k values for T. truncatus calculated using (A) the standard material method, (B) heat flux values from the superficial disc, and (C) heat flux values from the deep disc. Life history categories are (F) fetus, (N) neonate, (J) juvenile, (SA) sub-adult, (A) adult, (PF) pregnant female and (EA) emaciated animals. Values represent mean ± s.e.d. for each life history category.
- Fig. 7.
(A) Blubber thermal conductivity calculated using the standard material method plotted against blubber lipid content and (B) water content in T. truncatus.
- Fig. 8.
The difference between the deep and superficial heat flux disc measurements plotted against the material thickness for T. truncatus blubber, foam and wood.
- Fig. 9.
Blubber thickness, lipid content, thermal conductivity k and insulation values R for T. truncatus plotted against life history category. Life stages as in Fig. 6.
- Table 4.
Calculated mass-specific metabolic rates for neonatal and adult bottlenose dolphins
Neonates Adults Body mass (kg) 18.23±11.4 194.35±13.92 Insulation R (m2 deg. W-1) 0.10±0.01 0.12±0.01 Surface area (m2)* 0.308±0.13 1.759±0.16 Surface area/volume 27.48±1.27 12.48±1.92 Mass-specific metabolic rate (1 O2 h-1 kg-1) 0.301±0.017 0.111±0.02 Predicted Kleiber mass-specific metabolic rate (1 O2 h-1 kg-1) 0.331±0.01 0.182±0.005 -
Values are means ± s.e.m.
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↵* Surface area and volume were estimated by modeling the trunk (nuchal crest to anus) as a cylinder and the tailstock (anus to fluke insertion) as a truncated cone. The head and appendages were excluded from these calculations.
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