DUNKIN, R.C.*; MCLELLAN, W.A.; BLUM, J.E.; PABST, D.A.; Univ. of North Carolina, Wilmington; Univ. of North Carolina, Wilmington; Univ. of North Carolina, Wilmington; Univ. of North Carolina, Wilmington: Ontogenetic Changes in the Thermal Properties of Atlantic Bottlenose Dolphin Blubber

In Atlantic bottlenose dolphins (T. truncatus), the thickness and lipid content of thoracic blubber vary across ontogeny and with reproductive and nutritional status. This study investigated how these morphological and compositional changes may influence blubber�s thermal properties. Thermal conductivity (W/m&degC) and thermal insulation (m² &degC/W) of blubber were measured in normal, apparently healthy, individuals across an ontogenetic series (fetus through adult, n=36), in pregnant females (n=4) and emaciated animals (n=5). These thermal properties were determined by the simultaneous use of two experimental approaches, the heat flux disc method and the standard material method. In addition, blubber thickness, lipid and water content were also measured. Thermal conductivity and insulation varied significantly across ontogeny. Blubber from fetuses through sub-adults was significantly less conductive (range = 0.11 to 0.13 � 0.01 W/m&degC) than that of adults (mean = 0.18 � 0.02 W/m&degC). The conductivity of blubber from pregnant females was similar to non-adult categories while that of emaciated animals was significantly higher (0.24 � 0.04 W/m&degC) than all other categories. Blubber from sub-adults and pregnant females had the highest insulation values (0.18 � 0.012 and 0.18 � 0.030 m² &degC/W) while fetuses and emaciated animals had the lowest (0.05 � 0.010 and 0.07 � 0.015 m² &degC/W). In nutritionally dependent life history categories, changes in blubber�s thermal insulation were characterized by stable blubber quality (i.e. conductivity) and increased blubber quantity (i.e. thickness). In nutritionally independent animals, blubber quantity was stable while blubber quality varied.