Variation in outer blubber lipid concentrations does not reflect morphological body condition in humpback whales [RESEARCH ARTICLE]

Fredrik Christiansen, Kate R. Sprogis, Jasmin Gross, Juliana Castrillon, Hunter A. Warick, Eva Leunissen, and Susan Bengtson Nash An animal's body condition provides valuable information for ecophysiological studies, and is an important measure of fitness in population monitoring and conservation. While both the external body shape of an animal, as well as its internal tissues (i.e. fat content) can be used as measures of body condition, the relationship between the two is not always linear. We compared the morphological body condition (external metric obtained through aerial photogrammetry) of migrating humpback whales (Megaptera novaeangliae) with their outer blubber lipid concentration (internal metric obtained through blubber biopsy sampling) off south-west Australia early and late in the breeding season (spanning ~4.5 months). The external body condition index of juvenile and adult humpback whales decreased with 26.9 (from 18.8 to –8.1%) and 12.0 percentage points (from 8.6 to –3.4%) between the early and late phase, respectively. In contrast, we found no intra-seasonal change in blubber lipid concentration, and no difference between reproductive classes (juveniles, adults and lactating females), however the small sample size prevented us from effectively testing these effects. Importantly however, in the 33 animals for which paired metrics were obtained, we found no correlation between the morphometric body condition index and the blubber lipid concentration...
Source: Journal of Experimental Biology - Category: Biology Authors: Tags: RESEARCH ARTICLE Source Type: research