Although blubber covers the animal’s whole body, it is structurally different in the thoracic region and caudal peduncle region. The blubber in the thoracic area is more energetically active meaning when the animal is nutritionally stressed, fat in this region will be mobilized. Blubber in the caudal peduncle region is more structural and has a higher percentage of collagen fibers. At necropsy, cutting through blubber from near the pectoral flipper versus the caudal peduncle will clearly show the differences in these blubber regions.
At necropsy, blubber thickness is an important indicator of body condition and nutritional status. It is important to take multiple blubber thickness measurements when trying to assess nutritional status. In general, a dorsal, lateral, and ventral measurement at the level of the dorsal fin are a minimum for assessment of nutritional status. Assessment of the fat depot directly behind the blowhole called the nuchal fat pad, is also a good indication of nutritional status. This area will become concave in nutritionally stressed animals (see photo below) causing what is known as “peanut head” where the skull is prominent.
For more information about the integumentary system and blubber in cetaceans see Ling 1974, Pabst et al., 1999, Struntz et al., 2004, or Dunkin et al., 2005.
Detailed annotated images of the integument of a harbor porpoise are shown below.
