Meeting Abstract
Arctic seals must manage considerable seasonal changes in sea ice coverage, air and water temperatures, photoperiod, and prey availability. These species utilize blubber for onboard energy storage, thermoregulation, streamlining, and buoyancy, and this insulating layer changes in thickness and composition throughout the year. Specifically, seals rely on blubber as a critical energy reserve during physiologically taxing life-history stages such as breeding, lactation, and molt. Blubber thickness, along with complementary morphometric measures, can be used to assess overall body condition in seals. We used a modified truncated cones method to track within-individual, fine-scale changes in the body condition of three species of Arctic seal. Our study animals included 4 spotted seals (Phoca largha), 3 ringed seals (Pusa hispida), and 1 bearded seal (Erignathus barbatus) trained to participate in research procedures at two facilities in California and Alaska. We used a portable ultrasound machine to measure blubber thickness at 12 sites along the length of each animal. We used photogrammetric methods to measure standard length, curvilinear length, and body heights using scaled photographs. In addition, we collected direct measures of body length, girth, and mass. Ultrasound, photogrammetric, and direct morphometric data were collected weekly for a minimum of one year. Using a modified truncated cones method, seals were modeled as a series of consecutive cones in which the inner core represented lean mass, and the outer layer represented blubber mass. Separating lean mass and growth from dynamic changes in overall body condition enabled assessment of critical periods when seals are most reliant on blubber energy reserves.
