Body and Blubber Relationships in Antarctic Pack Ice Seals: Implications for Blubber Depth Patterns

Abstract

Morphometrics and blubber depths from all four high Antarctic seals (Weddell, Ross, crabeater, and leopard) were obtained during a midsummer research cruise in the Ross Sea as the physiological ecology component of the U.S. Antarctic Pack Ice Seals project. These data are the only in vivo measurements of all four species from the same location and time of year and focused on variances in morphometrics and blubber depth related to species, sex, and age. By controlling for location and season, this cross-species design provided the means to differentiate how blubber mass might be influenced in these groups. We measured both absolute blubber depth and ratio of blubber depth to body core diameter. We found that adult and younger animals showed differences in blubber depth, but male versus female seals did not show differences within any given species. However, when compared across species, the ratio of blubber ring depth to body core diameter suggests that adult Weddell seals differ in their use of blubber compared with the other three species. We propose that this difference in blubber pattern is most likely related to Weddell nutritional requirements during the breeding season having a greater influence on blubber depth than thermal requirements when compared with the other three species.

Health and condition in the adult Weddell seal of McMurdo Sound, Antarctica

“…Male Weddell seals are thought to have a reduced foraging effort during the breeding season due to underwater territory defense requirements (Harcourt et al, 2007), which could explain our findings of greater levels of blubber in non-reproductive females. However, neither Noren et al (2008) nor Castellini et al (2009) reported similar sex differences. Animals studied in Castellini et al (2009) were in the post-breeding season where fewer differences in body condition between the sexes may be present.…”

“…However, neither Noren et al (2008) nor Castellini et al (2009) reported similar sex differences. Animals studied in Castellini et al (2009) were in the post-breeding season where fewer differences in body condition between the sexes may be present. Male seals in Noren et al (2008) were larger than the female seals, which may contribute to the variance between the studies.…”

Seasonal and Ontogenetic Variation in Subcutaneous Adipose Of the Bowhead Whale (Balaena mysticetus)

“…It cloaks the body of marine mammals and has allowed cetaceans to colonize even very cold habitats (Parry, 1949;Koopman, 1998;Pabst et al, 1999;Todet, 2001;Hamilton et al, 2004). Blubber displays great variability in thickness, biochemical composition, stratification, and cell density in all marine mammals: pinnipeds, cetaceans, and sirenians (Iverson, 2002;Best et al, 2003;Struntz et al, 2004;Koopman, 2007;Rosa et al, 2007;Castellini et al, 2009). Composed primarily of low-melting temperature unsaturated fatty acids, cetacean blubber is an effective, lowmaintenance insulator in cold water and may be so effective that bowheads have specialized organs that cool them down (K€ akel€ a and Hyv€ arinen, 1996;Pabst, 1996;Iverson, 2002;Dunkin et al, 2005;Ford, 2013).…”

Weighing our measures: approach-appropriate modeling of body composition in juvenile Steller sea lions (Eumetopias jubatus)

“…Other studies have used this dual-cone model to estimate fat and core volumes in phocids (harbor seal, Phoca vitulina L., 1758; Rosen and Renouf 1997). Typically with pinnipeds, cone models are developed as a mirrored set of two truncated cones where two additional girth measures are taken in addition to the axillary girth (e.g., Castellini et al 2009). Unfortunately, limited sampling ability prevented the current analysis from following that path.…”

“…Alternative nonlethal methods, such as bioelectrical impedance analysis, have found varied levels of success (Arnould 1995;Tierney et al 2001); however, the most prevalent indirect methods for pinnipeds rely on various morphometricderived condition indices that vary by species (Castellini and Calkins 1993;Trites and Jonker 2000;Noren and Mangel 2004;Castellini et al 2009;Mellish et al 2011). There has been increasing recognition of the need for continued development of measures of condition (e.g., Beck et al 1993;Pitcher et al 2000;Castellini et al 2009). Unfortunately, there are few opportunities to develop a conservative and accurate alternative for comparison with isotope dilution methods.…”