Seasonal Changes in Blubber Distribution in Atlantic Harbor Seals: Indications of Thermodynamic Considerations

Abstract

Among its functions, the hypodermal blubber layer of pinnipeds serves as both an energy reserve and insulation. This study examined seasonal changes in blubber distribution and body morphology in a group of captive changesharbor seals to test whether these changes were designed to maximize insulative effectiveness. Seasonal changes were found in girth, blubber volume, mean blubber depth, and the ratio of blubber depth to body radius (d/r ratio). These changes were more evident in older seals. The d/r ratio demonstrated a smaller relative annual change than mean blubber depth. The d/r ratio also exhibited less variation along the length of the seal than blubber depth at any given time. Similar to reports for ringed seals, and contrary to those for southern elephant seals, the harbor seals preferentially lost blubber from overinsulated areas of the body. These results suggest that core tissue and blubber mass are lost in a manner that maximizes insulative effectiveness.

Environment and activity affect skin temperature in breeding adult male elephant seals (Mirounga angustirostris)

“…As the breeding season progresses, males deplete their blubber reserves in the competition to gain access to females. Similar to other pinnipeds such as harbor seals and Steller sea lions, northern elephant seal males appear to deplete blubber preferentially from certain areas when fasting (Mellish et al, 2007;Rosen and Renouf, 1997) (D.E.C., unpublished observations). Mean blubber thickness declines from 6.2cm early in the breeding season to 3.6cm by early March, but this proportion varies widely across the body surface (D.E.C., unpublished observations).…”

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

“…Past studies of in vivo blubber depth in seals have generally followed a paradigm where the morphometrics of individual animals were tracked through time, and changes in the ratio of blubber depth to whole body radius were related to season and thermal insulation (Ryg et al 1988;Rosen and Renouf 1997). In our study, we offer a somewhat different perspective on the relationship of blubber to the physiology of a phocid.…”

“…Second, the APIS data were derived from much larger phocids than those used in previous studies (Ryg et al 1988;Rosen and Renouf 1997). Because larger mammals have a lower massspecific metabolic rate than smaller mammals (Kleiber 1961), we could directly sample animals with different basal metabolic energetics and compare the thermal approach with the relationships of blubber to body core.…”

“…Fourth, in order to examine how blubber depth changed in relation to the metabolically active core, we modified earlier models (Ryg et al 1988;Rosen and Renouf 1997) that calculated the ratio of blubber depth to whole body radius. In our study, we examined total ring blubber depth in relation to core diameter in order to examine how blubber depth changed in relation to the metabolically active core.…”

Age-related differences in skeletal muscle lipid profiles of Weddell seals: clues to developmental changes

“…Diving phocids (true seals, Order Carnivora, Family Phocidae) must sequester adequate amounts of lipids to maintain sufficient blubber thickness to meet nutritional demands, buoyancy regulation and maintain thermoregulatory homeostasis (Burns et al, 2003;Castellini et al, 2009;Crocker et al, 1997;Gales and Burton, 1987;Kanatous et al, 2008;Noren et al, 2008;Rosen and Renouf, 1997;Ryg et al, 1988;Sato et al, 2003;Webb et al, 1998). Consequently, the selective pressures for maintaining blubber thickness are typically a combination of these demands, varying with age, diet and reproductive status (Castellini et al, 2009).…”