Adult Harp Seals Research Articles

From ice to ocean: changes in the thermal function of harp seal pelt with ontogeny.

Many animals exhibit ontogenetic changes associated with adaptations for survival. Harp seals (Pagophilus groenlandicus) live in the Arctic and rely on thick insulation to maintain thermal homeostasis. Adult harp seals primarily use blubber for insulation, but newborn harp seals rely on a lanugo pelt while nursing, as their blubber layer develops and their first-year pelage grows. This study compared ontogenetic changes in the thermal properties of harp seal pelts in water and in air. Thermal conductivity, pelt thickness, and thermal resistance were measured in water for pelts of harp seal neonates (1 day old), thin whitecoats (4 day old), fat whitecoats (9 day old), ragged jackets (2 week old), beaters (3 week old), and adults and compared to previously published measurements made on the same pelts in air. Pelt conductivity was significantly higher in water than air for pre-molt and molting pups (P ≤ 0.031). Unlike adult pelage, which flattened underwater, lanugo hairs lifted underwater, a phenomenon that has not been reported previously. Thermal resistance of the pelt was significantly reduced in water compared to air for neonates and thin whitecoats (P ≤ 0.0001). A mathematical model of conductive heat transfer for an ellipsoid bodyshowed volume-specific heat loss in water decreased and then stabilized as harp seals aged (P = 0.0321) and was significantly higher for neonates, thin whitecoats, and ragged jackets in water than in air (P ≤ 0.0089). Overall, pelt function is reduced in water for harp seal pups with lanugo, and this renders neonates and thin whitecoats particularly vulnerable to heat loss if submerged.

The fat and the furriest: morphological changes in harp seal fur with ontogeny.

Ontogenetic changes in physiological performance often exemplify the development of adaptations to environmental challenges. For mammals in polar regions, the extreme cold of the environment presents a constant challenge to thermal homeostasis. The harp seal (Pagophilus groenlandicus) is an Arctic species that shifts its thermoregulatory strategy with ontogeny. Adult harp seals primarily use blubber for insulation, but newborn harp seals instead rely on their fur coat while their blubber layer develops. Harp seal pups are weaned abruptly, less than 2 wk after birth, and must subsequently learn to swim and dive in frigid waters on their own. This study examined how the morphological characteristics of harp seal fur change with ontogeny. We compared hair length, hair circularity, and hair density for neonates (1 d old; n = 7), early-nursing pups (4 d old; n = 3), late-nursing pups (9 d old; n = 4), newly weaned (molting) pups (2 wk old; n = 5), late-weaned (molted) pups (3 wk old; n = 4), and adult harp seals (n = 4). Hairs were shorter (P < 0.001) and flatter (P < 0.001) in older animals. Additionally, hair density decreased with age (P < 0.001), in terms of both the average number of hair bundles per unit area and the average number of underhairs present in any given bundle. These morphological changes were associated with a reduced thermal resistance of the pelt in late-weaned (molted) pups and adults (P < 0.001). Results are consistent with known evolutionary patterns of fur morphology associated with the transition from fur to blubber in aquatic species, yet this is the first time such morphological differences have been demonstrated across age classes within a single species. Thus, the ontogenetic patterns described here for harp seals recapitulate the convergent phylogenetic patterns observed across secondarily aquatic species. Overall, the timing of these ontogenetic changes may limit the ability of harp seals to adapt to the deterioration of sea ice in the Arctic, as predicted with continued climate change.

Giardia and Cryptosporidium in harp and hooded seals from the Gulf of St. Lawrence, Canada

Giardia and Cryptosporidium are protozoan parasites known to cause enteric disease in terrestrial wildlife species (mammals, reptiles and birds). Few surveys for Giardia and Cryptosporidium in marine wildlife species, such as pinnipeds, have been reported. The objective of this study was to determine the prevalence and genotype of Giardia and Cryptosporidium in two species of pinnipeds, harp seal ( Phoca groenlandica) and hooded seal ( Cystophora cristata), from the Gulf of St. Lawrence, Canada. Faecal samples were collected from pup and adult seals and examined for the presence of cysts of Giardia and oocysts of Cryptosporidium using microscopy and immunofluorescent staining. Tissues from the small intestine of adult seals were also collected and examined for infections using the polymerase chain reaction (PCR) technique. Giardia cysts were found in the faeces of 42% (16/38) of adult harp seals, but in none of the harp seal pups (0/20). Although Giardia cysts were not detected in faeces of adult hooded seals (0/10) using microscopy, 80% tested positive for Giardia using PCR of intestinal tissue indicative of a true replicating infection. Both harp and hooded seals harboured infections with the zoonotic strain, Giardia duodenalis Assemblage A, as determined using a nested-PCR technique to amplify a small subunit ribosomal (SSU-rRNA) gene of Giardia. Cryptosporidium was not detected by microscopy, nor using the PCR technique on intestinal tissues from any of the 68 seals examined.

Seasonal distribution and dive behaviour of harp seals (Pagophilus groenlandicus) of the White Sea–Barents Sea stock

Eight adult female harp seals (Pagophilus groenlandicus) of the White Sea–Barents Sea stock were tagged with satellite-linked dive recorders during the nursing period and followed from breeding in late February 1995 until moulting in late April 1995. Another ten adult harp seals of both sexes were tagged and followed from moult in early May 1996 until breeding in late February the following year. Between breeding and moult the seals were distributed along the coasts of Kola of Russia and eastern Finnmark of Norway, coinciding in time and space with the spawning capelin (Mallotus villosus). Between moulting and breeding they encircled the entire Barents Sea, mostly in open water, using the water column from 20 to 300 m, and in so doing by and large reflecting the annual migrations of the capelin. Capelin is therefore assumed to be the main source of prey for the White Sea–Barents Sea stock of harp seals, to be substituted, in part, by amphipods (e.g. Themisto libellula) in mid-summer and polar cod (Boreogadus saida) and herring (Clupea pallasii) in late autumn and winter. These data provide a baseline for the evaluation of the effects of future climatic change in the rich Barents Sea ecosystem.

Distribution and diving behaviour of harp seals ( Pagophilus groenlandicus ) from the Greenland Sea stock

The distribution and diving behaviour of 16 adult harp seals (Pagophilus groenlandicus) from the Greenland Sea stock were studied in 1993 and 1999, using satellite-linked dive recorders (SDRs). The seals remained near the pack-ice edge in the Greenland Sea between breeding and moulting (April/May 1993; 6F) and during the first 7 weeks after moulting (June/July, 1999; 4F, 6M), there diving to depths of <100 m. In mid-July 1999, seven out of eight seals with active SDRs migrated into the Barents Sea, there diving to <400 m and sharing feeding grounds with the Barents Sea harp seal stock. Between September and December, six of these seals joined the eighth seal in the Denmark Strait until March 2000, there diving to depths of 100–400 m. Overall, dives were significantly deeper in the day and in winter than at night and in summer, with some regional differences. Harp seals are considered pack-ice-associated seals, but our tagged seals spent a considerable proportion of their time in open water, their distribution largely overlapping with that of capelin (Mallotus villosus).

Quantitative differences in the pineal ultrastructure of perinatal and adult harp (Phoca groenlandica) and hooded seals (Cystophora cristata).

Seals are unique among mammals in that newborns have a large pineal gland and extremely high plasma levels of melatonin at birth. Melatonin levels are also high in the seal fetus but decline rapidly during the first few days of life. The aim of the present study was to provide quantitative information about the ultrastructure of the seal pineal gland using fetal, newborn, and adult hooded seals (Cystophora cristata), and newborn and adult harp seals (Phoca groenlandica). The relative and absolute volumes of pinealocytes (Pi), arteries and veins, nerves, connective tissue, capillaries and glial cells, as well as mitocondria and lipid droplets in Pi, were calculated by use of point count analysis. Whereas the pineal ultrastructure was similar in fetuses and newborns, both seal species showed a pronounced and particular reduction in the volume of Pi and a similar reduction in pinealocyte mitochondria. There was also a shift from unmyelinated to myelinated pineal nerves in adults compared with fetal/newborns. The selective and marked reduction of Pi may explain the zonated pineal structure typical of the adult seal. The results demonstrate that the fetal gland is as large and active as that of the newborn seal and support the notion that the large size and high activity of the pineal gland in the newborn seal is a fading consequence of its prenatal condition.

Estimated pup production of harp seals Pagophilus groenlandicus in the White Sea, Russia, in 2000

Abstract Since the 1960s pup production of harp seals Pagophilus groenlandicus in the White Sea was estimated from aerial photographic surveys of visible adult females on the ice. Adult abundance estimations were underestimated because an unknown number of females were in the water during the survey. The absence of a reliable estimation of pup production constrained management initiatives. Aerial photographic surveys of whelping harp seals were conducted in the White Sea 10–12 March 2000. Using a systematic strip transect survey design approach, the number of pups present was estimated as 294 914 with a standard error (s.e.) of 36 168. When pups caught by Russian sealers in the White Sea before the aerial surveys (30 729 pups) were included the total estimated number of pups was 325 643 (s.e. 36 168), whereas the number of adult harp seals was 215 943 (s.e. 22 630). The pup estimate was not corrected for pups born after the survey, but this was not considered to be significant. The new estimation of pup production is higher than thought earlier.

Bioaccumulation of PCBs and chlorinated pesticides in seals, fishes and invertebrates from the White Sea, Russia

Persistent organochlorines (OC) contaminants, including polychlorinated biphenyl (PCB) congeners, Dichlorophenyltrichloroethane (DDT)- and chlordane (CHL) related compounds, hexachlorocyclohexanes (HCH) isomers and chlorobenzenes (CBz) were determined in blubber of harp seals ( Phoca groenlandica), ringed seals ( Phoca hispida) and bearded seals ( Eringnathus barbatus) as well as in fishes and invertebrates from the White Sea, in northwest Russia. Highest ∑PCB and ∑DDT concentrations were found in samples from two male bearded seals (means of 4150 ng/g lw and 3950 ng/g lw, respectively). Female harp seals had mean ∑PCB and ∑DDT concentrations of 1070±504 ng/g lw and 619±328 ng/g lw, respectively. Male and female adult ringed seals had similar mean ∑PCB concentrations as harp seals (955±385 ng/g lw and 999±304 ng/g lw, respectively). ∑CHL concentrations ranged from 63±29 ng/g lw in blubber of female adult ringed seals, to 322±156 ng/g lw in adult harp seals and averaged 465 ng/g lw in bearded seals. HCH isomers, mirex and chlorobenzenes were detected in all seal samples but were present at lower levels than ∑CHL, ∑DDT and ∑PCB. Concentrations of ∑CHL, ∑DDT and ∑PCB in ringed seals from the White Sea were within the range reported for the Barents Sea but lower than in ringed seals from the Kara Sea. Temporal trends were investigated by comparing concentrations of OCs in blubber of harp seal pups collected in 1992 with pups of the same age collected in 1998. The declines over the 6 year period ranged from approximately 33% for ∑DDT to 60% for ∑PCB. These declines are consistent with reports of declining concentrations ∑DDT in seawater from the White Sea and inflowing rivers in the 1980's and early 1990s. The major OC contaminants in fishes from the White Sea were DDT-related compounds and PCBs. Navaga ( Eleginus navaga) had the highest concentrations of the 5 fish species studied with mean ∑PCB of 41±6 ng/g wet wt. while lowest mean concentrations were present in cod muscle (16±8 ng/g ww). Concentrations of hexachlorobenzene (HCB), DDT, CHL—related compounds and PCB congeners were strongly correlated with trophic level of the organisms assigned using δ 15N values, while β-HCH, γ-HCH and cis-chlordane showed no relationship with trophic level. Food web magnification factors (FWMFs) for p,p′-DDE, α-HCH, oxychlordane and trans-nonachlor the White Sea were similar to those from marine food webs in the Barents Sea and the Canadian arctic, while FWMFs for HCB and PCBs were generally lower. Overall the results suggest that the White Sea marine food differs in terms of the availability of contaminants in comparison to studies of open ocean arctic food webs due to proximity to urban/industrial areas and greater importance of benthic food sources.

Reference values for serum biochemical parameters in free-ranging harp seals.

The harp seal (Phoca groenlandica) is one of the most important predators in the Northeastern Atlantic ecosystem. Establishing biochemical reference intervals is important for evaluating the health status of harp seals kept in captivity and for evaluating the effects of environmental changes on the health of populations in the wild. The purpose of this study was to determine reference values for serum biochemical parameters in wild adult harp seals using readily available current methods. Blood samples were obtained from 14 adult female harp seals and 9 suckling pups on the pack ice of the Greenland Sea in early March 1998. Seven seals were humanely killed on the ice by permission of the Norwegian Directory of Fisheries and in conjunction with several other research projects. The seals were sampled within 15 minutes postmortem. Remaining seals were captured alive and sampled via the extradural intravertebral vein. Serum biochemical parameters were measured using a Technicon Axon analyzer and included electrolytes (sodium, chloride, potassium, magnesium, and calcium), substrates (free fatty acids, triglycerides, fructosamine, and glucose), end products (urea and uric acid), and proteins (total protein, globulins, and albumin). Serum protein electrophoresis also was done. Data were tested for normality and reference limits were calculated as mean +/- 1.96 X SD. Results between groups were compared using 2-tailed t-tests. Serum levels of glucose and triglycerides were lower, but serum levels of urea were higher in dead animals than in animals that were captured alive. Serum levels for 7 of 17 parameters were significantly different in pups compared with adults. Separate reference intervals were calculated for adult seals and seal pups. Both sampling method and age should be considered when evaluating the results of future analysis of serum parameters in wild and captive harp seals.

Physiological effects of seawater intake in adult harp seals during phase I of fasting

Previous studies have shown that harp seals may drink considerable amounts of seawater. The current study was undertaken to study the physiological responses to bolus administration of seawater. Adult harp seals ( Phoca groenlandica) were fasted without access to water for 48 h and then given 1000 or 1500 ml of seawater by a stomach tube. Changes in urine and plasma parameters were thereafter monitored for another 12–20 h. Urine production and urine excretion rate of Na + and Cl − increased soon after administration and reached a maximum 3–4 h later. Urine osmolality was kept rather stable and high (∼1500 mOsm kg −1) following seawater administration, due to a drop in urine concentration of urea that was proportional to the simultaneous increase in urine concentration of NaCl. Plasma osmolality remained at approximately 340 mOsm kg −1, while plasma concentration of urea decreased some 20–25% due to increased excretion of urea when seawater was ingested. Despite bolus administrations of seawater of up to ∼2% of body mass, homeostasis was maintained and no ill effects observed. It is concluded that the concentrating abilities of the kidneys of harp seals are sufficient to prevent net loss of body water following seawater ingestion. Seawater ingestion may, moreover, increase urinary osmotic space and thus serve as a mechanism to excrete additional urea produced during phase I of fasting.

Giardiasis in pinnipeds from eastern Canada.

Cysts of Giardia sp. were detected in feces from the rectum of 20 of 74 pinnipeds examined from the eastern coast of Canada in 1997 and 1998 using a monoclonal antibody technique. Infected pinnipeds included 15 adult harp seals (Phoca groenlandica), four adult grey seals (Halichoerus grypus), and one juvenile harbor seal (Phoca vitulina). Cysts were not detected in 15 seal pups <1-yr-old. The highest prevalence (50%) occurred in adult harp seals collected near the Magdalen Islands in the Gulf of St. Lawrence. The overall prevalence of Giardia sp. in grey and harbor seals, excluding pups, from the Gulf and St. Lawrence estuary was 23%. Feces from 11 beluga (Delphinapterus leucas) and one northern bottle-nosed whale (Hyperoodon ampullatus) stranded in the St. Lawrence estuary were negative for Giardia sp. cysts. The significance of Giardia sp. in marine mammals, shown here for the first time in eastern coastal Canada, is unknown.

The effect of body fat on basal metabolic rate in adult harp seals ( Phoca groenlandica)

Three adult harp seals ( Phoca groenlandica) were fed different daily amounts of capelin ( Mallotus villosus), and their body composition determined by use of the tritiated water method at different levels of fattening. Basal metabolic rate (BMR) was measured after 5 days of fasting by indirect calorimetry, and was on average 1.1 W·kg −1 when 45% of body mass (BM) was fat and 2.3 W·kg −1 when body fat was reduced to 13% of BM. This suggests that body fat contributes little to BMR in these animals. It follows, that predictions of BMR on the basis of BM is questionable in seals, in which body fat may change seasonally between 20 and 60% of BM.

Organochlorines in mother and pup pairs in two Arctic seal species: Harp seal (Phoca groenlandica) and hooded seal (Cystophora cristata)

During the lactation period of two Arctic seal species, pairs of females with their respective pups were caught in the ‘West Ice’, a pack ice area in the Greenland Sea north of Jan Mayen. Blubber samples from pairs of harp seals (Phoca groenlandica) and hooded seals (Cystophora cristata) were analysed for 22 CB-congeners (∑CB), five DDT components (∑DDT), four chlor done-related compounds (∑CHL), three HCH isomers (∑HCH) and HCB using capillary GC-ECD in order to study interspecies differences and generation transfer of organochlorine (OC) pollutants. Highest concentrations of these OCs were found in adult hooded seals where average concentrations in blubber were 4.63 μg g−1 ∑ CB, 2.83 μg g−1 ∑ DDT and 0.98 μg g−1 ∑ CHL, representing five, four and two times the concentration found in adult harp seals, respectively. On the other hand, ∑HCH and HCB levels in adult harp seals were higher or the same as in hooded seals. Different food preference is probably the major factor causing the observed interspecies OC level variations. However, species-specific detoxification may also contribute to these results. An efficient generation transfer of OCs was found in both species. However, this transfer seemed to be selective with respect to OC-groups and certain CB congeners. Concentrations of highly chlorinated CB congeners were relatively less present in pups of both species. An increasing transfer barrier in the order: ∑ HCH ≈ HCB < ∑ CHL ≤∑ DDT < ∑CB seems to exist. The generation transfer of OCs demonstrates the importance of lactation as an excretory route of various CB congeners and pesticides in reproductive female seals but, more important, it demonstrates the need for a better understanding of the consequences this transfer might have for the young animals.

Body composition of harp seals

Using chemical analysis we measured the composition of 26 harp seals (Phoca groenlandica) representing both sexes, aged between 3 months and 30 years, and encompassing a wide range of body conditions. Predictive relationships between total body water and total body fat contents, total body protein content, and gross energy were calculated. These equations allow accurate estimation of harp seal body composition provided total body water content and body mass are known. Using these data we compared the accuracy of three existing equations that have been used to predict body fat content of other species. We found that in adult harp seals, lean body mass has a relatively stable hydration of 70% but the hydration of blubber varied with body condition. Lipid content, and thus energy density of blubber, increased with increasing body condition.

Summer feeding ecology of harp seals (Phoca groenlandica) in relation to arctic cod (Boreogadus saida) in the Canadian high arctic

The diet and feeding behaviour of harp seals, Phoca groenlandica, was examined in two high arctic locations. Fish otoliths were used to evaluate dietary composition and aspects of the population dynamics of the major prey species, arctic cod, Boreogadus saida. Harp seals, primarily adults, arrive in the high arctic in mid to late June and depart by early October. Their migration is undertaken specifically for feeding. Harp seals feed intensively on arctic cod, often occurring in dense multispecies aggregations in late summer. The average weight of harp seal stomach contents was high; glutted individuals contained as much as 6% of their body weight in food. Although arctic cod declined in abundance between years, size of cod ingested was similar between areas and years, and overlapped completely with cod taken by other marine mammals. Age/size segregation of arctic cod may account for poor representation of fish <3 years old in the seal diet. Widespread reproductive failure of arctic cod could have a profound influence on the energy balance of adult harp seals since there does not appear to be an alternate food source of equivalent energy value and abundance in arctic waters. Increasing harp seal populations will likely result in increased competition with a host of arctic cod predators, particularly ringed seals.

Neonatal growth and organ allometry of Northwest Atlantic harp seals (Phoca groenlandica)

Growth and organ allometry of neonatal harp seals (Phoca groenlandica) were monitored during the first 6 weeks of life from 1982 to 1984. At birth, pup mass was 9.9 ± 1.7 (1 SD) kg. After their 1st day of relatively slow growth, pups gained mass rapidly, increasing 2 kg/day throughout the remainder of the ~12-day nursing period. Two-thirds of this mass gain was accumulated as a layer of subcutaneous blubber. Pups lost mass at a rate of ~0.5 kg/day during the postweaning fast, utilizing energy stores from the viscera, muscles, and limited amounts of blubber. In neonates, liver mass fluctuated in conjunction with total body mass gain and loss. The liver of adult harp seals was large relative to terrestrial mammals of similar size, but relatively small compared with other pinnipeds. The heart of harp seals grew slowly in pups and did not lose mass during fasting, and in adults it was of similar size relative to other mammals. The spleen of neonates was large and grew quickly during nursing. Spleen mass was quite variable among postweaning animals. As would be expected for a large-sized, precocially born, relatively advanced mammalian neonate, pups are born with large brains that grow very slowly. Adult brain mass, in relation to body mass, was similar to that of other mammals.

Histology of reproduction in harp and grey seals during pregnancy, postparturition, and estrus

Reproductive tracts were collected on the eastern coast of Canada from adult female grey seals (Halichoerus grypus) during gestation and postparturition, and from adult female harp seals (Phoca groenlandica) during delayed implantation and postparturition. Reproductive tracts were fixed in 10% buffered formalin for light microscopy. The placental site and adjacent tissue were preserved in 2% glutaraldehyde – 1% paraformaldehyde for scanning electron microscopy. During the delay of blastocyst implantation, the endometria of the gravid and nongravid uterine horns were similar in microscopic appearance. During gestation, maternal septa were often surrounded by maternal epithelium deep into the placental labyrinth except distally, where the maternal cells were replaced by syncytium. Marginal hematomas increased in size and complexity throughout placentation. Following parturition, uterine regression occurred earlier in harp seals (10 days postpartum) than in grey seals (21–25 days postpartum). Postpartum changes were most pronounced in the placental site where the blood vessels underwent extensive reorganization. In some specimens, the extensively vascularized placental site of the previous pregnancy was still apparent 12 months later. Epithelial replacement in the uterus was complete in grey seals 21–25 days postpartum and sooner in harp seals. Cervical and vaginal stratification occurred in both phocids following parturition and increased towards estrus. A recently ovulated grey seal was obtained between 21 and 25 days postpartum. The vaginal stratification and the presence of sperm in their uterine horns indicated that grey seals began estrus about 12–17 days postpartum. In harp seals, estrus appeared to occur towards the end of the lactational period, about 10–12 days postpartum.

Immunohistochemical Identification of Cell Types in the Pars Distalis of Harp Seals, Phoca groenlandica

AbstractThe distribution of pars distalis mammotropic, somatotropic, luteotropic, folliculotropic, thyrotropic and corticotropic cells was examined in neonate, juvenile and adult harp seals (Phoca groenlandica) by means of immunohistochemistry, employing antisera to hormones of human or rat origin. All the cell types were evident in one day‐old animals, except for immunoreactive folliculotropic cells which were first apparent in five day‐old animals. Mammotropic cells were small and relatively inactive in neonatal animals compared with the juvenile and adults. Somatotrops increased in apparent activity between one and five days postpartum, were most active in the juveniles, and less so in the adults. The corticotrops, found predominantly in the anterior regions of the pars distalis, appeared to increase in number and activity in adult seals. The gonadotrops increased in numbers as the animals aged, but the cells tended to be smaller in the juvenile and adult animals. The thyrotrops were small cells found only in the central regions of the pars distalis. The distribution of immunostained cell types is compared with cell type characterization of the same pituitaries based on light and electron microscopic evidence alone.

Ventilation and gas exchange in unrestrained harp seals ( Phoca groenlandica)

1. 1. Unrestrained adult harp seals ( Phoca groenlandica) spent 87.7 ± 2.2% ( x ̄ ± SD) of the time diving and the mean dive time was 278.0 ± 35.3 SD. 2. 2. The mean metabolic rate was 3.24 ± 0.69ml O 2·kg −1·min −1 3. 3. The minute ventilation during the surface periods was 62.45 ± 7.32 l·min −1 and the oxygen extraction was 7.34 ± 0.40%. 4. 4. There was a strong negative correlation between metabolic rate and the percentage of time spent diving, and between metabolic rate and mean dive time. There was no correlation between metabolic rate and minute ventilation, or between metabolic rate and oxygen extraction. 5. 5. These results indicate that the ventilatory response of diving seals to an increase in the metabolic O 2 requirements is due to a change in dive pattern rather than an increase in ventilation or gas exchange.

Temperature regulation in freely diving harp seals (Phoca groenlandica).

Measurements were made of the relation between body temperature, respiration, diving pattern, and water temperature using three adult harp seals (Phoca groenlandica). Core temperature, ventilation, gas exchange, and diving pattern were not affected by water temperature ranging from 1.8 to 28.2 °C. The basal metabolic rate of the seals in this study was not significantly different than that predicted for terrestrial mammals of equivalent size. Expired heat loss and convective heat loss from the body accounted for 16% of the heat loss and were independent of water temperature. The remaining 84% of the heat was lost from the flippers which accounted for less than 14% of the surface area. Calculations of the ratio of convective heat transfer coefficients of the blubber layer indicate that internal conduction rather than external convection governed heat loss.