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At least 19 recordsLinked to original sources

PubMed2005

Variation in the fatty acid composition of blubber in Cape fur seals (Arctocephalus pusillus pusillus) and the implications for dietary interpretation.

Analysis of the fatty acid (FA) composition of blubber is a valuable tool in interpreting the diet of marine mammals. This technique is based on the principle that particular FA present in prey can be incorporated largely untransformed into predator adipose tissue stores, thereby providing biochemical signatures with which to identify prey species. Several studies of phocid seals and cetaceans have documented vertical stratification in the FA composition of blubber such that inferences about diet may vary greatly depending on the layer of the blubber that is analysed. It is not known whether blubber in otariid seals (fur seals and sea lions) also displays vertical stratification in FA composition. Furthermore, it is not known whether the FA composition of blubber is uniform in these species. In the present study, the vertical and regional variation in FA composition of blubber was investigated in seven adult female Cape fur seals (Arctocephalus pusillus pusillus). The proportion of monounsaturated fatty acids (MUFA) was greater in the outer (43.6+/-1.3%) than inner portion (40.9+/-1.2%; t(20)=5.59, P<0.001) whereas the proportions were greater in the inner than outer portions for saturated fatty acids (23.6+/-0.5% and 21.9+/-0.6%, respectively, t(20) = 5.31, P<0.001) and polyunsaturated fatty acids (PUFA, 35.5+/-0.7% and 34.5+/-0.7%, respectively, t(20) = 3.81, P < 0.001). There was an inverse relationship between MUFA and PUFA in the blubber, independent of sampling location. In addition, with the exception of the inner portion from non-lactating females, blubber from the mammary area had the highest proportions of 18:1omega9c and total MUFA, followed by blubber from the rump and neck, suggesting that the deposition and mobilisation of blubber lipids may not be uniform around the body in otariid seals. These results support the need for blubber tissue to be sampled from the same site on animals, and to the full depth of the blubber layer, to minimise variation in FA profiles that could occur if different sites and depths were sampled. Such standardisation of sampling will further aid in interpreting diet in otariid seals using the FA Signature Analysis approach.

Adipose Tissue↗

PubMed2006

Individual variation in the pup attraction call produced by female Australian fur seals during early lactation.

Otariid seals (fur seals and sea lions) are colonial breeders with large numbers of females giving birth on land during a synchronous breeding period. Once pups are born, females alternate between feeding their young ashore and foraging at sea. Upon return, both mother and pup must relocate each other and it is thought to be primarily facilitated by vocal recognition. Vocalizations of thirteen female Australian fur seals (Arctocephalus pusillus doriferus) were recorded during the breeding seasons of December 2000 and 2001, when pups are aged from newborns to one month. The pup attraction call was examined to determine whether females produce individually distinct calls which could be used by pups as a basis for vocal recognition. Potential for individual coding, discriminant function analysis (DFA), and classification and regression tree analysis were used to determine which call features were important in separating individuals. Using the results from all three analyses: F0, MIN F and DUR were considered important in separating individuals. In 76% of cases, the PAC was classified to the correct caller, using DFA, suggesting that there is sufficient stereotypy within individual calls, and sufficient variation between them, to enable vocal recognition by pups of this species.

Acoustics↗

PubMed1994

The metabolic characteristics of the locomotory muscles of grey seals (Halichoerus grypus), harbour seals (Phoca vitulina) and Antarctic fur seals (Arctocephalus gazella).

It is not known precisely how marine mammals are able to maintain muscle function during active swimming in breath-hold dives, when ventilation stops and heart rate falls. Examination of muscle biochemistry and histochemistry can provide information on the relative importance of different metabolic pathways, the contractile potential of the muscle fibres, the oxygen storage capacity of the muscle and the capillary distribution in these animals. In this study, samples of locomotory muscle were taken from wild grey seals (Halichoerus grypus), harbour seals (Phoca vitulina) and Antarctic fur seals (Arctocephalus gazella); Wistar rat muscle was analysed for comparative purposes. Activities of citrate synthase and beta-hydroxyacyl CoA dehydrogenase were higher in the harbour seal muscle than in the grey seal muscle, suggesting that harbour seals have a greater aerobic capacity. Both phocid muscles had a greater reliance on fatty acid oxidation than the fur seal or rat muscles. The myoglobin data demonstrate that the grey seals have the highest oxygen storage capacity of the three pinniped species, which correlates with their greater diving ability. Myoglobin levels were higher in all three pinniped species than in the Wistar rat. The fibre type compositions suggest that the muscles from the fur seals have higher glycolytic capacities than those of the phocid seals [fur seal pectoralis, 7% slow-twitch oxidative fibres (SO), 25% fast-twitch oxidative glycolytic fibres (FOG), 68% fast-twitch glycolytic fibres (FG); grey seal 57% SO, 5% FOG, 38% FG; area per cents]. However, the pectoralis muscle of the fur seal, although the most glycolytic of the pinniped muscles studied, has the highest capillary density, which indicates a high capacity for fuel distribution. These results show that, while pinniped muscle has an increased oxygen storage potential compared with the muscle of a typical terrestrial mammal, there are no distinct adaptations for diving in the enzyme pathways or fibre type distributions of the pinniped muscle. However, the muscle characteristics of each species can be related to its diving behaviour and foraging strategy.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed2000

Lipid composition of blood platelets and erythrocytes of southern elephant seal (Mirounga leonina) and antarctic fur seal (Arctocephalus gazella).

Erythrocyte and blood platelet phospholipid compositions were studied in three elephant seals and two fur seals, two species of marine mammals living in the Subantarctic region feeding on preys rich in (n-3) polyunsaturated fatty acids. Results were compared with those reported for related species and humans. In erythrocytes, the phospholipid (PL) and cholesterol (CHOL) contents were lower in pinnipeds than in humans. Phosphatidylcholine (PC) levels were higher in elephant seals than in fur seals, with a reverse trend for phosphatidylethanolamine (PE) and phosphatidylserine (PS). Both species had lower SM/PC ratios and PE plasmalogen concentrations than human. Erythrocytes were richer in (n-3) fatty acids (FA) in pinnipeds than in humans. In platelets, the PL content was lower and the CHOL content higher in elephant seals than in humans or in other phocid seal species studied to date. The SM/PC ratio was much higher than in other seal species or in man. In both species, the proportion of PE plasmalogens was higher in platelets than in erythrocytes. PL were more saturated in elephant seals than in fur seals. These results suggest that the erythrocytes and platelets of wild marine mammals may prove useful models to study the influence of dietary lipids on the structure and hemostatic function of these cells.

Animals↗

PubMed2004

Change in plasma cortisol and metabolites during the attendance period ashore in fasting lactating subantarctic fur seals.

Lactating fur seals (Arctocephalus tropicalis) alternate foraging trips at sea and pup attendance periods ashore. During the onshore nursing periods, lactating females do not have access to food and meet both their own metabolic requirements and milk production from their body reserve. Blood and milk samples were collected from females captured soon after their arrival ashore from a foraging trip and before their departure. Milk lipid but not milk protein content was positively related to the body condition index (BCI) of the female. During the 4-day attendance period ashore, females lost body mass, and plasma cortisol levels increased, whereas plasma urea concentration decreased and beta-hydroxybutyrate (beta-OHB) remained unchanged. The increase in cortisol level took place while blood urea concentration decreased and beta-OHB remained at a low level suggesting that it was independent from the transition from phase II to phase III that is indicative of the depletion of lipid body store as described in penguins. Thus, our results suggest that the increase in cortisol level in relation to decreasing BCI may either contribute to the mobilization of protein stores to ensure milk production when easily mobilized stores are used and/or could act as a re-feeding signal which is triggered well before females have depleted their body store.

3-Hydroxybutyric Acid↗

PubMed2004

Comparison of trace element accumulation in Baikal seals (Pusa sibirica), Caspian seals (Pusa caspica) and northern fur seals (Callorhinus ursinus).

Concentrations of 18 trace elements (V, Cr, Mn, Co, Cu, Zn, Se, Rb, Sr, Zr, Mo, Ag, Cd, Sb, Cs, Hg, Tl and Pb) were determined in liver, kidney, muscle and hair of Baikal seals, Caspian seals and northern fur seals. All the three species showed the highest concentrations of Hg, V, Mn, Se and Ag in liver, Cd, Co and Tl in kidney, and Cs in muscle among the soft tissues examined. The highest burdens of Zn, Rb and Cs were observed in muscle, Mo and Ag in liver, and Sb and Pb in hair in all the three species. Concentrations of non-essential elements, Rb, Cd, Cs and Hg, showed significant positive correlations among liver, kidney and muscle, whereas correlation coefficients for essential elements, Mn, Co, Cu, Zn and Se, between the three tissues were generally low for all the species, suggesting that homeostasis controls the concentrations of essential elements but not the non-essential elements in the tissues of these animals. Significant age-dependent increase was found in the concentrations of V, Se and Ag in liver and Hg in liver and kidney of all the three species. Hair concentrations showed significant positive correlations with Zn levels in liver and kidney and Hg in muscle for Caspian seals, Hg in liver and kidney for Baikal seals, and Pb in liver for northern fur seals. Furthermore, regression analysis using the data in the present study and in the literature showed significant positive correlations between Hg levels in hair, and liver, kidney and muscle for various species of pinnipeds. These results indicate the possibility of using hair samples for monitoring these trace elements in pinnipeds.

Aging↗

PubMed2002

Spatial aspects of organochlorine contamination in northern fur seal tissues.

Northern fur seals from the Pribilof Islands, Alaska (St. George Is. and St. Paul Is.) were examined for organochlorine contamination (OC) and whether the organochlorine levels differed between the populations and were at levels that may adversely affect their health. Fur seal blubber and milk samples were obtained from pups, sub-adult males, and adult females on both Pribilof Islands. These samples were analyzed for organochlorine contaminants including dioxin-like PCBs and other selected PCBs and pesticides by high performance liquid chromatography/photodiode array. Results showed that there are clear differences between the two islands in the patterns of fur seal OC distribution. Generally, these differences are confined to the PCBs with only minimal differences in the DDTs. There are also clear biological differences in the levels shown between milk, pup blubber, and sub-adult male blubber. When considering blubber, St. George Is. fur seals show higher OC levels than St. Paul Is., for both pups and sub-adults. On the other hand, milk samples from St. Paul Is. showed higher PCB levels than St. George Is. For the milk, the overall OC levels may impact the immune function of the pups, but are probably of only minimal impact to humans. However, for blubber, the overall toxic equivalency shows levels exceeding those levels recommended for human consumption at St. George Is. and approaching those levels at St. Paul Is. The concentration curves suggest that the movement of OC in and out of milk follows a complex set of reactions dependent on how the OC compounds on a congener level are associated with lipid. In fact, there is some evidence that they may not follow the lipid as closely as we had thought and that lipid levels can vary without impacting the total OC level in the milk.

Adipose Tissue↗

PubMed2003

How mothers find their pups in a colony of Antarctic fur seals.

In Antarctic fur seals, Arctocephalus gazella, mothers must identify their own young among hundreds or even thousands of pups, if they are to invest in their own offspring and avoid misdirecting their parental care. When returning to their breeding colony from a foraging trip of several days at sea, mothers have to find and identify their young before suckling can occur. There appears to be little confusion about which pup belongs to a mother, and adoption is absent or rare. Using behavioral observations, we investigated the means by which female Antarctic fur seals identified their pups in a breeding colony of about 750 mother-pup pairs on Kerguelen Island. We evaluated the importance of vision, scent communication, vocalizations, and rendezvous locations as possible explanations of how mothers find their pups. Every pup that a mother examined, whether her own or not, exchanged naso-nasal inspection with her, suggesting a strong role for olfactory communication in individual recognition. Both mothers and pups called to each other, and mothers that searched for pups over a longer period gave more calls and encountered more pups. Thus, vocalizations may have been used to attract pups that might be offspring. Nursing usually occurred in the same place from the end of one maternal visit to the colony and the arrival at the beginning of the next visit, suggesting that nursing locations may serve as a meeting place, or rendezvous, for mothers and pups. These results suggest that finding pups is a two-stage process for females, in which pups for sampling are attracted by calls or examined at the previous nursing location, and then individual identification is made by olfactory cues.

Journal Article↗

PubMed2001

Chemical characterisation of the oligosaccharides in hooded seal (Cystophora cristata) and Australian fur seal (Arctocephalus pusillus doriferus) milk.

Carbohydrates were extracted from hooded seal milk, Crystophora cristata (family Phocidae). Free oligosaccharides were separated by gel filtration and then purified by ion exchange chromatography, gel filtration and preparative thin layer or paper chromatography and their structures determined by 1H-NMR. The hooded seal milk was found to contain inositol and at least nine oligosaccharides, most of which had lacto-N-neotetraose or lacto-N-neohexaose as core units, similar to those in milk of other species of Carnivora such as bears (Ursidae). Their structures were as follows: Gal(beta1-4)Glc (lactose); Fuc(alpha1-2)Gal(beta1-4)Glc (2'-fucosyllactose); Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc (lacto-N-neotetraose); Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc (lacto-N-fucopentaose IV); Gal(beta1-4)GlcNAc(beta1-3)[Gal(beta1-4)GlcNAc(beta1-6)]Gal(1-4)Glc (lacto-N-neohexaose); Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-3)[Gal(beta1-4)GlcNAc(beta1-6)]Gal(beta1-4)Glc (monofucosyl lacto-N-neohexaose a); Gal(beta1-4)GlcNAc(beta1-3)[Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-6)]Gal(beta1-4)Glc (monofucosyl lacto-N-neohexaose b); Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-3)[Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-6)]Gal(beta1-4)Glc (difucosyl lacto-N-neohexaose); Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc (para lacto-N-neohexaose); Fuc(alpha1-2)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc (monofucosyl para lacto-N-neohexaose). Milk of the Australian fur seal, Arctophalus pusillus doriferus (family Otariidae) contained inositol but no lactose or free oligosaccharides. These results, therefore, support the hypothesis that the milk of otariids, unlike that of phocids, contains no free reducing saccharides.

Animals↗

PubMedDate not supplied

Genetic variability in Guadalupe fur seals.

The Guadalupe fur seal (Arctocephalus townsendi) population underwent one or two severe bottlenecks due to commercial sealing in the late 19th century. Since then the protected population has been growing steadily around their only rookery, Isla de Guadalupe, Mexico. We probed both nuclear and mitochondrial genomes using multilocus nuclear DNA profiling and mitochondrial DNA sequencing to estimate the level of genetic variability of the present population. Unlike other pinniped populations that have experienced similar historical bottlenecks, such as Hawaiian monk seals and northern elephant seals, high levels of genetic variability were found.

Animals↗

PubMed1985

Interhemispheric asynchrony of the sleep EEG in northern fur seals.

In northern fur seals the two brain hemispheres can generate the EEG slow waves during sleep not only simultaneously, as in all the terrestrial mammals investigated, but also independently as in dolphins.

Animals↗

PubMed1979

Nature of adenosine triphosphatase accelerating peptide from hydrolysate of fur seal muscle.

Ultrafiltered fur seal muscle hydrolysate was divided into eleven fractions by gel filtration on Sephadex G-15. One of the fractions (Fraction G9) accelerated the ATPase activity of carp myosin B to a rate about two-fold faster than that of the control. Fraction G9 showed a single ninhydrin spot in its silica gel thin layer chromatograph, and gave a positive test for tryptophan by the p-dimethylaminobenzaldehyde method, while tests for tyrosine, and for arginine were negative. The ion exchange amino acid analysis of its acid hydrolysate showed a predominant content of lysine, nearly equivalent to the amount of tryptophan determined from its UV absorbancy and the p-dimethylaminobenzaldehyde method. The N-terminal amino acid analysis gave di-DNP-Lys as the sole DNP-amino acid. The structure of the ATPase accelerating peptide fraction, Fraction G9, was deduced to be Lys-Trp.

Adenosine Triphosphatases↗

PubMed1991

Changes in plasma progesterone and prolactin concentrations during the annual cycle and the role of prolactin in the maintenance of lactation and luteal development in the Antarctic fur seal (Arctocephalus gazella).

Progesterone in Antarctic fur seals was undetectable from 1-2 days before parturition to 4-6 days after parturition. There was a rapid increase in progesterone to 20 ng/ml between 6 and 10 days post partum and this increase coincided with peak concentrations of oestradiol-17 beta at the time normally associated with oestrus and mating in this species. Newly formed corpora lutea were present in the ovaries by Day 9 post partum even though the seals had been isolated in an enclosure and not mated. Thereafter, progesterone remained detectable, but at a low concentration (5 ng/ml) throughout embryonic diapause. A similar pattern was observed in unmated females which suggests they enter a period of pseudopregnancy. Progesterone increased to 35 ng/ml between late February and mid-March, indicating activation of the corpus luteum at the end of diapause, and then declined slowly through the remainder of gestation. Plasma prolactin, measured against a human prolactin standard, was elevated from 1-2 days before parturition and peaked at 0-3 days post partum. It then declined slowly throughout the post-partum period and remained at a low level throughout embryonic diapause. Prolactin concentration declined to undetectable at the end of diapause and before the end of lactation. Reduction of prolactin secretion by injections of bromocriptine from Days 3 to 5 post-partum terminated lactation. Mothers, which normally leave their pups to feed at sea on about Day 7 post partum, did not continue to lactate beyond Day 7 although this did not appear to be associated with reduced prolactin secretion. Bromocriptine treatment appeared to prevent the post-ovulatory surge of progesterone although there was no long-term effect of bromocriptine on progesterone secretion during the early stages of embryonic diapause/pseudopregnancy. This study has shown that prolactin is an important hormone for maintaining early lactation in the fur seal and it probably also has a role in the control of ovulation and luteal development. Prolactin does not appear to be implicated in the control of lactation cycles in fur seals. Changes in plasma progesterone during the annual cycle show that the pattern in fur seals resembles that of some carnivores with embryonic diapause.

Animals↗

PubMed1978

Arteriovenous anastomoses in the skin of seals. II. The California sea lion Zalophus californianus and the northern fur seal Callorhinus ursinus (Pinnipedia: Otariidae).

The structure, distribution and density of arteriovenous anastomoses (AVAs) were studied in body and flipper skin of a California sea lion and a nothern fur seal. In both animals AVAs consisted of arterial, intermediate and venous segments, and were generally larger and more tortuous in the sea lion than in the fur seal. In the sea lion the majority of AVAs (72%) occurred in the deeper region of the dermis, and the density was significantly greater in the flippers than in the body. In the northern fur seal most AVAs (76%) occurred in the superficial region of the dermis; the density of AVAs in flipper skin was significantly higher than in body skin, and the density in the hind flipper was significantly greater than in the foreflipper. Arteriovenous anastomoses are important in the regulation of body temperature in seals; when these animals are on land, AVAs function to dissipate body heat, and vascular thermoregulation occurs in the flippers but notover the general body surface. Due to differences in distribution and density, AVAs play a more significant role in thermoregulation in the northern fur seal than in the California sea lion.

Animals↗

PubMedDate not supplied

Variation in the mitochondrial control region in the Juan Fernández fur seal (Arctocephalus philippii).

The Juan Fernandez fur seal (Arctocephalus philippii was allegedly extremely abundant, numbering as many as 4 million prior to sealing which continued from the late 17th to the late 19th century. By the end of the sealing era the species was thought to be extinct until they were rediscovered at Alejandro Selkirk Island in 1965. Historic records would suggest that the species underwent a substantial population bottleneck as a result of commercial sealing, and from population genetic theory we predicted that the genetic variability in the species would be low. We compared the mtDNA control region sequence from 28 Juan Fernandez fur seals from two islands in the Juan Fernandez Archipelago (Chile). Contrary to expectation, we found that variation in the Juan Fernandez fur seals is not greatly reduced in comparison to other pinniped taxa, especially given the apparent severity of the bottleneck they underwent. We also determined minor, but significantly different haplotype frequencies among the populations on the two islands (Alejandro Selkirk and Robinson Crusoe Islands), but no difference in their levels of variability. Such differences may have arisen stochastically via a recent founder event from Alejandro Selkirk to Robinson Crusoe Island or subsequent genetic drift.

Animals↗

PubMed1980

Populations, microhabitat preference and effects of infestation of two species of Orthohalarachne (Halarachnidae: Acarina) in the northern fur seal.

All of 116 northern fur seals examined, except black pups (up to 3 monts old), had nasal mites, Orthohalarachne attenuata and O. diminuata, with the mean density of 1,808 mites per subadult male, 435 per adult female, 251 per silver pup, and 21.5 per black pup. Only 63% of black pups examined were infested with both mites. Larvae represented as much as 99% of the total mite population (total samples), and the females of both species of Orthohalarachne accounted for more than 90% of the total population of adult mites. The O. attenuata adults inhabited the nasopharynx and O. diminuata adults were found primarily in the lungs. Larvae of both species occupied the mucus-filled turbinates. The heavy infestation with these mites appeared to result in impairment of respiration in fur seals, and could also cause lesions in the lungs and secondary alveolar emphysems, predispose to more serious diseases, or even kill the host animal.

Animals↗

PubMed2006

Sex steroid concentrations and localization of steroidogenic enzyme expression in free-ranging female northern fur seals (Callorhinus ursinus).

Recent precipitous population declines in northern fur seal (Callorhinus ursinus) and other Alaskan pinniped populations are due in part to reduced fecundity and have emphasized deficits in basic reproductive knowledge of these species. Following estrus and mating, fertilized female pinnipeds experience an obligatory delayed implantation lasting several months and non-pregnant (pseudopregnant) females are indistinguishable by sex steroid levels during this time. The current study examined circulating steroid concentrations and ovarian expression of key steroid-synthesizing enzymes in northern fur seals to identify changes associated with embryonic implantation, data necessary for estimating early pregnancy rates of the population. Blood samples were collected from 84 female fur seals captured on an Alaskan rookery from October 15 to November 30, a period spanning the end of the delay and subsequent uterine implantation of the fertilized blastocyst in this species. Concentrations of progesterone, estradiol, and estrone measured in blood collected during boreal fall were contrasted with samples collected during late summer from post-ovulatory females and males. Serum sex steroids were also related to ovarian expression of key enzymes responsible for androgen (17alpha-hydroxylase/17,20-lyase, cytochrome b5, and 3beta-hydroxysteroid dehydrogenase) and estrogen (aromatase cytochrome P450) synthesis. Enzymes necessary for androgen synthesis were highly expressed in ovaries, and accordingly, endocrine profiles were expanded to include DHEA, androstenediol, androstenedione, and testosterone. Estradiol concentrations were universally low and free and conjugated estrone were the primary circulating estrogens in fur seal sera. No implantation-associated peak was identified for estrogens or progesterone and mean values of progesterone and estrone were actually greater in female serum samples collected during summer than fall. However, there was a significant positive relationship between fall sampling date and testosterone concentration. Additionally, DHEA concentrations in females were lower in samples collected during the implantation period than during the summer embryonic delay. These data suggest androgens may play a substantial regulatory role in the embryonic delay of northern fur seals.

17-Hydroxysteroid Dehydrogenases↗

PubMed2003

The comparative energetics and growth strategies of sympatric Antarctic and subantarctic fur seal pups at Iles Crozet.

The period of maternal dependence is a time during which mammalian infants must optimise both their growth and the development of behavioural skills in order to successfully meet the demands of independent living. The rate and duration of maternal provisioning, post-weaning food availability and climatic conditions are all factors likely to influence the growth strategies of infants. While numerous studies have documented differences in growth strategies at high taxonomic levels, few have investigated those of closely related species inhabiting similar environments. The present study examined the body composition, metabolism and indices of physiological development in pups of Antarctic fur seals (Arctocephalus gazella) and subantarctic fur seals (Arctocephalus tropicalis), congeneric species with different weaning ages (4 months and 10 months, respectively), during their overlap in lactation at a sympatric breeding site in the Iles Crozet. Body lipid reserves in pre-moult pups were significantly greater (t28=2.73, P<0.01) in subantarctic (26%) than Antarctic fur seals (22%). Antarctic fur seal pups, however, had significantly higher (t26=3.82, P<0.001) in-air resting metabolic rates (RMR; 17.1 +/- 0.6 ml O2 kg(-1) min(-1)) than subantarctic fur seal pups (14.1 +/- 0.5 ml O2 kg(-1) min(-1)). While in-water standard metabolic rate (SMR; 22.9 +/- 2.5 ml O2 kg(-1) min(-1)) was greater than in-air RMR for Antarctic fur seal pups (t9=2.59, P<0.03), there were no significant differences between in-air RMR and in-water SMR for subantarctic fur seal pups (t12=0.82, P>0.4), although this is unlikely to reflect a greater ability for pre-moult pups of the latter species to thermoregulate in water. Pup daily energy expenditure was also significantly greater (t27=2.36, P<0.03) in Antarctic fur seals (638 +/- 33 kJ kg(-1) day(-1)) than in subantarctic fur seals (533 +/- 33 kJ kg(-1) day(-1)), which corroborates observations that pups of the former species spend considerably more time actively learning to swim and dive. Consistent with this observation is the finding that blood oxygen storage capacity was significantly greater (t9=2.81, P<0.03) in Antarctic (11.5%) than subantarctic fur seal (8.9%) pups. These results suggest that, compared with subantarctic fur seals, Antarctic fur seal pups adopt a strategy of faster lean growth and physiological development, coupled with greater amounts of metabolically expensive behavioural activity, in order to acquire the necessary foraging skills in time for their younger weaning age.

Animals↗