Energy intake and utilisation by nursing bearded seal ( Erignathus barbatus ) pups from Svalbard, Norway

Norwegian Polar Institute, Tromsø, Norway.
Journal of Comparative Physiology B (Impact Factor: 2.62). 02/1996; 166(7):405-11. DOI: 10.1007/BF02337884
Source: PubMed


In this study we measure energy intake via milk in nursing bearded seal (Erignathus barbatus) pups and determine how this energy is allocated into metabolism and storage of new tissues. This was accomplished using longitudinal mass gain records and the doubly labelled water technique on nursing pups in combination with cross-sectional data on changes in milk composition from bearded seal mothers. The pups (n = 3) were all less than a week old at the start of the experiments. Pups gained 3.3 +/- 0.4 of which 50% was fat, 14% protein and 36% water. Average daily water influx for the pups was 69.5 +/- 9.0 day-1. Average CO2 production during the study period was 0.99 +/- 0.10 ml.g-1.h-1, which corresponds to a field metabolic rate of 642 +/- 67 day-1, or 6.0 +/- 0.5 times the predicted basal metabolic rate according to Kleiber (1975). The pups drank an average of 7.6 +/- 0.5 kg of milk daily. This corresponds to a daily energy intake of 154 +/- 8 MJ, 47 +/- 14% of which was stored as new body tissue. Despite this high energy intake bearded seal pups do not get as fat as do other nursing phocids. This is in part due to their larger body size but also due to their very active aquatic lifestyle and the lower and more consistent fat content of the milk compared to other phocid species. Bearded seal mothers forage during lactation and may also be involved in teaching their pups to feed independently. All these data suggest that the lactation strategy of bearded seals differs from the phocid norm.

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    • "); pup mass of 46.7 kg, EEG of 21.4 g/MJ) (Iverson et al. 1993; Lydersen et al. 1996, 1997; Oftedal et al. 1996). "
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    ABSTRACT: As lactation is commonly very brief in phocid seals, the transfer of sufficient energy between mother and offspring is critical for their reproductive success. In this study, we investigated variation in the pattern of energy transfer and allocation during lactation in the spotted seal (Phoca largha Pallas, 1811). Temporal changes in milk composition, milk consumption, and pup mass gain were analyzed from birth to weaning in a spotted seal pup that was hand-reared on a donor-female’s milk. In addition, growth rates were measured in six pups raised in captivity but nursed naturally. We found that milk fat content increased and water content decreased during lactation. We calculated that spotted seal pup ingest a mean (±SD) daily energy of 39.5 ± 8.6 MJ/day, which corresponded to a daily mass gain of 0.9 kg/day. We found that the growth rates of the hand-reared pup and the six naturally reared pups did not differ, and overall, the mean (±SD) daily growth rate of spotted seal pups was 1.1 ± 0.2 kg/day before weaning and 0.6 ± 0.2 kg/day from birth to molt. Our study provides the first data on lactation patterns in this species.
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    • "The diet of bearded seals is reasonably well described across their range [53], [54] and it has been studied in Svalbard [17]. But, none of these earlier studies have examined the crucial late gestation period, when females need to acquire energy to fuel the growth of the pup as well as accumulating fat stores to help with the upcoming energetic costs of lactation [5], [55]. While stable isotope analysis can provide powerful insights into temporal and spatial differences in trophic relationships between predators and their prey, using the data to infer the actual diet can be more problematic. "
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    • "Milk composition in pinnipeds (high fat and low carbohydrate) has been driven by the constraints of fasting (Oftedal 1993). The fat content of seal milk is exceedingly high: 30–50% in otariids (Arnould and Hindell 1999; Costa and Gentry 1986; Gales et al. 1996; Georges et al. 2001; Trillmich and Lechner 1986) and over 50% in several phocid species (Iverson et al. 1993, 1995; Lydersen et al. 1996; Riedman and Ortiz 1979). This rate of lipid energy output in phocids requires extensive lipid mobilization from adipose reserves. "
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