Abstract
The purpose of this study was to evaluate the importance of exogenous water intake (snow/seawater) in hooded seal (Cystophora cristata) pups during their post-weaning fast. In this study, five hooded seal pups had ad lib access to snow and seawater for the first 12 and last 21 days of their post-weaning fast, respectively. Total body water and water flux were determined during both exposure periods by use of the tritiated water method. Blood samples were collected to monitor changes in hematocrit, plasma urea and plasma osmolality. Body mass loss was on average 0.36 kg day−1. Average total body water changed from 15.7 to 11.4 L, while total water influx changed from 15 to 18 mL day−1 kg−1 during snow and seawater exposure, respectively. Of this influx an average of 35% can be attributed to metabolic water, while approximately 8% was due to respiratory water influx. Interestingly, 56 and 58% of the total water influx was due to snow and seawater ingestion, respectively, amounting to 8 mL day−1 kg−1 snow (counted as liquid water) and 10 mL day−1 kg−1 seawater. Based on the results of the plasma parameters it is concluded that fasting hooded seal pups maintain water balance and homeostasis when access to snow or seawater is permitted. It is further concluded that snow and seawater intake, in addition to metabolic and respiratory water, is important for maintenance of water balance and excretion of urea during the post-weaning fast of hooded seal pups.
Highlights
The hooded seal (Cystophora cristata, Erxleben, 1777) lives in the North Atlantic where it breeds in four different geographical areas: the Davis Strait, off the coasts of Labrador and Newfoundland, the Gulf of St Lawrence, and the “West-Ice” being the pack ice between Jan Mayen and Greenland (Bowen et al 1985; Kovacs and Lavigne 1986; Lydersen et al 1997)
To assess the effect of fasting on body mass, the weight of each hooded seal pup was measured on the day of capture and 3, 5, 12, 19, 26 and 33 days after capture
The main finding in our study is that the arctic hooded seal pups eat snow and drink seawater in significant amounts during their post-weaning fast
Summary
The hooded seal (Cystophora cristata, Erxleben, 1777) lives in the North Atlantic where it breeds in four different geographical areas: the Davis Strait, off the coasts of Labrador and Newfoundland, the Gulf of St Lawrence, and the “West-Ice” being the pack ice between Jan Mayen and Greenland (Bowen et al 1985; Kovacs and Lavigne 1986; Lydersen et al 1997). The pups from the latter group are born in the second half of March (Rasmussen 1960).
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