Mass-transfer efficiency between hooded seal (Cystophora cristata) mothers and their pups in the Gulf of St. Lawrence

Abstract

We investigated the efficiency of mass transfer in hooded seals (Cystophora cristata) through serial mass measurements on mother – pup pairs during lactation. Data on birth mass, weaning mass, pup growth, lactation duration, mass loss during the postweaning fast, and adult female mass were collected during the breeding seasons of 1988 – 1991. Pups weighed 24.4 ± 2.6 kg (mean ± SD, N = 19) at birth; males (25.3 ± 2.3 kg, N = 7) did not differ statistically from females (24.0 ± 2.7 kg, N = 12). During the nursing period pups grew at a rate of 6.9 ± 1.2 kg (N = 28) per day. Weaning took place at 3.8 ± 0.5 days of age (N = 19). Mass at weaning was not related to mass at birth. Pups were weaned at 47.1 ± 6.7 kg (N = 25). The mean value for weaning mass of males (47.6 ± 7.1 kg, N = 10) was not significantly different from that of females (46.7 ± 6.8 kg, N = 15). Ten percent of weaned pups stole milk from females after their own mothers had departed. Weaners, which consistently lost mass, did so at a rate of 1.3 ± 0.8 kg per day during the early part of the postweaning fast. At parturition, mean maternal body mass was 236.5 ± 35.5 kg (range 172 – 306 kg, N = 19). Mean maternal mass loss per day was 10.1 ± 2.6 kg. Efficiency of mass transfer from females to their pups was 63.2 ± 12.8% (N = 26).