ENERGY-INTAKE AND UTILIZATION BY NURSING BEARDED SEAL (ERIGNATHUS-BARBATUS) PUPS FROM SVALBARD, NORWAY

In this study we measure energy intake via milk in nursing bearded sea l (Erignathus barbatus) pups and determine how this energy is allocate d into metabolism and storage of new tissues. This was accomplished us ing longitudinal mass gain records and the doubly labelled water techn ique on nursing pups in combination with cross-sectional data on chang es in milk composition from bearded seal mothers. The pups (n = 3) wer e all less than a week old at the start of the experiments. Pups gaine d 3.3 +/- 0.4 kg . day(-1) of which 50% was fat, 14% protein and 36% w ater. Average daily water influx for the pups was 69.5 +/- 9.0 ml . kg (-1) . day(-1). Average CO2 production during the study period was 0.9 9 +/- 0.10 ml . g(-1) . h(-1), which corresponds to a field metabolic rate of 642 +/- 67 kJ . kg(-1) . day(-1), or 6.0 +/- 0.5 times the pre dicted basal metabolic rate according to Kleiber (1975). The pups dran k an average of 7.6 +/- 0.5 kg of milk daily. This corresponds to a da ily energy intake of 154 +/- 8 MJ, 47 +/- 14% of which was stored as n ew body tissue. Despite this high energy intake bearded seal pups do n ot get as fat as do other nursing phocids. This is in part due to thei r 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 an d may also be involved in teaching their pups to feed independently. A ll these data suggest that the lactation strategy of bearded seals dif fers from the phocid norm.