No abstract

Female Grey seals transfer large amounts of energy rapidly and efficiently to their pups. Using information from serial weighings and from carcase analysis the energy costs of repro duction and the efficiency of lactation for female Grey seals have been calculated. Females use over 125·6 MJ/day for maintenance and milk production. Pups consume 71·2 MJ/day in milk and can convert 58·6 MJ/day into growth and stored fat. The gross efficiency of the transfer from mother to pup is about 57%. Over 80% of the females' energy reserves are used to feed their pups. This massive transfer of resources in a short time period is thought to be an adaptation of an offshore aquatic feeder which has to return to land to give birth.

No abstract

With 4 figures in the text)Female grey seals (Hulichoerus grypus) formed breeding aggregations on the island of North Rona, Scotland. Aggregations of females were associated particularly with gullies leading from the sea, leaving large areas of available space unoccupied. Changes in the degree of aggregation of females during the breeding season were similar in 1987,1988 and 1989. Pronounced aggregations occurred in the early and late parts of each breeding season.Of 67 breeding females marked in 1985,62 (93%)) returned to N. Rona to breed in at least one season up to 1989, but 18 (27%) were present in all five years. Females came ashore up to 14 days before giving birth and 82% were observed first in the vicinity of their subsequent pupping site. Between 1985 and 1989, marked females which returned were faithful to their previous pupping sites, even when the previous pup had died. There was no evidence of a gradual change in the location of individual pupping sites over time. This pupping site fidelity may generate aggregations whose location, timing and composition is predictable.