Dispersion and site fidelity of breeding female grey seals (Halichoerus grypus) on North Rona, Scotland

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.

Finescale topographical correlates of behavioural investment in offspring by female grey seals, Halichoerus grypus

“…18 Secondly, the distribution of pools of water differed at the two sites. In the UK grey seals show a preference for breeding close to water, in which mothers spend considerable time, as shown by our data (see also Anderson et al 1975;Boyd et al 1962;Hewer & Backhouse 1960;Pomeroy et al 1994). In contrast, their pups spend very little time in water.…”

“…Pup mass gain during lactation may then vary with colony topography, and may ultimately affect longer term survival of weaned pups as they leave the island, relying on their blubber reserves whilst learning to forage. Irrespective of such energetic considerations, separation of pups from their mother has been shown to increase pup injuries and mortality in a variety of pinnipeds; southern (Mirounga leonina) and northern (M. angustirostris) elephant seals (see Baldi et al 1996), South American fur seals (Arctocephalus australis) (Harcourt 1992), Antarctic fur seals (A. gazella) (Doidge et al 1984) and in grey seals (Anderson et al 1979;Baker & Baker 1988;Pomeroy et al 1994). …”

“…Females generally remain with their pups throughout lactation, but many observers have noted the tendency for lactating females to bathe in pools of water (Anderson et al 1975;Boyd et al 1962;Hewer & Backhouse 1960;Pomeroy et al 1994;Caudron 1998). When the locations of water and suitable pupping/nursing sites are spatially separated there will be increased travelling costs, in terms of time and energy expenditure, incurred by the mother.…”

Variability in individual rates of aggression in wild gray seals: fine-scale analysis reveals importance of social and spatial stability

“…Alternatively, until 77 recently, the available methodologies for calculating an individuals' dominance score or rank were best 78 applied to data spanning relatively long temporal scales (Boyd and Silk 1983;David 1987; Gammell et 79 (Pomeroy et al 1994;Twiss et al 1994). Inter-annual male associations and within-year spatial social 106 stability have been suggested as potential drivers of conflict reduction in gray seals (Anderson et al 1975; 107…”

“…In addition to dominance, we 115 included two density related spatial factors that vary at a fine temporal scale within a breeding season 116 (Twiss et al 1994) but have not been included in previous models of aggression for this system: 117 proximity to competitors as a measure of intensity of competition and, proximity to females as a measure 118 of ease of access to the contested 'resource'. These variables were chosen because although male gray 119 seals do not form distinct territories, male and female attendance shifts within a breeding season, 120 changing the social structure at a fine temporal and spatial scale (Pomeroy et al 1994, Twiss et al 1994. 121…”