Eight highly variable microsatellite loci were used to examine the genetic variability and differentiation of grey seals (Halichoerus grypus) at two widely spaced British breeding colonies. Samples were collected from adults and pups on the island of North Rona, off the north-west coast of Scotland, and on the Isle of May, situated at the mouth of the Firth of Forth on the east coast. Highly significant differences in allele frequencies between these two sites were found for all eight loci, indicating considerable genetic differentiation. Thus, although grey seals are known to range over very large areas outside the breeding season, site fidelity of adults and philopatry of pups for these breeding colonies must be sufficiently common to have effects, through genetic drift, at the sub-population level. Migration rate was estimated using Wright's fixation index (FST), Slatkin's private alleles model and the new statistic, RST, which is analogous to FST but which takes into account the process of microsatellite mutation. An almost 8-fold discrepancy between the values we obtained provides cautionary evidence that microsatellite loci may contravene one or more of the assumptions on which these methods are based.

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.

Microsatellites were used to conduct an extensive analysis of paternity of grey seals from two Scottish breeding colonies at North Rona (n = 1189) and the Isle of May (n = 694), spanning more than a decade. A maximum of 46% of pups at North Rona and 29% of pups at the Isle of May could be allocated a father, even though the majority of candidate males for specific study sites within each colony were believed to have been sampled. Based on the paternities which could be assigned, both colonies showed evidence of reproductive skew, apparently due to the presence of approximately five males who were exceptionally successful. Some males were assigned paternities at least 10 years before, and colleagues 10 years after, being sampled, implying a reproductive lifespan of at least 10 years, and there are indications that the real maximum lies in the range 15-20 years. Male grey seals appear to have at least two breeding strategies they can adopt. On land, some males benefit from a traditionally polygynous system. However, between 50 and 70% of grey seal pups born at a particular colony are not fathered by males who are likely to be sampled by us, implying that these males seldom venture ashore here. We conclude that aquatic mating may play a much larger role in the grey seal than has previously been thought.

Microsatellites were used to investigate fine-scale spatial and temporal genetic structure of a grey seal breeding colony, using samples collected throughout the colony (1997) and at a fine scale (2000-2002). Behaviour of breeding seals on North Rona, including philopatry and high breeding site fidelity, suggested female kin may cluster together. However, low F ST-scores indicated no genetic differentiation between the major breeding aggregations, categorised as regions in the colony. Nevertheless, the pairwise relatedness of mothers within regions was significantly higher than the relatedness of mothers between regions. There was evidence of kin clustering within only one region in the colony. Therefore, sustained philopatry appears sufficient to produce differences in relatedness at a within-colony scale (> 500 m), but not at finer scales. However, within one region, mothers' pairwise relatedness decreased significantly with increasing distance between pupping sites. Pairwise relatedness of neighbouring females within this region was also higher than expected. Conversely, in the other regions mothers that were considered likely to have social interactions, based on their spatial and temporal proximity, were not significantly more related to each other than random. This suggests the social associations of mothers on North Rona detected previously are unlikely to be influenced by kin selection.

(2000) 'Finescale topographical correlates of behavioural investment in o spring by female grey seals, Halichoerus grypus.', Animal behaviour., 59 (2). pp. 327-338. Further information on publisher's website:http://dx.doi.org/10.1006/anbe.1999.1320 Publisher's copyright statement: This is the author's version of a work that was accepted for publication in Animal Behaviour. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be re ected in this document. Changes may have been made to this work since it was submitted for publication. A de nitive version was subsequently published in Animal Behaviour, 2000Behaviour, , 59, 2, 327 338, doi: 10.1006Behaviour, /anbe.1999Behaviour, .1320 Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTGrey seals breed colonially on substrates ranging from ice to rocky or sandy beaches. Clear differences in seal behaviour patterns exist among such broad classes of breeding habitat.However, finer scale topographic variation is likely to influence individual behaviour with consequences for pupping success. We examine topographic influences on breeding female grey seal behaviour by quantifying topography at a sub-seal size resolution. Using sub-metre resolution Digital Terrain Models of two sites within a rocky breeding colony we compare site topography in relation to observed differences in female behaviour at these sites. Females at both sites showed a preference for breeding close to water (standing pools or sea) and frequently commuted between their pups and water. Topographic models indicated that one site was more costly for seals in terms of their locations and movements within the site. This was due to a lack of low elevation land adjacent to the main access points from the sea and the reduced availability of pools. Females at this site showed reduced pup attendance and an increase in energetically costly behaviours, whilst females at the lower cost site spent more time interacting with their pups and resting. These topographically induced behavioural differences are likely to affect the quantity and quality of pup provisioning by mothers and influence individual pupping site selection. Less costly sites are likely to be colonised preferentially and by larger, older and more dominant females, potentially generating fine scale spatial heterogeneity in female quality within the breeding colony.Whilst it may be obvious that topography is likely to...