Philopatry, site fidelity and local kin associations within grey seal breeding colonies

Colonially breeding animals such as grey seals typically have a discrete nu mber of breeding sites. The extent to which offspring are philopatric (retu rn to breed at their natal site) and the prevalence of philopatry by sex of pup has fundamental consequences for the social and genetic structure with in and between each colony. Grey seals born and marked by tagging and cohort brands at colonies on Nort h Rona, Outer Hebrides since 1960 and at the Isle of May, Firth of Forth si nce 1981 have shown philopatry. Overall re-sight rates of 1620 pups tagged at North Rona and 1667 pups at the Isle of May ranged from 0 to 17%. Althou gh most evidence of philopatry relates to females, males at each colony dis played philopatry. In addition, females born at N. Rona pupped closer to th eir natal sites than would be expected by chance (p =0.005), providing evid ence of fine scale natal site fidelity. Females born at the Isle of May did not show the same degree of fine scale natal site fidelity, but there was considerable individual variation. The spatial scale of philopatry shown by seals differed according to the local area within each island. Fidelity of known adult females to pupping sites at both colonies was high. In additio n, we found an instance of mother and daughter pupping together away from t he daughter's natal site. These data: (i) provide evidence of philopatry in both sexes at each site; (ii) describe occurrences of fine scale philopatry at both sites; (iii) sho w that mothers and offspring occupied the same areas on the colony, suggest ing the possibility of highly related groups within colonies, which would p rovide conditions for kin-specific altruistic behaviours; (iv) suggest the possibility of individual or kin recognition, even though contact between m others and offspring has been thought to cease after the 18 d lactation per iod.