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

Grey seals breed colonially on substrates ranging from ice to rocky or sand y beaches. Clear differences in seal behaviour patterns exist among such br oad classes of breeding habitat. However, finer scale topographical variati on is likely to influence individual behaviour with consequences for puppin g success. We examined topographical influences on the behaviour of breedin g female grey seals by quantifying topography at a subseal size resolution. Using submetre resolution digital terrain models of two sites within a roc ky breeding colony, we compared site topography in relation to observed dif ferences in female behaviour at these sites. Females at both sites preferre d breeding close to water (standing pools or sea) and frequently commuted b etween their pups and water. Topographical models indicated that one site w as more costly for seals in terms of their locations and movements within t he 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 a t this site showed reduced pup attendance and an increase in energetically costly behaviours, whilst females at the lower-cost site spent mere time in teracting with their pups and resting. These topographically induced behavi oural differences are likely to affect the quantity and quality of pup prov isioning by mothers and influence individual pupping site selection. Less c ostly sites are likely to be colonized preferentially and by larger, older and more dominant females, potentially generating finescale spatial heterog eneity in female quality within the breeding colony. (C) 2000 The Associati on for the Study of Animal Behaviour.