Pup density related to terrestrial habitat use by New Zealand fur seals

Features of the terrain are important in the selection of terrestrial habit at by otariid seals. Fur seals use rocky shorelines where terrain features such as crevices and ledges may provide shelter for pups. New Zealand fur s eals (Arctocephalus forsteri) are increasing in number and expanding their range, requiring them to select new habitat for breeding. Predicting popula tion expansion is important for assessing potential conflicts with commerci al fisheries. We quantified terrain features at 25 breeding colonies and 8 nonbreeding colonies around South Island. Univariate tests demonstrated som e differences in terrain between breeding and nonbreeding colonies, althoug h principal components analysis (PCA) did not reveal any obvious difference s. We suggest that the power to detect differences is reduced by the tenden cy for nonbreeding colonies to become breeding colonies over time as the po pulation increases. We found a significant relationship between pup density and terrain (i.e., PCA variables) within breeding colonies. The terrain oc cupied by high-density colonies contained more and smaller rocks, more crev ices and ledges, less-pronounced slopes, higher cliffs, and a more westerly exposure than that occupied by low-density colonies. Smaller rocks may pro vide more spaces in which pups can find shelter; less-pronounced slopes may facilitate pup mobility and higher cliffs may increase shading. We suggest that in addition to terrain features, other phenomena are also involved in breeding-site selection.