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Grey seal (Halichoerus grypus) pup mortality not explained by local breeding density on North Rona, Scotland

Twiss, S.D.; Duck, C.; Pomeroy, P.P.

Grey seal (Halichoerus grypus) pup mortality not explained by local breeding density on North Rona, Scotland Thumbnail


Authors

C. Duck

P.P. Pomeroy



Abstract

Pre-weaning pup mortality of grey seals Halichoerus grypus in a breeding colony (North Rona, Scotland, U.K.) was examined in relation to the density of local adult females over two breeding seasons. Accurate, fine-scale maps of daily seal locations within a GIS database permitted the extraction of measures of female density determined at a range of spatial scales from 5 to 50 m around each pup on the date of death. Adult densities around live pups provided the null distribution of adult densities, which were tested against the distribution of densities where deaths occurred. Pre-weaning pup mortality at this colony was not related to any of our density measures. The proportion of pups dying each day showed no seasonal trends. Analysis of topographic features from a sub-meter digital terrain model for locations where deaths occurred suggested that there were fewer mortalities in prime pupping habitats. This could have been a direct effect of habitat or the relative quality of mothers in these habitats. The distance separating mothers and pups tended to be greater on the periphery of the colony compared to more central areas. Pups in the peripheral areas may be more exposed to predation by gulls.

Journal Article Type Article
Publication Date Jan 1, 2003
Deposit Date Mar 17, 2014
Publicly Available Date Mar 17, 2014
Journal Journal of Zoology
Print ISSN 0952-8369
Electronic ISSN 1469-7998
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 259
Issue 1
Pages 83-91
DOI https://doi.org/10.1017/s0952836902003035
Keywords Halichoerus grypus, Pinnipeds, Breeding habitat, Pup mortality, GIS.
Public URL https://durham-repository.worktribe.com/output/1563828

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