Grey seal (Halichoerus grypus) pup mortality is not explained by local breeding density on the Island of North Rona, Scotland
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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.
Twiss , S D , Duck , C D & Pomeroy , P 2003 , ' Grey seal ( Halichoerus grypus ) pup mortality is not explained by local breeding density on the Island of North Rona, Scotland ' Journal of Zoology , vol 259 , no. 1 , pp. 83-91 . DOI: 10.1017/S0952836902003035
Journal of Zoology
This is the peer reviewed version of the following article: Grey seal pup mortality is not explained by local breeding density on the Island of North Rona, Scotland Twiss, S. D., Pomeroy, P. & Duck, C. D. Jan 2003 In : Journal of Zoology. 259, p. 83-9, which has been published in final form at http://dx.doi.org/10.1017/S0952836902003035. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.