Use of blubber fatty acid profiles to distinguish dietary differences between grey seals Halichoerus grypus from two UK breeding colonies

Abstract

The population structure of grey seals Halichoerus grypus has previously been studied using molecular biological techniques. These works may be complemented by studies of certain ecological factors which play an important role in providing information on habitat usage, dietary behaviour, local migrations, distribution and social structure. One such factor is the fatty acid composition of depot fats, which is strongly influenced by the fatty acid composition found in the prey. To examine the extent to which the fatty acid composition of seal depot fats can be used to distinguish between population~, blubber biopsy samples were obtained from female grey seals at 2 Scottish breeding sites, Rona (n = 23) and the Isle of May (n = 34) and the fatty acid compositions determined by gas chromatography. The patterns obtained were compared using both univariate and multivariate statistical procedures. Fatty acid profiles at the 2 breeding sites could be clearly differentiated, with only 1 seal out of 57 being rnis-classified. Thus, on the basis of blubber fatty acid composition, they may be regarded as 2 distinct foraging groups.

You are what you eat: describing the foraging ecology of southern elephant seals (Mirounga leonina) using blubber fatty acids

“…top predators from different regions may have different FA signatures and still have similar diets if the prey themselves have different diets). Despite these restrictive prerequisites, our study and others have detected interpopulation and seasonal variation in FA profiles of marine predators such as seals (Iverson et al 1997b;Walton et al 2000;Walton & Pomeroy 2003). However, when a predator is known to eat a wide range of prey species within a comparatively limited foraging range, the ability to use FA signatures to detect such variation is limited (Dahl et al 2000;Hooker et al 2001).…”

Antarctic fur seals foraging in the Polar Frontal Zone: inter-annual shifts in diet as shown from fecal and fatty acid analyses

“…Several indirect methods are now being used to provide dietary information in addition to the conventional fecal analyses. Lipids, particularly fatty acids (FAs), may function as dietary indicators by comparing FA signatures of prey items and consequent comparison with predator tissues that are high in lipid, such as milk (Iverson 1993, Brown et al 1999 and adipose tissue (Raclot et al 1998, Kirsch et al 2000, Walton et al 2000. This technique is based on the principle that unique arrays of FAs can be transferred largely unaltered up the food chain from prey to predator , Raclot et al 1998.…”

Blubber fatty acid profiles reveal regional, seasonal, age-class and sex differences in the diet of young Steller sea lions in Alaska

“…Despite some debate in recent years over the use of this method of dietary investigation in apex predators , Thiemann et al 2004, the qualitative use of FA has proven to be useful in elucidating geographical (e.g. Walton et al 2000), ecotype (e.g. Herman et al 2005) and sex (e.g.…”

“…In the absence of prey FA and calibration data, FA profiles of predators are useful to detect qualitative dietary changes and differences among demographic groups (e.g. Walton et al 2000, Beck et al 2005, Herman et al 2005, based on the established understanding that FA structures are transferred across trophic levels largely unchanged (e.g. Ackman & Eaton 1966, Cook 1991.…”