Journal des sciences animales et de la production animale Libre accès

Abstrait

Scale Matters Habitat Use and Selection by Two Sheep Breeds in Two Contrasting Alpine Environments

Nicolai Hermann Jørgensen , Geir Steinheim and Øystein Holand

We investigated summer foraging vegetation (divided into three quality classes) use and selection by free-ranging sheep at three temporal (season, 5 days, and hourly) and three spatial (95%, 50%, and 20% Utilization Distribution (UD)) scales. We fitted 51 ewes of the Norwegian breeds, Norwegian White Sheep (NWS) and Spaelsau (SP), with GPS collars in two environments, one poor (Spekedalen) and one rich (Bratthøa), during the grazing seasons 2013-2014. Habitat use was affected by vegetation class and environment, but not by breed, at all temporal and spatial scales. In Spekedalen, at all temporal scales, the use of “Less Good” vegetation decreased and “Very Good” increased with finer spatial scales, while the use of “Good” was fairly constant. In Bratthøa, at all temporal scales, the use of “Good” dominated at the coarsest spatial scale, whereas the use of “Very Good” increased and almost equaled the use of “Good”, at the two finest spatial scales. Habitat selection was affected by vegetation class at all temporal scales, by environment at the two finest temporal scales but not by breed. In Spekedalen, both breeds selected for “Very Good”, with increasing intensity with finer temporal scales, while “Good” and “Less Good” were in general selected against. In Bratthøa the selection for “Very Good” decreased towards neutral and the selection against “Less Good” approached neutral with finer temporal scales, while “Good” was selected weakly against at the two finest scales. The sheep habitat use and selection seem to be affected by the proportion and spatial heterogeneity of the vegetation classes. Indeed, in Spekedalen sheep were able select for the scarce “Very Good” patches at all temporal scales, increasing in intensity with finer temporal scales, while sheep in the rich Bratthøa showed a neutral selection for the two best and most abundant vegetation classes at finer temporal scales. Surprisingly, no breed specific effects were found. Our findings highlight the importance of the scare “Very Good” patches, at fine scales, in poor Spekedalen. Indeed, this high quality and productive class is even more important for nutrient extraction and acquisition than the use indicates.