FORAGING ON NORWAY SPRUCE AND ITS POTENTIAL ASSOCIATION WITH A WASTING SYNDROME IN MOOSE IN SWEDEN

We studied a sudden occurrence of moose (Alces alces) browsing twigs and stripping bark of Norway spruce (Picea abies) that coincided temporally and spatially with a moose wasting syndrome in southern Älvsborg County in southwestern Sweden from 1990 to 1992. Spruce is a low preference forage for moose across Sweden and reports on its use are limited. This study reports on the importance of spruce as moose forage and its qualitative value relative to other more commonly used moose browse species in this region. Rumen contents from moose collected in autumn contained low proportions of spruce twigs (1.5-2.3%), and only 2 animals (n = 155) had spruce bark in the rumen. Generally, there was little browsing damage on spruce, although damage was severe in local areas. Spruce contained low concentrations of macroelements (crude protein, calcium, magnesium, potassium, and phosphorus) and trace elements (aluminum, cadmium, cobalt, copper, iron, manganese, and zinc), thereby minimizing this as a possible explanation for moose browsing. We used in vitro dry matter disappearance (IVDMD) as a measure of digestibility of spruce bark and twigs, and found no differences between spruce trees that had been bark stripped by moose and a control group of undamaged specimens. In addition, average IVDMD values of 14-25% dry matter of spruce bark were considerably lower than those found for more commonly used moose browse species in Sweden. We discuss these results with respect to the potential mechanisms underlying moose bark stripping of spruce. We cannot confirm that a potential linkage between foraging on spruce and a wasting syndrome in moose exists, and suggest that further research in this area is warranted