The decline of moose (Alces alces) fitness : a result of poor browse availability and high browsing pressure? - A comparative study of two Norwegian Moose ranges

Abstract

There has been a recorded difference in carcass weights among moose (Alces alces) on the western side of the Oslo fjord compared to the eastern side over the last decades. So far, this reduction has been credited to density-dependent limitations in browse availability leading to a higher browsing pressure. I compared browse availability and pressure on clearcuts in two ranges with differences in moose fitness. I found that the western ranges have more preferred browse, but I did not find a significant difference in the availability of birch (Betula spp.). Browsing pressure was significantly higher in the east on older clearcuts, but the difference disappeared on younger clearcuts. In the east, older clearcuts were more heavily browsed than younger, but this was not the case in the west. This study concludes that browse availability today is not the reason for the difference in carcass weights. The problem must therefore rest with the western moose population, and needs further investigation. A culling of the population in a trial area could be conducted to further investigate this matter, or we have to wait until the fertile of the 1950's sites that led to the increase in moose fitness then, are logged again.