THE EFFECT OF RESOURCE DEPLETION ON THE FEEDING-BEHAVIOR OF A BROWSER - WINTER FORAGING BY MOOSE ON SCOTS PINE

(1) The foraging dynamics of a browser, the moose Alces alces L. exploiting depleting resources was studied experimentally. It was hypothesized that: (a) differences in the intake of twig biomass between tree stands in early foraging sessions would tend to even out as resource depletion progressed; (b) food item selectivity within stands would decrease, and (c) bite diameters would increase with time. (2) Artifical stands, composed of one browse species or a mixture of species, were set up in a forest area. The species includeed were Scots pine Pinus sylvestris L., aspen Populus tremula L. and grey alder Alnus incana (L.) Moench. Special attention was paid to the analysis of the pattern of Scots pine exploitation because this tree is of commercial interest. Moose browsing was assessed by counting bites and by measuring bite diameters. (3) Initially the total consumption of twig biomass in the pine + aspen stand was twice as high as that in the other two stands. This difference remained until almost half of the available biomass in the pine + aspen stand had been consumed. Within stands the preference for aspen over pine increased over time, whereas the preference for pine over alder decreased. Bite diameter on Scots pine showed a significant decline over time. (4) Browsing on Scots pine was only slightly affected by the species composition of the tree mixtures. Browsing intensities on individual pines was positively correlated with the amounts consumed on adjacent stems.