SPATIAL AND BEHAVIORAL-RESPONSE OF WHITE-TAILED DEER TO FORAGE DEPLETION

We tested predictions regarding the effects of forage depletion on pat terns of foraging effort, diet selection and quality, and patch select ion by white tailed deer (Odocoileus virginianus). Two deer were allow ed access to four 150-m(2) enclosures (patches) for 8, 16, 24, and 32 days, resulting in the exposure of the patches to deer for 16, 32, 48, and 64 animal-days and different levels of forage depletion. When the deer were given simultaneous access to all four enclosures, feeding p atch selection was markedly skewed toward heavily and lightly grazed e nvironments, while moderately depleted patches were selected least. De er primarily consumed woody browse in patches with low (16 days) and h igh (64 days) forage depletion, and forbs in patches that were moderat ely depleted (32 and 48 days). Deer responded to forage depletion by f oraging less selectively, reducing movement rates, and increasing aver age bite size. During the last phase of the trial, biting rates on for bs declined but increased on woody browse in response to declining for age availability. Diel foraging times remained unaffected by changes i n forage availability. The behavior of deer foraging in experimental p atches appeared to be consistent with predictions based on the maximiz ation of nutrient (protein) gain, although use of the most depleted pa tch was greater than expected. We conclude that vegetative biomass alo ne is a poor indicator of foraging rewards for highly selective herbiv ores.