LICHEN LITTERFALL CONSUMPTION BY WINTERING DEER AND ELK IN WESTERN MONTANA

Abstract

We studied arboreal lichen production and availability for Rocky Mountain elk (Cervus elaphus nelsoni), white-tailed deer (Odocoileus virginianus), and mule deer (O. hemionus) during winter in western Montana, USA. In May and June of 1997 and 1998, we collected lichen litterfall inside and outside exclosures to assess deer and elk use of lichens and recorded associated tree stand characteristics. Bryoria spp. and Nodobryoria spp. composed >99% of the lichen litterfall. Lichen litterfall use by deer and elk on 2-yr sites averaged 7.91 kg/ha for the severe winter of 1996–1997, and 6.02 kg/ha for the milder winter of 1997–1998. The greater use of lichens in winter 1996–1997 was probably due to increased ungulate densities in forested habitats during a severe winter. A strong linear relationship between lichen availability and lichens consumed suggested that lichen use was driven by availability rather than opportunistic foraging and that ungulates may have selected habitat partly because of lichen availability. Tree stand variables were partially correlated with lichen availability and consumption by ungulates but were different between winters, indicating that variables in addition to those we measured contributed to availability and consumption.