GYA Small Mammal and Fire Project
Natural burns are common in the boreal forests of the Rocky Mountains. While a considerable amount of research has focused on post-burn responses of vegetation and, more recently, large mammals, there have been few studies on responses of small mammal communities in these forests.
Prior to the massive fires in Yellowstone National Park (YNP) in 1988 Taylor (1973) reported mammalian species diversities in burns of different ages in the park and concluded that diversity was highest 25 years post-burn, just prior to canopy closure. Barmore et al. (1976) trapped small mammals in Grand Teton National Park (GTNP) immediately after the Waterfalls Canyon fire in 1974 and reported that burned sites had higher densities of deer mouse (Peromyscus maniculatus) and yellow-pine chipmunk (Tamias amoenus) than control sites and that red-backed voles (Clethrionomys gapperi) were equally abundant on burn and control sites. Wood (1981) trapped in two burns (1974 and 1976) and two adjacent unburned spruce/fir/lodgepole forests in YNP in 1978 and 1979 and reported three abundant species: the southern red-backed vole, the deer mouse, and the yellow-pine chipmunk. Trap success was higher in unburned forests for the former and higher in the burns for the latter two, although the red-backed vole was the most abundant species in both burned and unburned sites.
More recently, Stanton et al. (1991) and Stanton et al. (1992) studied small mammal community response from 1990 to 1991 following the 1988 Yellowstone fires on Huckleberry Mountain. Results of their work indicated that deer mice were more common in the burned areas and southern red-backed voles in the adjacent unburned forest for all three years. Over the course of the summer they observed increases in both species population sizes throughout the growing season. From 1990 to 1991 they also noted a significant increase in population size for both species on both burned and unburned grids. Their results suggested that red-backed voles were positively associated with log size and distance to nearest tree and negatively associated with the presence of woody stems in unburned forests. The deer mouse was positively associated with grassy ground cover and negatively associated with various aspects of woody vegetation. For both species, due to low sample sizes for red-backed voles and the lack of a significant discriminate function for the deer mouse, no microhabitat discrimination was detected in the burns.
Results of these studies suggest that observed responses of small mammals to fire are somewhat unpredictable and that these may in fact be due to responses to fine grain microhabitat variables rather than the coarse effect of fire on the landscape. In addition, to our knowledge, there are no studies that examine responses from immediately post-fire over long time periods (> 4 yrs, West, 1982) using consistent techniques. Attempts to detect long term trends have involved sampling burned sites of different ages and comparing small mammal densities and diversity to contemporary control sites (Taylor 1973). Because of the lack of consistent methodologies used in previous studies and the limited research on long-term responses of small mammals to natural fire we revisited in 1997 and 1998 the Huckleberry Mountain sites originally studied by Stanton et al. (1991, 1992) from 1989 to 1991 following the YNP fires of 1988. It is our hope that we can continue to periodically revisit these sites to follow patterns of small mammal recolonization and microhabitat use following the 1988 fires.
This work has been supported with funds provided by the University of Wyoming/ Casper College Center, University of Wyoming/ National Park Service Grant Program, Wyoming INBRE, and University of Wyoming/ NSF-EPSCoR Community College Grant Program.