Summer Habitat Use by Snowshoe Hare and Mountain Cottontail at Their Southern Zone of Sympatry

The snowshoe hare (Lepus americanus) is a habitat specialist with a broad geographic range associated with boreal and subalpine forests in North America (Hall 1981, Hodges 1999a,b). It reaches southern range limits in the Southern Rocky Mountains in northern New Mexico, USA. Here, scant and mostly anecdotal evidence suggests that it is restricted to high-elevation, subalpine conifer forests dominated by Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa; Findley et al. 1975, DeVelice et al. 1986, Pase and Brown 1994). These southwestern forests lack several plant species, including lodgepole pine (Pinus contorta), jackpine (Pinus banksiana), black spruce (Picea mariana), birch (Betula spp.), and balsam poplar (Populus balsamifera), that, in more northern latitudes, are considered important habitat elements for snowshoe hare, especially in terms of cover (Bittner and Rongstad 1982, Litvaitis et al. 1985, DeVelice et al. 1986, Ferron and Ouellet 1992, Bryant et al. 1994, Pase and Brown 1994, Moir and Fletcher 1996). Methods for managing subalpine forests for snowshoe hare in the Southern Rocky Mountains are particularly important because of a current effort to reintroduce Canada lynx (Lynx canadensis), which is a specialized predator of snowshoe hare (Hodges 1999a,b, Colorado Division of Wildlife 2002). Another leporid, the mountain cottontail (Sylvilagus nuttallii), occurs throughout the intermountain region of western North America, also reaching the southern extent of its range in the American Southwest (Hall 1981). Throughout this broad zone of sympatry, the two leporids segregate in ecological distribution with no reports of syntopy (Bittner and Rongstad 1982, Chapman et al. 1982, Chapman and Wilner 1986). The mountain cottontail typically is associated with lower-elevation sagebrush (Artemisia spp.)–dominated habitats (Orr 1940, Chapman 1975, 1999, Chapman et al. 1982). However, it is a habitat generalist and at more southern latitudes it also occurs in higher-elevation habitats including juniper (Juniperus spp.) and pinon pine (Pinus spp.) woodlands and middle-elevation montane conifer forests, which are dominated by ponderosa pine (Pinus ponderosa), white fir (Abies concolor), Douglas-fir (Pseudotsuga menziesii), and blue spruce (Picea pungens; Bailey 1931, Durrant 1952, Findley et al. 1975, Hoffmeister 1986, Fitzgerald et al. 1994, Frey and Yates 1996). Mountain cottontails also occur in subalpine conifer forest in areas of the Southwest and Southern Rocky Mountains where snowshoe hare are absent, such as the White Mountains in eastcentral Arizona and the Pikes Peak massive in central Colorado (Warren 1910, Armstrong 1972, Hoffmeister 1986). Findley et al. (1975) reported a specimen each of mountain cottontail and snowshoe hare from Goose Lake, Taos County, New Mexico, USA. This locality is at 3,542 m elevation, which is in the subalpine conifer forest zone. These records suggested that less ecological segregation between snowshoe hare and mountain cottontail might occur in the American Southwest, including the potential for local syntopy. Thus, the purpose of our study was to assess habitat use of snowshoe hare and mountain cottontail in subalpine conifer forests at their southern point of sympatry in the Southern Rocky Mountains.

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