Research Article Displacement of Mountain Caribou From Winter Habitat by Snowmobiles DALE. R. SEIP, 1 British Columbia Forest Service, 1011 4th Avenue, Prince George, BC V2L 3H9, Canada CHRIS J. JOHNSON, University of Northern British Columbia, 3333 University Way, Prince George, BC V2N 4Z9, Canada GLEN S. WATTS, British Columbia Ministry of Environment, 4051 18th Avenue, Prince George, BC V2N 1B3, Canada ABSTRACT Mountain caribou are an ecotype of woodland caribou (Rangifer tarandus caribou) that live in subalpine forests in south- eastern British Columbia, Canada, extending into northern Idaho and Washington, USA. These caribou are listed as Threatened in Canada, Endangered in the United States, and are the subject of recovery planning efforts in both countries. Many areas of mountain caribou winter habitat experience intensive use by recreational snowmobilers. During 4 surveys, we recorded caribou on all 4 census blocks with little or no snowmobile activity (x ¯ density ¼ 0.41 caribou/km 2 ), but during 3 of 4 years, we observed no caribou on the census block with intensive snowmobile activity. The year we observed caribou on the snowmobile block, most were using areas inaccessible to snowmobiles. We used a Resource Selection Function (RSF) based on radiotelemetry data for the area to compare habitat quality among the different census blocks. The absence of caribou from the intensive snowmobile area during most years could not be explained by differences in habitat quality. The RSF predicted that the intensive snowmobile area could support 53–96 caribou (95% CI). We conclude that intensive snowmobiling has displaced caribou from an area of suitable habitat. We recommend that snowmobile activity be restricted from all or most high-quality mountain caribou habitat as part of the recovery planning process. ( JOURNAL OF WILDLIFE MANAGEMENT 71(5):1539–1544; 2007) DOI: 10.2193/2006-387 KEY WORDS British Columbia, displacement, mountain caribou, Rangifer tarandus caribou, resource selection function, snowmobiles. Mountain caribou are an ecotype of woodland caribou (Rangifer tarandus caribou) that live in the mountains of southeastern British Columbia, Canada, and into northern Idaho and Washington, USA (Heard and Vagt 1998). These caribou are listed as Threatened in Canada, and Endangered in the United States. Both countries are involved in recovery planning efforts to maintain these caribou. One recognized threat to mountain caribou populations is disturbance on winter range by snowmobiles (Mountain Caribou Technical Advisory Committee 2002). Mountain caribou live in a zone of very deep winter snowpack that makes it impossible to feed on ground vegetation in winter. Consequently, these caribou feed primarily on arboreal lichens during the winter months. Throughout late winter, caribou are located primarily in subalpine forest and subalpine parkland habitat in areas of gentle terrain (Terry et al. 2000, Apps et al. 2001, Johnson et al. 2004). These habitats contain abundant arboreal lichens and provide spatial separation from predators in the valley bottoms (Seip 1992). Deep snow, open forests and gentle terrain also make these areas attractive to recreational snowmobilers. Snowmobile use in some areas is intensive with entire mountain tops criss-crossed with snowmobile tracks. Snowmobile activity is increasing within mountain caribou range as new forest roads increase accessibility, and improved snowmobile technology increases their ability to reach new areas. There is concern among wildlife managers that disturb- ance by snowmobiles will displace mountain caribou from preferred habitat areas (Simpson 1987, Simpson and Terry 2000, Mountain Caribou Technical Advisory Committee 2002, Kinley 2003). The fright and flight response of caribou and reindeer to snowmobile disturbance has been documented (Simpson 1987, Mahoney et al. 2001, Reimers et al. 2003), but abandonment of preferred habitats has not been reported. Anecdotal observations suggest mountain caribou in British Columbia no longer use historic ranges where snowmobile activity is now common, but this relationship has been difficult to quantify. This lack of evidence has led to acrimonious debate during recovery planning regarding the need to restrict snowmobile activity within mountain caribou winter ranges. On several winter flights to census mountain caribou we observed that one mountain block with very intensive snowmobile use had few or no caribou despite the presence of habitat that appeared similar to neighboring mountain blocks supporting hundreds of caribou. To more rigorously evaluate this relationship, we used a resource selection function (RSF) to quantify the relative value of habitats (Manley et al. 1993) across the different mountain blocks surveyed for caribou. We then used survey data for undisturbed blocks, our final RSF, and a habitat-based population density estimator (Boyce and McDonald 1999) to predict the expected number of caribou on the snowmobile block. We then compared the number of caribou observed in the intensive snowmobile area to the number of animals predicted based on habitat. STUDY AREA The study area was the winter range of the Hart Ranges caribou herd in central British Columbia (548N, 1218W) about 100 km east of Prince George (Fig. 1). The core winter range was a series of discrete mountain blocks separated from the more contiguous Rocky Mountains to 1 dale.seip@gov.bc.ca Seip et al.  Caribou Displacement by Snowmobiles 1539