Vancouver Island COSEWIC assessment and status report: chapter 5
Habitat
Habitat requirements
Vancouver Island marmots require three essential habitat features: 1) suitable soil structure for burrow construction, 2) suitable grass-forb vegetation to eat, and 3) microclimatic conditions that permit summer foraging and winter hibernation.
Natural habitat consists of subalpine meadows that generally occur at 900-1500 m (Bryant and Janz 1996). These meadows are thought to be created and maintained by avalanches or snow-creep, fire or a combination of processes (Milko and Bell 1986), and tend to be both small and uncommon on Vancouver Island compared to the B.C. mainland or the Olympic peninsula (Fonda and Bliss 1969, Kuramoto and Bliss 1970). Bryant (1998) used GIS to conclude that natural sub-alpine meadows comprised ~1% of the ~1000 km² Nanaimo Lakes core area of marmot distribution. Meadow habitat is even rarer south of Lake Cowichan and in areas such as Strathcona Provincial Park (Bryant 1993).
Since 1972 , marmots or fresh burrows were reported from 47 sites on 15 mountains (Bryant and Janz 1996). Reproduction has been observed at 34 sites on 14 mountains. Except for 2 sites, all colonies active since 1972 were located within the Nanaimo, Cowichan, Chemainus, Nitinat and Cameron River drainages on south-central Vancouver Island. The 2 other colonies were on Mount Washington, separated from other known colonies by ~95 km.
Most natural meadows occupied by marmots during 1972-2006 encompassed only a few hectares; consequently most recent colonies in natural habitats were small, typically containing one or two family groups and fewer than five adults (Bryant and Janz 1996).
Habitat trends
Prehistoric bones of M. vancouverensis recovered from caves or archaeological digs indicate that the geographic range has shrunk over the last few centuries or millennia (Calvert and Crockford 1983, Nagorsen et al. 1996). This trend is supported by data on tree growth (Laroque et al. 2001) and pollen deposition (Hebda et al. 2005). Vancouver Island marmots were apparently more widely distributed, and presumably more abundant, during warmer and dryer conditions that prevailed over several periods in the past.
Habitat protection/ownership
Most historically occupied (1972-2006) marmot habitat occurs on private land. The landscape surrounding natural habitat patches has been heavily modified by logging (Bryant 1998). Logging began in the region in the late 1940s and accelerated rapidly during the 1960s and 1970s. Less than 15% of the primary forest remains, most of it above 900 m. The result is a landscape with progressive replacement of mature forests with younger ones, combined with a growing number of logging roads and an increasing impact at higher elevations.
Two marmot habitats are legally protected under the B.C. Ecological Reserves Act (Haley Lake Ecological Reserve; 127 ha) or the B.C. Wildlife Act (Green Mountain Wildlife Critical Habitat Area, 260 ha). Considerable potential marmot habitat is protected within Strathcona Provincial Park (Bryant 1993).
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