American Bison - Buffalo Field Campaign

at other thermal features (Meagher 1973). Upland sagebrush-
bunchgrass sites are utilised to a lesser extent in winter
(Meagher 1973). The summer diet of Yellowstone bison utilising
the Hayden Valley was more than 90% graminoids, with one-
half of these being mesic grasses, sedges, and rushes (Olenicki
and Irby 2004).
6.2.1.2.6 Northern forests
Bison at EINP are highly selective for upland grasslands year-
round, and to a lesser extent, select sedge meadows in winter,
and shrubland and aspen forest in spring and summer (Cairns
and Telfer 1980; Telfer and Cairns 1979). The bison’s year-
round diet was virtually exclusively herbaceous vegetation with
approximately 80% of the winter diet and 65% of the summer
diet sedges (Carex spp.; Table 6.1; Telfer and Cairns 1979).
Plains bison foraging at Prince Albert National Park (PANP)
selected the sedge Carex atherodes, and consumed more
sedges than grasses year-round (Table 6.1; Fortin et al. 2002).
The foraging strategy favoured short-term energy gain over long-
term gain for most of the year (Fortin et al. 2002). However, bison
also selected Carex in spring, when a diet of more digestible
grasses would have enhanced short-term energy gain (Fortin et
al. 2002). Bison may avoid shifts in diet to facilitate maintaining a
consistent microbial rumen flora (Fortin et al. 2002).
6.2.1.2.7 Arctic lowland taiga
Introduced plains bison at Delta Junction, Alaska, feed on
sedges and fescue grasses in winter (Campbell and Hinkes
1983). In contrast, plains bison introduced to the vicinity of
Farewell, Alaska, feed on willows (Salix spp.) almost exclusively
in summer, and a mixture of willow and shrubs in the autumn
(Waggoner and Hinkes 1986). Some potential exists for
competition with moose (Alces alces) for willow in riparian,
alluvial areas, although the two species select shrubs of different
sizes (Waggoner and Hinkes 1986). The drastic differences
between the diet of plains bison at Delta Junction and those at
Farewell are directly related to forage availability. The Farewell
area is almost exclusively riparian willow growth with little in the
way of graminoids due to a dominant very rocky braided river
substrate. In contrast, the Delta Junction area is characterised
by extensive stands of grasses and sedges and domesticated
grains. These differences underscore the importance of forage
availability in influencing bison diets.
6.2.1.3 Habitat and dietary overlap
Originally, plains bison associated with pronghorn (Allen 1967;
Yoakum 2004), elk (Miller 2002) and mule deer (Odocoileus
hemionus) throughout much of their range, and with moose
(Boer 1997) along the northern and high elevation range
limits. Of the sympatric species, the seasonal distributions of
pronghorn and plains bison were most similar, but their diets
46 American Bison: Status Survey and Conservation Guidelines 2010
were most divergent (Schwartz and Nagy 1976; McCullough
1980; Marlow et al. 1984; Wydevan and Dahlgren 1985; Singer
and Norland 1994). Although these two species tend to have
little dietary overlap, some competition for total biomass may
occur (Lovaas and Bromley 1972). Similarly, sympatric plains
bison and mule deer may overlap in habitat selection in winter
(Cairns and Telfer 1980), but their diets differ (McCullough 1980;
Wydeven and Dahlgren 1985; Singer and Norland 1994).
Plains bison and elk exhibit extensive range overlap in winter
(Cairns and Telfer 1980; Barmore 2003), but less in spring and
summer (Cairns and Telfer 1980). The diets of both species are
predominantly graminoids from autumn through spring, with
bison favouring sedges and elk favouring grasses (Barmore
2003; Singer and Norland 1994). Dietary overlap with grasses
continues into the summer (McCullough 1980; Telfer and Cairns
1979), although the bison’s diet contains more grass and less
forbs and woody plants than that of elk (Marlow et al. 1984;
Wydeven and Dahlgren 1985).
Plains bison and domestic cattle diets were most similar for grass
consumption during the autumn and winter at a lightly grazed
short grassland site, and during the spring at a nearby heavily
grazed site (Peden et al. 1974). Bison and cattle summer and
autumn diets in a shrub-steppe region were almost exclusively
grasses (Van Vuren 1984; Van Vuren and Bray 1983). The diets of
bison and domestic sheep were most similar during autumn at a
lightly grazed short grassland site (Peden et al. 1974).
6.2.2 Wood bison
6.2.2.1 Original distribution and ecoregions occupied
Zooarchaeological evidence, combined with documentary
records and oral narratives of aboriginal peoples in Alaska,
Yukon, and Northwest Territories, indicate that the original range
of wood bison included northern Alberta, north-eastern British
Columbia east of the Cordillera, the Northwest Territories south
and west of Great Slave Lake, the Mackenzie River Valley, and
large areas of interior Alaska (Gates et al. 1992; Lotenberg 1996;
Stephenson et al. 2001; van Zyll de Jong 1986). The original
distribution of wood bison in northern Alberta and southern
Northwest Territories centred on the Interior Plains Physiographic
Region, where they ranged over the interconnected and
overlapping glacial lake basins and major river valleys, where
soil conditions are conducive to development of sedge-grass
meadow plant communities (Gates et al. 1992). The total range
of wood bison was more restricted than that of plains bison.
Contemporary wood bison herds in the boreal regions exist
in comparatively natural systems. They remain part of a fairly
diverse, large ungulate fauna, which represents the prey base
for several predators. Wood bison distribution overlaps with
that of moose, elk, boreal and northern mountain ecotypes of