Chapter 1: Wood Buffalo Park

The bison is also living now in the Slave River Lowland area and in the Wood Buffalo Park, southwestern Northwest Territories. How much food do they find there at the northern limit of the bison’s range? How do they get at their food in winter, when hard, drifted snow is covering the ground? How do they survive the blizzards up there in winter? How long and how warm is their hair coat in winter? Would they also be able, to live still further north in the arctic tundra, just like the reindeer and the muskox? Would they be able, to live, where it is so cold in summer, that trees cannot grow? What have scientists found out about this?

J. Dewey Soper reports in his article, "History, Range, and Home Life of the Northern Bison" in Ecological Monographs Vol. 11, October, 1941, Number 4, pp. 347-412 about the bison, which is living now in the Wood Buffalo Park: Wood Buffalo Park. The park boundaries of this great, unfenced domain enclose an area of 17,300 square miles. Of this 3625 square miles lie in the Northwest Territories, and the remainder in the Province of Alberta. From the southern boundary in latitude 58° 05´ to the northern in 60° 40´, the length is 178 miles; at its widest part, between Slave River and longitude 115° 37´, it is 145 miles. (1941:349)


Plant production

The greater part of the bison range supports an abundant vegetation. This varies widely in character, however, depending upon slope, elevation, soil, and drainage. ... It is within the bounds of these grass-producing lowlands, that the majority of the bison herds spend the winter. In many parts, the rankness and luxuriance of this forage is remarkable. On the open plains division west of Slave and north of Peace rivers, it averages two to three feet (61-91 cm) high by early fall, to stretch mile upon mile in a level, amber-green sea of splendid yield. Thousands of bison graze here, as soon as the ground is sufficiently frozen in early winter, to bear their weight. In lower and wetter sections the vegetation is even ranker and reaches to four, five, or even six feet (121 cm, 152 cm, 183 cm) in height. In particularly favourable areas south of the Peace, and even north to the Nyarling and Upper Buffalo rivers, the writer has seen grasses, exceeding a height of seven feet (213 cm)." Soper, J. D. (1941:370, 372)

Hair coat of adult bison

How thick is the hair coat of the bison in late fall and in winter, when it has reached its full length?

J. D. Soper: "Full-grown plains bison, taken in November,1933, west of park head quarters (in Wood Bison park): Close, thick under-fur on belly, lower sides, flanks, forelegs, and neck, brussels brown (Ridgeway: 1912). Over the same areas, longer pelage (especially lengthened guard hairs)... Length of pelage of this full-grown bison in November 1933:

Rump and hips 45-90 mm

Mid-dorsal (back) area 30 mm

Sides 30-40 mm

Ventral (belly) surface 50-60 mm

Guard hairs in some areas 150 mm

Sides of hump 65-70 mm

Top of hump 110-130 mm

Long hair on forelegs 150-190 mm

Top of neck 140-160 mm

Below hock (ankle of hind foot) 20 mm

Above hock (guard hairs) 210 mm

Below knee 15-20 mm

Soper, J. D. (1941:377)


Forage. "Forage grows particularly rank in the moist lowlands. This is especially true of the flood plains of Peace and Slave rivers, and the Peace-Athabaska Delta. As elsewhere mentioned, vegetation commonly attains a height of three or four to seven feet (91 cm, 122 cm, 213 cm). While only restricted sections support the heavier yields, vast areas support excellent fodder, at least two and a half to three feet (76-91 cm) high. This more important winter food consists mostly of sedges and of some grasses. Many of these are also identified with sloughs and pond margins of the uplands."

Insect pests. "Of these the mosquitoes and ‘bull-dogs’ are the worst. The mosquito hordes get in their worst work early in the season, as the bison is shedding his thick, matted coat in large patches, when his rear parts are reduced almost to a state of nudity. It is during this time, that the animals are most active in wallowing in sand baths and lathers of mud." Soper, J. D. (1941:394)

Winter feed in snow

"Rooting through the deepening snows is a time- and energy-consuming business. This is done with muzzle and head, forcing the snow back and up. Observation shows, that the animals are kept busy, to obtain enough feed during the daylight hours. Compelled to be diligently on the move, they are seldom, if ever seen lying down in winter, except for the long night’s rest." Soper, J. D. (1941:400)

"With snow always at hand in winter, there is no lost time from feeding in long return marches to the watering places, as is the case in summer. Thick, gloomy weather sees the herds less early astir on the plains; brilliant weather is more stimulating. In gentle snowstorms, digging for forage in the open goes on a usual, but let a blizzard break and one and all promptly retire to the shelter of the woods. Such storms may last for days; regardless of their duration, however, the animals never appear in the open. With a particularly violent storm, they will sometimes even remain in seclusion for two or three days after it ends. It is under these circumstances, that the herds direct their attention to scanty and inferior foodstuffs in the woods, which are ordinarily ignored.

"After a snowstorm, there is unusual activity. The woods disgorge their occupants and scattered herds once more dot the plains. Trails are freshly opened and the familiar laceries (= craters in the snow) again break the virgin snow fields in all directions. With characteristic energy and indomitable strength, the mature batter their way through, followed by the young, and before long, meadow and plain are deeply crenellated (= covered) with the scraggy, snow eruptions of the feeding grounds." Soper, J. D. (1941:400)

"Excessive snowfall with mid-winter thaw, sleet, and freezing again at severe sub-zero temperatures, is unquestionably the gravest danger. Commenting on reported occurrences of this kind, Raup (1933:20) writes as follows: ‘An event of more recent years should be noted in this connection. The winter of 1927-28 was an unusual one, due to an early spring thaw. About the middle of March, there were four days of a warm, southwest wind, with an excessive thaw, when the snow was melted so much, that the packed sleigh trails were left as icy ridges, making travel difficult. Following the fourth day, which was the warmest, there was a hard freeze, making a glare of ice and a crust about half an inch thick. The buffalo were not seen in the open places after this freeze. They entered the woods or the small sheltered sloughs, where the thaw had not been so great nor the crust so thickly formed." Soper, J. D. (1941:404)

The rare Wood bison (Bison bison athabascae) on a forest-meadow in the southwestern Yukon Territory, re-introduced onto its former range. From Eric Fairclough, Minister of Renewable Resources, Yukon Bison Management Plan 1998 to 2003 p. 1.


W. A. Fuller (1962:12) reports under the heading, "The biology and management of the bison of Wood Buffalo National Park" in Can. Wildl. Serv. Wildl. Mange. Bull. Ser. 1(16): "Winter is undoubtedly the most difficult season for bison. Extreme cold per se seems to have little effect on them, and they may be seen grazing on prairies in temperatures of –50°F (-45.5°C) on calm days. Extreme cold, coupled with even a moderate wind (over 8 to 10 m.p.h. (13.9-16.1 km/h)), however, will send them to the shelter of the wood. Grazing is then confined to a narrow zone around the edge of the prairies, next to the timber. Winds, stronger than about 15 m.p.h. (24.1 km/h), are rare in periods of extreme cold. Likewise, a succession of windy days is uncommon in midwinter. Three days is commonly the duration of the most severe winter storms. Since dense woods, which give protection from the wind, are everywhere well interspersed with grazing areas, the bison are secure from the damaging effects of cold, with or without wind.

"Snow conditions may be of great importance. Heavily crusted snow hinders the animals in their foraging and also makes travel more energy-consuming, thus aggravating the effects of prolonged cold. Fortunately, winter thaws are rare on the bison range. ... The difficulty is, of course, less serious for a social species, than for a solitary one. The bulls were seen, to take the lead and break a trail, while the weaker animals followed in single file, with much less expenditure of energy." Fuller, W. A. (1962:12)

"The area, that presently carries the greatest concentration of bison, is the extensive delta plain of the Peace River, lying between Peace River and Lake Claire. Those meadows are covered largely with an almost pure stand of a meadow sedge (Carex trichocarpa var. aristata). That species is a staple food of the bison in both summer and winter, but is especially important in the latter season, because it cures into hay on the stem and produces a green shoot, rich in stored nutrient. The river flood-plains, abandoned channels, and dry beds of oxbow lakes also contain an abundance of that species, which undoubtedly accounts for their popularity as winter range.

"The upland prairies are distinguished from the meadows by their more xerophytic (dry) conditions, which favour grasses, rather than sedges. Blue-joint grass (Calamagrostis canadensis), blue grass (Poa pratensis), wheat grasses (Agropyron spp.), and June grass (Koeleria cristata) are common and important food plants. ... Muskeg (peat bog) is widely distributed, generally avoided." Fuller, W. A. (1962:14, 15).


Snow Density on Arctic Tundra

How would the bison fare, if it tried to live on the arctic tundra, some 1200 km further north, near the present arctic coast. Up there, no trees are able to grow, because the summer is too cold and too short. In the arctic tundra, there are no trees, where the bison would be able, to hide in winter in deep forests, when a blizzard is blowing. Would the bison be able, to find up there enough food in winter, when the arctic tundra is covered with drifted snow, with snow packs? What have scientists found out about this?

How dense is the snow on the arctic tundra in northern Alaska and further south in the taiga, in the forest-tundra and northern boreal-forest? Will the muskox be-able-to graze there everywhere? We should remember here: The muskox on the arctic tundra on the Taimyr Peninsula, central northern Siberia, is able to graze in snow, which has a density of up to 0.25 g cm³. Also the bison, in the northern part of its range, in the southern part of Canada’s Northwest Territories, is grazing in winter in snow, which has a density of up to 0.25 g cm³.

The muskox is only able, to live in the Far North, if it can gain more energy from the food, which it is able to take in per day, than it must spend, while searching for and digging out this food beneath the snow. In order to survive the long arctic winter, when the best pastures in the lowland are buried beneath drifted snow, the muskox may be-able-to do two things:

1.      It may look for a lush pasture in the lowland, close to sea-level, where the wind cannot drift it over with dense snow. There might be a few places, where there are mountains or steep rock-cliffs, which shelter this fertile lowland during the winter from the storms. The snow-cover will not become then as dense, as out on the wind-swept open tundra or polar desert.

2.      If there are no such fertile lowland meadows, close to steep mountains or rock cliffs, keeping the wind away in winter, the muskox will only be-able-to find then enough food during the long arctic winter in places, which are fully exposed to the winter storms: It must stay then at places, where it is the coldest in winter, where the wind has blown the snow away: That is, on top of wind-swept ridges, hills, and mountains. And on the steep cut-banks of the rivers. But at these places, there is only very little food.

How dense is the snow on the arctic tundra of Alaska? Will the muskox be able, to graze there everywhere during the long arctic winter? What have scientists found out now about this?

Carl S. Benson, Geophysical Institute, University of Alaska, Fairbanks, and Matthew Sturm, U.S. Army CRREL, Fort Wainright, AK report about the "Structure and wind transport of seasonal snow on the Arctic slope of Alaska" in: Annals of Glaciology 18 (1993 :261-267). What have they found out? – They write: "Tundra snow, which is found mainly on the Arctic slope, north of the Brooks Range, is wind-packed, dry, and sastrugu- sculptured, with depth hoar-frost at its base.

"Taiga snow, which is found in the taiga, between the Brooks and Alaska ranges, is characterized by low-density (< 0.2 cm³), loosely consolidated, depth hoar-frost, which makes up most of the snow pack in the lowland brush and forest areas. - The winter snow on the Arctic slope of Alaska lasts for nine months each year." (1993:261)

"Tundra snow: The basal depth hoar-frost forms in the first layers of winter snow are subjected to extremely strong temperature gradients (>1° cm) immediately after deposition and for many months thereafter. ... The net relief of tundra tussocks ranges from 10 to 40 cm and, typically, the veneer snow is 20-40 cm deep as well. During autumn, the first few snowfalls may melt off from the tops of tussocks and leave pockets of new snow between the tussocks. Melt-water, draining from the tops, often saturates the snow between the tussocks, to produce icy zones.

"After snow has filled the inter-tussock areas, subsequent snowfalls tend to drift over the tussock tops. ... As the winter progresses, even dense wind slabs can begin to metamorphose into depth hoar. We have observed wind slabs as dense as 0.35 g cm³ metamorphose into depth hoar-frost by the end of the season. In other cases, wind slabs of density 0.40-0.35 g cm³ have lasted intact from mid-December to the end of March. ...

"Depth hoar-frost densities range from 0.15 to 0.25 g cm³, while medium-grained and wind-packed layers can range from 0.2 to 0.55 g cm³. The mean veneer density is at its minimum in less windy areas. A good example is the headwater region of Imnavait Creek (68°37´N, 149°17´W) near Toolik Lake, which is dominated by katabatic flow north from the Brooks Range. In 1985 an average density of 0.25 g cm³ was measured in the Imnavait watershed (Liston, 1986); in 1989 the average in this region was 0.28 g cm³. Higher densities occur in the areas farther out on the Arctic coastal plain and along the coast, where the stronger east-west winds predominate; there the average density generally exceeds 0.3 g cm³. An example is a mean density of 0.324 g cm³, which we measured in the Prudhoe Bay area (Benson and others, 1975)." - Benson, C. S. et al. (1993:262, 263)

Imnavait Creek, February 14, 1990. Height of snow-layer up to about 40 cm. With hummocks, which rise up in there 10-40 cm from the ground-surface. Snow-density from top to bottom: 30-40 cm snow-height, upper part, wind slab, extremely fine-grained, 0.40 g cm³, lower part, 0.30 g cm³. 10-25 cm height, depth hoar-frost, chains of cups 0.23 to 0.27 g cm³

Imnavait Creek, February 14, 1990. Temperature at snow/ground interface. Air temperature –24°C. Where the snow lies on the ground, below a snow height of 20-40 cm: The temperature varies from about –15 to –23°C. - Benson, C. S. et al. (1993:262) Fig. 1.


Mean snow depth and density in northern Alaska

Depth range m

Mean density g cm³

Maximum density g cm³

Taiga snow ( mostly depth hoar-frost ) 0.4-0.9 m



Tundra snow



Veneer facies (depth hoar-frost and wind-packed) 0-0.06 m



New snow



Medium grained



Wind slab



Depth hoar-frost



Drift facies (all wind-packed) 1-10 m



Mean snow depth and density of tundra and taiga snow. Benson, C. S. et al. (1993:263) Table 1.

Fig. 2. Typical cross-section through a drift in the tundra snow cover near Lake Noluck in the north-central Brooks Range. Cross-section through this drift-trap. - Benson, C. S. et al. (1993:263)

Upper half of this drifted snow, 0-1 m from surface: 25-45 g cm³

Lower half of this drifted snow, 1-2 m from surface: 40-45 g cm³

At bottom, on ground surface less, about 25 g cm³.

Fig. 5. Stratigraphic detail of the 1966 drift at the river bluffs at Atqasuk on the Meade River. Atqasuk (70°29´N, 157°25´W) on the Meade River about 95 km south-southwest of Barrow. The river banks are 10-20 m high and the meander loops provide exposure to wind, which drifts from all possible directions. (1993:264) Figure 5.

Temperature in this snow-drift: -2°C near surface of this snow-drift. The temperature in this snow-drift goes down from –2° C near the surface to –11°C on top of the frozen ground.

Snow-density in this snow-drift: 0.217 g cm³ near surface, going down to 0.420 g cm³ in middle of this snow drift, at a depth of about 1 m. - Benson, C. S. et al. (1993:264)


Large Wood bison bull (B. b. athabascae) on the Yukon Bison Range, west of Whitehorse grazing in a forest-meadow. Note, please, his steep hump. From Eric Fairclough, Minister of Renewable Resources, Yukon Bison Management Plan 1998 to 2003 p. 3.