Ecology - Stop 4

As we approach the mouth of Timber Creek, we see the most obvious landmark in this area, Timber Hill or (meaning Spruce Knoll), which is also called Timber Ridge. Sticking up above the Old Crow Flats, Timber Hill is the only geological feature in the floor of the Old Crow Basin that is actually part of the structures that form the Basin rather than those that fill it. The hill is made of the same kind of rock as the mountains along the north side of the Basin. Vuntut Gwitchin traditional stories refer to this ridge as the lodge of the prehistoric giant beaver, whose fossil remains are found along the Old Crow River.

If we explore further along the creek we would notice signs of recent and historic long-term occupation; trails, log cabins, and clearings (Figure 1.4). Grassy clearings are often the sign of forest clearing on a local scale which was to obtain logs for the construction of cabins in historic times. Some of the smaller clearings result from former fishing camps, but the major reason for the long-term occupation of this area by the Vuntut Gwitchin was its importance as a trapping area.

Figure 1.4b Click the photo to enlarge.

The Old Crow Flats provide important wetland habitat for many truly aquatic species, and also for other life forms, important to the Vuntut Gwitchin, that depend on water for special habitats, especially waterfowl, moose, mink, and muskrat. With so many lakes and ponds with interconnecting streams, the Old Crow Flats are especially known for an abundance of muskrats. The importance of winter trapping to the Vuntut Gwitchin is demonstrated in the 1999 Old Crow community calendar (VGFN 1999) which summarizes the traditional winter activities.

November (Divii Zrii "sheep month"), marks the beginning of winter snow cover and is the main month for trapping marten, fox, lynx, and snowshoe hares (VGFN 1999). In December (Khah Zhak Dha’aii Zrii, "short days month") the snow cover remains relatively shallow (Russell et al. 1993) and the muskrat harvesting season ("ratting") begins. The first activity is "the staking of rat houses over the innumerable lakes of the Old Crow Flats... before the rat houses are covered by heavy snow" (Balikci 1963). The Vuntut Gwitchin hunted moose and caribou during this month as well. December is also trapping season for mammals such as mink, marten, fox, weasel, wolverine, wolf and lynx (VGFN 1999).

Figure 1.4a Click photo to enlarge.

Through the cold of January (Cha’kah Zrii, "cold weather month") and February (Ahtr’aii, "windy month") the snow depth increases (VGFN 1999). This month is very cold but people still go out on the land to hunt and trap for martin, mink, fox, lynx, weasel, rabbit, ptarmigan, moose and caribou.

Winter is a quieter time on the Old Crow Flats. Most of the 100 or more kinds of birds that may be seen here in summer have long since departed for their wintering grounds far to the south. Only a few birds, including ptarmigan, raven, gyrfalcon, and snowy owl, remain in the northern Yukon year-round.

How do these few birds and many mammals survive the cold winters of the northern Yukon?

During the northern winter, birds and mammals maintain their normal body temperature in the face of prolonged low temperatures through a combination of structural or physiological adaptations, including insulation and heat exchange mechanisms, and behavioural adaptations, including posture, orientation, the use of natural shelter, and the modification of the natural environment for shelter. In winter the thick layer of insulating underfur or feathers common to most northern animals permits the maintenance of body temperature at the extreme temperatures associated with the northern climate. Wolves, foxes, ptarmigan, and snowshoe hares all conserve heat in winter by adopting a sphere-shaped posture while resting, and all use snow in some way to conserve heat, either by digging dens, by allowing drifts to cover them, or sheltering under snow on tree branches. Hares in particular make use of the shelter provided by trees, preventing the escape of their body heat through radiation to the open sky.

The most ecologically important aspect of weather and climate to the land and wildlife of Vuntut National Park is the snow; its distribution, depth, hardness, duration and layering of the snowcover. Snow provides insulation and shelter for people and animals. Snow protects vegetation from cold and wind, and provides moisture for plant growth in the spring. Snow also provides a surface for winter travel; on snowshoes, by dogteam, or snowmobile. On the negative side, snow can prevent large herbivores from feeding, and can slow the spring growth of plants. Snow can cause an abrupt end to the growing season, and can create conditions that make travel on the land impossible. Fall storms which deposit freezing precipitation directly onto the surface or over a thin, wet layer of snow, can have disastrous results on populations of caribou and muskoxen (see Climate).

"There was one winter I remember when the ground just froze. It snowed, then it rained and froze and the caribou couldn't get at their food. That affected the health of the herd in a serious way." (Gladys Netro in Sherry and Vuntut Gwitchin First Nation 1999).

Climate in the form of temperature variations also has a powerful impact on the movement of mammals in the Old Crow Special Management Area in winter, especially for moose and caribou. In winter there are higher temperatures at higher elevations and lower temperature in the Flats, the opposite to what occurs in summer. The Old Crow Basin holds the cold air. Thus the Porcupine Caribou Herd winters on the higher plains and mountains south of the Old Crow Flats, not in the Flats themselves (Russell et al. 1993). Hunters too seek the more moderate climate of the higher altitudes when possible.

Figure 1.4f Click photo to enlarge.

Nor do moose stay in the Old Crow Flats for the winter. The moose from the northwestern portion of the Flats migrate back into the Brooks Range of mountains across the border in Alaska (Figure 1.4c d e). Two main reasons are suggested for why they don't stay (U.S. Fish and Wildlife Service 2000). The first is access to food. In the Flats snow drifts deep into the willows (reaching an average depth of 70 cm in 1997), whereas in the mountains, willows are protected from the wind and average snow depth is 50 cm. Secondly, the level of cold experienced on the Flats is considerably greater than in the mountains, as the dense and heavy cold air slides down off the mountains and settles or pools in the Flats. In the higher mountain valleys of Alaska moose experience warmer winter temperatures and easier access to willows, a primary winter food.

It has been suggested that with global climate change, the moose population of Vuntut National Park may benefit if wintering habitats of high cover and food availability, such as deciduous shrub areas, become increasingly available as taiga vegetation moves north as global temperatures increase (Environment Canada 2000). The ecosystem changes that may result from global climate change will probably have a diverse range of effects on plants and animals of this area.

For the grazing and browsing species like moose and caribou, late winter is a critical time. Snow depth, hardness and extent are greatest at this time and affect these herbivores that must either dig through it or find wind-blown areas or shallow snow. In late winter body condition may be poor depending on the winter conditions and female caribou and muskoxen are pregnant at this time. These and other factors affect the dynamic balance between predators such as wolves and their prey such as caribou and moose.

Poor weather may be one of the causes of the decline in the Porcupine Caribou Herd population which has been apparent since 1989, though all the components are not fully understood (International Porcupine Caribou Board 1998). The birth rate in 1991 was low following a winter of deep snow where most of the caribou spent the winter. Survival of calves was lower than usual in 1992, a year in which late snow melt during spring migration delayed part of the herd in arriving on the calving grounds (International Porcupine Caribou Board 1998). The summer of 1992 was short and snow was again deep that winter, resulting in smaller age classes for those years. Survival of calves was lower than average during the summer of 2000, probably due to the lateness of the spring.

When things are tough, such as winter conditions, this is when competition between caribou and muskoxen might become a factor in survival. Recent research work on Banks Island by GNWT biologists indicates that there is a significant overlap in the diets of muskoxen and Peary caribou, and that the muskox population has expanded into critical caribou calving, and summer and winter ranges (Nagy et al. 1996).

However, research in other areas suggests that the feeding habitats of caribou and muskoxen are mutually exclusive and the lack of competition is attributed to the food habits and feeding behaviour of the species (Gray 1987). Some earlier studies of the situation on Banks Island found little evidence to suggest that muskoxen and caribou were competing (Wilkinson and Shank 1974).

As Vuntut National Park was established with the view to protect the range of the Porcupine Caribou Herd, the possible competition between this species and the muskoxen is an ecological factor of some importance to conservation and management policies.

The use of snowmobiles may have an important impact on both vegetation and small mammals. Snowmobiles may compress snow to such an extent that the layer of space at ground level is destroyed. Thus movement of mammals that normally burrow under the snow at ground level is impeded. A study of the thaw response of tussock-shrub to all-terrain vehicle disturbances in Alaska showed that season of activity is very important (Racine and Ahlstrand 1991). No specific studies have been made of the impact of vehicular traffic in winter or other seasons on extremely sensitive terrain of the Old Crow Flats.

Stop # 4. Timber Hill

Ts'ivi Shuh

Winter Ecology