Effects of winter recreation on bison

Authors(s): M. Cherry and S. Kratville

Publication: Effects of winter recreation on wildlife of the Greater Yellowstone Area: a literature review and assessment. Report to the Greater Yellowstone Coordinating Committee. Yellowstone National Park, Wyoming.

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Publication Date: 0000-00-00

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Abstract: POPULATION STATUS AND TREND Bison (Bison bison) once roamed most of central North America and are native to the Greater Yellowstone Area (GYA). In the 1870s and 1880s, bison were nearly eliminated by market hunting; only a few small isolated populations remained. In Yellowstone National Park, poaching further reduced bison numbers, and, in 1902, 23 bison were counted in the Pelican Valley area of the park. To preserve the species, park managers imported 21 bison from captive herds in Montana and Texas and intensively managed the animals at the "Buffalo Ranch" in the Lamar Valley using livestock techniques. By the winter of 1926-27, the bison population had grown to more than 1,000 (Meagher 1973). The ranching operation ended in the mid- 1930s, when National Park Service (NPS) policy shifted from simple preservation to conservation of species in more natural conditions. The captive herd then intermingled with the remaining wild bison herd that survived in Pelican Valley. From the late 1930s through 1967, NPS managers utilized herd reductions to achieve range management goals. In 1967, when manipulative management of wildlife populations ceased, 397 bison were counted in the entire park. Bison numbers were then allowed to fluctuate in response to environmental factors. Since 1967, the bison population increased to a peak of 3,956 in the winter of 1994-95 and then declined to 3,398 in the winter of 1995-96. In 1968, in response to livestock industry concerns about the disease brucellosis, the NPS proposed a program to control bison at the boundary of the park. Hazing, herding, baiting, physical barriers, and scare devices were used to discourage bison from leaving the park, generally with little success (Meagher 1989). Shooting bison was used as a last resort. From 1968-84, only a small number of bull bison were removed as they attempted to move beyond the park boundary. Beginning in 1985, the state of Montana used hunting to control bison moving from the park into Montana. In the severe winter of 1988-89, following summer drought and area fires, hunters in the state of Montana shot 569 bison as they left the northern portion of the park. Bison continued to leave the park each winter in varying numbers, and, in the extremely severe winter of 1996-97, Montana state officials and park rangers shot or captured and sent to slaughter 1,084 bison. This, added to estimates of 300-400 dying from such natural causes as extreme weather, winter kill, and starvation, brought the total bison population in Yellowstone down to an estimated 2,000 animals in spring 1997 (NPS 1998). After reproduction, the early winter population count was 2,105 bison for the winter of 1997-98. LIFE HISTORY Bison are highly social animals. Females and subadults wander together in large herds with bulls, singly or in small bands, on the periphery of the group. The rut occurs in late summer (July and early August), and calves are born in April and May. At a few hours of age, a calf can keep up with its mother (Meagher 1973). A large bison bull may stand six feet at the shoulder and weigh 2,000 pounds. Female bison are similar in appearance to males, although they are smaller and have more slender horns that point forward. Bison have a heavily muscled neck that supports a massive head, which is swung back and forth in winter to move snow from forage. HABITAT Bison are grazers and consume large amounts of sedges and grasses. Bison do use forested areas. In winter bison are typically found in open meadows and thermally influenced areas. Yellowstone's bison winter in three fairly distinct areas with some overlap of animals between the wintering areas at various times during the year. These wintering areas are called the Northern (Lamar Valley), the Mary Mountain (Hayden Valley-Firehole River), and the Pelican Valley. HUMAN ACTIVITIES Winter recreational use can have several impacts on wildlife. These include harvest of animals (via trapping, hunting, poaching), habitat modification, pollution, and disturbance. These impacts can have a number of effects on wildlife species, including behavioral change or death. Behavioral change may consist of altered behavior, altered vigor, or altered productivity. The abundance, distribution, and demographics of populations can be affected, and this can result in changes in species composition and interactions among species (Knight and Cole 1995). Alteration of wildlife movements or displacement from normal wintering areas can result in higher energetic costs for winter-stressed wildlife, potentially decreasing production of young. Occasionally, direct mortality may occur as in the case of snowmobile-wildlife collisions. There have been various studies related to winter recreation and its impact on wildlife as evidenced by recent literature reviews by Caslick and Caslick (1997) and Bennett (1995). However, there are few completed studies that specifically focus on the effects of winter recreation on bison. POTENTIAL EFFECTS MOVEMENTS Bison establish a network of trails and travel routes in the winter as the snow depth and crust become severe. Bison often use rivers, streams, and marshes for travel as well as packed and groomed snowmobile trails (Aune 1981, Bjornlie and Garrott 1998). Groomed trails may be used extensively by bison; snow-packed roads used for winter recreation in Yellowstone National Park may be a major factor relating to the expanded distribution of bison in the park (Meagher 1993). According to Aune (1981), bison utilized groomed snowmobile trails regularly to travel from place to place. Bison were not observed using ski trails. Bjornlie and Garrott (1998) and Kurz (1998) also found that bison use the groomed roads as part of their network of trails; however, the majority of bison movements took place off of established roads and trails. DISPLACEMENT The most dramatic physiological defense response is observed when wildlife are provoked by humans on foot (Gabrielsen and Smith 1995, Cassirer 1990). The magnitude of the response depends on the distance, the movement pattern of the person(s), and the animal's access to cover. Animals will respond in a passive or active manner, depending on species and the particular situation. In their initial response to human disturbance, bison usually "freeze" body movements, and there may be increased interaction among the bison group (Aune 1981). However, bison will also flee in response to disturbance; they usually flee by galloping or trotting away from the source of the disturbance (Aune 1981). The visual stimulus of a snowmobile or skier seems to initiate the flight response. Except for coyotes, Aune (1981) and Cassirer (1990) found that all wildlife species observed (mostly big game) reacted more quickly to an approaching skier than to a snowmobile, and the flight distance was generally greater from skiers. Bison were found to respond dramatically to skiers who were off established trails. All wildlife species studied, including bison, were wary of people on foot. Most snowmobile-wildlife encounters occurred either early in the day (between 8 and 10 a.m.) or late in the day (between 5 and 6 p.m.). Most snowmobile-bison interaction occurred because of the bison's presence on groomed trails, and the number of interactions increased with snow depth (Aune 1981). Many bison flee when they encounter snowmobiles because they are "herded" down the trail by snowmobilers. Heavy human activity may temporarily displace wildlife from areas within 63 yards of the trail (Aune 1981). Heavy human activity sometimes occurs in areas that are winter range for big game such as bison. Snowmobile use is often more predictable and localized than skier activity and may cause less displacement of animals. Varied topography and good cover may reduce the frequency and intensity of displacement. Even a natural barrier, such as a river, may result in higher tolerance of snowmobile activity. ENERGY EXPENDITURE Winter recreational activity may significantly increase wildlife's expenditure of fat reserves. At the time of Aune's (1981) study, wildlife species in this area were dramatically increasing in population size, so the impact of winter recreational activity was apparently not influencing reproductive success. In some situations, wildlife may become habituated to human disturbance and the physiological responses decrease (Gabrielsen and Smith 1995). Wildlife, including bison, that are habituated gradually during the first two weeks of human disturbance (Aune 1981) may expend less energy when disturbed after that time. Bison may use groomed snowmobile trails, packed trails, and plowed roads for travel through areas where surrounding snow is deep. However, bison may not use these trails if the packed routes are not within foraging areas or do not lead to them (Bjornlie and Garrott 1998). These types of routes facilitate bison movement by making movement more energy efficient. Bison may no longer be "snowbound" in locations where they have had to spend the winter in the past. Increasing numbers of bison have adapted to snow-packed roads and are using them as a travel route to access forage sites (Meagher 1993). Despite the presence of snow-packed roads, bison continue to use natural corridors, such as riverbanks where snow depth is ameliorated (as along the Madison) or the riverbed itself, to reduce energy expenditures. Bison in the GYA are particularly affected by human use of the following Potential Opportunity Areas (POA): (4) Groomed motorized routes (5) Motorized routes Bison may also be an issue in POA (3) scenic driving routes. This depends on the effect that plowed roads have on bison movement, and how long this has been occurring. The road to Cooke City from Mammoth has been plowed since the 1940s. This road traverses the northern winter range. This area is considered big game winter range due to lesser snow depths in winter. Bison are known to travel on the plowed road, but it is unknown if the road facilitates travel to winter ranges that were not used by bison in the past or allows them to exit from areas where the snow becomes too deep. There may be some concern in areas where cross-country skiing occurs, primarily POA (9) backcountry nonmotorized areas, because of the potential for stressing bison in the winter and causing energy loss. CONTINUING RESEARCH There are several bison research projects ongoing in the GYA, including: 1. Determining forage availability and habitat use patterns for bison in the Hayden Valley of Yellowstone National Park. 2. Seasonal movements and habitat selection by bison in Yellowstone National Park. 3. Development of aerial survey methodology for bison population estimation in Yellowstone National Park. 4. Spatial-dynamic modeling of bison carrying capacity in the greater Yellowstone Ecosystem-A synthesis of bison movements, populations dynamics, and interactions with vegetation. 5. Population characteristics of Yellowstone National Park bison. 6. Bison interactions with elk and predictive models of bison and elk carrying capacity, snow models, and population management scenarios in the Jackson Valley. 7. Bison use of groomed roads in the Hayden Valley and Gibbon Canyon to Golden Gate areas of Yellowstone National Park. 8. Statistical analysis and synthesis of 30 years of bison data. 9. The effects of groomed roads on the behavior and distribution of bison in Yellowstone National Park. 10. Assessing impacts of winter recreation on wildlife in Yellowstone National Park. MANAGEMENT GUIDELINES o Where possible, consider rerouting snowmobile trails so that they are located outside of critical bison winter ranges and bison concentration areas. o Where major bison migration routes intersect groomed snowmobile trails or snowmobile-use routes, consider relocating snowmobile trails or user routes. o If bison are traveling plowed highways that have berms, plow frequent "pull-outs" where bison can escape from vehicular traffic. o Increase interpretive contacts with snowmobilers, skiers, and snowshoers to educate these winter recreational users about off-trail use and wildlife responses. o Consider restricting human use in areas of critical wildlife winter range. o Continue to study the influence of packed trails on bison movement and distribution. Determine if this influence is acceptable where it varies from historical versus critical winter use. LITERATURE CITED Aune, K. E. 1981. Impacts of winter recreationists on wildlife in a portion of Yellowstone National Park, Wyoming. Thesis, Montana State University, Bozeman, Montana, USA. Bennett, L. E. 1995. A review of potential effects of winter recreation on wildlife in Grand Teton and Yellowstone National Parks: a bibliographic data base. University of Wyoming Cooperative Fish and Wildlife Research Unit, Laramie, Wyoming, USA. Bjornlie, D., and R. Garrott. 1998. The effects of winter groomed roads on the behavior and distribution of bison in Yellowstone National Park. 1998 Annual Progress Report, Montana State University, Bozeman, Montana, USA. Caslick, J., and E. Caslick. 1997. New citations on winter recreation effects on wildlife. Unpublished report. National Park Service, Yellowstone National Park, Wyoming, USA. Cassirer, E. F. 1990. Responses of elk to disturbance by cross-country skiers in northern Yellowstone National Park. Thesis, Montana State University, Bozeman, Montana, USA. Gabrielson, G. W., and E. N. Smith. 1995. Physiological responses of wildlife to disturbance. Pages 95-107 in R. L. Knight and K. J. Gutzwiller, editors. Wildlife and recreationists: coexistence through management and research. Island Press, Washington, D.C., USA. Knight, R. L., and D. N. Cole. 1995. Wildlife responses to recreationists. Pages 51-60 in R. L. Knight and K. J. Gutzwiller, editors. Wildlife and recreationists: coexistence through management and research. Island Press, Washington, D.C., USA. Kurz, G. L. 1998. 1997-98 Hayden Valley bison monitoring progress report. National Park Service, Yellowstone National Park, Wyoming, USA. Meagher, M. 1973. The bison of Yellowstone National Park. National Park Service Science Monograph 1:1-161. ---. 1989. Evaluation of boundary control for bison of Yellowstone National Park. Wildlife Society Bulletin 17(1):15-19. ---. 1993. Winter recreation-induced changes in bison numbers and distribution in Yellowstone National Park. Unpublished data. National Park Service, Yellowstone National Park, Wyoming, USA. NPS (National Park Service). 1998. Draft Environmental Impact Statement for the Interagency Bison Management Plan for the State of Montana and Yellowstone National Park. Publication D-655. May 1998. PREPARED BY: Marion Cherry, Forest Biologist, U.S. Forest Service, Gallatin National Forest, Bozeman, Montana, USA. Sandra Kratville, Wildlife Biologist, U.S. Forest Service, Gallatin National Forest, Bozeman, Montana, USA. REVIEWED BY: John Mack, Wildlife Biologist, National Park Service, Yellowstone National Park, Wyoming, USA. Gregg Kurz, Wildlife Biologist, National Park Service, Yellowstone National Park, Wyoming, USA.

Keywords: Bison , Bison bison, Greater Yellowstone Ecosystem, Human activity, Hunting, Population, Mortality, Habitat, Poaching, Yellowstone National Park, Wildlife, Management, Livestock, Disease, Brucellosis, Forage, Food, Grazing, behavior, distribution, animal, mammal, ungulate, bibliography, elk, Cervidae, Cervus elaphus, Wapiti, Jackson Hole, National Elk Refuge, Grand Teton National Park