Most elk, bison and trumpeter swans barely reacted last winter to the presence of snowcoaches and snowmobiles in Yellowstone National Park, according to a study released Tuesday.
Scientists watched more than 2,100 interactions between over-snow vehicles and wildlife last year to try to determine how they responded.
Of those, 81 percent of the animals had no apparent response or they looked and then resumed what they were doing, the study said.
A larger debate
The research is part of a larger debate over the use of snowmobiles and snowcoaches in Yellowstone and Grand Teton national parks.
Opponents of snowmobile use - along with previous Park Service studies - have raised concerns about the effects of the machines in winter when wildlife are stressed by weather and scarcer food supplies.
The study, intended to help park officials draw up a long-term plan for winter activity in Yellowstone, suggested that most elk and bison can become habituated to the machines over time.
Although some individual animals may be affected by vehicles in the winter, the overall populations don't appear to be harmed, according to the study.
"We suggest the debate regarding the effect of motorized recreation on wildlife is largely a social issue as opposed to a wildlife-management issue," said the study, prepared by researchers from Yellowstone and Montana State University.
The lead authors, Yellowstone's P.J. White and Troy Davis, couldn't be reached for comment Tuesday.
The National Park Service is in the midst of its third in-depth study of the snowmobile issue in Yellowstone and Grand Teton. A draft is scheduled to be completed next year.
Meanwhile, limited numbers of snowmobiles and snowcoaches are being allowed in as long as the machines meet pollution and noise standards and all riders are accompanied by a commercial guide.
Key debate topic
For years, park wildlife has been a key topic in the debate over snowmobiles along with noise, pollution and the economic impact on nearby communities.
The latest study was conducted between December 2004 and March 2005, during a winter with below-average snowpack and a below-average number of visitors.
The response to over-snow vehicles among elk, bison and swans varied, but most seemed unfazed. Nine percent showed attention or alarm, 7 percent left the area and 3 percent showed a flight response, according to the study.
Bison and elk tended to react more when the number of snowmobiles or snowcoaches in a group increased. The animals were also more likely to react when people stopped their vehicles and approached.
Even when wildlife are faced with vehicles in the winter, the energy required to respond typically isn't great, the study said.
Overall, the populations of elk and bison in the park appear to be stable, the study said, and any "adverse effects" in the winter "have apparently been compensated for at the population level."
Previous Park Service studies have indicated concern about harm to wildlife in the winter, even if the overall population isn't affected. A Park Service snowmobile plan in 2003 said regulations, policies and executive orders "clearly state that disturbance to wildlife, regardless of population-level effects, is unacceptable in the national parks."
An analysis of the temporary three-year plan that's currently being implemented - which sets a daily limit of 720 snowmobiles and 18 snowcoaches - said the Park Service's goal of minimizing the "active response" by wildlife would not be achieved.
The authors of the latest study make several recommendations, including attempting to keep people more than 100 yards away from wildlife groups, reducing the number of riders in groups that stop to observe wildlife, reducing the number of wildlife stops and reducing the amount of time that people interact with animals.
