Effects of winter road grooming on bison in Yellowstone National Park

The effects of winter recreation-specifically snowboarding-on wildlife in Y ellowstone National Park (YNP) have become high-profile management issues. The road grooming needed to support over snow travel in YNP is also being e xamined for its effects on bison (Bison bison) ecology. Data were collected from November 1997 through May 1998 and from December 1998 through May 199 9 on the effects of road grooming on bison in Madison-Cibbon-Firehole (MGF) area of YNP. Peak bison numbers occurred during late March-early April and were strongly correlated with the snow water equivalent measurements in th e Hayden Valley area (1997-1998: r(2) = 0.62, P < 0.001; 1998-1999: r(2) = 0.64, P < 0.001). Data from an infrared trail monitor on the Mary Mountain trail between the Hayden and Firehole valleys suggest that this trail is th e sole corridor for major bison distributional shifts between these locatio ns. Of the 28,293 observations of individual bison made during the study, 8 % were traveling and 69% were foraging. These percentages were nearly ident ical during the period of winter road grooming (7% and 68%, respectively). During this period, 77% of bison foraging activity and 12% of bison traveli ng activity involved displacing snow. Most travel took place off roads (P < 0.001). Bison utilized geothermal features, a network of trails they estab lished, and river and stream banks for travel. Bison road use was negativel y correlated with load grooming, with peak use in April and lowest use duri ng the road-grooming period. Bison in the MGF area of YNP neither seek out nor avoid groomed roads. The minimal use of roads compared to off-road area s, the short distance traveled on the roads, the decreased use of roads dur ing the over-snow vehicle (OSV) season, and the increased costs of negative interactions with OSVs suggest that grooming roads during winter does not have a major influence on bison ecology.