Here's a quote from the 3/9/2007 Yellowstone National Park Daily Report:
Special Information
The road from Lake to West Thumb is closed to snowmobiles but is open to snow coaches due to bear activity.
I've seen motorcycles deal with bison on the road, and I've had to do it myself, but I don't think I've ever seen snowmobiles dodging grizzlies (or vice-versa). That could be the "ultimate slalom course", hungry adult male grizzlies recently emerged from their dens. Now, a snowcoach vs. a pair of hungry adult male griz might be more entertaining than the WWF.
WAHOO!!
Ballpark