Ten ecologically important habitats, which support 16 rare and some threatened species, consist of black bear dens, elk, deer, goat and sheep seasonal ranges, wildlife migration corridors, and waterfowl staging and nesting areas. The 29 species of small animals include the ground squirrel, considered the grizzly bear's most reliable prey, the marmot, living at 6800 to 8000 metre elevations, porcupine, beaver, and rock rabbits (Pika) that are often seen on rock slides and talus slopes. In the deer family are the hoofed animals whose antlers fall off and re-grow each year: moose about the size of horses can be seen along the Icefields Parkway; the Wapiti (Elk), the most dangerous animal in the park, the white-tailed deer, and the woodland caribou are all given appropriate protection. The Bighorn rams have massive, permanently spiraled horns, while the all-white mountain goats have short black spikes. Both migrate easily between low grassy slopes and alpine meadows, although the goats prefer a more rugged terrain. Sadly, the wood bison no longer inhabit the park, but plains bison may be viewed in the `Bison Paddock'. Wolverines, pine martens, ermine, the long-tailed weasel, and the fisher can all be seen in forested areas. Wolf, coyote, lynx and cougar, Canada's largest cat, are all rarely sighted and their populations are carefully monitored. Bears that become used to humans are still a safety hazard in spite of the instructions and information the park provides its tourists. Grizzlies inhabit backcountry wilderness, subalpine forest and tundra. As part of a comprehensive study, over 20 silvertip grizzlies have been radio-collared. The smaller black bears wander through valley-bottom-forested areas.