Grizzly bears roam only the northern part of the park. Predation on large mammals must be carried out by seldom seen black bears, rare mountain lions, and coyotes, who largely feed on rodents. Red foxes (rare here), lynxes, and bobcats are crafty and formidable, but at best threaten only the young of large mammals. Formidable predators of a smaller scale are the many members of the weasel family, including two weasels, the badger, pine marten, wolverine and fisher (very rare here), and mink. The prey of these creatures includes many of the more familiar small mammals, such as shrews, hares, chipmunks and golden-mantled ground squirrels, Uinta ground squirrels, red and flying squirrels, mice, pocket gophers, woodrats, voles, and muskrats, and also small birds, bird eggs, reptiles, and amphibians. Porcupines and beavers are both large rodents and both feed on bark, but their defenses differ. Beavers escape to their snug lodge protected by the surrounding water, while porcupines are protected by quills. But porcupines sometimes fall prey to fishers and maybe smaller cats and other critters able to get at their unprotected faces and bellies. [Illustration: _The vigorous, brief blooms of alpine plants edge a high mountain meadow, with only the tips of peaks as a backdrop._] Bird watchers are content here just to see the rare trumpeter swan—on the Elk Refuge, or at Christian and Hedrick Ponds. Other large birds include bald eagles, ospreys, sandhill cranes, Canada geese, and great blue herons. The water ouzel (dipper) walks underwater in fast current, a marvel to behold. Bold and brassy are the crafty magpies, who won’t hesitate to let you know if you annoy them. More than 100 species of birds have been identified in the park. Four major natural communities provide a way of understanding the park’s wildlife patterns. The water communities include lakes, ponds, rivers, and streams. The sage and grassland community is the most extensive and most often overlooked. The forest community appears randomly distributed, but soil moisture properties, the direction it faces, elevation, and weather patterns influence where trees grow. Blue spruce and cottonwood thrive along valley streams. Aspen, Douglas-fir, and lodgepole pine inhabit the valley and lower slopes. Sub-alpine fir, Engelmann spruce, and limber pine stand on mountainsides and in canyons. The edges where communities meet are richest in wildlife. The alpine community crowning the highcountry shares the least characteristics and organisms with the other three communities. Water communities call to mind perhaps the trout and beaver (see pages 48 and following), and lakes, ponds, streams, and rivers interrupt or dot the other three communities. In winter moose inhabit the river flats to browse the cottonwoods and willows.