The plant and animal composition of the riverine world varies with the rate of water flow. In slow water areas, such as the Oxbow Bend, where the river has cut off and abandoned a former looping meander, bottom-rooted aquatic plants attract herbivorous animals—moose, mallards, golden-eyes, and cinnamon teals—to graze these underwater gardens. Such quiet stretches also attract carnivores to exploit the greater variety of prey. Great blue herons stand motionless along the shoreline, waiting to spear passing fish or the mice, frogs, and snakes at water’s edge. Mink and coyote patrol the shoreline. Insects are important river denizens, as the fly fishing angler’s art attests. The nymphs of mayflies and stoneflies and the larvae of caddisflies eat algae and other plant detritus, in the process becoming attractive fare for the cutthroat trout and Rocky Mountain Whitefish. The caddisfly larvae have adapted to fast water by constructing protective body cases from sand grains, pebbles, plant stems, and other stream bed materials. The faster the current, the heavier the case, which enables the larvae to settle rapidly into a new cranny, should they be swept away. The sturgeon used to populate the Snake in what are now park waters, but the erection of more than 20 hydroelectric and irrigation dams downstream so changed the river that these very large fish are now hard pressed to survive above the Columbia River confluence. [Illustration: _Shaped like a short-handled dipper, the Snake River progresses westward through the nation’s largest chunk of wilderness outside Alaska. The Snake’s drainage also figured in historic exploring expeditions and scientific, military, and railroad route surveys during the 19th century. Some important expedition and survey routes are shown on this map._] Expeditions and Trappers [Illustration: “Beaver Flats”] [Illustration: “John Colter Visits the Crows 1807”]