"I saw immence quantities of buffaloe in every direction...they are extreemly gentle the bull buffaloe particularly will scarcely give way to you. I passed several in the open plain within Þfty paces, they viewed me for a moment as something novel and then very unconcernedly continued to feed."
— Meriwether Lewis, May 4, 1805

The namesake ungulates of Montana's National Bison Range are in fact rather ungentle. The month after Meriwether Lewis penned the lines at left, he described three bulls rushing him at "full speed" (a peeved buffalo can charge at 30 miles an hour). During summer breeding season, the males–which weigh up to 2,000 pounds–are particularly pugnacious; their bellowing can be heard some three miles away. A bull finds a possible partner and then "tends" to the cow by standing between it and the herd for as long as several days, shoving or head-butting any potential rivals. (When a bull sneers, it may appear hostile, but his lip curl is actually a "flehmen" response–smelling the cow to detect sexual readiness.)

These 18,500 acres have been a haven for bison for nearly 100 years, ever since Teddy Roosevelt set aside this and other preserves to prevent the permanent loss of Bison bison. (Lewis and Clark's journals tell of plains blackened with the beasts, but by TR's day, hunting and habitat loss had reduced their numbers to fewer than 600.) The continent's largest land mammal, the buffalo's bigness adapts it to the prairie: Its muscular hump helps hold up its massive head, which becomes a snow shovel in winter to uncover grass. A bulky coat keeps the buffalo toasty–snow can land on its back without melting–and come summer its thinned fur still helps cushion the blows during the fight for females.

As bison adapted to the prairie, so the prairie adapted to them. Native grasses like rough fescue and bluebunch wheatgrass grow from the base of their stems instead of the tips like most plants, so they can recover quickly when their tops are munched off. Even the buffalo's wallows–which under their rolling weight turn into dust bowls–make room for annuals when they become little wetlands in the rainy months. The bison rolls to get rid of pesky insects but also to claim its domain. The bull shows off his physique to females and kicks wimpier fellows from the wallow. –Elisa Freeling