Theodore Roosevelt National Park Feature

The park's landscape is one of prairies marked by cliffs and rock chasms made of alternating layers of sandstone, siltstone, mudstone, and bentonite clay. In spring the prairies are awash with tall grasses, wildflowers, and shrubs including the ubiquitous poison ivy. The pesky plant also inhabits the forests, where you find box elders, ash, and junipers among the trees. To avoid the rash-inducing plant—and scrapes and bruises that may come from rocks and thick undergrowth—it's always advisable to hike with long pants and sturdy boots.

More than 500 American bison live in the park. These normally docile beasts look tame, but with a set of horns, up to a ton of weight and legs that will carry them at speeds in excess of 35 mph, they could be the most dangerous animals within park boundaries. Rangers tell visitors repeatedly not to approach them. Some mountain lions also live in the park but are rarely seen. The same goes for prairie rattlers.

On the less-threatening side of the park's fauna, a herd of more than 900 elk live in the South Unit. As many as 150 feral horses are also in the South Unit. The North Unit has some longhorns, which are often found in the bison corral area, about 2½ mi west of the visitor center.