Big Bend is famous for its natural resources and spectacular geology. The park is home to more than 1,200 species of plants (including approximately 60 cacti species), 11 species of amphibians, 56 species of reptiles, 40 species of fish, 75 species of mammals, 450 species of birds, and about 3,600 species of insects. The park boasts more types of birds, bats, and cacti than any other national park in the United States.

Big Bend National Park also marks the northernmost range of many plants and animals, such as the Mexican long-nosed bat. Ranges of typically eastern and typically western species of plants and animals come together or overlap here. Here many species are at the extreme limits of their ranges. Latin American species, many from the tropics, range this far north, while northern-nesting species often travel this far south in winter. Contrasting elevations create additional, varied micro-climates that further enhance the diversity of plant and animal life and the park’s wealth of natural boundaries.