Natural History: Tallgrass Prairie
	In the eastern tallgrass prairie, oak groves like this are not uncommon. (Eric Ulaszek)

Though very little of the North American tallgrass prairie remains, it once covered the Midwest, parts of Iowa and Minnesota, and the eastern edges of Kansas, Nebraska, South Dakota, and North Dakota, from which it extended northward into Canada.

The eastern part of the tallgrass prairie (most of Iowa, Missouri, Illinois, parts of Indiana, and little pieces of Ohio) was actually a mix of prairie and forest.

In parts of the eastern tallgrass area, islands of prairie ranging between one and twenty miles in diameter were surrounded by forest. In other sections, islands of forest were surrounded by prairie. In yet other places, islands of savanna (grassland with scattered trees) were surrounded by forests. The forests were different, however, than the forested areas of the eastern United States, which were dominated by beech and maples. The forests of the eastern tallgrass prairie tended to be dry, and were made up mainly of oaks and hickories. The boundaries of the forest and prairie areas were not absolute. If the climate was dry for several years, the smaller oak trees would die and grasses would take over. During a series of wet years, oak seedlings would become established in the grasslands, and the forest would expand a bit.

This area is mostly under cultivation or developed now, but prior to Euro-American settlement it contained a variety of habitats. The presence of both prairie and forest and the intermingling of these two habitats resulted in a great diversity of animal life. Most of the animal species found in the tallgrass prairie were also found in the eastern forests, although a few species were unique to the tallgrass prairie.