The 100th meridian splits the Great Plains states of Nebraska, Kansas and the Dakotas roughly in half, and also serves as a general guideline for the presence of mule deer on the Plains. To the west, mule deer roam the prairies and grasslands. East of 100 degrees, the forked horn deer forfeit lands to the dominance of the whitetail until muleys all but disappear from the map. For many hunters in this region, a deer tag is good for either species. In areas where both deer cohabitate, it's possible for that hunter to target both species in the same day.