Every summer evening, more than a million Mexican Free-tailed Bats leave the entrance of Selman Bat Cave, one of the Oklahoma's largest maternity colonies. Maternity colonies contain only female bats and their offspring. The bats travel over 2,000 kilometers from Mexico to this colony every spring to give birth to and rear their young before they return to Mexico in autumn.

The Oklahoma Wildlife Department organizes tours of Selman Bat Cave, but the area is only open to the public during these bat viewings. Visitors must pre-register and pre-pay to attend: registration begins in May. Visitors meet at Alabaster Caverns State Park and travel by bus to the bat-viewing area in front of the cave entrance. This Oklahoma attraction is the bats, not the cave, which is so full of bat guano that it would be extremely hazardous for humans to enter. There is an 800m nature trail hike available, however, with professional biologists as guides.