This photo of Towosahgy State Historic Site in Mississippi County, within the New Madrid Floodway, reveals perhaps the real reason that Mississippian culture native Americans built mounds up and down the middle Mississippi Valley at Cahokia, St. Louis, the Bootheel and counties adjacent to the big river:

This photo, by the Missouri Dept. of Conservation for DNR-Division of State Parks, was taken May 10.
The mound you’re looking at is 180′ wide x 250′ long at its base and is about 16 feet high. And yes, those are deers, coyotes and a turkey on the mound.

UPDATE: May 12- 7:45:We just found out from a reliable source that there are 43 deer, 10 turkey and 3 coyotes on the mound, and that they are being fed by humans.

Towosahgy State Historic Site is a former fortified village and civil-ceremonial center for the Mississippian peoples who lived in southern Missouri between A.D. 1000 and A.D. 1400. It is located near the town of East Prairie.