The giant ground sloth may be the most beloved of all of Iowa’s Ice Age animals, thanks to Rusty the Giant Sloth charming generations of students since he went on display at the University of Iowa’s Museum of Natural History in 1985. Rusty’s contemporaries, the mammoth and the giant beaver, also have a kind of megafauna charisma. But are any of them really as impressive as the Iowa Pleistocene snail? This snail, no bigger than your thumbnail, is still here after 400,000 years, while the giants are all gone.
The Iowa Pleistocene snail (Discus macclintocki) is only 5 to 8 millimeters in size, and lives up to seven years. Its high-spiral, almost dome-shaped shell is either brownish or greenish in color. And for decades, everyone thought the tiny survivor was extinct.
It was just assumed the Iowa Pleistocene snail was extinct when the species was first identified from fossilized shell remains in 1928. It wasn’t until 1955 that living examples were discovered in northeast Iowa. In large part that’s because the Iowa Pleistocene snail can only survive in a very specific environment, the cool atmosphere created by algific talus slopes in the Driftless Area.
The Driftless Area is the section of northeastern Iowa, as well as adjacent parts of Illinois, Wisconsin and Minnesota, that was never covered by glaciers during the last ice age, and therefore didn’t have glacial till (or “drift”) deposited on it, creating a geological zone unique in those states. Algific talus slopes are only found in the Driftless.
The algific talus slopes are sometimes called “hills that breathe.” Algific means “cold producing” and talus means “loose rock.” Cracks and holes in the limestone or dolomite of these hills lets water and snowmelt sink beneath them, where it combines with already existing deposits of ice and rocks that are chilled by the ice. Air that returns to the surface after passing over the subterranean ice and cold rock formations creates a microclimate on the hillside that is cool in the summer and not overly frigid in the winter. That’s what the Iowa Pleistocene snail needs, because it can only survive in temperatures below 50 degrees and above 14 degrees.
Iowa has more algific talus slopes than any other state, so it’s not surprising it has the largest number of Pleistocene snail population groups. Largest, however, doesn’t mean large. Since 1955, researchers have identified 30 population groups in Iowa, all occupying friendly sections of algific talus, and one in Illinois.
It’s estimated that about 75 percent of the snail’s original habitat has been destroyed since 1850, through logging (the snails only eat leaf litter, mostly from birch, maple and dogwood trees), cattle grazing (cattle will eat the snails along with a mouthful of grass, and crush them under hoof as well), road construction, pesticide use and quarrying. Even well-meaning eco-tourist types can pose a threat, accidentally treading on the tiny snails they are climbing a hillside to see.
The U.S. Fish and Wildlife Service added the Iowa Pleistocene snail to the Endangered Species List in 1978. Eleven years later in 1989, the Driftless National Wildlife Refuge was established to help protect the remaining habitat of the Iowa Pleistocene snail and the northern wild monkshood, a threatened species of flowering plant that thrives on algific talus slopes.
Unfortunately, the wildlife refuge does nothing to protect the snails from another major threat, climate change. Algific talus can only do so much to counter a hotter planet with more violent weather, and unfortunately, the Trump and Reynolds administrations are doing little to help. If human-driven climate change continues unchecked, humans may adapt, but the Iowa Pleistocene snail may end up as just a museum exhibit next to the giants it outlived.
This article is from Little Village’s December 2025 Peak Iowa issue, a collection of stories drawn from Hawkeye State history, culture and legend. Browse dozens of Peak Iowa tales here.
