By Mike Reiter, Polk County Naturalist
Worldwide, there are 260 species of turtles, with 55 native to the United States. Wisconsin has only 11 turtle species, with the most common being the Western Painted Turtle. The Painted Turtles are the ones most often seen on logs and rocks catching the sun’s rays to warm their bodies. Like all reptiles, the turtles, being coldblooded, need the warmth of their surroundings to become more active.
Certain types of turtles are sometimes referred to as tortoises or terrapins. Tortoises are land dwelling turtles and terrapins usually refer to turtles that are harvested for food. The endangered ornate box turtle is Wisconsin’s only terrestrial turtle, which can completely close its shell when frightened. The threatened Blanding’s and wood turtles are semi-terrestrial while the other eight species are considered primarily aquatic.
The top shell of the turtle is called a carapace while the bottom shell is the plastron. Bridges join the two shells together. The turtle’s ribs and backbone are fused to the carapace. Scutes are the large “scales” that cover the shell. While softshelled turtles are “scuteless”, all others have 13 scutes, which, according to a Native American legend, depict the 13 “new moons” in a calendar year.
Most turtles will breed in the spring then move on shore to lay their eggs in a sandy spot. Blanding’s turtles have been known to travel more than 1.5 miles from water to lay their eggs. Small turtles lay fewer eggs than larger ones. Stinkpot turtles lay 3-5 eggs while large snapping turtles will deposit 30-80 eggs at a time. Turtle eggs usually hatch in 60 -90 days depending on species. Others will hatch later while some may overwinter. A glycol-like antifreeze will keep the eggs from freezing solid during the winter.
Turtles eat a variety of things including plants or slow moving prey. Aquatic turtles always eat in the water but some semi-aquatic ones will eat on land such as the Blanding’s and wood turtles. Turtles have a good sense of smell and can also see color. They swallow their prey whole or at times use their claws to tear it apart before consuming it.
All our turtles, except for the ornate box turtle, spend the winter under water, either buried in the mud or are semi-active on the bottom of lakes and ponds. The ornate box turtle will bury itself on land in sandy soil below the frost line to wait out the cold winter months.
The Wisconsin eleven include the Smooth Softshell, Spiny Softshell, Ornate Box, Blanding’s, Ouachita Map, False Map, Common Map, Painted (two subspecies), Wood, Common Snapping and Common Musk turtles.
Predation, fragmentation and loss of available habitat and human interaction will continue to put pressure on these very unique animals. We must do everything in our power to assure they continue to thrive and prosper as they have over the last 200 million years!