River Turtles

The St. Croix and Namekagon rivers are home to eight species of turtles. Look for them basking, like this common map turtle, on rocks, logs, and along the shores.

NPS/VanTatenhove

What is a turtle?

Turtles are reptiles that have unusual skeletons which form a protective shell around the animal. The top shell is called a carapace while the bottom is a plastron. Some types of turtles have top and bottom shells that are fused together while other turtle species have separate tops and bottoms. Turtles sometimes escape danger by “hiding” in their shells. Some turtles can tuck their heads and legs into their shells farther than other types.

A Reptile Lifestyle

Like most reptiles, turtles are coldblooded. This means that their blood temperature changes depending on the air or water temperature around them. Turtles bask in the sun to warm their bodies which helps them to digest their food. Even though some turtles are mostly aquatic, they all breathe air and have lungs. Their skin is covered with scales.

Turtles lay leathery eggs which females bury in sandy soil using their sharp claws. Young are on their own, but if they survive the first few years, they have a good chance of living a long time—some species for over 60 years.
Most of the turtles along the St. Croix and Namekagon rivers eat a variety of things, including plants and animals. Turtles don’t have teeth but use their hard beak-like mouths to cut.

Although adult turtles have few predators, turtle eggs are an important food source for many animals, including skunks and raccoons.

Like most reptiles, turtles hibernate in winter. They bury themselves in mud along the shores or under the water, slowing their heart rates and breathing, and stopping most body functions. Once the weather turns warm again, they reappear and become a common sight in the park.

 

many turtles cross roads searching for appropriate nesting areas. Traffic poses a deadly threat.

NPS/Butler

Turtle Trouble

When people build new roads through forested areas, turtle habitat is broken into smaller and smaller pieces. This process is called habitat fragmentation. Individual turtles could be lost on busy roads trying to get to nesting sites that may no longer be in their original habitat areas.

If females are on their way to a nest site and they are hit by a car, not only is the female lost, but her eggs and potential young are lost as well.
Habitat fragmentation and resulting road mortality is one of the most serious threats to turtles. Recent turtle surveys also showed an increase in nest disturbance by ATV usage. Water pollution is also a threat.

Protecting Nest Sites

Many turtle nests go undetected by people once weather helps to erase signs of digging. Walking over nests can crush turtle eggs. Signs are posted on sandy banks along the St. Croix and Namekagon rivers to protect turtle nest sites.

 

Turtles of the Riverway

These two turtle species prefer large river habitat and are most common on the lower reaches of the St. Croix River, below Highway 8.

Smooth Softshell

Turtle Apolane mutica
This large turtle is the only softshell in North America without bumps or spines on the front of its carapace.

False Map Turtle

Graptemys pseudogeographica
Often mistaken as painted turtles, this species is characterized by a yellow mark behind its eyes and a carapace that comes to a point in the middle.

 

These turtles are commonly seen on the middle and upper St. Croix River and the Namekagon River.

Common Map Turtle

Graptemys geographica

A good way to distinguish a map turtle from a painted turtle is to look for a “keel” or pointed midline down the turtle’s carapace. They can reach nearly 11 inches in length and can often be seen basking in large groups.

Spiny Softshell Turtle

Apolane spinifera

These turtles look much like the smooth softshell turtles, but with bumps along the front edge of their carapaces. They also have dark spots on their legs and feet.

 

These species are common throughout the Riverway.

Painted Turtle

Chrysemys picta
Reaching up to 10 inches in length, painted turtles have red bars or crescents around the edges of their carapaces. There are no jagged edges are on the back end of their shells.

Snapping Turtle

Chelyfra serpentine
The large head and jaws of snapping turtles make them easy to identify even in the water. Their tails are long and bumpy.

 

On the state threatened lists for both Wisconsin and Minnesota, these two turtles are rarely seen.

Blandings Turtle

Emydoidea blandingii
These turtles prefer slow moving water with a lot of vegetation such as backwater channels. Their domed carapace and bright yellow chin are characteristics to look for.

Wood Turtle

Clemmys insculpta
The carapace of a wood turtle looks like it has been carved from real wood. Wood turtles typically spend more time on land than other river turtles. They often stamp their front feet. Biologists think this behavior may be an effort to sound like rain and bring earthworms to the surface.