Thursday, March 1, 2012

Turtle Dreams

All winter long, I have been watching the most graceful swimmer. She uses her arms and legs in perfect concert, making subtle motions to move up and down, hang vertically, or even spin quickly through the water. The path of her webbed toes is similar to the sculling motion of a canoe paddle that experienced boaters use for side slipping, or the hand motions of a human treading water. It almost looks as if she is caressing the water. For many long minutes, I get lost in her movements, dreaming of spring ice-out.

This aquatic ballerina is Shaun, our pet turtle. She is a red-eared slider, the most common species of pet turtle in the world. Native to the south-central United States, Shaun will be active and highly entertaining all winter, especially when we have extra minnows or worms to feed her. In the wild, red-eared sliders and many other types of turtles hibernate.

Most of Wisconsin’s eleven turtle species spend the winter underwater. This is an amazing feat, since reptiles are air-breathers. Even in the summer, turtles stay underwater for long dives. Winter ice cover simply means an extra-long dive. Because they are cold-blooded, hibernating turtles cool down with the water and have a very low metabolic rate. This lowers their need for oxygen, and with their lack of movement, also reduces the production of lactic acid in their muscles.

Some gas exchange may occur directly through their thick, leathery skin, helping to provide some oxygen and release some waste gases even without breathing. To make absorbing oxygen through their skin most effective, you would think that turtles would try to hibernate in the most oxygen-rich water possible. In fact, map turtles (named for the markings on their shells) do hibernate on the river bottom where fresh water can flow over them.

In contrast, painted turtles bury themselves in the mud. Painted turtles that live in the north are better than southern turtles at surviving long hibernation dives with low oxygen. As acid accumulates in their blood, they buffer the pH by increasing basic cations like magnesium, calcium, and potassium.

Snapping turtles spend winter in a low-oxygen environment similar to painted turtles– under mud in the shallows of small ponds. While the lack of oxygen is stressful, the shallows may warm up faster in spring and reduce the length of their hibernation. As it is, turtles do not feed much when the water temperature is below 65 degrees. Up here, this means that turtles may spend the entire school year hardly feeding if at all!

Turtles have amazing strength and tenacity. For many months, their breathing, movement, and almost all heart activity stops. Then in spring, they resume life where they left off. For 200 million years or so, turtles have done this and prospered with few changes.

In many Native American creation myths, the turtle is a central figure. It is told: When the early world was still covered by water, Great Turtle dove deep to bring up mud on his strong back. All the continents grew from that first bit of soil.

Great Turtle’s long dive culminating in the birth of the world is not unlike our present turtles emerging from hibernation into the awakening spring.

Until then, I get to enjoy Shaun’s aquatic ballet while dreaming of summer when her relatives will emerge, and we, too, can swim!

For over 44 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 13470 County Highway M. The new exhibit, The Joy of Birds: Feathers in Focus opened in May, 2011. Find us on the web at to learn more about our exhibits and programs. Also discover us on Facebook, or at our blogspot,

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