Monday, June 14, 2010

Turtle Crossing

Susan Thurn,
CNHM Director of Education

Beware! It’s turtle crossing time! Over the weekend, I was saddened to find a 20+ year-old snapping turtle dead on the side of the road. Phone call questions have also come into the Museum asking about turtles and how to cope with their change in lifestyle that impacts ours this time of year. Motorists are likely to see turtles crossing roads near lakes, rivers and wetlands right now because the roads separate the aquatic habitat, from the drier soils in upland habitats that female turtles prefer for egg-laying. Their nests also end up in our backyards and driveways, making for an exciting experience!

All Wisconsin turtles lay their eggs on land, usually in a nest that they dig. Painted turtles may nest twice in the same season, but other species only once. Most turtle species begin their nesting around dusk or dawn, although it can occur throughout the day. Snapping turtles can lay 30-80 eggs, while smaller turtles lay up to five eggs. Once the eggs are laid, the female departs, allowing the eggs to hatch on their own. There is great danger in making a roadside nest. The mortality from automobiles is significant because turtles are very slow to mature, taking up to 20 years to reach sexual maturity. This makes it important for motorists to drive with caution in wetland areas in order to protect our female turtles.

Although the danger is over once the female adult turtles have left the nest, the danger has just begun for the eggs. Turtle eggs can take 60-90 days to incubate, and so are often uncovered and eaten by predators such as raccoons, foxes, skunks and crows. With cooler summer temperatures incubation can take longer. Turtles that hatch in the fall overwinter in the nest, using a glycol/sugar antifreeze to keep the eggs or hatchlings from freezing. Summer temperatures actually determine the sex of many Wisconsin turtles. Blanding’s, painted, box, and snapping turtles produce more females at higher temperatures, while more males are produced at lower temperatures.

For those who might find a turtle who has laid eggs in their yards or driveways, and are looking for a way to protect the nest from their pets, or predators, resources suggest placing an object over the nest site such as a oven shelf or plastic egg crate that might prevent predators from digging to get the eggs. This past week’s rain might also help erase the scent that many turtles leave behind, making it more difficult for predators to smell the eggs.

Help a turtle by allowing them time to cross roads, while keeping safety in mind. Road mortality is especially significant for our rare and endangered Blanding’s and wood turtles. However, even our more common snappers or painted turtles can experience mortality rates that cause populations to decline and suffer. Almost half of Wisconsin’s turtles are experiencing declines. Giving turtles the time to move out of the way or occasionally using a stick to help them move to safety can truly help an animal that is a fascinating part of a diverse northern Wisconsin.

Nature Watch is brought to you by the Cable Natural History Museum. For 40 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 and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County Highway M or on the web at to learn more about exhibits and programs.

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