The month of June is prime time for Minnesota's eight species of turtles to lay their eggs. Females are leaving lakes, rivers and wetlands and crossing roads in search of higher nesting grounds. The females are gravid (or swollen with eggs) and seeking proper places to deposit their eggs. The carefully chosen location is usually out in the open because the warm sun is important for the development of their young. Turtles will travel fairly long distances to find a suitable spot. It is at this time, when turtles cross country roads and busy highways, that many are killed.
The female turtle uses her hind feet to dig a hole as deep as her feet can reach. After the eggs are laid, she covers them with soil. Some turtles take pains to make the finished nest look natural so it won't attract raccoons and other predators. When the job is done, the turtle departs. She plays no further role in the future life of the eggs or the baby turtles when they hatch. Minnesota's two most common turtle species, the snapping turtle and the painted turtle, lay 20 to 40 eggs at a rate of about two per minute.
The incubation period for birds can be exact, for their eggs are kept warm by warm-blooded parents. But turtles are coldblooded and cannot provide warmth. So the time it takes to hatch is varied. It usually takes two or three months, sometimes longer, for the eggs to hatch. The young turtles are then on their own to find water and fend for themselves.
Each year, thousands of turtles are killed on roads, especially during nesting season. Turtles wait as long as age 14 to reproduce. Then they must nest for years to compensate for a high rate of predation on their eggs and young. A mature female killed on a road is a significant loss for the turtle population.
Jim Gilbert's Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays. His observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.