The turtle hatchlings are emerging from their nests, and turtles are starting to dig nests and lay eggs. The Masked Biologist explains this interesting survival mechanism in this week’s Wildlife Matters.
In the world of turtles, we are wrapping up the hatchling emergence period, when turtle hatchlings, not much bigger around than a golf ball, have been digging their way out of the nests and instinctively heading toward the closest water body. Meanwhile, the nesting/egg laying period for painted turtles, wood turtles, and snapping turtles is getting started. That’s right—in terms of our calendar year, hatched turtles emerge just before adult turtles lay their eggs.
I have seen many turtles digging nests and laying eggs over the years, but I have only seen one hatchling emerge from a nest. I was turkey hunting several years ago on Memorial Day weekend when a tiny painted turtle hatchling emerged from the ground between my feet and scooted downhill toward the marsh. That little turtle wasn’t hatched that spring, or even that year. The incubation of turtle eggs varies, depending on weather conditions. If the nest is laid late enough in the summer, or if the summer has too many cool days, the hatchling turtles will hang out in the nest all winter and emerge the following spring. This means those eggs were laid almost a year prior, survived predation, and at least one turtle hatched and stayed underground all fall, winter, and spring to emerge right in front of me and scramble to the water.
It is difficult to pin down the exact time that turtles lay their eggs, because there are many factors that affect nesting, everything from age of the turtle to availability of nesting areas and the temperature. Some turtles may even nest more than once a year, although once in spring is probably most common. A female turtle will excavate a shallow depression in looser material, sand or gravel, and deposit her eggs in it. She will push material back over it and leave, her work done. The eggs and hatchling turtles will be completely on their own.
Unfortunately, even under ideal circumstances, turtle nests don’t do very well. Only 5 percent of eggs laid survive to hatch; and of those only 1 percent may survive to reproductive age. So, take the snapping turtle for example. An average clutch size might be 30 eggs. So, out of three snapping turtle nests, maybe 5 eggs will hatch out baby snappers. Of those, maybe 1 or 2 will live to the age of 7 or 8 years, which is likely the minimum age for a female snapper to lay eggs. Those aren’t very good odds. Painted turtles may lay ten eggs or less, making it far more difficult to overcome such low survival rates. Now perhaps you see some of why five of Wisconsin's 11 turtle species are experiencing significant population declines. Nests laid in road shoulders, driveways, recreational trails and other developed areas are subject to more disturbance and predation, further worsening the odds.
The winter we had last year, with early and thick snow cover, probably helped hatchling turtle survival; they hibernate in the ground by surviving subfreezing temperatures (they let themselves partially freeze). Survival will still be difficult; the hatchlings are food for fish, snapping turtles, herons, raccoons, mink, muskrats, and other predators. I expect that this spring’s turtle crop will be a healthy one, with all the water and the warm temperatures. The egg-laying season that is starting now? Well, only time will tell. You can do your part to try to improve the odds. If you see a turtle crossing the road, you can help it across in the direction it was heading, not the direction it came from. If you see a turtle laying eggs on your property, you can easily build a predator exclosure to help protect the eggs for the next 10-12 months. If there is a problem with the location of a nest, for example it was dug in a construction area, you might be able to call a wildlife rehabilitator and ask them about alternatives but don’t try to move the eggs yourself. The odds are already against turtles from the day the eggs are laid, so anything we can do to improve their chances can make a big difference for populations for years to come.