Watch for Migrating Turtles on Roads

By TOM GONIEA
Fisheries biologist, Fisheries Division
Michigan Department of Natural Resources

As spring transitions to summer and the warm temperatures roll in, Michiganders weary of winter excitedly begin adventuring across the state. It’s a time of renewal and reinvigoration for many.But as you head out, be on the lookout for turtles, which are also on the move this time of year.

Late spring and early summer are times when turtles are moving en masse across the landscape. The females are actively looking for nesting sites, and males also just kind of wander this time of year, moving between the lakes, ponds and streams they call home.

This overland movement often involves crossing roads, which unfortunately results in noticeable levels of turtle mortality throughout the state. That roadkill can be high enough to affect local populations and likely is the largest direct loss of adult turtles by humans.

“I receive calls every year from people in my area about dead turtles on the roads and have few answers for them,” said Scott Heintzelman, fisheries biologist and Central Lake Michigan Unit manager for the Michigan Department of Natural Resources. “It is particularly sad to see or hear about turtles that have been intentionally hit on the road.”

Turtles don’t begin mating and laying eggs until age 8-10 and have extremely low natural mortality as adults. If not crushed by a car tire, they can and often do live for many decades.

Their low mortality as adults and ability to lay eggs annually for 20-50 years is necessary to overcome the extremely high mortality rate of juveniles and losses of turtle eggs.

With turtles, almost all the natural predation (what we might call “the circle of life”) is concentrated on the eggs and baby turtles, which are easy targets and tasty morsels for Michigan’s racoon, opossum and skunk populations. A floating baby turtle is also irresistible to bass or wading birds like great blue herons.

As a result, the conservation of these animals really hinges on the protection and survival of the adults, who have already survived the gauntlet of predator threats as juveniles themselves.

The interesting thing about turtles is not that they can live for 50-100 years in the wild, it is that they really must live and reproduce for that long to maintain stable populations. In fact, the margin on adult turtle populations is so slim that a 6% annual mortality for adults is often enough to threaten sustainability and push local populations toward local extinction.

Let that sink in for a second.

That means that in a population of 100 adult turtles, if six or more are lost every year, that population could decline and eventually disappear.

Comparatively, while popular Michigan game species like walleye or white-tailed deer can easily withstand sustained annual adult mortalities of 35% and 40%, respectively, turtle sustainability is threatened by very small increases above that 6% threshold.

“Turtles face many threats, but perhaps the most preventable is direct mortality from vehicle strikes,” said Jennifer Kleitch, the DNR’s endangered species specialist. “Michigan is home to 10 native species of turtles, three being listed as threatened and one being of special concern. Everyone can do their part in helping conserve these rare reptiles by following some simple steps.”

Michigan’s native turtle species are:

• Wood turtle (Glyptemys insculpta) – state-threatened.
• Spotted turtle (Clemmys guttata) – state-threatened.
• Eastern box turtle (Terrapene Carolina) – state-threatened.
• Blanding’s turtle (Emydoidea blandingii) – special concern.
• Common map turtle (Graptemys geographica).
• Common musk turtle (Sternotherus odoratus).
• Common snapping turtle (Chelydra serpentina).
• Painted turtle (Chrysemys picta).
• Red-eared slider (Trachemys scripta subspecies elegans).
• Spiny soft-shell turtle (Apalone spinifera).

Because adult survival is so important for turtles, anything the public can do to help reduce roadkill during spring and summer months can greatly benefit local populations.

The public can help by taking the following small steps:

• • When you see a turtle in the road while driving, slow down and try to avoid hitting it, if it is possible to do so safely. However, do not veer to avoid hitting turtles.
  • Be aware near bridge crossings and stretches of road near lakes, streams and wetlands, where turtles are likely to be.
  • Don’t attempt to hit or run over turtles on purpose. Not only is it harmful to the turtle and the local turtle population, it’s also dangerous for you, your passengers and other vehicles on the road.
  • If you choose to help a turtle cross the road (and you can do so safely), place the turtle across the road in the direction it was heading. Otherwise, the turtle may attempt to cross the road again to get to its desired location once you leave.
  • When you find a turtle, don’t pick it up and take it home. When an adult turtle is taken from its home range, that affects its local population in the same way as if it had died. All its potential future offspring are taken out of the ecosystem, too.
  • Except when they are in the middle of the road or other location where they’re in immediate danger, turtles are exactly where they should be and do not need to be moved or helped by people.
  • Report turtle sightings on MIHerpAtlas.org to help scientists measure changes or trends in their populations.

There’s not much the DNR, the Michigan Department of Transportation, county road commissions or other agencies and groups can do to keep these slow-moving animals from wandering onto roadways, but as professional natural resource managers, we can do our best to share their story and highlight this annual threat to turtle populations.

According to Heintzelman, “Maybe the suggestions provided and sharing some insight as to what makes these animals so special might save a few turtles this spring and summer.”