Be careful when driving near forests, or beside wetlands and water during May and June. Many female turtles and terrapins are actively crossing roads to get to the other side to lay eggs and give rise to the next generation.
Unfortunately, scores of slow moving turtles die every year as road kill due to speeding vehicles. In the July 29, 2008 issue of Conservation Magazine, James Gibbs and Gregory Shriver, both of the State University of New York in Syracuse, suggest that many turtle populations in the United States, which has among the highest turtle diversity in the world, are disappearing due to deadly traffic encounters.
According to the article, Gibbs and Shriver simulated the movements of three groups of turtles: land turtles and large and small pond turtles. To estimate the likelihood that turtles would be hit while trying to cross roads, the researchers integrated the simulated turtle movements with road densities and traffic volumes for each state. The results suggest that roads threaten both land turtles and large pond turtles. In many regions more than 5 percent of these turtles are likely to die while crossing roads, which is a death rate more than these populations can sustain. Other studies have shown that most turtle species cannot withstand death rate increases of more than 2-3 percent. Turtle road kill was particularly high in the northeast, southeast, and the Great Lakes-Big Rivers region, which is where U.S. roads and traffic are most concentrated.
Down in South Jersey at the Wetlands Institute in Stone Harbor, studies indicate terrapins are dying on roadways as well. Over the last 25 years scientists have found on average 500 dead diamondback terrapins on local roadways each summer. Road traffic increases in May and June due to a surge of summer tourists.
The news is more bleak as suggested from a May 16, 2013 article in Scientific-American. Across the U.S. vehicles hit an estimated one million to two million animals every year, the equivalent of a collision every 26 seconds, according to insurance industry records. But official numbers of animal–vehicle crashes include only reported collisions, which generally means those with large animals and that result in disabled vehicles, says Jon Beckmann, a biologist with the New York City–based Wildlife Conservation Society. "If you run over a raccoon or skunk, those are rarely reported. When you include those smaller animals, the numbers are probably well up in the millions more." The animal generally comes out on the losing end of the encounter. Aresco calculated that in 2001 a turtle attempting to cross a busy highway had a 2 percent chance of surviving.
These numbers are high enough to seriously reduce turtle populations and could well account for the fact that many turtle species around New York Harbor, including Raritan Bay, have nearly vanished in recent decades with the rise of roadways and speeding vehicles and the loss of habitat. Bog turtles, small, semi-aquatic turtles, are endangered species in both New York and New Jersey. The spotted turtle, the yellow polka-dot turtle, is listed as a species of special concern in New York State.
New York Harbor is an estuary, and the Northern diamondback terrapin seems especially vulnerable to road kill. The diamondback terrapin is the only turtle tolerant of brackish waters in estuaries. It can be found swimming in salt marshes, bays and tidal creeks. Breeding populations exist in Jamaica Bay, Sandy Hook Bay, and the Navesink River. Yet, populations are slowly dwindling due to habitat loss and road kill. The diamondback terrapin is listed as a species of special concern in New Jersey.
What can be done to help stop turtles from being threatened by collisions in heavily trafficked areas around New York Harbor? At first the situation might seem hopeless in our busy and built-up man-made environment, but solutions are within hand if people are willing to help.
We need to protect a turtle’s home and habitat. Turtles need more open space, parks and large areas of continuous habitat to move and limit their interactions with roadways. The best way to have continuous habitat is to design roads with wildlife in mind. When planners design or re-design highways and byways, we need to urge that wildlife crossings are in place, vegetated overpasses or underpasses spanning major interstates to reduce vehicle collisions with wildlife, both large and small.
Of course the least expensive and easiest solution would be for people just to slow down at "animal crossing" warning signs. But studies show that few people do slow down, and in fact, some people actually speed up. Sadly, wildlife speed zones don't reduce road kill, at least not without increased enforcement.
While a turtle’s hard outer shell has protected it for thousands of years, it can do nothing but crack open from the pressure of a tire travelling at high speeds. People have created this problem and people need to solve this problem if we care about turtles.