Long Island turtle tunnel to build on wildlife underpass success

The days are getting longer, minute by minute, rising temperatures are warming the soil and sand, and Long Island’s woodland and wetland creatures are awakening from their winter torpor.

For most of them, whether scaled, feathered or furred, this is the season when mates must be found, nesting sites prepared, eggs laid and babies reared. That means a lot of movement across the landscape, whether the trip to fulfill their genetic destiny amounts to a few yards or many miles.

In a suburban setting crisscrossed by roads, those journeys can be dangerous.

One stretch of road separating Cedar Beach from Mount Sinai Harbor has become especially perilous for diamondback terrapins. Female diamondbacks crawl out of the harbor and head north toward Long Island Sound to lay their eggs in the sandy coastal forest, Alan Duckworth, an environmental analyst with the Town of Brookhaven, explained. But on the way there, or back, they have been getting hit by cars on Harbor Road, which bisects the narrow peninsula.

The terrapins, he determined, needed a traffic tunnel.

Four years ago, Brookhaven built an underground passageway in Middle Island, on a winding road where spring peepers, wood frogs and other amphibians were getting killed as they tried to cross from one vernal pool to another.

Without intervention, according to John Turner, an ecologist at Seatuck Environmental Association who first discovered the carnage, the frog populations in those small ephemeral wetlands might slowly disappear — and with them, their lively springtime songs. 

But after the tunnel was installed, roadkill there plummeted, from dozens or even hundreds in a busy night to almost none. 

Luke Ormand, also an environmental analyst for the town, installed a wildlife camera at the tunnel's entrance, and the images he collected proved its value — and not just for amphibians. The camera recorded opossums, mice, raccoons, snapping turtles, chipmunks, groundhogs, black racer snakes, squirrels and rabbits, all darting, sauntering, crawling and slithering back and forth through the tunnel. 

"If we could charge a toll for each one of them, we could balance the town budget," Turner quipped.

A terrapin underpass

 Diamondback terrapins, whose shells are marked with distinctive geometric patterns, are the only North American turtles that thrive in brackish water. On Long Island they inhabit the marshes, tidal creeks, bays and estuaries from Jamaica Bay to the Peconic Bay.

Like other terrapins, they were heavily hunted for soup through the early 1900s; since 2018, harvesting diamondbacks has been outlawed in New York. They are not on the state's endangered or threatened list, but they have been designated a species of special concern, as they are still vulnerable to habitat destruction, including from shore-hardening structures like bulkheads and sea walls, toxic algal blooms and global warming, as well as car strikes.

Five years ago, Brookhaven installed black plastic tubing as a barrier along the south side of Harbor Road at Cedar Beach — just 6 inches high, but nevertheless a daunting obstacle for a short-legged reptile. The hope was to prevent them from crossing and encourage them to make their nests in the sand on the harbor side.

But Turner, who is also a consultant to Brookhaven's land management department, started thinking about a more durable and effective solution, and proposed a series of tunnels, like the Middle Island frog tunnel, for the imperiled expectant mothers of Cedar Beach. 

Last year, the town received a grant of $109,000 for the project from the Long Island Sound Futures Fund, part of the National Fish and Wildlife Foundation, and the town will contribute $119,500.

When egg-laying season begins, typically in June and extending into July, researchers at Seatuck will monitor the females’ movements with wildlife cameras and drones. Those images will help them identify the most popular crossing routes and therefore the best spots for a tunnel.

Wildlife fencing on either side of the road will replace the black tubing, helping to direct the animals toward the underpass. Terrapin fencing can be substantially lower than frog fencing, Turner noted, since turtles aren't skilled jumpers or climbers.

Next winter, well before next year’s reproductive season, the tunnels will be installed and ready for travelers.

Meanwhile, in Middle Island, the wood frogs and spring peepers have been singing loudly for several weeks, announcing their availability to mates. As the weather warms and the smaller vernal pools begin to dry up, they’ll start their move to the larger, deeper pond on the other side of East Bartlett Road. 

Already, Ormand reported the tunnel is welcoming its first spring travelers. "Right when the snow was finally melting, the first chipmunk appeared, and the first groundhog appeared."