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Sunday, October 11, 2020

Save Rhode Island's Terrapins!

Volunteers Discover R.I.’s Rarest Turtle at New Sites

By TODD McLEISH/ecoRI News contributor

Diamondback terrapins have been found in 15 new Rhode Island locations, joining the species’ largest population in Barrington. (Todd McLeish/ecoRI News photos)

A pilot project using volunteers to scout for new populations of Rhode Island’s rarest turtle, the diamondback terrapin, turned up 15 new sites where the turtles have been confirmed. But despite the new populations, the biologist who led the project said the state’s terrapins are no less threatened than they were before the new populations were discovered.

Herpetologist Scott Buchanan, a wildlife biologist at the Rhode Island Department of Environmental Management, said that prior to 1990, when a population of terrapins was discovered in Barrington, “no one had seen a terrapin in Rhode Island in many years.” 

Additional populations were discovered elsewhere in the state in the past decade, and when Buchanan was hired in 2018 and began asking around, he heard a number of unconfirmed reports of terrapins being observed elsewhere in Rhode Island.

“That led me to think that they’re probably more widespread in the state than the narrative would lead us to believe,” he said.

So he examined maps to identify “reasonable places” where he could send volunteers on a regular basis to see if they could spot the terrapins, the only turtle in the region that lives in salt marshes and brackish waters. Four volunteers each visited two to four sites twice a week from late May through mid-July, and an additional volunteer surveyed a dozen sites. During each visit they scanned the water with binoculars for three 5-minute periods and counted any turtle heads they observed.

The discovery of 15 new sites was a revelation to Buchanan.

“What it means is that they are much more widespread than we had thought,” he said. “It’s encouraging from a conservation standpoint, but at many of these sites, we have little or no information about how many turtles may be there, whether they are successfully breeding, or whether they are established populations. We don’t want to be overconfident or get too comfortable with the fact that there are multiple sites containing the species.”

Most of the newly discovered terrapin sites are in coves along mid and upper Narragansett Bay. They’re still mostly absent from the lower bay, according to Buchanan.

“What we’re seeing now is probably a shadow of their former distribution and abundance,” he said. “They’re out there, that’s excellent, but we know there’s lots of places they don’t occur. All the evidence suggests that they’re still absent from many places where they were historically present. And the types of abundances that we’re documenting are probably far less than historic abundances.”

Buchanan speculated that the newly discovered populations in the upper bay may be the result of dispersal from the Barrington population, which has grown to number in the hundreds because of extensive conservation efforts.

Diamondback terrapins are the only turtle in the region that lives in salt marshes and brackish waters.

Despite the success of the survey project, Buchanan is still concerned for the state’s diamondback terrapins. Most terrapin eggs are consumed by what he calls “human-subsidized predators,” including coyotes, raccoons, skunks, and dogs. 

Terrapins are also at risk of being illegally collected for the pet trade, which is why he prefers not to reveal the location of the newly discovered sites. They also face drowning in crab traps, injury from being struck by boats, and automobile strikes as females cross roads on their way to their nesting territories.

“The big threat, though, is sea-level rise and salt marsh decline,” he said. “They’re an obligate salt marsh species; if sea level rises and marshes disappear, they don’t have a chance. That’s something I’m especially worried about over the next 10, 20, 30 years along the Rhode Island coast. Salt marshes are critical as a source of food and a place where they overwinter and take shelter, especially the juveniles and hatchlings.

“This new information we have is very encouraging, but it doesn’t mean we should let our guard down. They’re still a species that warrants conservation, even without sea-level rise. We must remain vigilant.”

Having identified the location of additional terrapin populations, Buchanan hopes to prioritize those sites for future conservation efforts, modeled after the successful nest-protection and monitoring efforts in Barrington.

“Knowing where they are, there are lots of small steps you can do to improve their conservation,” he said. “Things like small-scale habitat management, create barriers to keep them off busy roads, public outreach to ensure boaters use caution, adapt local pot fishery management.”

The success of the pilot project to identify new diamondback terrapin populations has inspired Buchanan to double or triple the effort next summer at numerous additional locations. He also hopes to continue the project for many years to eventually be able to identify population trends at each site. He will be seeking additional volunteers this spring to survey coastal sites around the state in June and July. Those interested in volunteering should contact Buchanan at scott.buchanan@dem.ri.gov.

Rhode Island resident and author Todd McLeish runs a wildlife blog.