2009 Summary and Discussion of
Diamondback Terrapin Population Study
at Nockum Hill, Barrington, RI

20th study year,
sponsored by the Barrington Land Conservation Trust

The first terrapins we saw nesting this year was on June 7, the last reported on July 12. One hundred twenty-two individuals were identified, 7% of which were newly marked. Of the 77 turtles marked in 1990, 19 returned to nest and one was run over on the Wampanoag Trail. Two unidentified turtles were also killed on the trail this year, one only about 8 years old. Due to the high count of rainy and cloudy days this summer, large number of terrapin nested on a relatively small number of sunny days.

Three hundred twenty-nine eggs from 21 nests were relocated to the large predator excluder (PE#1). Individual PE's were placed directly over 17 nests as well (about 240 eggs). Many fewer than usual nests were depredated this year - about 75, compared to 203 in 2008 and similar numbers in past years. It appeared that a resident coyote might have removed the more common skunks and raccoons, and done most of the scavenging him/herself. Late in the season, some of the digging appeared to be the work of one or more young coyotes. Locations of depredated nests were similar to past years - greatest numbers on the point and sandpit, lesser numbers on the high road, low road, wildflower fields, back pit and farm field. Off-site nesting attempts were reported at the end of Henry Drive, Acre Avenue and Bowden Ave, as well as the three killed on the Trail.

A count of female terrapins seen over the last 5 year period (2005-2009) was 256 (compared to a 266 count in 2008 and 264 in 2007. An annual "guesstimate" of the total population - 256 mature females, perhaps half that number males - 128- and an unknown number of juveniles - perhaps 425 in all. Over the last 20 years we have marked 374 female terrapins, 5 of which are now confirmed dead.

The addition of individual PE's may be of benefit to the hatchlings in that the eggs can develop just as laid on site, and the hatchlings leave the nest directly. This was a trial year, likely one that will continue, with or without the use of the large excluder. Only one individual PE was scavenged; however it does mean close watch at hatching time, as the hatchlings are clearly visible under the wire. In total, we counted 298 hatchlings released from both protected excluders and unprotected "free" nests. We found at least a dozen unprotected nests the eggs from which hatched and emerged successfully.

Since temperatures this summer were unusually cool and sunny days fewer than usual, there may well have been some effect on the sexual development of the hatchlings and possible long=term effects on the local population. According to Don Lewis (Wellfleet investigator) males will develop if temperatures are below 82 degrees Farenheit and females at over 86 degrees, with a mix at 82-86 degrees.

Innovations this year were written protocols for both the ongoing study itself as well as for any outside investigators. A planning meeting was held in April, and a post-season follow-up meeting is scheduled for November.

BHS student Evan Bulman served as intern for the land trust. Brian Williamson, completing a research project in conservation biology at Roger Williams University spent many hours in the field, as did Matt Woods, as an intern under the supervision of Bob Caron, teacher at Bristol Community College (MA). Both Bob and Charlotte spent many hours at the hill. Greg Brown, Matt Woods and Bob Caron all pitched in to make the 17 new PE's. Pete McCalmont, manager of the Doug Rayner Wildlife Refuge at Nockum Hill, kept the trails mown, cut back much of the overgrowth and directed DPW to mow the fields in late fall. The Barrington Police Force used the pistol range, coordinating appropriate times with Pete to avoid nesting and hatching seasons. In September DPW built up the western berm of the range to prevent bullets from going outside the range.

Charlotte Sornborger
Barrington Land Conservation Trust
October 26, 2009

RIDEM-Fish and Wildlife Division Permit # is 2009-52, issued to Charlotte Sornborger "to Collect Diamondback Terrapins for study and research"