2007 Summary and Discussion of
Diamondback Terrapin Population Study
at Nockum Hill, Barrington, RI

18th study year, sponsored by The Barrington Land Conservation Trust

The observed nesting season began on June 5 and ended on July 6. This year we observed a total of 124 terrapins up to nest, of which 14 were newly marked and 110 were recaptures. Five of those recaptures could not be clearly identified. Over the last 18 years of the study, we have marked 356 individual female terrapins; of these, 6 are known dead. No terrapin kills were reported this year.

One way to estimate the number of terrapins living in and near the Hundred Acre Cove area is to count the individuals we have seen at least once in the last 5 years. As of the 2007 season, this number is 264; in addition, there may be as many as half that number of males (which do not come on land) and an unknown number of juveniles – possibly 425 or more in total for the terrapin population. Note: Alex and Charlotte observed heads of about a dozen males or juveniles in the northwest corner of the cove proper in July.

Newly marked terrapins represented 11% of the 124 terrapins observed, falling in a range of 8 -21% over the last 10 years. This indicates that there is a relatively steady number of “recruits” (new turtles) over this time period. The average size of all terrapins seen this year was 203 mm., of newly marked ones- 195 mm., indicating that most of the recruits were probably young turtles hatched during the time of the study.

Predation rose this year (192 depredated nests), returning to levels seen prior to 2005 when 8 predators were removed. Possible action in 2008 will be discussed over the winter. Locations of depredated nests were: sandpit -75; point – 52; high road – 14; wildflower field -12; low road – 6; back pit – 5;beach-3; agricultural fields-2. One unscavenged nest was found on 8/30, with tracks of several hatchlings emanating from it.

Twenty-three nests were relocated to the predator-excluder in the sandpit. Of these 336 eggs, 231 live hatchlings emerged ( 68%), between 8/20 and 9/14. The hatchlings were released on the hill and marsh at various locations. The plastron size of the hatchlings varied from 17 to 30 mm. Note: In late May 2 live hatchlings were observed traveling down the path to the beach area, indicating their successful overwintering on the upland.

Participating in this year’s study were:
Alex Patterson, URI student project (advisor, Tom Husband)
Emily Stulik, Skidmore College, BLCT intern
Erin Horn, candidate for Master’s degree, Hofstra University, NY
Pete McCalmont, Nockum Hill property manager for the BLCT
Tom Wells, steward, property management
Cheryl Wiitala, The Nature Conservancy, Providence Regional Office
Charlotte Sornborger, project overseer

Groups that visited Nockum Hill this summer to view nesting/hatching were Roger Williams Park Youth Study Program, Audubon Society of RI Traveling Camp and various home-schooled groups. In late September all Barrington 6th grade classes will make field visits for scientific study.

Nockum Hill Management

Tom Wells and Pete McCalmont spent many hours cutting back shrub overgrowth and removing non-native invasive plants. Pete also kept the walking paths mowed throughout the summer. DPW mowed the wildflower fields in the spring. The harbormaster had the 5 mph buoys in place before the nesting season; the buoys seem to be having good effect, as we saw only one terrapin with a new propeller-type injury. Pete rototilled and planted another area with native grasses; these plants grow in such a fashion as to allow spaces between the plants, suitable for terrapin nesting.

In September the Town Council voted (3-2) to place a “no dogs” ordinance for the Doug Rayner Wildlife Refuge, enforcing the “this is not a place for dogs” rule of the refuge. There was considerable controversy at the 9/4 meeting, but perhaps a growing understanding that wildlife refuge zoning is a unique category, requiring special rules to maintain the viability of the range of fauna and flora on the site.

The pistol range was brought back in to use after a hiatus of 5+ years. We appreciated the fact that the police department informed us of their plans and restricted their use to non-nesting season. They also posted signs, alerting potential visitors that the shooting range was in use. This use is compatible with the Nockum Hill Management Plan.

Copies of the primary documents of this study are kept by the Barrington Land Conservation Trust (www.blct.org) and disk copies of the accumulated data are filed with the Rhode Island Natural History Survey at URI (www.rinhs.org). Yearly reports are sent to RIDEM Fish and Wildlife and the Barrington Conservation Commission. Local contacts for the study can be found at the BLCT website, Charlotte Sornborger (c_sornborger@hotmail.com) or by phone (401-245-8467).

* General information about the diamondback terrapins can now be found in a new book by Barbara Brennessel, (Ph.D., Biology Department, Wheaton College, Norton, MA), Diamonds in the Marsh, A Natural History of the Diamondback Terrapin, University Press of NE, 2006. Dr. Brennessel and her interns worked with the Nockum Hill group in the summer of 2005.

ADDENDUM - Seen at Nockum Hill between June 1 and August 30, 2007