Published on October 15, 2021

Summer Proves Productive for Diamondback Terrapins

Diamondback Terrapin hatchling in hand © Karen Kishpaugh
© Karen Kishpaugh

Although the data analysis hasn’t been finalized, it appears 2021 was a record breeding season for diamondback terrapins monitored by 120 volunteers and staff in Wellfleet, Eastham and Orleans. More than 5,000 baby turtles from more than 400 monitored nests were released along the edges of local salt marshes, surpassing last year’s total by more than one thousand hatchlings!

Nest Protection

Diamondback terrapins, a native species that lives in salt marshes and small embayments, are considered threatened in Massachusetts and for more than 20 years the sanctuary has been protecting nests in June and July to give turtles a better chance of producing young and rebuilding the population. The small cage-like structures installed over nests, predator excluders (PEs), are designed mainly to discourage common digging predators like foxes, coyotes, and raccoons.

Looking at two busy nesting sites—Wellfleet's Lieutenant Island and the sanctuary—the productivity of protected nests (that is, the percent of healthy hatchlings released) was 79% this season compared to 69% in 2020, and 79% in 2019. As for nests we missed and didn’t protect—or wild nests—productivity was only 45% (34% in 2020, 47% in 2019). It’s clear that protecting nests is highly effective.


New crow guards, an additional layer of fencing installed over and around PEs to keep newly emerged hatchlings from being attacked by crows, worked well this summer. Fourteen young turtles were killed by crows last summer on Lieutenant Island. But this year, the crows struck out!

Another encouraging stat for 2021: there were fewer instances of adult female terrapins hit by cars as they crossed roads to nest. Overall, five terrapins were killed by cars, compared to eight last year. Losing just one breeding female is very costly to a population, since a healthy female may lay 1000 or more eggs in her lifetime.

Thanks to Our Team

We want to thank our hardworking corps of terrapin volunteers, many of whom handled multiple shifts each week during a very hot and humid summer, for their dedication to protecting these turtles and helping them be more successful! You can read more about this summer's terrapin season and how the conservation program began.