Basking Diamondback Terrapins in Buzzards Bay Estuary

After ten years of intensive research and focused conservation efforts on the SouthCoast of Massachusetts, Turtle Journal savored the image above from Buzzards Bay’s Sippican Harbor.  In 2003, this population of terrapins teetered on the brink of extirpation.  Thursday afternoon’s display of basking and “dating” turtles sported more diamondback terrapins than we have ever recorded.  The rock shown above held five mature females and three mature males.  Surrounding rocks held more adults, as well as basking juveniles.

Sue Wieber Nourse Captures Basking Terrapin #329

Sue Wieber Nourse spotted a mature female terrapin basking in the Spartina grass at the water’s edge.  She swooped into the spot and hand-captured mature female #329, an important player in restoration of the Buzzards Bay terrapin population.

Female Diamondback Terrapin #329

Terrapin #329 is a very large, mature female terrapin.  She tips the scales at 1.5 kilograms and her shell measures 8.5 inches long.  From a conservation perspective, these large, mature females are the most important factors in producing new recruits to the population.  They lay larger eggs that yield larger, more viable hatchlings; their natal nesting site has proven viable over the years.

Terrapin #329 Nesting at Tabor’s Schaefer Oceanology Lab

Last July 2nd, Sue checked the Tenbrook Beach at Tabor Academy’s Schaefer Oceanology Lab where she previously served as director.  Under her leadership, this beach from 2003 through 2005 had yielded the first protected nests in Buzzards Bay as the beginning of the Turtle Journal conservation program. 

Terrapin #329 Nesting at Schaefer Oceanology Lab, July 2012

On this July 2012 morning, Terrapin #329 was laying her second nest of the year, and Sue was able to harvest the 12 perfect eggs, protect them through incubation and return 12 perfect hatchlings safely to the abutting nursery salt marsh.  Such conservation efforts have proven a huge boost to the terrapin population in Buzzards Bay.  See Rare Turtle Nests at Schaefer Oceanology Lab.

Female Diamondback Terrapin #701

On Thursday we also recaptured mature female #701.  She is even larger than #329, registering 1.7 kilograms and 8.7 inches long.  We last saw this lady on 21 May 2010 in the Sippican Harbor mating aggregation.

Female Diamondback Terrapin #601

We first captured mature female #601 on that same day in May 2010, and we have seen her each year since in the Sippican Harbor mating aggregation.  On Thursday, this younger female weighed only 1.1 kilograms and measured just 7.4 inches long.

Female Diamondback Terrapin #253

Turtle #253 is a large mature female who we have been tracking since June 2004.  She weighs 1.5 kilograms and her carapace measures 8.2 inches long.

Female Diamondback Terrapin #340

We encountered mature female Terrapin #340 again on Thursday.  Don Lewis netted her as she cavorted with male Terrapin #41 (see below).  You may recall Turtle #340 from last Thursday, May 10th, when Don discovered her pairing with male Terrapin #304.  Clearly, she is a popular lady in the Sippican mating aggregation.  (See Sippican Harbor Terrapins.)

Female Diamondback Terrapin #41

We found two new terrapins on Thursday whom we had never observed previously.  Mature female Terrapin #41 beamed a broad smile during her first interaction with humans.

Male Diamondback Terrapin #40

On the other hand, bashful male Terrapin #40 hid inside his cowl to demonstrate his disdain for this first encounter with researchers.  He did, however, sport a dashing Buzzards Bay mustache to compensate for the lack of a smile.  Although sexually mature at five years old, Terrapin #40 weighed only 193 grams and measured just 4.3 inches long.  Fully mature males achieve only half the linear size and less than a quarter of the mass of mature terrapin females.

Sue Wieber Nourse Holds a Handful of Terrapins

Friday brought a sunny interlude, a southerly breeze and mid-60 temperatures to Marion.  Sue Wieber Nourse and Don Lewis packed kayaks, paddles and nets, and headed to Head of Sippican Harbor to check activity in the mating aggregation.  Brisk winds kept turtle action to a minimum with only a few snorkeling heads and two basking turtles perched on rocks.

Four Diamondback Terrapins from Sippican Harbor

Don spotted a pair of diamondback terrapins near the south bank.  A large female snorkeled across the surface while a male bobbed behind her.  Don thrust paddle into the water and powerd his kayak on an intersecting course.  The female dove for the oozy bottom and the male followed intently, focused exclusively on the object of his affection.  Don swooshed his long pole net in front of the female, and in a single stroke scooped the adorable couple into the kayak.

Adorable Couple: 340 Female Followed by 304 Male

This adorable couple, Female #340 and Male #304, illustrates the gender dimorphism of the diamondback terrapin species.  Typical adult females are twice the linear size and more than four times the mass of adult males.  Both turtles had previously been captured and marked by the Turtle Journal team in Sippican Harbor.

Female Diamondback Terrapin #340 (Sippican Harbor)

Female #340 is quite a feisty lady.  Sue captured and marked her last April 17th in Head of Harbor.  Since last year, she has grown .25 centimeters in length and width, and added 9 grams to her healthy weight. 

Male Diamondback Terrapin #304 (Sippican Harbor)

Handsome Male #304 was first captured and marked by Don on July 30th, 2006.  In the last seven years, he has grown nearly 1.5 centimeters in linear dimensions and gained 80 grams weight.  As you can see above, he sports a stylish “mustache.”

Female Prepubescent Female #37 (Sippican Harbor)

Juvenile Terrapin #37 is a new capture in Head of Sippican Habor.  She’s only four years old, measures 10.5 centimeters carapace length and weighs 173 grams.  She has passed safely through the long list of lethal challenges that confronts hatchlings and juvenile terrapins, and #37 has a good chance of reaching maturity and nesting in another three or four years.

Female Prepubescent Female #38 (Sippican Harbor)

Sue netted Juvenile #38 in Little Neck Cove across from the Marion Town Landing.  This five-year-old prepubescent female measured 11.0 centimeters long and hit the scales at 210 grams.  Like #37, she has beat the longest odds against terrapin survival, and with any luck, she will reach maturity and begin nesting in another three years.

Don Lewis Studies Two Tiny Juvenile Horseshoe Crabs

The Turtle Journal team revisited our “secret” horseshoe crab nursery on Thursday afternoon.  We last checked this spot on April 18th; see Salt Marsh Awakening: Juvenile Horseshoe Crabs Active on Outer Cape Cod. 

Rufus Examines Tiny Juvenile Horseshoe Crab

We wanted to get a sense of how well these ancient creatures may be doing, particularly in this long, chilly Spring.  In the decade we have been checking this location each Spring for juvenile horseshoe crabs, we have never before seen so much activity.

Three Tiny Juvenile Horseshoe Crabs

Dozens of juvenile crabs from tiny to small to mid size bounced around the salt marsh tidal pool like Tonka Toy bulldozers plowing through a playground sandbox.

Juvenile Horseshoe Crabs Bulldoze Serpentine Mazes

We can only laugh at their antics as they carve serpentine mazes in the oozy bottom.  Adult horseshoe crabs are beneficial auto-tillers of tidal and subtidal zones, a skill they obviously seem to practice from birth.

Juvenile Horseshoe Crab Left Compound Eye

The exceptional compound eyes of horseshoe crabs never cease to amaze us.  Much of our knowledge about human eyesight came from studies of these compound eyes.  Dr. H. Keffer Hartline received the Nobel Prize for his research on horseshoe crab vision in 1967.

Two Tiny Juvenile Horseshoe Crabs in Nursery

While documenting the science of this horsehoe crab nursery is rewarding per se, we confess that watching these juveniles spin around the tidal pool like pre-teens driving their first amusement park bumper cars can be mesmerizingly delightful.  So much so that you forget that you’re even doing science.