Northern Diamondback Terrapin
Malaclemys terrapin terrapin
on Cape Cod, Massachusetts

Malaclemys terrapin terrapin


  • Elusive, non-migratory, medium size turtle of the salt marsh
  • Hard, hingeless shell; top greenish, bottom golden color
  • Carapace (top) with 13 scutes ringed concentrically like diamond facets
  • Plastron (bottom) symmetrically bisected with 6 sections per side
  • Light grayish skin adorned with dark spots
  • Large, powerful webbed feet with sharp claws

  • Eight to 9 inches long, weighing up to 3.5 pounds
  • Broad head; deep shell; small, thin tail
  • Nearly 5 inches long, weighing about 2/3 of a pound
  • Narrow head; shallow shell; large, thick tail
  • About 1 inch long and weighing about a ¼ of an ounce
  • Salt marshes and adjoining rivers, creeks, coves, and bays
  • Nests dug into sandy spots on surrounding uplands with remarkable site fidelity
  • Winter brumation (hibernation) under mud of protected creeks and coves
Annual Cycle
  • Active: late April through mid October
  • Mating: spring with pairing also observed in summer after nesting season
  • Nesting: early June through late July
  • Hatching: late August–mid-October; some over-winter in nest to emerge May/June
  • Brumation: mid-October through late April
  • Two clutches each year, about 18 days between clutches
  • Clutch size: average 12 eggs; range 6 to 22 eggs
  • Light-bulb shaped nest with narrow neck and wide egg chamber; several inches deep
  • Predation: raccoon, skunk, crow, fox, coyote, fly maggots, red ants, roots, human activity
  • Incubation: average 75 days; range 64 to 100 days; emerge about 5 days after pipping
Life Cycle
  • Hatchlings disappear into shallow marshes
  • Juveniles remain close to marsh creeks
  • Females mature in 8–10 years at around 6 inches and 1.5 pounds
  • Males mature considerably earlier
  • Gender ratio: approximately 2 to 1 (female to male)
  • Lifespan still to be determined, but oldest confirmed over 35 years of age
  • Snails, crabs, shrimp, minnows, mussels, worms, carrion
  • Ranges from endangered to species of special concern from state to state
  • Listed as threatened by Massachusetts Natural Heritage & Endangered Species Program
  • Wellfleet Bay Wildlife Sanctuary, 508-349-2615; 24/7 turtle line, 508-349-0954

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