Description: The Diamondback Terrapin (Malaclemys terrapin)
ranges from 5-10 inches (12.7-25.4 cm) in carapace length. Terrapins
are sexually dimorphic, with males being much smaller (5-6 in),
while females are considerably larger (9 in) as adults. There
are currently seven subspecies of diamondback terrapin recognized
throughout it's large range. The diamondback terrapin's carapace
color varies from a brown-ebony to a darker, almost black.
On the carapace, each scute has multiple "diamond-shaped"
rings which may be the origin of this species' name. The turtle's
skin can range anywhere from dark gray to stark white, which is
complimented with black irregular spots. Males are often melanistic
(very darkly colored), and sometimes have black markings on their
upper jaw, resembling a mustache.
Habitat: Diamondback terrapins can be found along the
Eastern Coast of the U.S., from Cape Cod (Massachusetts) to Texas.
They are most common in salt marshes and shallow bays.
They are usually found in brackish water and occasionally
travel out into the open ocean, however, they cannot tolerate
full-strength salty water for long periods of time, or they may
Habits: Diamondback terrapins reach sexual maturity at
about 3.5 years in males and 6 years in females. They breed during
the months of March and April and nest during May and June. There
have been reports of large groups of terrapins congregating in
bays to mate in the early spring. Although diamondback terrapins
are an aquatic turtle and spend the majority of their life in
water, they do leave the water to bask and lay eggs, like many
other species of aquatic turtles. One biological advantage these
turtles have acquired over time is the ability to survive in salt
waters of variable salinities. Like sea turtles, diamondback terrapins
posses salt glands around their eyes, allowing them to secrete
excess salt from their blood, and survive in salty environments.
Conservation Status: Terrapins have a long history of
exploitation by humans. For decades they were harvested for food
and were often eaten in turtle soup. Although terrapins are no
longer harvested in most areas, they often enter crab traps and
drown. Additionally, degradation of salt marshes and nesting beaches,
and road mortality of nesting females also hurt this species.
Although terrapins have declined greatly in the Northeast and
parts of Florida, they are still fairly common in our region and
are currently listed as a non-threatened species, although it
has been considered a status review species for over a decade.
Dr. Whit Gibbons at the Savannah River Ecology Lab is conducting
the longest-running study of Diamondback Terrapins. Over 25 years
Dr. Gibbons and other members of the SREL herpetology lab have
made over 3500 captures of about 1500 individual terrapins in
several salt marsh creeks at Kiawah Island, South Carolina. His
research has shed light on Terrapin population dynamics and has
demonstrated that the Kiawah population is declining due to mortality
in crab traps.
Hoyle, M.E., and Gibbons, J.W. 2000. Use of a marked population
of diamondback terrapins (Malaclemys terrapin) to determine
impacts of recreational crab pots. Chelon. Conserv. Biol. 3: 129-133.
Gibbons, J.W., Lovich, J.E., Tucker, A.D., FitzSimmons, N.N,
and Greene, J.L. 2001. Demographic and ecological factors affecting
conservation and management of the diamondback terrapin (Malaclemys
terrapin). Chelon. Conserv. Biol. 4: 66-74.
Tucker, A.D., FitzSimmons, N.N., and Gibbons, J.W. 1995. Resource
partitioning by the estuarine turtle, Malaclemys terrapin:
trophic, spatial and temporal foraging constraints. Herpetologica,
Tucker, A.D., J.W. Gibbons, and J.L. Greene. 2001. Estimates
of adult survival and migration for diamondback terrapins: conservation
insight from local extirpation within a metapopulation. Canadian
Journal of Zoology 79:2199-2209.
Dorcas, M. E., J. D. Willson, and J. W. Gibbons. 2007. Crab trapping
causes population decline and demographic changes in diamondback
terrapins over two decades. Biological Conservation 137:334-340.
Account Author: Andrew M. Grosse, University of Georgia
- edited by J.D. Willson