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DISTRIBUTION & HABITAT
Terrapin
populations occur along much of the East Coast and Gulf Coast of the U.S.
Although the length of this range covers thousands of miles, terrapins
only inhabit the thin strip of estuaries and coastal marshes right along
the coast, so their actual range is quite small in area.
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Terrapins
inhabit coastal marshes, tidal creeks, estuaries, bays and coves. These
waters are brackish; meaning they
are mixtures of fresh and salt water. Marshes containing salt-marsh cordgrass (Spartina alterniflora) are important feeding habitats
for terrapins. Cordgrass marshes can be seen in
many places throughout Gateway NRA, at the Jamaica Bay Wildlife Refuge (JBWR) and the
Sandy Hook Unit in NJ. Cordgrass marshes look
like flat islands of grass, and are often covered by water during high
tide.
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NATURAL HISTORY
Terrapins
primarily feed on invertebrates such as mollusks and crustaceans. Where
there are many terrapins, their active foraging can have a significant
impact on their prey, and so terrapins may be an important component of
coastal food webs. However, it is probably impossible to truly understand
the natural ecological significance of terrapins now, because their
numbers have been so low for so long.
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Within
Gateway NRA, the only major terrapin nesting areas we know of are in
Jamaica Bay Wildlife Refuge and the Sandy Hook Unit. The majority of the
research on nesting terrapins in our region has been conducted at JBWR,
but these results are probably typical of terrapins throughout the
region. Mating occurs in May and June, when aggregations of more than 100
terrapins can sometimes be seen in the offshore channels. In June and
July, female terrapins come on shore to nest, and this is when visitors
have most of their "close encounters" with terrapins. They nest
most commonly in dunes, grassland, shrubland,
beaches, and sand and gravel trails. Females lay 3 to 18 eggs per nest,
but average about 11. Some females can lay two nests per year. After
nesting, females join the males in the deeper bays and estuaries, where
they feed until hibernation.
Eggs take 70 days or more to hatch, and some hatchlings emerge in the
late summer and early fall. The other hatchlings overwinter in their
nests, and emerge the following spring. Like many turtles, terrapins grow
slowly, taking 3-8 years to mature (males mature earlier than females).
No one knows how long they may live.
Survival
is tough for the diamondback terrapin at any stage in life, but no age is
as perilous as the incubation and hatchling stages. Predators destroy
many nests. Little is known about behavior of terrapins that do manage to
hatch, but their survivorship is likely to be very low. Hatchlings tend
to avoid open water, and they prefer burrowing under shoreline debris,
mud and tidal wracks of cordgrass.
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HISTORY OF A MEAL
Terrapins
were once highly prized for their meat, and connoisseurs of the nineteenth
and early twentieth century considered them a delicacy. Starting in the
mid-1800s, terrapins were harvested in huge numbers to make soup. This led
to the loss of many populations, especially those near large cities. The
close proximity to New York City, coupled with the fact that Long Island
terrapins were considered to be the best tasting on the market, lead to
severe declines in many local terrapin populations. By the mid-1930s
terrapins had become so rare in the Long Island-New York City region that
naturalists thought the species was locally extinct.
Luckily
for terrapins, the onset of World War I and the Great Depression resulted
in a rapid end of the turtle soup industry. Since that time, terrapin
populations in many areas have slowly and steadily recovered. This recovery
is now threatened by a number of new threats.
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THREATS TO TERRAPINS
Predation – Predators
such as raccoons and foxes often pose a serious threat to turtle eggs,
hatchlings, and occasionally even adult turtles. While raccoons and foxes
occur naturally at Sandy Hook, neither originally occurred at JBWR.
Studies conducted at JBWR in the early 1980s suggested that the great
reproductive success of terrapins there was due to the fact that there
were no raccoons or foxes.
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Nest
survivorship was an astonishingly high 93%! With about 2,000 nests
being laid each year, the Jamaica Bay terrapin population became one of
the largest and most robust populations in New York State. However, in
the early 1990s, depredated terrapin nests were seen in noticeable
numbers at JBWR. Although nest predation appeared to be minor until
1995, the situation got worse. By 1998, over 1,300 depredated nests
were found at JBWR, and in 1999, more than 1,800 depredated nests were
found. In the last few years the survivorship of terrapin eggs has
dropped to less than 3%. While this is startling, this new rate is
actually quite similar to rates seen at terrapin populations elsewhere
in their range.
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The
cause of this change? A dramatic increase in the raccoon population. Little
is known about how raccoons colonized JBWR or how many live there now. Park
officials attribute the increase in raccoons to humans, because people
sometimes release "nuisance" urban raccoons into parks. Not only
is this illegal, but it obviously harms native species. The availability of
garbage has probably also played a role in raccoon population increases.
The
impact of other predator species is not as well studied as that of
raccoons. Foxes occur in the Sandy Hook Unit. Laughing gulls and crows may
also eat terrapin nests in Gateway. In addition to these nest predators,
"root predation" has been observed at JBWR. This occurs when the
roots of beach plants actually invade a nest, penetrate eggs, and absorb
their nutrients.
Development – A number of
other human actions harm adult terrapins, as well as eggs. One important
threat to terrapin survival is development of their habitats. Dredging,
filling, and marshland alterations reduce the aquatic habitat critical to
terrapin survival. In our area, lawns and bulkheads now replace many of the
areas that were once terrapin nesting beaches.
Collection – Although
terrapins will never be harvested like they were during the heyday of the
soup industry, harvesting and collection continues today. It is illegal to
harvest or remove terrapins from GNRA without a permit. Many terrapins
unintentionally drown as by-catch in crab pots. Fitting crab traps with Bycatch Reduction Apparatus (BRAs), as is occurring in
New Jersey, can reduce incidental" bycatch.
Other Threats Posed by Humans – Especially
around urban regions, tide-borne debris may harm nesting terrapins and
hatchlings. Automobiles also injure and kill terrapins. Hundreds of
terrapins are killed on Long Island and New Jersey roads each year. Marine
vehicles such as boats, wave-runners and jet-skis may also kill terrapins
in our local waters.
Release of Captive Terrapins – While
releasing turtles from pet stores and food markets might seem like a humane
action, it is illegal and may be dangerous to local populations. Released
turtles may introduce new diseases into native populations, with
potentially disastrous results.
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SOLUTIONS
The
future of diamondback terrapins at Gateway is uncertain. The Sandy Hook
population appears to be large and stable. At Jamaica Bay Wildlife
Refuge, raccoons are a new and serious problem, and that terrapin
population appears to be vulnerable.
Visitors
are strongly discouraged from doing anything that might disturb terrapins
because human disturbance can prevent females from nesting. While it is
temping to approach a terrapin, remember, these wild animals are afraid
of humans. The best way to view terrapins is with binoculars, at a
minimum of 150 feet. That way, you are less likely to scare a terrapin
and more likely to witness nesting take place. If you encounter a
terrapin up close, try to walk past it as quietly and quickly as
possible. Be sure to let park staff and a researcher (see below) know
where and when you see turtles, so they can add your observations to the
ongoing research.
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At
JBWR, the Park Service has taken measures to reduce human/terrapin
encounters by closing the sand trail (known as the "Terrapin
Trail") during the critical nesting season. Unfortunately, some
visitors ignore this closure. Trespassing onto the trail during this time
is not allowed. Please respect this rule.
In addition to walking with caution, care should also be taken while
driving the roads in and around Gateway. Drive slowly and carefully to
avoid hitting terrapins crossing roads, especially in June and July.
Visitors should also be aware that collection of terrapins anywhere in
Gateway is harmful to the overall population, and is also ILLEGAL.
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RESEARCH
In
an effort to learn more about diamondback terrapins, the Park Service at
Gateway NRA and researchers from the Department of Biology, Hofstra
University, continue to study terrapins throughout the Park. Research
efforts are focused on studying the raccoon population, collecting more
information on the nesting biology of terrapins, learning more about
remote nesting sites, studying the daily and seasonal movements of
terrapins, and making better population estimates. As researchers learn
more about Gateway terrapins, more can be done to help preserve this
population. Each year a large volunteer effort makes this possible, and
your help would be greatly appreciated.
If you would like to learn more about terrapins or about opportunities to
participate in the on-going research in this area, please contact:
Dr. Russell Burke
Department of Biology, Hofstra University
Hempstead, NY, 11549
(516) 463-5521
Click
here to find out more.
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