The Snapping Turtle, Chelydra serpentina – Part I, Natural History and Behavior in the Wild (with notes on size records)

The story sparked memories of large snapping turtles I have known, and once again brought to mind how spectacular these relatively common creatures are. We tend to take them for granted here, but they make quite an impression to the uninitiated – hatchling snapping turtles are all the rage in the pet trade in Japan, being described in the media as “tiny dinosaurs” (not far off, in my opinion!).

Until this month’s catch, the largest wild-caught snapper on record was a 76 pound animal (the carapace measured 22 inches) taken from a deep lake in the northeastern USA. The vast majority of very large snapping turtles come from the northern parts of their range (the same holds true for their gigantic cousin, the alligator snapping turtle, Macroclemmys temmincki). As an indication of just how rare such creatures are, consider the following – a review of commercial turtle fisherman’s records show that of 84,000 adult turtles reported, only 160 topped 50 pounds in weight. Of these, only 4 weighed 60 pounds or more. These largest individuals were all males – the heaviest female known tipped the scales at 44 pounds.

Relatively small ponds on Long Island, NY have produced some giants – two that I worked with weighed 54 and 63 pounds when captured. The heavier of these, now a massive 80 pounder, is on exhibit at the Cold Spring Harbor Fish Hatchery (http://www.cshfha.org/).

Of the many large snapping turtles that I have encountered in the wild and in zoos, two in particular stand out (a “small” 15 pound white snapper from NJ is also memorable). Both were found wandering on land (highly unusual) near the Bronx River, in the heart of the Bronx, NY, and showed evidence of recent battles with (most likely) even larger males. The first was delivered to a friend who does animal rehabilitation from his facility in NYC. In order to check the turtle for injuries, we put him on the sidewalk and commenced to hose him off. As the turtle lumbered down East 4th Street, I was, as is usual in such situations, treated to interesting observations of my fellow New Yorkers – some gathered and traded stories while others walked briskly around it as though the 45 pound monster were no more than an upturned garbage can barring their progress!

The second turtle weighed 49 pounds, but was quite emaciated due, I believe, to a severely injured lower jaw that had healed but limited his ability to feed. I installed this fellow in a large outdoor pond near the Bronx Zoo’s reptile house. He soon learned to respond to the sound of my palm striking the water, and would gingerly take a trout (yes, he was spoiled!) from my hand. As they say “Don’t try this at home!” – snappers, even long-term captives, have notoriously well-developed striking abilities, and can cause severe damage injuries (this animal was prevented from doing so by his damaged jaw).

I have worked with most of the giants of the turtle world – leatherbacks, Galapagos and Aldabra tortoises, giant Asian soft-shells and alligator snapping turtles – and will write about them from time to time. For now I’ll pass along some more information about snapping turtles in the wild, and address their care in captivity in Part II of this article.

RANGE
Most of southern and eastern Canada and the United States, east of the Rocky Mountains; subspecies range from Mexico to Ecuador. Widely introduced – California, Nevada and other states in west USA, Japan.

HABITAT
Shallow streams, swamps and ponds to deep lakes and rivers; ponds in city parks and on farms. Some populations inhabit brackish water (tidal rivers and marshes) and have evolved a means of excreting excess salt (Note: I live near a population of these remarkable “salt water snappers” and will report back on them in the future). Rarely leaves the water except to lay eggs; often basks while floating at the surface.

STATUS IN THE WILD
Often the most common turtle within its range and still to be found in quite large cities, yet threatened by collection for the food trade in some areas. In NYC, is relatively common in Central Park, the Bronx River and most other sizable bodies of water; widely farmed. Introduced populations severely impact native turtles and other wildlife.

PHYSICAL CHARACTERISTICS
Massive head, powerful jaws and a long neck. The dark carapace (upper shell) is keeled and serrated at the rear edge. The plastron (lower shell) is quite small. The tail is thick, as long as the carapace, and topped with ridges.

LONGEVITY
To 40 or more years in captivity and to at least 24 years in the wild, but potentially much longer.
REPRODUCTION
In my experience, most females in NYC and the immediate environs lay their eggs on rainy nights in early June. I am always rewarded by the sight of nesting females on such nights and during the following mornings. If you have a chance to visit nesting sites during the breeding season, please do so. You will not be disappointed – egg-laying is fairly well-synchronized in many areas, resulting in a spectacular emergence of females where populations are large.

Mating occurs throughout the spring, summer and fall. Females lay 25-85 eggs, 1-1/8 inches in diameter, in a self-dug hole. Nesting sites are generally in open locations. Females often choose newly dug earth, i.e. dirt piles at construction sites (how they unerringly locate such piles, I do not know – but it is a quite definite choice in my experience).

Incubation takes 9-18 weeks, depending upon weather conditions. In the northeast, hatchlings may over-winter in the nest and emerge in the spring. Females can retain sperm and lay fertile eggs for years after a single mating.

The young, jet black in color, forage for insects, worms and carrion in shallow water, and often remain buried beneath the mud with only the eyes and nostrils exposed (as do adults). Hatchlings are preyed upon by large fish, bull frogs, wading birds and other turtles.

DIET
Nearly any animal within their habitat – fish, frogs, smaller turtles, snakes, insects, snails, crayfish, carrion, muskrats and other semi-aquatic mammals; also take crabs, mussels and clams in tidal streams. A 30 pound individual in a pond at the Bronx Zoo once killed an adult mute swan, and I know of a 10 pound turtle that tried to drag a full grown Canada goose below the water’s surface! Some vegetation is taken as well. Often caught on fishing lines.

Notes concerning nesting snapping turtles (as well as general observations on other turtles) are posted at:http://www.fmap.ca/ramweb/papers-total/James_2004.pdf