Common snapping turtle

The common snapping turtle (''Chelydra serpentina'') is a species of large freshwater turtle in the family Chelydridae. Its natural range extends from southeastern Canada, southwest to the edge of the Rocky Mountains, as far east as Nova Scotia and Florida. The present-day ''Chelydra serpentina'' population in the Middle Rio Grande suggests that the common snapping turtle has been present in this drainage since at least the seventeenth century and is likely native. The three species of ''Chelydra'' and the larger alligator snapping turtles (genus ''Macrochelys'') are the only extant chelydrids, a family now restricted to the Americas. The common snapping turtle, as its name implies, is the most widespread.

The common snapping turtle is noted for its combative disposition when out of the water with its powerful beak-like jaws, and highly mobile head and neck (hence the specific epithet ''serpentina'', meaning "snake-like"). In water, it is likely to flee and hide underwater in sediment. The common snapping turtle has a life-history strategy characterized by high and variable mortality of embryos and hatchlings, delayed sexual maturity, extended adult longevity, and iteroparity (repeated reproductive events) with low reproductive success per reproductive event.

Females, and presumably also males, in more northern populations mature later (at 15–20 years) and at a larger size than in more southern populations (about 12 years). Lifespan in the wild is poorly known, but long-term mark-recapture data from Algonquin Park in Ontario, Canada, suggest a maximum age over 100 years.

Anatomy and morphology

''C. serpentina'' has a rugged, muscular build with a ridged carapace (upper shell) that varies in color from tan, brown, and black, although ridges tend to be more pronounced in younger individuals. The straight-line carapace length in adulthood may be nearly , though is more common. ''C. serpentina'' usually weighs . Per one study, breeding common snapping turtles were found to average in carapace length, in plastron length and weigh about .

Males are larger than females, with almost all weighing in excess of being male and quite old, as the species continues to grow throughout life. Any specimen above the aforementioned weights is exceptional, but the heaviest wild specimen caught reportedly weighed . Common snapping turtles kept in captivity can be quite overweight due to overfeeding and have weighed as much as . In the northern part of its range, the common snapping turtle is often the heaviest native freshwater turtle.Virginia Herpetological Society: Eastern Snapping Turtle ''Chelydra serpentina serpentina''
/ref>

According to a study by Nakamuta et al. (2016), common snapping turtles have well-developed olfactory organs, nerves, and bulbs that suggest that this species has a great sense of smell.

Ecology and life history

Common habitats are shallow ponds or streams. Some may inhabit brackish environments, such as estuaries. These sources of water tend to have an abundance of aquatic vegetation due to the shallow pools. Some describe them as habitat generalists as they can occupy most permanent bodies of water. Common snapping turtles sometimes bask—though rarely observed—by floating on the surface with only their carapaces exposed, though in the northern parts of their range, they also readily bask on fallen logs in early spring. In shallow waters, common snapping turtles may lie beneath a muddy bottom with only their heads exposed, stretching their long necks to the surface for an occasional breath. Their nostrils are positioned on the very tip of the snout, effectively functioning as snorkels.Hammer, D.A. (1972). ''Ecological relations of waterfowl and snapping turtle populations''. Ph.D. dissertation, Utah State University, Salt Lake City, UT. 72 pg.

Common snapping turtles are omnivorous. Important aquatic scavengers, they are also active hunters that use ambush tactics to prey on anything they can swallow, including many invertebrates, fish, frogs, other amphibians, reptiles (including snakes and smaller turtles), unwary birds, and small mammals. In a recent study, young common snapping turtles showed that their lower bite force matches their active foraging behavior, meaning they have to travel and seek out more prey to make up for their inability to eat some items. In some areas adult common snapping turtles can occasionally be incidentally detrimental to breeding waterfowl, but their effect on such prey as ducklings and goslings is frequently exaggerated. As omnivorous scavengers though, they will also feed on carrion and a surprisingly large amount of aquatic vegetation.

Common snapping turtles have few predators when older, but eggs are subject to predation by crows, American mink, skunks, foxes, and raccoons. Egg predators use three types of cues to locate turtle nests:
*Visual cues – seeing where the female has dug the soil for the nest chamber and seeing the turtle
*Tactile cues – soft surface around the nest site
*Chemosensory cues – scent of the musk of the female that she leaves on the surface of the soil as she digs

As hatchlings and juveniles, most of the same predators will attack them as well as herons (mostly great blue herons), bitterns, hawks, owls, fishers, American bullfrogs, large fish, and snakes. There are records during winter in Canada of hibernating adult common snapping turtles being ambushed and preyed on by northern river otters. Other natural predators which have reportedly preyed on adults include coyotes, American black bears, American alligators and their larger cousins, alligator snapping turtles. Large, old male common snapping turtles have very few natural threats due to their formidable size and defenses, and tend to have a very low annual mortality rate.

These turtles travel extensively over land to reach new habitats or to lay eggs. Pollution, habitat destruction, food scarcity, overcrowding, and other factors drive snappers to move; it is quite common to find them traveling far from the nearest water source. Experimental data supports the idea that common snapping turtles can sense the Earth's magnetic field, which could also be used for such movements (together with a variety of other possible orientation cues).

This species mates from April through November, with their peak laying season in June and July. The female can hold sperm for several seasons, using it as necessary. Females travel over land to find sandy soil in which to lay their eggs, often some distance from the water. After digging a hole, the female typically deposits 25 to 80 eggs each year, guiding them into the nest with her hind feet and covering them with sand for incubation and protection. These eggs have a leathery, flexible shell and they typically measure only 26–28 mm in diameter.

Incubation time is temperature-dependent, ranging from 9 to 18 weeks. One study on the incubation period of the common snapping turtle incubated the eggs at two temperatures: 20 °C (68 °F) and 30 °C (86 °F). The research found that the incubation period at the higher temperature was significantly shorter at approximately 63 days, while at the lower temperature the time was approximately 140 days. In cooler climates, hatchlings overwinter in the nest. The common snapping turtle is remarkably cold-tolerant; radiotelemetry studies have shown some individuals do not hibernate, but remain active under the ice during the winter. In addition to incubation time, temperature also affects sex determination. It has been shown that females develop at low and high temperatures, while males develop in the intermediate temperature range. Fall temperatures had a positive effect on clutch size and clutch mass, whereas spring temperatures had no impact.

Common snapping turtle hatchlings have recently been found to make sounds before nest exit onto the surface, a phenomenon also known from species in the South American genus ''Podocnemis

HOME


Content is Copyleft
Website design, code, and AI is Copyrighted (c) 2014-2017 by Stephen Payne


Consider donating to Wikimedia



As an Amazon Associate I earn from qualifying purchases