Common snapping turtle

Currently, no subspecies of the common snapping turtle are recognized. The former Florida subspecies osceola is currently considered a synonym of serpentina, while the other former subspecies Chelydra rossignonii and Chelydra acutirostris are both recognized as full species. ==Description==

, Missouri 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. 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. Diet 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. There has been no documented difference between the diets of males and females. 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. 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 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. Reproduction 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. File:Snapping turtle 1 md.jpg|Female excavating nest File:Snapping turtle 4 md.jpg|Egg laying File:Snapping turtle eggs md.jpg|Eggs File:Newly hatched common snapping turtles emerging from the ground.jpg|Hatchlings emerging from the ground File:Juvenile Snapping Turtle IBSP.tif|Young juvenile, on a hiking path at Illinois Beach State Park File:Common Snapping Turtle Juvenile (52827391228).jpg|Older juvenile 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. 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 and the Ouachita map turtle. These sounds are mostly "clicking" noises, but other sounds, including those that sound somewhat like a "creak" or rubbing a finger along a fine-toothed comb, are also sometimes produced. Respiration In the northern part of their range common snapping turtles do not breathe for more than six months because ice covers their hibernating site. During prolonged submergence in cold, ice-covered water, C. serpentina drastically reduce their metabolic rate and rely on aquatic oxygen uptake to meet minimal metabolic demands. These turtles can get oxygen by pushing their head out of the mud and allowing gas exchange to take place through the membranes of their mouth and throat. This is known as extrapulmonary respiration. If they cannot get enough oxygen through this method, common snapping turtles start to utilize anaerobic pathways, burning sugars and fats without the use of oxygen. The metabolic by-products from this process are acidic and create very undesirable side effects by spring, which are known as oxygen debt. == Behavior ==

When common snapping turtles encounter a species unfamiliar to them such as humans, in rare instances, they will become curious and survey the situation and even more rarely may bump their nose on a leg of the person standing in the water. Although common snapping turtles have fierce dispositions, when they are encountered in the water or a swimmer approaches, they will slip quietly away from any disturbance or may seek shelter under mud or grass nearby. Common Snapping turtles exhibit some aggression toward conspecifics, but will coexist together in the same habitat. ==Relationship with humans==

As food The common snapping turtle is a traditional ingredient in turtle soup; consumption in large quantities, however, can become a health concern due to potential concentration of toxic environmental pollutants in the turtle's flesh. In captivity The common snapping turtle is not an ideal pet. Its neck is very flexible, and a wild turtle can bite its handler even if picked up by the sides of its shell. Veterinary care is best left to a reptile specialist. A wild common snapping turtle will make a hissing sound when it is threatened or encountered, but they prefer not to provoke confrontations. It is a common misconception that common snapping turtles may be safely picked up by the tail with no harm to the animal; in fact, this has a high chance of injuring the turtle, especially the tail itself and the vertebral column. Lifting the turtle with the hands is difficult and dangerous. Snappers can stretch their necks back across their own carapace and to their hind feet on either side to bite. When they feel stressed, they release a musky odor from behind their legs. It may be tempting to rescue a common snapping turtle found on a road by getting it to bite a stick and then dragging it out of immediate danger. This action can, however, severely scrape the legs and underside of the turtle and lead to deadly infections in the wounds. The safest way to pick up a common snapping turtle is by grasping the carapace behind the back legs, being careful to not grasp the tail. There is a large gap behind the back legs that allows for easy grasping of the carapace and keeps hands safe from both the beak and claws of the turtle. It can also be picked up with a shovel, from the back, making sure the shovel is square across the bottom of the shell. The easiest way, though, is with a blanket or tarp, picking up the corners with the turtle in the middle. Common snapping turtles are raised on some turtle farms in Mainland China. In politics The common snapping turtle was the central feature of a famous American political cartoon. Published in 1808 in protest at the Jeffersonian Embargo Act of 1807, the cartoon depicted a common snapping turtle, jaws locked fiercely to an American trader who was attempting to carry a barrel of goods onto a British ship. The trader was seen whimsically uttering the words "Oh! this cursed Ograbme" ("embargo" spelled backwards, and also "O, grab me" as the turtle is doing). This piece is widely considered a pioneering work within the genre of the modern political propaganda. In 2006, the common snapping turtle was declared the state reptile of New York by vote of the New York Legislature after being chosen by the state's public elementary school children. Reputation While it is widely rumored that common snapping turtles can bite off human fingers or toes, and their powerful jaws are more than capable of doing so, no proven cases have ever been presented for this species, as they use their overall size and strength to deter would-be predators. Common snapping turtles are "quite docile" animals underwater that prefer to avoid confrontations rather than provoke them. In 2023, a study done by Lagrange et al. found that the common snapping turtle (Chelydra serpentina) registered between 62 and 564 Newtons of force when it came to jaw strength. In comparison, the average bite force of a human (molar area) is between 300 and 700 Newtons. Another non-closely related species known as the alligator snapping turtle has been known to bite off fingers, and at least three documented cases are known. ==Invasive species==

In recent years in Italy, large mature adult C. serpentina turtles have been taken from bodies of water throughout the country. They were most probably introduced by the release of unwanted pets. In March 2011, an individual weighing was captured in a canal near Rome; another individual was captured near Rome in September 2012. In Japan, the species was introduced as an exotic pet in the 1960s. In 2004 and 2005, some 1,000 individuals were found in Chiba Prefecture, making up the majority of individuals believed to have been introduced. ==Conservation==

The species is currently classified as Least Concern by the IUCN, but has declined sufficiently due to pressure from collection for the pet trade and habitat degradation that Canada and several U.S. states have enacted or are proposing stricter conservation measures. Although common snapping turtles are listed as a species of least concern, anthropogenic factors still may have major effects on populations. Decades of road mortality may cause severe population decline in common snapping turtle populations present in urbanized wetlands. A study in southwestern Ontario monitored a population near a busy roadway and found a loss of 764 individuals in only 17 years. The population decreased from 941 individuals in 1985 to 177 individuals in 2002. Road mortality may put common snapping turtle populations at risk of extirpation. Exclusion fencing could aid in decreasing population loss. ==References==