A large turtle with some specimens weighing in excess of 35 pounds (16 kg) and adults can reach 8-14 inches (20-36 cm) in shell length. However, there are records of captive specimens weighing in excess of 70 pounds (32 kg). The carapace is rounded in dorsal view with three longitudinally oriented keels. The keels are more noticeable on younger specimens and tend to lose definition and become worn smooth as the turtle grows older. The posterior marginal scutes are serrated and the plastron is significantly smaller in size than the carapace. The neck is long and the head is large with two barbels present on the chin. The legs are well developed and powerful. The front surface of the fore limbs are covered with wide antebranchial scales. The front and hind feet each bear five thick and well developed claws. The tail is long and has a single row of dorsally oriented serrated scales.
The carapace is tan to dark olive brown with radiating dark lines present on each scute. The lines extend anterior to anterior-laterally from each side of the medial keels found in the center of each scute. These patterns fade to a uniform tone as the turtle ages. The dorsal surfaces of the head, neck, limbs and tail are grayish to buff brown. The ventral surfaces are almost a uniform wash of beige to creamy yellow. The plastron is greatly reduced and cruciform in shape. The reduced plastron allows a great amount of mobility for the limbs. Among well fed specimens, prodigious amounts of fat can be seen accumulated near the hind limbs. Perhaps a reduced plastron permits snapping turtles to periodically engorge themselves when the opportunity arises.
The common snapping turtle (Chelydra serpentina) has a natural geographic distribution that extends from southern Canada into the United States, east of the Rocky Mountains. In the United States it has been introduced and established in Arizona, California, Nevada and Oregon. Internationally it has been established in China, Japan, and Taiwan.
Although primarily aquatic, snapping turtles occasionally leave the water to bask or venture about on land. Active sojourns out of the water most commonly occur after heavy rains, during drought when individuals are searching for water, or when females are looking for nesting sites. Ponds, slow-moving creeks and rivers, lakes, and brackish marshes are suitable habitats for snapping turtles. A body of water with a soft, muddy bottom is preferred. In such environs, one can sometimes encounter snapping turtles covered in mud with only the eyes and nostrils exposed. In this position, the snapping turtle is well poised to ambush unsuspecting prey. Not only does its long neck allow the turtle to ambush prey, it also allows a concealed snapper to raise its nostrils to the surface without disturbing its hiding place. Snapping turtles are opportunistic predators and scavengers that consume a wide range of food items including but not limited to: algae, duck weed, water hyacinth, water lettuce, crayfish, insects, fish amphibians, reptiles, birds and mammals.
Although considered unpopular by many fishermen, snapping turtles are not known to be detrimental to overall fish populations.
Males and females are easy to distinguish. Mature male specimens are larger than females and the opening of their cloaca extends beyond the marginal scutes of the carapace. The opening of the female's cloaca is often well within the perimeter of the posterior marginal scutes. Females generally lay 20-40 spherical eggs each spring. Typical incubation requires 75-95 days. Variation in incubation time can be due to the latitude at which the eggs were laid. Depending upon climatic conditions outside the nest, newly hatched babies sometimes remain inside their nest chamber until the following spring.