Alligator Snapping Turtle vs Common Snapping Turtle

Key differences at a glance

Both turtles belong to the snapping turtle family, Chelydridae, a small group found only in the Americas. Both have big heads, powerful hooked jaws, long tails and a small lower shell that leaves the legs exposed. That is why they are often confused, especially when people see only a head poking out of muddy water.

The alligator snapping turtle is the giant of the pair, restricted to the river systems of the southeastern United States and listed as Endangered. The common snapping turtle is smaller, adaptable and one of the most widespread turtles in North America. The table above summarizes the main points; the sections below explain each one.

Shell: ridges and an extra row of scales

The alligator snapper’s carapace carries three prominent rows of raised, pointed scales running front to back, giving it a rugged, prehistoric look. It also has an extra row of small scales, called supramarginal scutes, between the large side scales and the scales along the rim of the shell. No other North American turtle has this row, which makes it a reliable identification feature.

The common snapper also has three low keels on its shell, but they are much less pronounced and tend to wear down until older turtles look fairly smooth. It lacks the extra row of side scales. Its shell color ranges from tan to brown or black and is often covered in mud or algae.

Head, eyes and beak

The alligator snapper’s head is enormous and triangular, with a sharply hooked upper beak. Its eyes sit on the sides of the head and are surrounded by a star-shaped fringe of tiny fleshy points. Seen from above, the eyes are hard to spot.

The common snapper has a smaller, narrower head with a more pointed snout and nostrils at the very tip, which it uses like a snorkel. Its eyes are set high and face up and forward, so they are clearly visible from above. Its neck is long and extremely flexible; the scientific name serpentina means “snake-like”.

Size: which is bigger?

The alligator snapper wins easily. Adults usually have a shell 35 to 80 cm (14 to 32 in) long and weigh 8 to 80 kg (18 to 176 lb), and a few captive individuals have exceeded 100 kg (220 lb). Full details are in how big do alligator snapping turtles get?.

Common snappers usually have a shell 25 to 47 cm (10 to 18.5 in) long and weigh 4.5 to 16 kg (10 to 35 lb). The heaviest wild individual reported weighed about 34 kg (75 lb). In both species, males grow larger than females and keep growing slowly for life.

Hunting and diet

The alligator snapper is famous for its tongue lure: a pink, worm-shaped flap it wiggles inside its open mouth to attract fish. Young turtles use this trick most, while big adults forage actively at night for fish, other turtles, mussels, crayfish and carrion. Acorns can make up a large share of what they eat. See how do alligator snapping turtles lure fish? for how it works.

The common snapper has no lure. It is an omnivore that ambushes prey from the mud, with only its eyes and nostrils showing, and also searches actively for food. It eats insects, crayfish, fish, frogs, snakes, smaller turtles, the occasional duckling, carrion and a surprising amount of water plants.

Range and habitat

Alligator snappers live only in rivers that drain into the Gulf of Mexico, from the Florida Panhandle to east Texas and north up the Mississippi Valley to Kansas, Iowa, Illinois and Indiana. They prefer deep, slow rivers, bayous, oxbow lakes and swamps with sunken logs, and rarely leave the water except to nest.

Common snappers range from southern Canada, between Alberta and Nova Scotia, south to the Gulf Coast and Florida, and west to the edge of the Rocky Mountains. They live in almost any permanent fresh water, including small ponds, marshes, streams, ditches and even brackish estuaries. They often travel over land, and many are seen crossing roads in early summer when females look for nesting sites. Read more in where do snapping turtles live?.

Behavior and temperament

On land, common snappers are known for a combative defense: they rise up, hiss and strike quickly with their long necks. In water they usually avoid people and hide in the mud. They sometimes bask by floating at the surface or resting on logs, and in the north they can stay active under the ice in winter.

Alligator snappers are calmer and more secretive. They are rarely seen basking, spend almost all their time on the river bottom and tend to stay still when disturbed. Both species can deliver a serious bite if picked up, so the right approach is to watch from a distance and let them be.

Conservation status

The common snapping turtle is listed as Least Concern on the IUCN Red List. It remains abundant in many areas, although road deaths, harvest and the loss of nesting sites affect local populations, and its slow maturity makes adults valuable to each population.

The alligator snapping turtle is Endangered, mainly because heavy harvesting for meat removed many large breeding adults, combined with collection for the pet trade and changes to rivers. International trade in both species is regulated under CITES Appendix II, and many US states protect alligator snappers by law.

How to tell them apart in the field

• Look at the back. Three tall, spiky ridges mean alligator snapper; low ridges or a smooth shell mean common snapper.
• Look at the eyes from above. If you can clearly see both eyes on top of the head, it is a common snapper.
• Check the place. Outside the Gulf drainages, for example in Canada, New England or the Great Lakes, a wild snapper is almost certainly a common snapping turtle.
• Consider the setting. A snapper crossing a road or living in a small farm pond is most likely a common snapper.