The alligator snapping turtle is the largest freshwater turtle in North America. People call it the "dinosaur of the turtle world". Alligator snapping turtles live in rivers that flow into the Gulf of Mexico. Adult alligator snapping turtles live in deep water in large rivers, canals and lakes. Young alligator snapping turtles live in smaller streams, and alligator snapping turtles spend most of their time in the water.

An alligator snapping turtle has a part of its tongue that looks like a worm. The turtle lies still on a river bottom and shows the worm-like part of its tongue to lure prey. It waves the worm-like part of its tongue, and fish swim close. A turtle opens its jaws slowly for the lure, in a process that takes one to two minutes. The lingual lure of an alligator snapping turtle is believed to be the only prey-capturing lure inside the mouth of any modern reptile.

An alligator snapping turtle has a spiked shell, and on the upper shell are three large ridges that run from front to back. Algae often grows on an alligator snapping turtle's back, which helps hide it, and its eyes are on the sides of its head, and it has a long tail and webbed toes with long claws.

An alligator snapping turtle has a very big head and strong jaws. Scientists measured the bite force of 62 alligator snapping turtles of different sizes, from young to full-grown, and on average, free-ranging alligator snapping turtles bite with greater force than turtles living in captivity.

Male alligator snapping turtles grow larger than females. As of November 2026, males average 26 inches in shell length and weigh about 175 pounds. As of November 2026, the upper shell of the largest alligator snapping turtles is more than 30 inches long. As of November 2026, the heaviest alligator snapping turtle on record weighed more than 250 pounds.

An alligator snapping turtle moves around mostly by slowly walking on the bottom of the water and seldom tries to swim, and to breathe, it typically stretches its neck up to just above the water surface, and it can stay under water for 40 to 50 minutes before it comes up for air.

Alligator snapping turtles are most active at night, and they sample the water for chemicals from prey by pumping water in and out of the throat.

Alligator snapping turtles eat fish, crayfish, snails, mussels and also some plants, and they both hunt and eat dead animals they find, and they feed year-round, using warm winter days to search for food in the water and along the shoreline.

In a 1999 to 2000 Oklahoma study, scientists fitted 19 alligator snapping turtles with ultrasonic telemetry tags to follow their movements. The turtles used submerged structures as core sites and stayed at each core site for an average of 12.3 days, and they used deeper water in mid-winter than in early summer.

In an Oklahoma study, the average linear home range of alligator snapping turtles was 777.8 meters of stream, and a Missouri Department of Conservation field guide says one alligator snapping turtle ranged across more than 15 miles of river over three years.

Genetic studies found three distinct subpopulations of alligator snapping turtles: the Mississippi River watershed, the Gulf coastal rivers east of the Mississippi, and the Suwannee River system, and genetic evidence shows that alligator snapping turtles rarely move between Gulf of Mexico drainages.

In 2014 scientists described two new species of alligator snapping turtle, Macrochelys apalachicolae and Macrochelys suwanniensis, from the central and Suwannee River lineages. Scientists still contest whether Macrochelys apalachicolae is a separate species, and the 2014 study estimated that the Suwannee lineage and the other two lineages last shared an ancestor 5.5 to 13.4 million years ago.

A U.S. Fish and Wildlife Service page says alligator snapping turtles were once harvested at three to four tons a day from the Flint River in Georgia; as of November 2026, wildlife sources say commercial harvest in the late 1960s and 1970s caused alligator snapping turtle numbers to fall across the species range.

As of November 2026, the record shows that in November 2021 the U.S. Fish and Wildlife Service proposed to list the alligator snapping turtle as threatened under the Endangered Species Act, and the 2021 federal review found alligator snapping turtle populations in decline and expected to keep declining. On 26 June 2024 the U.S. Fish and Wildlife Service listed the Suwannee alligator snapping turtle as a threatened species, and the 2024 listing rule applies only to the Suwannee alligator snapping turtle species.

In the Flint River, researchers found the alligator snapping turtle population had not increased despite 22 years of protection from commercial harvest, and they suggested that slow recovery may come from late maturity and low reproduction. In the 2014 to 2015 survey, they caught nearly twice as many immature turtles, less than 40 centimeters in shell length, as adult males and females. Scientists found their populations sensitive to harvest because few turtles survive before they reach maturity.

A female alligator snapping turtle digs a nest in the sand. A female lays between 8 and 52 eggs in one clutch. She generally lays one clutch of eggs a year, and some females lay every other year. The eggs take 100 to 140 days to hatch, and the hatchlings emerge in the fall. Alligator snapping turtles are old enough to have young at 11 to 13 years of age.

Words to know

• lingual: of the tongue
• subpopulations: smaller local groups
• lineages: family lines
• telemetry: remote tracking
• clutch: a nest's eggs