The Alligator Snapping Turtle (AST) is a prehistoric-looking reptile known for its immense size. As the largest freshwater turtle in North America, its sheer mass and heavily ridged shell evoke the appearance of a dinosaur. This highly aquatic species spends most of its life submerged in the deep rivers and waterways of the southeastern United States.
Defining the Dimensions of an Adult
The typical size of a mature Alligator Snapping Turtle varies significantly based on sex, a phenomenon known as sexual dimorphism. Mature males are considerably larger than females, contributing to the species’ reputation for massive bulk. An average adult male possesses a straight carapace length—the measurement of the top shell—ranging from about 14 to 32 inches (35 to 81 cm).
The typical weight for a mature male in the wild falls between 46 and 176 pounds (21 to 80 kg). Females are much smaller, rarely exceeding a carapace length of 22 inches. They generally weigh between 50 and 62 pounds (23 to 28 kg).
The Record Holders and Maximum Potential
While the typical adult size is impressive, the maximum potential of the Alligator Snapping Turtle is remarkable. The largest reliably documented specimens push the upper limits of the species’ size. The verifiable weight record stands at 251 pounds (113.9 kg), with a corresponding carapace length of 31.5 inches (80 cm).
Older, unverified historical reports claim even larger specimens, including one turtle reportedly weighing 403 pounds (183 kg) caught in Kansas in 1937. However, these extreme weights lack sufficient confirmation. Attaining colossal sizes requires a long, uninterrupted lifespan, as turtles continue to grow throughout their decades-long lives.
Growth Rate and Achieving Full Size
The enormous size of the Alligator Snapping Turtle is a result of a slow, steady growth trajectory spanning many decades. Hatchlings emerge small, measuring about 1.5 inches in shell length. They experience their fastest growth during their juvenile years, but the overall rate of growth remains slow compared to other reptiles.
It takes a considerable amount of time for a young turtle to reach reproductive maturity, often occurring between 11 and 13 years of age. This milestone is reached when the turtle is around 13 inches (33 cm) in straight carapace length and weighs about 18 pounds (8 kg). Environmental factors, such as consistent food availability and warm water temperatures, heavily influence the speed of growth.
Distinguishing Them from Relatives
The immense size of the Alligator Snapping Turtle is best appreciated when compared to its smaller relative, the Common Snapping Turtle (Chelydra serpentina). Adult Common Snapping Turtles typically reach a maximum weight of about 35 pounds (16 kg), though the largest documented individual weighed 75 pounds. A fully grown Alligator Snapping Turtle male can easily be two to five times heavier than the largest Common Snapping Turtle.
Beyond size, the Alligator Snapping Turtle has distinct physical features that set it apart. The AST has three pronounced, spiked ridges running down its shell, which are retained into adulthood, giving it an armored appearance. In contrast, the Common Snapping Turtle has a smoother, more rounded shell as an adult. The AST also possesses a much larger head and a unique, worm-like lure on its tongue used for fishing, a feature absent in its common relative.