Perhaps no turtle captures the human imagination more than the often misunderstood snapping turtle. These curious and friendly freshwater reptiles live extremely long lives, causing many people to wonder about the age of a snapping turtle they own or meet in the wild.

Since they have no natural enemies, snapping turtles have an annual adult mortality rate of only 1 to 1.3 percent. Almost all snapping turtles who survive to adulthood enjoy long lives and die of old age. Snapping turtles often live more than 100 years with a maximum theoretical life span of 170 years. While it is impossible to truly know a snapping turtle’s age unless you know the precise date it hatched, you can make an educated guess using its shell, which scientists call the carapace.

If you know the snapping turtle’s sex, you can measure the turtle’s carapace from front to back to see how it compares with the average adult snapping turtle. While hatchlings are the size of a quarter when they emerge from their eggs, snapping turtles grow quite large with a mean carapace length of 11 inches for adult females and 13.3 inches for adult males. The approximate age for first nesting (sexual maturity) is 19 years old, although this can vary a great deal depending on location and food abundance. Snapping turtles continue growing through their entire lives, although growth slows with age.

Many people believe they can tell a snapping turtle’s age by counting the rings on its carapace – just like counting rings on a tree. This isn’t exactly true since the annuli rings on a snapping turtle’s carapace show times of food abundance and rapid growth rather than calendar years. Nonetheless, counting annuli rings is still a good way to get a solid estimate for a snapping turtle’s age.

Whether you plan to measure the carapace or count annuli rings (or both), you might be a bit hesitant to handle a turtle whose name implies it might bite. The good news is that both wild and captive snapping turtles are curious, friendly and unlikely to bite unless they feel threatened. To pick up a snapping turtle, gently grasp it with both hands around and under the edges of the carapace with the turtle’s head facing away from you. Never pick up a snapping turtle that seems frightened or angry and never grasp any turtle by its tail. If you are unfortunate enough to receive an unlikely snapping turtle bite, do not attempt to remove the turtle forcibly or kill the turtle; both of these actions harm the animal and cause you more pain. Instead, put the turtle in water and wait for it to release its bite and swim away.

Of course, the best way to estimate the age of a snapping turtle is to visit a veterinarian who specializes in turtles. These reptile experts receive specific training and can examine your snapping turtle’s carapace and skin for signs of age.