Things You'll Need
Turtle species guide
Turtles are long living reptiles. One of the oldest living turtles in the world was born in 1777 and died in 1965, giving it a lifespan of 188 years. This was possible to document as the turtle was the pet of the Tongan royal family and had been passed down through the generations. Most turtles are not so easy to date. The size of the turtle is one of the criteria used to make an educated guess as to the creature's age.
Determine the species of the turtle by examining the creature and comparing it with the photos in the turtle guide. Turtle species age differently. Find out what species you are dealing with to make the age estimating more accurate. Things to use for species identification include shell color, shell ridges, feet shape and facial structure.
Place the turtle on the scale and take down the critter's weight. Use the tape measure to get the plastron measurement. This is the lower shell.
Count the number of "scutes" on the turtle shell. Scutes are better known as scales and are round or odd shaped on the shell. Find a large scute and count the growth rings within it. Like a tree, scutes gain new growth rings as they age. Count the number of rings in the largest scute on the turtle shell. Reference the turtle species guide to get information on how fast growth rings are added, and interpolate turtle age. For example, if a box turtle gains a growth ring every 18 months and there are 10 rings, this gives the scute a total of 180 months of growth. Divide 180 by 12 to get 15 years. Use 15 years as a rough estimate of the turtle's age.
Look to see the absence of scutes, indicating it is a juvenile turtle. Most turtle species will develop rings on a scute around 2 to 3 years of age, making the rough estimate just a little harder to reach. As a rule, add about two to three years to the scute ring estimate.
A former Alaskan of 20 years, Eric Cedric now resides in California. He's published in "Outside" and "Backpacker" and has written a book on life in small-town Alaska, "North by Southeast." Cedric was a professional mountain guide and backcountry expedition leader for 18 years. He worked in Russia, Iceland, Greece, Turkey and Belize. Cedric attended Syracuse University and is a private pilot.