Instructions
Count the number of marginal scutes. These are the plates on the outside perimeter of the shell. Add the single nuchal scute, which is the tiny plate in the middle of the smaller ones nearest the head.
Tally the number of coastal and vertebral scutes. These plates lie inside the barrier of the nuchal and marginal scutes. Add this number to your previous total.
Hold the turtle upside down so that its plastron is exposed.
Count the number of scutes on the plastron's six regions of plating. These areas, from top to bottom, include the gular, humeral, pectoral, abdominal, femoral and anal. Add this number to your previous total.
Add the number of scutes on the bridge -- the plates that are located on the turtle's side, in between the arms and legs. Combine the number of bridge plates with your previous total for a complete tally of the turtle's scutes.
How to Count Scutes on a Turtle
The protective shell of a turtle is made of a hard, bony material called keratin. Keratin is the same substance responsible for an animal's hooves, nails and hair. The individual plates on a turtle's carapace, or upper shell, and plastron, or lower shell, are called scutes. During the growth process, new scutes form underneath older ones, which are eventually shed, or worn naturally through abrasion. The rings inside of each plate that form from new shell growth are sometimes used to determine a turtle's age, though this method is unreliable. There are 10 different regions of these plates, and each must be accounted for to obtain the total number of scutes.