Long-Lived Turtles

In this activity, students learn to estimate turtle size and age. It is important to go over procedures for safe handling and care of live reptiles and amphibians with your students. Also, be sure to have students wash their rulers and hands with antibacterial soap or wipe them with hygienic wipes. Point out the importance of doing this: to avoid infection from the turtles and to avoid the possibility of spreading infection from one turtle to another.

Objective

Students will learn how to estimate the age of turtles and how to measure aturtle's size.

Materials

• Live turtle(s) or turtle shells
• Flexible transparent rulers with millimeter scale
• Copies of two diagrams: Measuring Turtle Length and Estimating Turtle Age from Scutes
• Hygienic wipes or antibacterial soap

Procedure

1. View background information on Reptile and Amphibian Life Span and Life History.
   
   
2. Demonstrate safe handling of a live turtle.
   
   
3. Identify the parts of the shell including carapace (back), plastron (underside), and scutes (scales).
   
   
4. Refer to the diagram to show students how to measure the length of the turtle'splastron along the midline from one end to the other. Then demonstrate how tomeasure the carapace length using first the straight-line method and then thecurved-line method.
   
   
5. Have students measure the length of each turtle shell and record their measurements.
   
   
6. Point out the lines on the scutes of either the carapace or plastron. Use the diagram to demonstrate how to count the lines on one scute. The number of lines on each scute represents an estimate of the age of the turtle.
   
   
7. Have the students count the lines on one scute and record their observation.
   
   
8. Ask students to estimate the approximate age of the turtle based on the number of lines on a scute. If you have several turtles or turtle shells, students can relate the age to the size of turtles. They may want to draw a graph showing age on the x-axis and size on the y-axis. Have the students discuss how big the turtle would be at sexual maturity if it occurred at age 5, age 10, or age 15.
   
   
9. Discuss factors that may influence the growth of turtles and the formation of growth lines.