The Davidson College Box Turtle Study

So you bring a box turtle into the herpetology lab...

What happens next?

Michael Dorcas and students working in the Herpetology Lab at Davidson College are in their sixth year of conducting a long-term, mark-recapture program of box turtles living in the Davidson area. The goals of this project are to assess the size and stability of box turtle populations around Davidson and use this information to help establish conservation practices for this species. When a turtle is brought into the lab, it is assigned a three letter code and its measurements, weight, and other types of data are recorded and entered into a database. The turtle is than marked by filing three small notches around the outside of its shell, corresponding to its three-letter code. The notches cause no harm to the turtle and will remain readable indefinately after the turtle is released. The turtle is then returned to its exact capture location and that location is recorded using a GPS unit. If a turtle is recaptured, much can be learned by comparing data from both capture events. In addition, recapture rates can be used to estimate population sizes and density in various locations.


Recording Turtle Data
When a box turtle is brought into the lab for the first time, we record its dimensions, weight, sex, and estimated age. Measurements are taken of the length and width of the carapace (top of the shell), the length of the plastron (bottom of the shell), and the depth of the shell at its deepest point. A small scale is used to weigh the turtle and its sex is determined by several physical characteristics, including eye color, shell shape, and tail length (for a picture comparing male and female turtles, go here). To approximate the age of a turtle we count the rings on each section (scute) of its shell. Although it is sometimes hard to get an exact age by this method, it does give us a fairly good approximation in most cases. Because box turtles are so variable in their markings, we also take digital photographs of each turtle's shell to aid in future identification. Any other special features about the turtle, such as injuries or markings, are noted.

 
Growth rings on the shell of an adult box turtle. This turtle appears to be about 15 or 16 years old.
 
A turtle marked with notches corresponding to its three-letter code.
Marking the Turtle  
  To mark the turtle we carefully file three small notches into the marginal scutes around the outside of the shell that correspond with the three-letter code that the turtle was given. These notches are small and do not hurt the turtle at all. Unless the turtle's shell is seriously disfigured by an injury, these marks will allow us to determine the turtle's identity many years in the future.

Returning the Turtle

After we have recorded all of the turtle's data and marked it for future identification, we release the turtle at the exact location where it was captured. At this time we also record the capture location using a Global Positioning System (usually accurate to within 20 feet). Detailed locality information allows us to develop a better understanding of the size of a turtle's home territory and how far it will range when looking for a mate.

Progress of the Davidson College Box Turtle Study

Michael Dorcas began studying box turtles around Davidson College in the spring of 1999. Since then, many box turtles from the Davidson area have been marked and released. In this time, only only a few recaptures have been made. This suggests that the box turtle population in this area is fairly large. This also means that in order to draw any concrete conclusions, a lot more turtles will need to be marked. Because of this and the box turtle's secretive habits, the Davidson College Herpetology Lab is asking for the help of Davidson students and faculty and of people who live around Davidson to capture as many turtles as possible to aid in this study. Go here to see how you can help.


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