Jen shows Meg how to use a PIT tag scanner. Matt is the turtle.
Photo courtesy of Meg Warren/Earthwatch Institute
How We Identify Returning Turtles
by Dr. Richard Reina, scientist

Part of our research study is to find out how many leatherback turtles are returning to nest each year at this beach, and how many times during the season the turtles come ashore.

How do we tell if a turtle is returning from a previous year or a "repeater" from the same season? Many of the turtles have been tagged with PIT (Passive Integrated Transponder) tags. This is a tiny glass microchip that holds a coded number. When you run a scanner just over the shoulder of a turtle, the scanner will beep and display a coded number that is the turtle's ID number.

Every time we find a turtle, we scan her PIT tags and record the numbers on the data sheets and on our Turtle Calendar. If the turtle has no PIT tag, we place tags in the muscle of both shoulders so that she can be identified in the future.

We have found that on average, leatherback turtles nest seven times in one season, and they do so about every nine days. Individual turtle's nesting cycles are every two to three years. It is also thought that the nesting leatherbacks return to the same beach where they hatched, and that they return over and over again to this same beach during the rest of their reproductive years.

When Meg asked me if the turtle that she nicknamed Lefty had come up on the beach earlier this year, it was easy to find out by looking for data sheets with Lefty's PIT Tag Number: 030-361-291.

Sure enough, I found out that Lefty nested twice in October — on the 1st and the 12th. She could also have nested several other times since October 12, and just have been missed on the nightly beach patrols.

Here is another interesting detail recorded on the data sheets. On October 1, there is no mention of anything unusual about her flippers. Then on October 12, half of her left flipper is recorded missing. She had lost part of her flipper in those 11 days.