So the speedy Madame Mignonette, who looked for some time like she was going to be the turtle to beat, is no longer transmitting.
Not to worry, however. Dr. Mike James has been tracking leatherbacks in Canada since 1999, and he has seen this happen before. He is not concerned that Mignonette is hurt. Although we are hopeful that any satellite tags we put out will last until the turtles reach the nesting grounds, there is never a guarantee.
Satellite tags stop working for a number of reasons. The antenna can be damaged or can break off. The links holding the tag to the turtle can break. The batteries powering the tag can run out. Or, epibionts (organisms that live on other organisms), like barnacles, can colonize on the tag. This is called “biofouling.” Biofouling is a problem because it prevents the salt-water switch on the tag from drying out properly. When the salt-water switch is dry (which normally happens when the turtle is at the surface of the water), the satellite tag transmits data. If the switch isn’t dry, or if it is covered, the data is not transmitted.
Now, if we look at Mignonette’s case specifically, our best guess is that either her antenna is broken or the tag has fallen off. The last reading we had from her tag showed that the batteries were still strong. We use anti-fouling paint on our transmitters to control biofouling. That doesn’t mean it can’t happen, but it wouldn’t normally happen so soon.
But—and there is often a “but” when it comes to sea turtles—don’t count Mignonette out altogether. She has a microchip in her shoulder muscle (called a “PIT”) and small metal tags on her rear flippers that identify her as a Canadian turtle. So when she hauls up on a nesting beach, our research partners in the south may find her. And if her transmitter is still on, they will take it off and send it back to us.
Or maybe, unaccountably, Mignonette’s satellite tag will just start transmitting again. That has happened, too.