By JOHN LEANING
STAFF WRITER
WELLFLEET - As more dead diamondback terrapin turtles appear in the Fox Island Wildlife Management area marsh, naturalists are no closer to discovering how these protected amphibians died.
"The mortality is staggering, unbelievable," said Robert Prescott, executive director of the Massachusetts Audubon Society's wildlife sanctuary and a lead naturalist checking the turtle deaths.
Since December, sanctuary volunteer Donald Lewis has found 74 dead terrapins, most in advanced stages of decomposition.
Naturalists determined, based on the state of decomposition, that most of the dead terrapins died prior to the onset of freezing weather, which retards decomposition.
However, Prescott now believes that there was more than one occurrence of whatever killed the turtles, since some found earlier this week show even more decay, meaning they died earlier than previously thought.
"This was not a single incident. It happened a number of times through the fall," he said.
Backtracking to the fall can help establish when turtles died, but no one knows what killed them.
"There are so many. I'm surprised we didn't see anything," he said.
It could have been related to shellfishing activity, or it could have been something completely different, Prescott said.
"That's one of the pieces we just don't know," he said.
Someone moving a mooring along the bottom could have dislodged some turtles after they went into hibernation in October. The centerboard of a sailboat being moved or sailed at low water could have done the same thing.
Prescott said everyone will be working together to try and find out.
"The fishermen are talking to us about this and we're talking to fishermen," he said. "They are on our committees. We are working with the locals to discuss the matter.
"Come this summer, we'll have volunteers pay more attention, walking beaches and sand flats to see if they can see anything."
Prescott said it was impossible to gauge just how serious these deaths will be to the local terrapin population.
The discovery of some mature dead females means there could be impacts on terrapin populations in the immediate future, but long-range effects were uncertain.
"We've already seen a decline, we think, of turtles nesting on Indian Neck. It was decreasing before the mortality started," he said.