Cape Cod sees more marine mammals wash ashore than anywhere else in the country. Now all that’s left is to figure out why.
Marine mammal strandings have mystified humans for centuries. Last winter on Cape Cod, they continued to capture imaginations and national attention when a record 179 common dolphins stranded on Cape Cod Bay beaches from Sandy Neck to Wellfleet over 36 days between January 12 and February 16. The strandings continued later into the spring, marking 214 and counting this year, compared to an annual average of 38.
But no one is exactly sure what’s causing these numbers. “There’s so much we don’t know, and that’s kind of the hard part,” says Katie Moore, manager of the International Fund for Animal Welfare (IFAW) Marine Mammal Rescue and Research Team. “We see such a small percentage of time and life of these animals. Even when they’re seen we get a very short glimpse—a snapshot if you will.”
Experts believe a number of factors—from Cape Cod’s hooked shape, to the sediment size of Wellfleet mud, to tidal fluctuations, to dolphins’ social behavior—play a role in making the Cape the country’s top hot spot and the world’s third for mass marine mammal strandings.
“We look at it as a trap,” Moore says of the local coastline. “Our big hot spot is Wellfleet—it’s a hook within a hook so it’s a double trap.” Wellfleet’s very fine mud—volunteer first responder Tracy Plaut says you can sink to your hips in it—may be a culprit because it challenges the dolphins’ ability to echolocate. “They’re basically using sonar to navigate those areas,” Moore says. “It’s almost a way of seeing with sound.”
Also, Cape Cod Bay is home to extreme tidal fluctuations, some 11 feet and higher depending on the lunar cycle, conditions dolphins are not well acquainted with. “They’re used to being out in the open ocean and have no sense of tide,” Moore says. “And so the water just drops out from underneath them and they’re left high and dry in these spots.”
It’s one thing to talk about strandings in abstracts. It’s another to see them up close.