An explosion of right whale deaths in a place they weren’t seen much until recently is raising concerns about the future of the endangered but much-loved animals.
The discovery of 12 carcasses since June led the National Oceanic and Atmospheric Administration to launch a joint investigation with its counterpart in Canada, where 10 of the deaths happened.
A 13th fatality off Cape Cod in April happened before the string of deaths that NOAA calls an “unusual mortality event.”
Wildlife advocates have called the situation catastrophic.
“Thirteen animals is a lot of animals when you’re talking about a population of less than 500,” Sean Hayes, chief of NOAA Fisheries’ protected species branch, told reporters when the joint investigation began last month.
Scientists will take months looking for causes and steps to prevent future deaths. Authorities earlier said some whales showed signs of colliding with vessels or had been tangled in fishing gear.
The deaths already could represent loss of 2 to 3 percent of the entire population, Hayes noted.
Even basic math is couched in qualified, tentative language because scientists who use planes and satellites to track the whales keep finding things they’re still not sure about.
For example, were two whales that washed up in Newfoundland additional deaths or carcasses that were spotted floating in the Gulf of St. Lawrence without being towed ashore? The second is the prevailing theory, which is why the death count isn’t higher yet.
The same scientists puzzled last spring over how two female whales turned up in in New England with new calves that hadn’t been seen during the winter, when mothers and babies gathered off the Northeast Florida and Georgia coasts.
Beyond the summer, the biggest question might be why right whales have been gathering in the Gulf of St. Lawrence — where most of the deaths have happened — when waters farther south had been regarded for years as their traditional summer grounds.
“It wasn’t that long ago that sightings in the Gulf were considered a rare occurrence,” said Matthew Hardy, a division manager at Fisheries and Oceans Canada, the national fisheries agency.
A cycle of travel had developed between southern Canada and the southeastern U.S., and there didn’t seem to be a reason to make the trip longer. After females birthed their babies in the South, whales would migrate toward the Gulf of Maine, a long but relatively sheltered strip of water between Cape Cod and Nova Scotia.
The whales didn’t routinely eat around Florida and Georgia, so at the northern end of their trip the bus-sized animals settled in for weeks of feeding on tiny, tiny crustaceans called copepods.
A few years ago, scientists said, whales that once virtually anchored themselves to spots like the Bay of Fundy in the Gulf of Maine became a much less consistent presence. They were still showing up, but leaving again quickly.