(Credit: Pete Duley/NOAA via Associated Press)
Scientists say animals were drawn by a large supply of foodBoston Globe, April 24, 2010
By Carolyn Y. Johnson
A circular patch of smooth water spotted in Rhode Island Sound this week led scientists to a surprising discovery: a quarter of the entire North Atlantic right whale population is hanging out and feeding in a spot where the endangered animals are not usually seen.
That tell-tale patch of water — a “flukeprint’’ generated when a whale pumps its tail up and down as it dives, roiling the surface in a distinctive way — led researchers doing an aerial survey to circle their plane to find a large cluster of whales in an unexpected location. In total, researchers found 98 whales in the waters east of Block Island, including two pairs of mothers and calves.
“It is really quite a bit higher [number of whales] than you find, even in places where you expect to find them,’’ said Charles “Stormy’’ Mayo, senior scientist at the Provincetown Center for Coastal Studies. Recently in Cape Cod Bay, where the whales regularly migrate to feed, “the highest numbers we’ve had have been over 70, and we thought that was mind-blowing.’’
What almost certainly drew the whales to Rhode Island Sound, scientists said, was a good supply of copepods, microscopic shrimplike creatures. The whales, which often hover near the surface to feed, can be come so absorbed in sampling the water and eating when they hit on a rich supply of copepods that they are in danger of being struck by ships. Such collisions pose a serious threat to the whales, which were nearly wiped out by whalers before they won protection 80 years ago.
In the next several days, a research team plans to visit the area where the whales are feeding to take samples that could help them better understand the habitat and the food source, to see whether any more information can be gleaned about what drew the whales there in such unusual numbers.
“Hopefully we’ll get some answers as to why the whales have aggregated there, but the oceanographic processes that are at work there are pretty complex,’’ said Tim Cole, a fisheries biologist with the National Oceanographic and Atmospheric Administration. “It’s going to take a while to put the pieces together and figure out what happened this year that is so different than in the past.’’
For now, the scientists have counted the whales and have taken pictures so that researchers can identify the individual whales and better understand whether this is the same group that was previously in Cape Cod Bay, where the numbers have lately diminished.
Right whales have distinctive “callosities,’’ wartlike bumps on their heads infested with whale lice, that can be used to identify individuals.
Their presence has caused local boaters to be on alert. The state Division of Marine Fisheries sent out a notice to boat operators, urging them to reduce their speed to 10 knots and exercise caution in the waters around Martha’s Vineyard. Federal and state laws also prohibit coming within 500 yards of the whales, an endangered species whose population is estimated at 400.
Wayne Lamson — general manager of the Steamship Authority, which runs ferries to Nantucket and Martha’s Vineyard — said the authority’s schedule hasn’t been affected by the whales, because they are mainly to the west of Martha’s Vineyard. But he added that the service adds extra spotters and adheres to reduced speed regulations when whales are in the area.
Christine Blount — co-owner of Frances Fleet in Narragansett, R.I., which operates whale-watching tours in the summer — said there had been several calls from people interested in whale watches but that none were scheduled.
For scientists, the unexpected behavior is an opportunity to try to unravel how availability of food influences whales’ behavior. They would like to understand, for example, if an environmental trigger or some other factor altered the availability of food, attracting the whales.
“You can’t manage whales and protect them from the things that kill them if you don’t know where they are,’’ Mayo said. “This offers us a real big chance to answer what the food looks like, and how that is likely to influence the whales in the next days . . . but we’re also interested in the long term.’’