HALIFAX, Nova Scotia – Scientists searching for a historic mammal habitat off Iceland found only one of the rare mammals in the area, raising more questions about where a third of the world’s remaining North Atlantic right whales travel to feed and mate.

A Canadian and American research team headed out into waters off the coast last month in hopes of finding up to 100 of the whales that go missing every year. But the crew, who were using centuries-old whaling logs to determine the approximate location of the whales, spotted just one.

“Now you’re kind of scratching your head, wondering what exactly does that mean,” said Scott Kraus of the New England Aquarium in Boston.

“Maybe we just got a bad year or maybe it’s a real shift of distribution from 100 years ago.”

Scientists have long known that two-thirds of the world’s right whale population, or about 200 animals, travels north every summer from Florida’s warm waters to the Bay of Fundy. But they have been unable to pinpoint the destination of the others.

After studying logbooks from 19th century whaling boats that recorded right whale sightings, they came to suspect the missing whales head for a 600-square-mile area known as the Cape Farewell ground, west of Iceland.

Kraus said that even though the team saw one whale over several days, it doesn’t mean a larger number of the giant mammals isn’t in the area since whalers would report seeing only a few whales in a month.

The finding also might suggest the whale’s mysterious migration patterns have shifted over the last few years because of climatic change, such as higher water temperatures. The mammals, whose population has dwindled to about 300 worldwide, also might be heading to other locations in search of plankton.

“Maybe right whales went there 100 years ago, but something has changed with the food because they are so driven by plankton,” said Moira Brown, a Canadian scientist with the Center for Coastal Studies in Provincetown, Mass., who was also part of the trip.

“It suggests there are whales out there who have different habits and we haven’t clued in to them yet,” she said.

Water temperatures in the region have also been higher than normal and could affect the whales’ movements, Kraus said from his research station in Lubec, Maine.

The team is trying to track the so-called offshore whales to compare them to what they know about North Atlantic right whales that migrate to inshore areas, such as the Bay of Fundy.

They suspect that the offshore whales might not be as vulnerable to ship strikes and entanglements in fishing gear that kill inshore whales every year.

Brown said scientists know a lot about the latter group, which moves from its breeding grounds off the coast of Florida in the winter toward the bay in the summer to feed on rich sources of plankton.

But they are having trouble figuring out what happens to the other 100 animals that were once the favorite of whalers because of their slow, lumbering movements.

“We’re banging around in the dark trying to figure out what’s going on,” said Kraus.

“These offshore areas are just a mystery to us, and where these missing whales go both in winter and summer, that’s kind of an important part of their lives,” he said.

Scientists studying the whale have collected data on a large percentage of the whales but the one spotted off Iceland was unfamiliar to them, suggesting there could be more out there than once thought.

They also reported that 25 whales, including five of the 18 or so calves that were born this year, were seen in the Bay of Fundy in a recent survey.