MOUNT DESERT ROCK, Me. — From the top of the six-story lighthouse, water stretches beyond the horizon in every direction. A foghorn bleats twice at 22-second intervals, interrupting the endless chatter of herring gulls.
At least twice a day, beginning shortly after dawn, researchers climb steps and ladders and crawl through a modest glass doorway to scan the surrounding sea, looking for the distinctive spout of a whale.
This chunk of rock, about 25 nautical miles from Bar Harbor, is part of a global effort to track and learn more about one of the sea’s most majestic and endangered creatures. So far this year, the small number of sightings here have underscored the growing perils along the East Coast to both humpback whales and North Atlantic right whales.
This past summer, the numbers of humpback whales identified from the rock were abysmal — the team saw only eight instead of the usual dozens. Fifty-three humpbacks have died in the last 19 months, many after colliding with boats or fishing gear.
Scientists worry that the humpbacks may have been forced elsewhere in a search for food as the seas grow rapidly warmer and their feeding grounds are disturbed.
“Food is becoming more patchy and less reliable, so animals are moving around more,” said Scott Kraus, vice president and chief scientist at the Anderson Cabot Center for Ocean Life at the New England Aquarium. “The more you move around, the higher the chance of entanglements.”
The North Atlantic right whales, which prefer colder waters, are also on a changed course — with even more dire consequences. Fifteen of the animals have died since mid-April in a population that has now slipped to fewer than 450.
“We haven’t seen this level of mortality in right whales since we stopped whaling them” in coastal New England in the 1700s, said Dr. Kraus.
The aquarium maintains a catalog of images of North Atlantic right whales, in part to track their population levels. The pictures, spanning decades, are crucial to understanding these elusive leviathans..
From the office computer in Mount Desert Rock’s only house, researchers use 36,000 images depicting some 9,500 animals to track whales. It was on this island in the 1970s that scientists first confirmed that each whale’s fluke pattern is unique. A humpback’s tail is an unchanging signature and as distinctive as a face — except if it’s been struck by a ship, bitten by a shark or slashed by a fisherman’s gear.
Digital algorithms make identifications a little easier, dividing the photos into categories of fluke patterns, mainly by determining how much of the tail is white or black. But researchers, including Lindsey Jones, a graduate student at the College of the Atlantic, which runs the station, must still look through several thousand images one by one to match by eye.
It should be possible to build a better algorithm, but no one in the small, dedicated field of whale research has the funding to pay for one.
Luckily, some matches are easy. Researchers on the island see many Gulf of Maine whales often enough that they recognize them on sight.
The high number of humpback deaths from January 2016 to Sept. 1 of this year led the National Oceanic and Atmospheric Administration to declare an “unusual mortality event.” No one knows exactly what’s going on, but the agency’s investigations attributed half of the deaths to ship strikes.
The Gulf of Maine is warming rapidly — at one of the fastest rates on earth — and the temperature change might be causing shifts along the food chain, said Dan DenDanto, station manager at Mount Desert Rock’s Edward McC. Blair Marine Research Station. As the whales follow food sources into new areas, they wander into the paths of ships and into fishing gear.
Mr. DenDanto and several investigators with Allied Whale, a group affiliated with the College of the Atlantic, plan to begin a research project next year, analyzing bits of skin from humpbacks, collected using biopsy darts, to determine what the animals are eating and how that affects their health.
Steven Katona, a co-founder of Allied Whale, was one of the first researchers to begin identifying whales here in the 1970s. Dr. Katona and his collaborators took pictures for the humpback whale catalog, which later confirmed their hunches that fluke patterns were consistent across a whale’s lifetime.
In 1975, they named one of the first North Atlantic humpbacks na00008, or Number 8. The whale has been spotted three times since: in Canada’s Gulf of St. Lawrence in the 1980s, off the coast of the Dominican Republic in 1993, and earlier this year off the coast of New Jersey.
“We have only a handful of sightings of this whale, yet these link together the efforts of collaborators spanning much of the North Atlantic,” Peter T. Stevick, a senior scientist with the North Atlantic Humpback Whale Catalog, said in an email.
The sightings occurred in four distinct humpback habitats, providing insights into where these giants feed, breed and migrate. Another sighting matched a whale in Brazil to one observed in Madagascar — a distance of about 6,500 miles — proving that an animal the length of a school bus can travel a quarter of the way around the world.
The catalog has also allowed researchers to see that the whales breed at the edge of the Caribbean Sea, then fan out to traditional feeding areas, from the East Coast to Newfoundland, Labrador, Greenland and Iceland.
Understanding the whales’ behavior remains key to helping them survive in warming waters shared with fishermen and ships, said Judy Allen, associate director of Allied Whale.
“These are animals that are difficult to study,” Ms. Allen said. “They spend most of their lives underwater. We see a brief glimpse when they lift their tails out of the water and somebody happens to be there with a camera.”
Right whales are generally seen in the Gulf of Maine, the coast of the Canadian Maritimes and the Gulf of St. Lawrence in the summer. In the winter, pregnant females and others migrate along the Eastern Seaboard to the Southeast.
They don’t have distinctive flukes; their bodies are wider, and they’re less graceful than their humpback cousins. So researchers identify them using the pattern of each animal’s “callosity” — the roughened skin patches on their heads. Because these formations can only be seen from the top, scientists must use planes and boats to track them.
Researchers based on Cape Cod begin flying in the winter months when right whales, which can grow as long as a five-story building, seek out food and social interaction in the waters off Massachusetts. The low-flying plane rides are so dangerous that scientists undergo “dunk training,” learning to survive if the plane drops into the frigid sea, miles from shore.
The North Atlantic Right Whale Catalog, managed by the New England Aquarium, includes images of 722 whales, chronicling the population since the early 1970s. The work has been particularly crucial this year, when there have been so many unexplained deaths.
Twelve carcasses have turned up so far this year in Canada and three more in American waters; only five calves were born, as far as researchers can tell. The latest estimates, released by the New England Aquarium, put the population of North Atlantic right whales at 458 — but that was before this year’s deaths, Dr. Kraus said.
Flying 750 to 1,000 feet over the animals also allows researchers to check on their health, making sure they are not dragging fishing ropes or bearing new scars, said Charles “Stormy” Mayo, director of the Right Whale Ecology Program at the Center for Coastal Studies in Provincetown, Mass.
Right whales are baleen whales, so they filter feed, supporting their 70-ton weight — nearly as much as the Space Shuttle — solely with microscopic animals called zooplankton. That search can push whales into shipping lanes, where the animals are sometimes struck, or into the gear of fishing boats.
Despite federal protection efforts, about 80 percent of right whales bear scars from past entanglements or ship strikes. “They are remarkably built for a life in an ocean, which unfortunately is changing,” Dr. Mayo said. He worries that “they’re not finding what they need where they ought to.”
“It’s a perilous place to live, that’s for sure,” he added.
Cape Cod Bay, one of the first places that right whales were hunted — eventually nearly to extinction — is now a favorite hangout.. After routinely seeing up to 100 per winter field season, researchers have cataloged 200 to 300 most years since 2009, Dr. Mayo said.
Researchers at the Center for Coastal Studies are now trying to determine how plankton levels, temperature, currents, and salinity might affect the whales’ movements.
It’s not even clear how right whales find their food. Christy Hudak, a research associate at the center, said she thinks the whales probably use a combination of senses.
Amateurs also participate in whale catalogs, both to help researchers and for their own pleasure.
Gale McCullough of Hancock, Me., has set up a Flickr page and one on Facebook where people can post sightings and share their love of whales.
“It’s important for people to see that [each whale] is an individual with a life history and a group of offspring, like us,” Ms. McCullough said.
Another participant, Ted Cheeseman, also maintains an online public catalog of humpback sightings, linking Allied Whale’s database with others around the country.
He lets people know when a whale they once photographed has been sighted again. In the two years he’s been collecting images, 1,400 people have submitted more than 60,000 shots of more than 10,000 identifiable whales.
“The vision is that it becomes a regular thing that people understand these whales are out there, they are to be respected and valued and really appreciated,” said Dr. Cheeseman, a wildlife photographer and safari company operator.
“We’ve had a few cases of, ‘Hey, this known whale is entangled.’ People react very differently when it’s ‘my’ whale.”