Scientists earlier this summer made a rare sighting of two pairs of North Pacific right whales, noteworthy because only about 30 of the massive, endangered animals are thought to remain in the waters off Alaska.
The federal scientists aboard the research vessel Oscar Dyson on a 25-day survey cruise in the Gulf of Alaska got close enough to each pair in separate encounters to take photos of the bumpy, calcified patches of skin on their heads. The unique markers, which are like fingerprints, then helped scientists to determine two of the whales had never been seen before.
“It certainly is very exciting and gives us hope that there are other animals out there that we don’t know about,” said Jessica Crance, a Seattle-based marine mammal scientist with National Oceanic and Atmospheric Administration Fisheries. “We were around the animals for several hours in each encounter.”
The animals are some of the most endangered in the North Pacific and their scarcity has helped to cloak their migration movements — and even their calving grounds — in mystery. They can reach 64 feet in length and 100 tons.
Scientists also were able to make acoustic recordings of two of the whales. Their vocalizing — unlike the more melodic sounds of humpbacks — sounds more like growls, and at times like the beating of a drum.
The North Pacific right whales have wide, flat backs, deeply notched flukes and are dark — almost black — in color.
They were once thought to number more than 26,000 but their numbers tumbled in the 19th century as whalers found them easy to target, and rich in oily blubber and baleen.
Even in the 20th century, after receiving international protection, the right whales continued to be the target of illegal whaling. Today, a population of several hundred remains in the western North Pacific off Asia, while the smaller population off Alaska is estimated to have fallen to about 30.
Scientists are unsure just why right whales have had such a tough time rebuilding their populations. One possibility is a scarcity of breeding females, which could be a legacy of the hunting days when right whale females with calves moved slower and may have been easier to target, according to Crance, who says that males are currently thought to outnumber females by a ratio of at least 2 to 1.
The sightings came on a marine mammal survey cruise that departed Aug. 1 from Kodiak, Alaska, with 10 NOAA Fisheries scientists, observers and crew.
The Gulf of Alaska is a migration route and important feeding ground for many other marine mammal species. The vessel made a series of zigzagged transects, or paths, off the gulf shelf and deeper waters known as the slope.
The survey, supported by NOAA Fisheries and the U.S. Navy, documented sightings of 667 marine mammals, including Dall’s and harbor porpoises, and whales including fin, humpback, sperm and orcas.
Some of the orcas are residents of the Gulf of Alaska that feed only on fish. Other whales are transients that eat marine mammals and squid.
On Aug. 21, observers peering through binoculars spotted the distinctive V-shaped blows from the first pair of right whales. They found them in an area 25 miles south of Kodiak Island called Barnabas Trough that is rich in krill, tiny crustaceans that are one of the whales’ favored foods.
Through the photographing of the whales’ head bumps, called callosities, scientists were able to conclude that one of the whales was the same one detected by a Canadian science team June 12 off Haida Gwaii, B.C. This bolstered the case for what could be an annual migration along the West Coast, according to Crance.
On Aug. 24 the scientists observed the other pair of right whales about 100 miles to the west.
Right whales do not typically move about as breeding pairs, and the sex of the four whales sighted in August could not be determined, according to Crance.
Another unknown is the life span of these whales. They are thought to live for more than a half century, maybe 70 years.