Named for the stark white fur that rings their necks and flippers, Arctic ribbon seals hardly look real. Unlike many of their southern kin, these fancy pinnipeds avoid dry land and are rarely seen by humans. And yet, curiously, one of them just showed up in Washington state, the second sighting in five years.
Biologists with NOAA Fisheries Service spotted the animal early last week when it hauled out on Long Beach Peninsula, an arm of land along Washington's Pacific coast. Ribbon seals (Histriophoca fasciata) typically inhabit icy waters from the Bering Sea north to the Arctic's Chukchi and eastern Siberian seas – so what was this animal doing thousands of miles from home?
Some have speculated that the seal could be the same individual who made an appearance in both Washington and Canada back in 2012, a male known as "B310" (a sub-adult at the time):
Because every ribbon seal possesses the same banded colouration, it's tricky to get an ID match from just one photograph. The exact size and position of the markings does vary in each seal, but a detailed analysis will be needed to confirm B310's "second coming". We do know with certainty that both sightings were of a male seal, since females sport a brown-and-white version of the banded coat:
Judging by the animal's size and clarity of the bands, we can also say that this seal was at least nearing adulthood. That's because baby ribbon seals look almost nothing like their parents.
It's thought that high-contrast colouration helps to break up a ribbon seal's shape against the bulbous icebergs that form in Arctic waters. But for the pups, who spend their first months above the ice, a nondescript coat is the key to good camouflage. The fluffy, white youngsters (which have been rather perfectly described as "soft, velvety clouds of unbridled joy and obesity") don't sport those signature markings until they're about five weeks old.
According to the NOAA Fisheries team, the ribbon seal on Long Beach Peninsula appeared healthy and returned to the water shortly after the photo was taken. Anyone who encounters the animal in the coming weeks is being encouraged to report the sighting.
Ribbon seals are relatively unwary when hauled out, and that certainly contributed to their decline in the 1960s, when unregulated hunting for their fur, blubber and oil caused the population to decline by some 30,000 animals in the Bering Sea alone.
Increased protections have seen an end to wide-scale hunting over the years, and it's estimated that between 200,000 and 250,000 ribbon seals now cruise the world's oceans. But these numbers, cautions the NOAA Marine Mammal Laboratory (MML), come from surveys done in the 1970s.
The MML team is currently doing research to get a better population estimate, and to learn more about how the seals use their precious sea-ice habitat. Unfortunately, some of their findings have been worrying.
Of the ten ribbon seals sampled and tagged during a research cruise earlier this year, seven of the animals showed patchy baldness, with one male affected by lesions and pustules. The symptoms are similar to those observed in ringed seals a few years ago, when a mysterious outbreak killed scores of animals, leaving experts puzzled.
That spate of seal deaths was labelled an "unusual mortality event", and although a few cases have been reported more recently, investigations are still underway to determine the cause of the disease. The good news is that the baldness does not seem to be hindering the ribbon seals severely. It's possible that they were merely infected in the initial outbreak and are still recovering.
NOAA Fisheries researchers have been tracking ribbon seals since 2005, using satellite tags that make your average pinniped look a bit like robo-seal. The goal is to learn more about their seasonal migrations, foraging behaviour and haul-out locations. If only Washington's recent visitor had been wearing one, we might know a bit more about his unusual stopover.
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Top header image: NOAA
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