Beluga body scrub session filmed
A film crew has captured the remarkable scene of hundreds of beluga whales indulging in a mass "body scrub" to slough off their skin.
The mammals come en masse into shallow Arctic estuaries where scrubbing their bodies on the stony seabed helps them moult their skin.
"They definitely seem to enjoy it," recalled director Elizabeth White.
Filming for the BBC documentary Frozen Planet, she and her team captured the behaviour up close and from the air.
Ms White was in charge of the ground-based shoot on Somerset Island in the Canadian Arctic, for which she stood "marooned" on a tower in the middle of the estuary.
This was the best way to get close to the whales, as the tower would be surrounded by water when the tide came in.
"This tower [was used] by the scientists who study the whales here," Ms White explained to BBC Nature.
"The belugas would swim all the way up to it; they'd even rub themselves against it, which was a bit unnerving."
From this vantage point Ms White and the team captured super slow motion shots of the whales splashing and apparently playing in the water.
They also fixed underwater cameras and microphones to the tower's scaffold, capturing some of the squeaks and cries that have earned belugas the nickname, "canaries of the sea".
The sounds the whales made, Ms White said, was lovely.Piggybacking babies
Scientists think that the warm, fresh water of the estuary softens the animals' skin.
"You see quite big chunks of blubber around that have just been sloughed off," said Ms White.
To capture aerial shots of hundreds of the white whales in the turquoise water, director Vanessa Berlowitz and cameraman Michael Kelem boarded a helicopter.
"Above marine mammals you can't fly below 300m (1,000ft)," explained Ms White. "But even from this height, [they] managed to get footage of the babies riding on the mothers' back - something that's never been filmed before."
The juvenile whales ride on their mothers' backs occasionally in order to save energy.Stranded youngster
During their time filming the moult, the crew witnessed one of the hazards the whales encounter when swimming in such shallow water.
"We were there for the lowest tide and one of the youngsters got stranded when we were there," said Ms White.
"The poor little thing got stuck on a sandbank."
Fortunately, she said, this happened late in the day. And with strong sunlight shining on it, and no polar bears around, the young whale was able to escape as soon as the tide came in.