A humpback whale was caught on video doing something rarely seen or documented in the species: swimming in what amounts to a headstand, its head underwater and its tail catching the breeze like a sail.
The "sailor" in the footage is a mother humpback whale swimming with her calf, with her tail sticking up well out of the water.
According to scientists with the National Oceanic and Atmospheric Administration (NOAA), the behavior is commonly seen in southern right whales, but not so much in humpbacks.
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"We're not entirely sure why the whales do this," said Ed Lyman in a press release. Lyman is a resource protection specialist for the Hawaiian Islands Humpback Whale National Marine Sanctuary, the NOAA marine reserve where the behavior was recorded.
"We think this could be another way for them to rest, nurse, or just try to stay cool," Lyman said. "More observations will be needed to confirm this theory."
Other types of whale relaxation have been captured on video. Resting humpback whales were caught napping in this 2014 video, the animals drifting underwater head-first, although their tails are not protruding from the water. Sperm whales, too, have been recorded snoozing, as in this 2011 footage.
The new humpback video footage was shot off Maui in mid-February, considered a peak observation time for humpback whales at the sanctuary.