When one of the largest animals in the ocean takes sleep, it can look pretty weird.Photos have surfaced online showing sperm whales gathered together, seemingly motionless and arranged vertically in the water.
The whales, which are roughly the size of school buses, almost always appear to be “standing” and clustered in pods of five or six.
French photographer and filmmaker Stephane Granzotto captured this behaviour while diving in the Mediterranean, where he was documenting sperm whales for his photo book on the creatures titled Cachalots.
A study published in 2008 in the journal Current Biology was the first to conclusively document the whale’s vertical sleeping position.
Sleep had previously been observed in some captive cetaceans by monitoring eye movements, but how whales in the wild rested was significantly less understood.
Using data-collecting tags suction cupped to 59 sperm whales, researchers from the University of St. Andrews and the University of Tokyo measured the animals’ periods of inactivity.
The whales were found to spend seven percent of their day in these vertical sleeping positions near the surface of the water, where they napped from 10 to 15 minutes.
Researchers suggested at the time that they might be one of the world’s least sleep-dependent animals. Whales in captivity have been found to use only half their brain while sleeping, a behaviour scientists think could help them avoid predators, maintain social contact, control breathing, or continue swimming.
The study also noted observations from a video shot in northern Chile that showed whales did not wake from their surface naps until a ship approaching with its engines off unintentionally bumped into them. This suggests whales in the wild might enter a full sleep, unlike their captive counterparts.
Scientists already knew that sperm whales in the Pacific Ocean have vocal clans.
Richard Connor, a dolphin and whale expert at the University of Massachusetts, Dartmouth, believes that these behavioural and vocal differences started as random variations that eventually developed into part of a clan’s culture.
“It’s probable that these groups travel in different areas and they track habitats, which includes … prey ” said Sarah Mesnick, an expert on sperm whale social structure at the Southwest Fisheries Science Center in California.
“They know those areas. They transmit that information socially through the groups.”
The ongoing research into sperm whale culture suggests there’s more at stake for the species, which still faces threats due to climate change and buildup of toxic metals, Gero adds.
That’s because if one sperm whale clan goes extinct, that’s it: All that tradition and ancient wisdom specific to their niche are lost.