Sperm Whales Take 12-Minute, Vertical Cat Naps

by Owen James Burke


Sperm Whales off Pico Island, Azores, Portugal (Photograph: Magnus Lundgren)

Unlike humans, whales are “conscious breathers,” which means they have to be awake to breathe. It is for this reason that most whales sleep horizontally, so as to wake up every few moments, take a breath, and fall back asleep. Sperm whales (Physeter macrocephalus), however, slumber vertically.

No one really knows why sperm whales choose to sleep in this manner, but it’s an evolutionary trait that might happen to serve them well.

The position other whales assume in order to sleep is commonly referred to as “logging” because from a distance they appear to be logs floating on the surface. Sadly, this is often how whales meet their maker as they turn off half of their brains when they sleep, and ships often can’t see them, so it’s usually too late by the time they notice an approaching danger is near. (This is often the cause of the sinking of many small boats, too.)

Sleeping below the surface with only their heads up, sperm whales present that much less vulnerable surface area than the other species, and probability has it, it would seem, that they are that much less likely to be struck by maritime traffic.

Unique in many ways and growing to 60 feet in length, sperm whales are the largest predatory animal, the largest toothed animal and the deepest diving mammal on the planet. Unlike any other cetacean, rapid eye movement (REM), otherwise only associated with terrestrial animals, has also been recorded by scientists observing sperm whales. And being the deepest diving mammal, they can dive up to 3 kilometers, which, research suggests, also allots them a good deal of time to catch up on rest, of which they only collect about 2 hours on a daily basis.


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