For years, scientists believed that whales slept with half of their brains still functioning allowing them to stay alert in the case of predators. However, this all changed when a group of researchers stumbled upon an unusual and eerie group of sleeping sperm whales in the Caribbean in 2008.
The whales were sleeping, but nothing like had ever before been observed in captivity. The whales were sleeping “standing up” in an odd vertical position clustered in groups of 5 or so. But this wasn’t the weirdest thing about the cluster of creatures, however, the most unusual aspect was how unaware they were of the researchers’ presence. They continued to float motionless, seemingly in a state of paralysis.
The boat of researchers tried to slowly move out of the way of the whales without disturbing them, for they feared that if awoken, they might try to defend themselves and possibly sink the boat. Not all went according to plant. The boat slowly drifted into the whales and awoke one of the sleeping giants. Luckily for the researchers, after the whole pod was awoken, they all swam away.
This encounter rewrote how we understand whale’s sleep in the wild.
Image Source: Franco Banfi/Solent News & Photo Agency
The general scientific consensus around whale biology was that they slept somewhat aware and somewhat motionless, but nothing like the researchers found. When Patrick Miller, a researcher at the University of St. Andrews, first saw the footage from the chance encounter, some previous data he had collected began to make sense.
He and a team of other researchers had attached suction cup data loggers to a group of 59 sperm whales to monitor their behavior. To their surprise, they found that the whales had spent 7% of their time drifting motionless in the water. Connecting this with the newfound footage, Miller was able to connect this odd vertical sleeping to the period of motionless drifting he observed in his data.
Researchers now understand that sperm whales seem to sleep fully vertical while drifting near the surface or at about 10 meters below the water. They take brief naps throughout the day lasting for about 10 to 15 minutes each during which they do not breathe or move.
The most shocking thing about this finding is just how little researchers have determined that these whales sleep. At just 7% of inactivity, sperm whales may be the least sleep-dependent animal on earth. For comparison, belugas and grey whales sleep on average 32% and 41% of their time respectively.
If humans were to sleep like sperm whales do, it would be like taking 6 15 minute naps throughout our entire day. And you think you’re sleep deprived now.
At the time of this discovery, sperm whales beat out the previous sleepless record-holder, giraffes, who only sleep about 8% of their days away in small brief naps.
Sperm whales have figured out how to survive off of quick power naps and all by sleeping in perhaps one of the creepiest ways of any animal in the ocean.