Let sleeping dogs lie, they say, but what do you do for sleeping sperm whales? When photos of sperm whales standing in the ocean surfaced, people were understandably puzzled about what was happening.
In the photos, the whales are “standing” in pods of five or six. They float upright in the water, motionless, which was probably quite a sight for divers who have come across the pods. The whales are apparently sleeping, albeit in a stranger position than what we consider to be normal.
Studying the sleep behavior of these whales has revealed previously unknown information about how wild cetaceans sleep. Scientists have observed how cetaceans in captivity sleep by observing eye movements, but animals in the wild behave somewhat differently from those in captivity. Thus, whales in the wild might have different sleep behaviors than those in captivity. These differences, as well as the reasons why sperm whales sleep “standing” upright, are what researchers have been trying to make sense of.
About 10 years ago, something quite nerve-wracking happened to a group of researchers sailing off the northern coast of Chile. They were on their vessel, the engines turned off, studying the behavior of sperm whales in the area. The vessel accidentally drifted into the midst of a pod of whales floating upright in the water, their noses sticking out of the surface.
The researchers, understandably, were quite shaken. Not a single one of the whales reacted to the approaching vessel, though two were facing the boat. The researchers decided to simply try to quietly make their way past the pod with the engines still off. They figured that if they turned the engines back on, it might distress the whales.
However, their plan to quietly mosey on without disturbing the whales didn't work. The boat accidentally bumped into one of the whales as it drifted past the pod. The whales then dove timidly away from the boat.
Previous research has found that whales spend about 7% of the time inactive. Researchers had tracked the movements of 59 sperm whales, and they discovered that the whales stopped swimming for some time. When the researchers in Chile literally bumped into a pod of sleeping whales, it became clear what was happening when there were sperm whales standing upright in the water.
Since sperm whales sleep only 7% of the time, it's probably the least sleep-dependent animal in the world. It's possible that whales in the wild are capable of full sleep, while whales in captivity sleep with half their brains still active.
The problem with these findings, however, is that they're observational. This means that no one really knows for sure if the whales are indeed sleeping, and if they were, how deeply they're sleeping. Researchers would need to do brain scans to confirm to findings, but there's no technology that can make this possible yet.
If you go diving sometime in the future and encounter sperm whales standing upright in the water, it may be best to let them, well, stand.
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