When aboard one of our tours, we do our very best to provide you with plenty interesting information about the animals you are viewing, and help you interpret their behaviour. However, there are some questions that very few people ask, that we think offer fascinating insights into the whale brain, well worth sharing with you.
One of these questions is how do whales sleep? Here’s the answer. Orca and Humpback Whales are known as ‘conscious breathers’, this means they have the ability to remain alert and ensure their blowhole is at the surface of the water in order to take a breath. This voluntary system means they must keep at least part of their brain awake to trigger each breath. This is very different to humans, who have involuntary respiratory systems. Our involuntary respiratory system allows us to breathe even while our conscious mind is asleep. If Orca were to fall asleep in the same way we do, they would be at risk of drowning.
Some whales and dolphins get around this by taking ‘naps’, where they are actually only half asleep. During these naps, the whale shuts down half of its brain, along with the opposite eye, while the residual half of its brain remains alert. The awake half reminds the whale to breathe when it reaches the surface, as it continues to swim, generally side by side with other pod members. This attentiveness of half of the brain also allows them to keep track of other pod members, as well as watch for predators and obstacles. After a maximum of two hours, the whale reverses this process, resting the active side of its brain and waking up the sleeping half. This process is sometimes referred to as ‘cat-napping’.
Other larger Cetaceans, such as Sperm Whales are able to hold their breath long enough to remain stationary underwater while sleeping. These animals are equipped with a much larger lung system than Orca, which allows them to exchange more air with each breath, and have a higher tolerance for carbon dioxide.
So now we know why whales sleep, let’s talk a little more about their brains. Orca have a particularly fascinating brain structure, so we’ll focus on them for now. To start, Orca have the second largest brain to body-size ratio in the animal kingdom. Much larger than a human brain, an Orca’s brain can weigh as much as 15 pounds (6.8kgs).
In the brain of an Orca, the limbic system (the part of the brain that processes emotion in mammals) is much more elaborate and developed than in the human brain. This area – known as the paralimbic region – has an extra lobe of tissue that sit next to the limbic system, which is not found in humans. Scientists believe this suggests the possibility that this part of their brain is evolved not only for processing emotion, but also for cognitive thinking.
The complexity of the paralimbic system in Orca suggests that they are doing something very complex while processing emotion – on a surface level this can be observed by the deep social cohesion within family pods. Some scientists believe that Orca have more than just a sense of self as an individual, but also as a social group. The idea is that when you look at how they communicate with one another, how they move amongst each other and how they respond when an individual becomes injured or stranded, they demonstrate a highly elaborate emotional depth unmatched in other mammals, including humans.
This is blog only skims the surface of the complexities of a whale’s mind, and anatomy – a fascinating topic that we hope share further with in future blogs. Until then we hope you enjoyed these fascinating insights into the whale brain!