The lives of whales are truly fascinating. Here are five facts you probably didn't know!

Whales sleep with one half of their brain awake

Humans find it very easy to have prolonged periods of unconscious sleep. When we drift off at night, we’re not aware of our surroundings for long periods of time.

However, whales sleep in a very different way because their breathing is not automatic. They have to actively and consciously decide when to breathe, in order to stay alive.

To do this, whales only allow one half of their brains to sleep at a time. The other half stays alert so they that continue to breathe (and also are conscious of potential dangers in their surroundings). This is called unihemispheric slow-wave sleep.

Scientists have found that whales (and dolphins) only close one eye when they sleep and they alternate which half of the brain sleeps at a time. When sleeping, whales will often rest motionless at the surface, breathing regularly, or they may swim very slowly and steadily just under the water’s surface.

A team of scientists observed sperm whales ‘drift diving’ close to the surface water in 2008. In other words, they were taking a nap together as a group. The researchers onboard found that the sperm whales spent just 7% of their day napping, for bursts of around 10 to 15 minutes each time.

You can tell how old a whale is from its earwax

Accessing info to figure out the age of a whale or dolphin has been difficult in the past for researchers. But there is one surprising way that we can learn about whales – their earwax!

A dense wax plug builds up in a whale’s ear canal (this is particularly the case for some species of baleen whales and in sperm whales) and grows consistently throughout its lifetime. Think of it a bit like tree rings that keep adding over the years.

These ear plugs allow researchers to age a whale and also to see what sort of pollutants and stresses they were exposed to throughout their lives.

When it comes to how old a whale is, the trick is to look out for alternating light and dark layers within the ear plug material. Light layers are associated with periods of feeding and dark ones are connected with periods of migration or when the whale wasn’t feeding.

Usually, a year in the life of a whale will be made up of one light and one dark layer so that’s how researchers can figure out how many years the whales were alive.

Earplugs are gathered from whales that have died from ship strikes, strandings or entanglement in fishing gear.

The technology with earplug analysis has advanced greatly in recent years though it still involves painstaking work. A new technique from Baylor University was used on a single earplug obtained from a male blue whale that died from a ship strike. Researchers could quantify lifetime levels of two hormones and 42 contaminants from this one earplug – some very valuable information.

You can find out more about what was discovered about this blue whale’s life in this 2013 Smithsonian Magazine article.

The team at Baylor University have gone on to discover lots more from ear plug data from whales. A 2018 paper looked at stress hormone levels in ear wax, showing how hunting and climate change have impacted whales. The team used samples from three types of baleen whales, from both Pacific and Atlantic Oceans.

Humpback whale breaching

We’re still figuring out why some whales breach

Breaching is when a whale leaps out of the water, bringing almost all of its entire body up in the air for a large jump. It’s an amazing sight to behold – not one you would easily forget!

But exactly why whales breach is still not clear to us. There are a few different possibilities – including courting other whales, shaking parasites off their skin or simply to make a sound by splashing back in the water (they may be communicating to other whales, including signalling a warning).

Baby whales that have lost their mothers have been observed breaching repeatedly – probably to send both a visual and audio signal to its mother.

The other strong possibility is that the whale is playing. There may not be any other reason apart from the explanation that jumping out of the water and splashing back down is fun!

Whales can live for more than 200 years

Many species of whales live for between 70 and 100 years. But we know that some whales live a lot longer.

The oldest known whale is a bowhead whale – at a whopping 211 years old. The whale had been hunted for food by native people in the Arctic and subsequent testing using amino acids from the eye concluded its age was well over the two century mark.

Previously, three bowhead whales killed in northern Alaska were estimated to be between 135 and 172 years old. In this same area of Alaska, hunters have reported finding ivory and stone harpoon points (from previous attacks) in the blubber of freshly killed bowhead whales. These implements hadn’t been used since the 1880s.

Orca sometimes beach themselves to hunt

When a whale beaches itself, it’s usually because it is ill, disorientated, injured or dying. It’s not something a healthy whale usually does as it’s a risky move if it gets stuck and can’t get back to the safety of water.

But the orca whale is willing to take the risk on occasion. In the Peninsula Valdés in Argentina, a small group of orca hurl themselves out of the ocean to catch and kill beach-dwelling sea lion pups. The activity needs to be very carefully timed with a wave coming into the beach and it’s all about getting in the right position at the right speed.

It’s a surprise move, to take the sea lions unaware. The orca aims to successfully catch its prey and then catch the next wave off the beach. A steep and pebbled beach helps them to roll back to the water.

Tourists can spot this occurring from a look out point at Punta Norte on the Peninsula Valdés though it’s important to point out that there’s a very short window to spot it each year.

The peak season for orcas to hunt this way is 10 to 15 days, usually in March or April. This is when baby sea lions are learning to swim. The attack time is only two hours before until two hours after high tide.

This feeding behaviour was first documented in 1976 and scientists believe it to be a learned behaviour rather than instinctive.

Check out this great video from Associated Press showing the orcas in action.