Why do hammerhead sharks hold their breath?

These sharks got their name because of the unusual shape of their head

Keeping warm when you are out and about in cold weather is simple - trap in warmth by wearing layers like coats, gloves and hats.

But what about in the animal kingdom where bobble hats are hard to come by?

Well, scientists have discovered that hammerhead sharks adopt a very clever technique for maintaining their body temperature when hunting for food in very cold waters.

They hold their breath!

Why might that help? It's all to do with their gills, where a lot of their body heat escapes.

The gills of a hammerhead shark can be seen here. This particular picture was taken of a shark in an aquarium

In the deepest parts of the ocean, the water temperature drops considerably. Some areas, it is as cold as five degrees Celsius, which can be dangerous for cold-blooded creatures like sharks.

If their bodies drop in temperature too much, their eyesight and brain function can be impaired. Their muscles can also stop working, meaning they are no longer to keep swimming, which can be fatal.

But researchers studying scalloped hammerhead sharks have observed them travelling down to waters over 20 degrees colder than they are used to closer to the surface.

How did they track hammerhead's movements?

The team managed to attach specially designed sensors to three of the sea creatures off the coast of Hawaii.

We don't envy the person who had to attach the sensor to one of these guys

The sensors, which were around the size of a can of fizzy pop, recorded their location, the speed of tail motion, and body orientation - whether the shark was diving down or swimming up to the surface.

They also observed the water temperature and the sharks' body temperatures and noticed that the hammerheads managed to keep their body temperature the same even when diving to extremely cold depths of the ocean.

They believe the sharks do this by closing their mouth and gills when swimming at these depths. They then hunt for dinner for as much as 5-7 minutes and then swim back up to the warmer waters again.

They scientists concluded that the sharks closed their mouths and gills in order to trap in warmth and not allow their body temperature to escape into the colder water around them.

The study makes the scalloped hammerhead shark the first deep-diving fish known to hold its breath, Mark Royer says, who is the marine biologist behind the study.

It's "astounding and a completely unexpected surprise", he added, and remarking that the meal at the bottom must be pretty special to put themselves in that kind of risky situation.

Amazing what some creatures do for a tasty snack eh?!