I think whales are some of the most impressive and majestic animals on the planet. There’s just something about their size, their power, and their grace that never fails to be awe-inspiring. Whales are also extremely fascinating creatures, and today’s animal is one of the stranger ones.

Sperm whales are the largest toothed whales in the world, and are also the largest toothed predators on the planet. They are found in an extremely broad range of ocean, living in any waters that are ice-free and over 1,000 m deep. Where they are seen near the shore, it is where the continental shelf drops off to deep waters quite quickly.

The distribution of sperm whale sightings worldwide. Image by Kurzon, CC BY-SA 3.0, via Wikimedia Commons

Sperm whales are very large, with males reaching over 20 m in length, and females growing to 12 m in length. Sperm whales have grey, wrinkly skin that lightens with age. Sperm whales don’t have dorsal fins; instead they have a bunch of ridges on their backs. Their tail flukes are massive and quite thick; proportionally they are the largest of any whale. They also have the largest brain of any known animal, which weighs in at around 7.8 kg. That’s pretty big for a brain!

Of course, the thing sperm whales are most known for are their giant heads, which make up a third of the whales’ total body length. This massive noggin houses the whales’ spermaceti organ, which is filled with fats and waxes. The head of a mature male sperm whale can contain up to almost 2,000 litres of spermaceti, and is why these whales where so valued by whalers.

So what is the purpose of this massive organ? That has been the subject of some debate, with people suggesting the spermaceti organ is used for buoyancy, or as a battering ram in fights between males. Both these theories are not well supported, and it is now known that the spermaceti organ is used to generate strong sounds, for use as echolocation and communication.

Sperm whales are known for their diet of mostly squid, including giant and colossal squid. They are deep dive hunters, searching for prey at depths of 300 to 800 m, and sometimes much greater depths. They can dive for over an hour, and have a number of unique adaptations to help them deal with these deep water dives.

They have extra flexible ribs to help cope with pressure changes during dives, as well as reduce nitrogen intake and conserve oxygen. The circulatory system of sperm whales is also adapted to deep-sea dives. The aorta expands as it leaves the heart, to ensure blood pressure and flow stays the same, even as outside pressures change and the heart rate slows. Sperm whales have high levels of myoglobin in their muscles to store oxygen, and have very high levels of red blood cells in their blood to carry as much oxygen as possible. When oxygen is running low during dives, the whale can direct blood to the brain to ensure it stays well oxygenated.

A sperm whale and calf. Mothers care for their calves for over a decade. Image by Gabriel Barathieu, CC BY-SA 2.0, via Wikimedia Commons

From the eighteenth to twentieth centuries, sperm whales were hunted for the spermaceti in their heads and sperm oil found in their blubber. This oil was used in candles, soaps, as lubricants, and in many other important products. This hunting of course took a considerable toll on sperm whale populations, but there are still thought to be hundreds of thousands of sperm whales worldwide, and a ban on commercial whaling mean the population now has time to recover. So hopefully these great predators can recover and continue to scour the ocean depths for tasty squid.