One of the most fascinating animals on earth also happens to be the largest toothed predator on earth. The Sperm Whale (Physeter macrocephalus) can grow up to lengths of 16 meters in males and roughly 12 meters in females. These whales are found just about everywhere across our oceans: other than the artic areas. The reason for such a vast distribution of this species is the desire for feeding and breeding. These whales may travel as far as 2000 meters down into the ocean in order to find sufficient food and breeding grounds. Despite their large size in comparison to other animals on the surface, this colossal animal decides to dive to these great depths in order to prey on organisms such as the Giant Squid (Architeuthis dux) which helps in order to maintain the sperm whales regular diet of roughly 1 ton of prey per day.

Diving range of several air-breathing marine mammals including sperm whales. Credit: Pierangelo Pirak / BBC Earth

Battles of Giant proportions

Due to the huge mass of the sperm whale, they are required to take a large input of food every single day. As they are able to dive to such great depths, they are able to encounter larger species which are not found on the surface, such as the Giant Squid. Many sperm whales are seen with scars on their heads and bodies which are taken from the Giant Squid in a struggle for the Whale to catch its prey. The Squid is able to use its sharp teeth on the end of its suckers in order to defend itself however; often the whale is too much of a match for the Squid and the Whale will catch its prey.

Video: A Sperm whale encountering and battling with a Giant Squid.

Conditions down below the surface

There is an enormous difference between the conditions of the ocean at the surface compared to the conditions of the ocean at 2000 meters deep. The first and most obvious change between the two is the pressure of the ocean waters at such a depth. Every 10 meters deep in the water the pressure increases by an atmosphere. Humans notice this change in pressure after only a few feet, when 2000 meters down there would be 200 atmospheres of pressure on these whales which if not adapted greatly would crush the whale under its own weight. However deep diving whales such as the sperm whales are much more flexible than humans. The key adaptation which these whales have for this is their rib cages, which are bound by loose cartilage which means as the pressure of the deep sea increases the rib cage is able to bend and even collapse in order to avoid snapping any of the bones at these pressures. Allowing the sperm whale to experience this extreme environment as frequently as it would like to in order to feed and then return to the surface unharmed to take a breath.

A Sperm whale surfacing for oxygen. By Vilmos Vincze

Being mammals these whales require oxygen to breathe and live, thus on these long deep dives they are required to store large amounts of oxygen. This is achieved through haemoglobin transporting oxygen around the body similar to how humans transport oxygen using the haemoglobin in the blood. However these whales are adapted to be able to sustain large amounts of oxygen storage through the red blood cells due to the fact that in sperm whales, 60% of their red blood cells is haemoglobin therefore have larger amounts to transport the grater amount of oxygen required to dive down for these long periods of time, up to 90 minutes.

Hunting in the dark deep

When 2000 meters below the waters surface, there will be zero visibility from natural night sources from about the water, which begs the question, how can these Sperm whales be such efficient hunters while essentially hunting blind? The sunlight can only clearly penetrate the oceans waters up to roughly 200 meters, however the visibility is extremely minimal at around 1000 meters depth, known as the midnight zone. The Sperm whale is also greatly adapted for this lack of visibility through its ‘Echolocation‘ they use this through making clicking noises which are created in the head of the whale which are amplified using the spermaceti organ. These clicks will then go out through the phonic lips of the whale out into the surroundings bouncing off terrain and prey around this area. These sound waves will rebound back to the whales head and are received in the lower jaw in an area filled with oils, allowing the Whale to visualise its surroundings in order to hunt in areas where no light is present, allowing the whale to be a dominate predator in the harsh environment of the deep ocean.

Diagram of how echolocation is produced and recieved by Sperm Whales. Credits: Museum of New Zealand Te Papa Tongarewa, 2007
Diagram of how echolocation is produced and recieved by Sperm Whales. Credits: Museum of New Zealand Te Papa Tongarewa, 2007

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