The Deep Sea, Galapagos

The boat comes to a standstill, I look around, there’s no land in sight, only the great blue expanse stretching on and on into the horizon. Suddenly, an inhabitant of the ocean breaks out of its bounds as a striped dolphin leaps in a long arc, followed by another, and then another.

Unlike many of the other species in the Galapagos, striped dolphins are extremely widespread, found in the majority of the world's waters. They are also some of the most fantastic jumpers of all the dolphins, reaching heights of up to 20ft (5m), performing stunning acrobatics, pursuing each other and twirling midair like a gymnast’s ribbon. This is often accompanied by a behaviour dubbed ‘roto-tailing’, which is exactly what it sounds like: as the dolphin leaps out of the water, it spins its tail rapidly, like a corkscrew. It’s unclear why they do this; it might be to shed parasites, it might be to communicate with the rest of the pod, or it might be simply for fun.

As the dolphins recede into the distance, we don scuba gear and descend. Underwater, I hear a sonorous, rumbling call. One of my companions grips my shoulder, and she silently, frantically points behind me. I turn, and then I see them, a pod of some of the largest animals in the world - sperm whales.

Sperm whales (Physeter macrocephalus) are superlative in many ways. They have the largest brains in the animal kingdom, and they are the largest of the toothed whales (one of the two main groups of whales), with male ‘bulls’ reaching up to 52ft (16m) in length and weighing around 45 tonnes. They are also some of the deepest diving animals in the world, having a range from the surface of the ocean to the pitch-black depths of over 7,380ft (2,250m) below sea level, making them the third deepest diving mammal. Sperm whales make these forays into the inky depths to hunt giant squid, their arch-enemy, a mysterious creature never seen alive by humans.

Sperm whales are highly social animals. Their far-reaching voice is made possible by a huge organ found on the top of its head, which contains the strange white substance called spermaceti from which the whale is named. This organ allows it to produce powerful, high-pitched clicking sounds, which it uses both to communicate with other whales and to echolocate.

Whales desperately need the help and protection of international conservationist bodies. Sperm whale spermaceti was once one of the most sought-after commodities in the world, and if you’ve ever read Moby Dick you’ll know the great variety of uses 19th-century industry had for this white, waxy substance - from candles to industrial lubricant to cosmetics. Victorian whalers had no idea that human actions could threaten the existence of entire species, and when whale numbers began to dwindle, they assumed they had just got better at avoiding their vessels. So, instead of leaving the declining populations alone to allow them to recover, they intensified whaling. Unfortunately, by the time the world got together to ban the sale of spermaceti, whale populations had been decimated.

Today, whaling operations continue to defy international bans on the practice, catching whales for their blubber and meat, and the massive fleets of commercial fishing boats routinely kill whales in bycatch. The great increase in global shipping since the 1950s has also increased ocean noise pollution, disrupting the whales’ echolocation and communication, making it difficult for them to breed and hunt.

Like most wild animals across the world, human society, the demands of our economy and the changing climate are posing challenges to whale populations that will be hard for them to meet. We can only hope that we as a species wake up to their plight and begin to rigorously police irresponsible shipping, whaling and the industrial vandalism of our seas.