Whales, gliding beneath the dark surface of the ocean, have millions of years’ worth of stories to tell.
Writer: Sijia Yu
Editor: Nirvan Marathe
Artist: Amaranta Chavez
70% of Earth is made up of ocean–this is an unfathomable concept with many mysteries still to be uncovered. Can you imagine that there are ocean-dwelling creatures a hundred times bigger than elephants? Taking its place among some of the biggest animals to ever have existed on Earth, the whale has its own fascinating evolutionary story.
Scientists have proven that hippopotami are the closest relatives of whales. Both whales and hippopotami evolved from four-legged, even-toed, hoofed artiodactyl ancestors that lived on land around 50 million years ago. However, around 8 million years ago, the ancestors of whales moved to the ocean and evolved into the marine animals we see today. In early times, they lived in the near-shore environment, but as they spent more and more time in the water, their feet were slowly replaced by flippers and their tails became stronger, enabling them to swim. What’s more, their fur turned into thick blubber in order to overcome the massive heat loss in water, which could explain how whales can grow so big. One of the earliest marine mammals is the Basilosaurus, a prehistoric archaeocete whale that existed around around 41 to 34 million years ago. This presents a connection between the whale and its ancestor, although compared to current whales, Basilosaurus had sharp teeth to chew food rather than swallowing it whole like the blue whale.Understanding the evolution of whales is a complex challenge which still poses several questions for scientists to answer.
The Sperm Whale
The term “sperm whale” is derived from the semi-liquid, waxy substance found within the whale’s head. These whales have a unique appearance, flaunting a large head which contains the largest brain in the world; the mass of an adult sperm whale’s brain is 7.8 kg. However, almost counterintuitively, the intelligence of sperm whales is generally lower than that of other whales. This colossal brain plays an important role in producing sound. Sound is generated by air passing through a pair of phonic lips at the front end of the nose. Researchers found that sperm whales can emit sound at 230 decibels, which is the loudest sound produced by any animal in the world. Sperm whales rely on sounds to communicate with other whales and echolocate food.
Sperm whales mainly feed on giant squid, which they usually dive 1 to 2 kilometres underwater to hunt for, using strong sounds to identify their location before stunning them. If you see white scarring on a sperm whale, it usually means they have experienced an intense fight with a giant squid. Squid beaks are hard to fully digest, so they accumulate in the intestine as the sperm whale digests food, stimulating the intestine to generate a waxy substance called ambergris. Ambergris is usually excreted as faeces or vomit from the mouth of the whale, but is in fact a rare and valuable material. When it is dried, it can serve to stabilise fragrance so it is often used in the perfume industry–sometimes, at a cost up to two times higher than that of gold.
How does a sperm whale reproduce? Females usually become fertile from 9 years old, with their pregnancy period lasting between 14-16 months, culminating in the birth of a lone calf. They give birth once every 4-20 years. The birth of the calf is a social event in the sperm whale society due to the vulnerability of the newborn to predation. As a result, other adults will protect the calf by encircling it, providing a shield from predators, such as killer whales. Various other examples of social behaviour provide evidence to show that sperm whales are social animals, often living and travelling together in groups of 6-9.
Around the 19th century, whales experienced a massive culling–known as whaling–with sperm whales being one of the main targets for their meat and blubber. Sperm whale was one of the main targets. The hunters usually used grenade harpoons to hunt whales. The development of motorised ships boosted the whaling industry, bringing huge profits to merchants and hunters alike. However, as an increasing number of whale species are being hunted and even being driven to extinction, various nations have finally launched the much overdue international convention for the regulation of whaling, which determines catch limits for merchant whalers to protect whale populations. Luckily, in the face of international action, whale populations are generally beginning to recover in numbers, however there is still a long way to go before numbers are fully restored.
Whales, one of the most impressive ocean-dwellers on Earth, have millions of years of untold history. Luckily, by exploring the extensive history of these creatures, researchers are determining and promoting limits on whaling and the sale of whale-derived products, so whale populations may one day return to normal levels. Hopefully, in light of recent international action, progress will continue trending upwards.