Baleen Whales: Giants of the Ocean

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It’s World Whale Day this coming Sunday, a day to celebrate whales and draw attention to the numerous threats they face. The first Whale Day was in 1980 in Maui, Hawaii. It was set up to highlight the threats faced by humpback whales visiting the island group. Humpbacks are one of 14 species belonging to the suborder Mysticeti, the baleen whales. These huge animals include the largest that has ever lived, the blue whale. They also include the longest-living mammal, the bowhead whale, thought to be able to live to over 200 years old. Let’s meet these giants of the ocean.

Humpback whales have distinctive dorsal fins

How the Whale Became

Millions of years after life first emerged from the water to live on land, early whales went back into the sea. Our modern whales are descended from the same terrestrial four-legged hoofed mammals that gave rise to hippos, giraffes and deer. In fact, hippos are whales’ closest living relatives. Palaeontologists believe that around 50 million years ago, whales’ ancestors lived by the water’s edge and began to spend more time in the water itself. Those with features better suited to this semi-aquatic lifestyle gradually evolved into fully aquatic animals that only came to the surface to breathe. The earliest of these fully aquatic individuals still had tiny back legs, although their forelimbs had become flippers. All whales actually still have pelvic bones. These may not be as much of a useless remnant, or vestigial, feature as once thought, though. To help them breathe without leaving the water, their nostrils migrated to the top of the head.

Approximately 34 million years ago, the ancestors of baleen whales split off from their toothed cousins, the Odontoceti. Early whales swam in warm, shallow seas. But at about this time, changes in the Earth’s geography due to India’s ongoing collision with Asia produced colder, deeper waters in some regions. This resulted in a huge increase in the variety and sheer biomass of tiny marine plants called diatoms. This could support more of the creatures that fed on them, including protein-rich plankton. Baleen whales evolved to take advantage of this newly plentiful food source. They eventually developed large plates fringed with bristles made of keratin to help them filter out the tiny animals from a mouth full of water. Toothed whales, including those that became sperm whales, orcas and dolphins, continued to feed on larger prey such as squid, fish or other mammals.

Humpback feeding — This humpback whale’s baleen is just visible as a pale fringe attached to the top of its mouth

Growing Bigger

In a further development, around 10 million years ago, some baleen whales began using a technique called lunge feeding. By surging up from below swarms of krill, plankton and small fish, lunge feeders can catch huge numbers in their gaping mouths. The accompanying water is pushed out through the baleen which acts as a sieve to trap the target food. This technique increased the amount of food the whales could catch. This in turn meant those with bigger mouths did better and lunge feeding whales got ever larger. They also developed large, pleated throats that could expand to hold even greater amounts of water. Today, this group of baleen whales, including the blue, fin, minke and humpback whales, are called rorquals. Non-rorquals include the bowhead, grey and southern and northern right whales, still not small animals by any stretch.

Blue whales are the largest animals that have ever lived

This isn’t the most dramatic of lunges, but illustrates how whales scoop up huge mouthfuls of water to feed

Baleen whales’ large size allows them to travel vast distances. Blue whales in particular have to be able to travel a long way because their diet is so specialised; they only eat krill. Travelling the oceans looking for large swarms of krill is partly what has made the blue whale the biggest animal ever to have lived. Their great size gives them the energy to do this. Baleen whales also travel the seas in order to reproduce. For example, grey whales make one of the longest annual migrations of any mammal, up to 12,000 miles in total. This species spends the summer feeding in nutrient-rich Arctic waters. In the autumn they begin to travel south to their breeding grounds in Baja California. Here pregnant females give birth in the safe, sheltered lagoons. Those not giving birth will mate with the males who have also travelled south. The return trip north begins in early spring.

Grey whales migrate up to 12,000 miles annually

Songs of the Sea

Unlike the Odontoceti, baleen whales don’t use echolocation to find food and ‘see’ under water. However, they do make extensive use of sound to communicate with each other. In 1967, biologist Roger Payne began listening to the array of clicks, moans, whistles and sighs that male humpback whales make during the breeding season. His research showed that these weren’t just random sounds. The whales repeated phrases and whole groups of males would often produce the same sounds. They could only be described as songs. Remarkably, the songs also vary slightly each year as the animals learn new phrases from each other. They also differ between populations. In 1970, Payne released a record, Songs of the Humpback Whale, which became a huge bestseller. By helping humans relate to the humpbacks, it was also profoundly influential in kickstarting the movement to end whaling.

Humpback whales — Although other baleen whales ‘sing’, humpback songs are the most complex

Some blue and fin whales also sing, as well as minke whales, although the sounds of blue and fin whales are at too low a frequency for humans to hear without being speeded up. Because water is denser than air, sound can travel much more efficiently though it as well as much further. Whales also make use of a particular property of the ocean. At certain depths, distortion is drastically reduced, and sound can travel faster and further again. By vocalising in this zone, fin and blue whales’ calls can travel up to 13,000 miles. As an interesting aside, blue and fin whales occasionally hybridise. Some biologists believe this could explain the unusual, higher frequency call patterns recorded from an individual dubbed the loneliest whale in the world.

The Bloodiest Industry

Humans have caught whales for centuries. Industrial levels of whaling with explosive harpoons, though, began in the mid-1800s and thousands of whales were slaughtered each year by the turn of the 20^th century. Factory ships could process huge numbers of animals at sea for their meat and oil. Whale oil was used in a large range of products including lighting, machine lubrication, varnish and even margarine. The market for oil collapsed due to the increased use of easier to obtain materials such as petroleum by the middle of the century. But some whaling continued and, inspired partly by Roger Payne’s record, the call to ban hunting grew. The International Whaling Commission (IWC), set up to limit catches in 1946, introduced a complete moratorium on commercial whaling in 1986. (The IWC allows certain indigenous populations to carry out subsistence hunts with catch quotas set every few years).

Fin whales were once hunted in huge numbers in the Southern Ocean and elsewhere

However, not only does the moratorium only apply to members of the IWC, but IWC members Norway and Iceland have lodged objections. Iceland continued to hunt fin and minke whales until 2018 and Norway still kills 5-600 minkes a year. Having left the IWC in 2019, Japan hunts sei, Bryde’s and minke whales. Despite some small signs of recovery, whale populations are still far below the levels they would have been before industrial whaling began. Any large-scale hunting prevents this picture from changing. There are hopes, though, that a declining interest in eating whale meat in both Norway and Japan will prompt their respective governments to stop supporting whaling.

No Safe Haven

It is not just whaling that threatens these ocean giants, however. They, and their toothed cousins, face a number of newer problems. The expansion of commercial shipping around the globe increases the likelihood of ship strikes on whales. Many whale’s migration routes pass through or close to some of the busiest shipping lanes in the world, including those into San Diego and Los Angeles. There is particular concern about ship strikes and northern right whales. Commercial whaling brought this North Atlantic species especially low and only around 400 animals survive today. Increased ship traffic also affects whales’ ability to communicate over the miles as the constant engine sounds drown out their calls. Entanglement in fishing gear is another huge threat, with animals routinely trapped and drowned.

Global shipping — Commercial shipping is an increasing threat to whales

Climate change is also a huge concern. There are fears that warming oceans will affect food availability. In addition, species such as the bowhead whale will suffer if a reduction in sea ice in the Arctic opens up the region to more gas and oil exploration. Not only do seismic surveys disturb whales, but there is an increased risk of pollution. Less ice also allows orcas to hunt in new areas. Finally, ice-free passage around the Arctic has allowed a few isolated grey whales to return to the Atlantic from the Pacific. Historically, grey whales did live in the Atlantic until the 17^th century when whaling killed them off. Their return might seem like a cause for celebration. But these individuals have no memory of feeding grounds or historic migration routes and are unlikely to survive.

World Whale Day

This World Whale Day, take a moment to salute those giants of the ocean, the baleen whales. Industrial levels of whaling may have ended, but they, along with their cousins the toothed whales, face an increasing number of new threats. Climate change, ship strikes, noise and chemical pollution, entanglement and plastic ingestion are just some of the perils threatening populations that are still far below their historic levels due to over-hunting. ‘Save the Whales’ may have been a clarion call in the 1970s and 80s, but the fight to save these gentle giants is far from over.