Whale of the Month - Humpback Whale
Species fact file
Common names: humpback whale
Icelandic name: hnúfubakur
Scientific name: Megaptera novaeangliae
Family: Balaenopteridae (rorqual whales)
Max length: 15 (males), 16m (females)
Humpback whales are the most well-known of all baleen whales. Their cosmopolitan distribution and distinctive looks – stocky body, dark colouration and gigantic pectoral fins – makes them an instantly recognisable icon of the world’s oceans. Humpbacks are famous for their displays at the surface of the water, from impressive breaches to spyhopping and slapping the water with their tails and flippers. It is for good reason that this species is a favourite of whale watchers all across the globe.
Before the rise of whale watching, humpbacks – like most of the large whales – were threatened by commercial whaling. But they are an example of an encouraging success story: although humpbacks were hunted heavily throughout their range, and some populations were reduced by over 95%, they have made such a strong comeback that they are now listed as Least Concern on the IUCN Red List. Here in Iceland, they were a rare sight until as late as the 1970s, but are now one of the most common cetacean species to be found in these seas. People come from all over the world to see humpback whales in Iceland.
Like most baleen whales, humpbacks are migratory. They travel annually between their breeding grounds near the equator and their feeding grounds near the poles. Some humpbacks travel such distances that their migrations are among the longest of all mammals – yet, surprisingly, we still do not fully understand the purpose of these epic journeys. It is thought that warm, tropical waters are the safest place for calves to spend the first few months of their life. However, there is little food for humpback whales in these regions, so to compensate for their fast over winter, humpbacks spend their summers in sub-polar seas where prey is much more plentiful.
The main feeding grounds in the North Atlantic are the Gulf of Maine, the Gulf of St Lawrence, Newfoundland, Labrador, Greenland, Iceland, and Norway. Individuals seem to have strong fidelity to their feeding grounds and return to the same place year upon year; newborn calves travel to the feeding grounds in spring alongside their mothers, and will go on to choose that same feeding ground every year for the rest of their lives.
Whales from all of these different feeding grounds migrate to a single breeding ground in the West Indies. There is some evidence of a second breeding ground in the North Atlantic, which many humpback whales from the Iceland and Norway feeding grounds migrate to, but its location is still unknown.
Our understanding of migration routes has been built up over many years using photo identification. Each humpback whale has its own unique pattern of black and white markings on the underside of the tail, or flukes. These markings act as a sort of fingerprint – a way to identify each different whale.
By comparing photographs taken across many years and between completely different parts of the world, we can match humpback whales from their feeding grounds to their breeding grounds and learn about the timings and the route of their migration. Photographs of humpback whales are collected all over the world and compiled into regional catalogues – as of 2020, the Icelandic catalogue included 1434 humpback whales.
Humpback whales feed on a wide range of prey and have a range of different hunting tactics. In Iceland, capelin is thought to be their main prey, but they may also feed on other schooling fish such as sand eel and some plankton too. Humpback whales in the Antarctic feed almost entirely on krill. In the western Atlantic, sand eel has in recent years become an important prey for humpbacks, while off the Pacific coast of North America humpback whales still mainly hunt fish like herring.
Along with lunge feeding and gulp feeding – hunting techniques used by all rorqual whales – humpbacks are famous for their unique method of catching schooling fish called ‘bubble net feeding’. Bubble net feeding is not instinctive: this is a learned behaviour, and only humpbacks in certain locations know how to use this technique.
Bubble net feeding involves swimming under a school of fish and then spiraling upward while blowing out a continuous stream of bubbles. This rising curtain of bubble encircles the fish and corrals them into a tighter ball. As the fish are forced towards the surface, the whales can lunge through the centre of the school with open mouths to feed. Solitary humpbacks are quite capable of using bubble nets to feed, but this is often a collaborative affair involving two or more whales. Recent research suggests that bubble net feeding is more efficient when done as a group, and that individual whales may actually have a preference for which role they carry out.
In the Gulf of Maine, humpback whales have developed a variation on bubble net feeding. So-called ‘lobtail’ feeding involves slapping the surface of the water several times with the tail flukes before blowing bubbles in the same place, then lunging through the water to capture prey. The rise in the use of lobtail feeding coincided with a change in the humpbacks’ main prey after the herring stocks crashed. Perhaps this new method is better suited to hunting sand eel? Lobtail feeding has only ever been observed in this region and, like bubble net feeding, it appears to be passed from one whale to another through social learning.
Humpback whales are famous for their songs. These are among the most complex vocalisations in the animal kingdom – they consist of multiple, layered components called subunits, units, subphrases, phrases, and themes. In one year, all males in a population sing the same song but the composition of the song changes over time.
In the Pacific, songs are passed between breeding grounds, sweeping eastward from Australia to French Polynesia. Recent research suggests that some song types may even be passed as far east as Ecuador. Humpback whales in the Southern Hemisphere have multiple separate breeding grounds but there is some mixing in their Antarctic feeding grounds; if there is overlap of migration routes or interaction between humpbacks of different breeding populations during the summer feeding season, this could allow males to learn new songs from one another.
In the North Atlantic, humpback whale songs change gradually, but in the Pacific, song revolutions – that is, a complete change in song type – occur every two to three years.
Biologists define culture as knowledge or behaviour that is shared between members of a community through social learning. Cetaceans are among a wide range of animals known to have cultures. But culture is quite a challenge to study in whales and dolphins; experiments in captive are only possible with a few species, and otherwise we have to rely on observations of cetaceans in the wild. In this case, it can be difficult to rule out other factors such as genetics, ecology, and environmental changes as having an influence on behaviour.
Humpback whales are often referred to in discussions of culture in cetaceans. Studies have shown how behavioural traits, such as a song type or a hunting tactic, are passed between whales by social learning – in some cases, sweeping rapidly through whole populations or even across an entire ocean. Cultural change on this scale is unheard of in any animal other than ourselves.
The sheer geographic extent of this cultural transmission and the speed at which one song type is replaced by another makes humpback whale song a particularly interesting case study for researchers. Answering questions about cultural evolution requires data spanning long periods of time – hence why so much in this subject is only just beginning to come into focus. Understanding how culture evolved and continues to evolve in cetaceans can shed light on how these same processes occur in other animal groups, including the ongoing changes in our own languages, cultures, and traditions.
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Cultural change in humpback whale song in the Pacific Ocean