Humpback Whale
The Humpback Whale is arguably one of the most iconic whale species alive today, famed for their mournful underwater songs and incredible acrobatics, top of the bucket list for many whale watching expeditions. Growing anywhere from a colossal 14-17 metres in length and weighing up to 40 metric tonnes, these marine giants can be found in all major ocean basins and migrate long distances between mating and calving grounds in warm tropical waters.
Part of the Baleonopteridae family, consisting of the blue, fin, Bryde, sei and Minke whales, Humpbacks are Baleen whales, meaning they have huge keratinous plates in their mouths to sieve out planktonic prey. They are also classed as rorqual whales, the largest of the Baleen Whale species. They have a distinctive hump before their dorsal fin (hence the name), long flippers, grooves from jaw to navel and small bumps or tubercules on their jaw and flippers which are suspected to have a sensory role, since they develop early in the womb and are densely packed with nerves. Their dorsal side is blue-black, and their ventral side mottled white.
Mitochondrial DNA from North Pacific, North Atlantic and Southern Hemisphere populations revealed that Humpbacks evolved in the Southern Hemisphere and colonised the Northern Hemisphere around 200,000 to 500,000 years ago. For a migratory species, their genes show remarkably little similarity, indicating there is not much gene flow between populations, and over time it is likely Humpbacks will form genetically distinct populations that may need to be treated separately for conservation purposes. We are already seeing this with a small, non-migratory population in the Arabian sea. Analysis of DNA from their tissues showed that this population emerged in the Southern Indian Ocean and is extremely genetically isolated from the rest of the species. They were also have poor genetic diversity and there is evidence of genetic bottlenecks in their history, events were numbers fell very low, leading to few members left to breed and so poor genetic diversity. These concerning genetic signatures has led the IUCN to classify this small population as endangered on the IUCN red list.
Like so many whale species, Humpback Whales were pushed almost into extinction by decades of unregulated whaling for their meat and oil. In the 1960’s, it is estimated there were as few as 5000 Humpback Whales left. Thanks to intensive conservation work, increased awareness and policy and a moratorium on commercial whaling by the International Whaling Commission in 1986, we have seen partial recoveries of whale species all over the world, with Humpbacks back up to an estimated 135,000 animals. However, the oceans aren’t safe for these gentle giants yet, with issues with fishing gear entanglements, boat collisions, plastic and noise pollution.
Bubble nets, breaches and bursting into song: the wonderful behaviour of the Humpback Whale
Like other rorqual whales, Humpbacks are ‘gulp’ feeders; they take in huge mouthfuls of food at once, rather than swimming along and continuously filter feeding like Bowhead Whales. But unlike the other rorqual whales, Humpbacks perform an unusual feeding technique called the ‘bubble net’ method. The whales swim downwards in circles and then using their blowholes, they release several bubble bursts, creating a spiral ‘net’ of bubbles that corrals and traps small fish and krill. The whales then lunge from the bottom of the net to gulp down their prey. Their long, narrow flippers make the whales perfectly designed to carry out the sharp turns needed to create their bubble nets. Although bubble netting is rarely seen, as they generally perform this phenomenon out in the open ocean, Humpbacks have been recorded making loud, trumpeting vocalisations. Scientists hypothesise this could be used to keep prey in the middle of the bubble net, although no one is sure yet.
From left to right: an example of bubble net feeding as seen from above, with the perfect spiral formation shown. The second image shows a simulation of four whales creating a bubble net. The final image shows a snapshot of several Humpbacks lunge feeding. (image from Bryngelson and Colonius, 2019).
Often seen on nature documentaries, Humpbacks perform breaching, an amazing physical feat that involves the whale heaving more than 40% of its considerable body above the waters surface. Although it is a common image when you google Humpbacks to see the whale against the sky, framed in a glorious spray of water, the massive amount of energy this requires makes it a pretty rare act. As is often the case with animal behaviour, the exact reason remains a mystery. Sociality and communication is a likely explanation, especially as Humpbacks sometimes breach in groups, similar to the highly social Orca. There are observations that increased wind speed causes more breaching, which may be a way for the whales to communicate over a loud ocean surface. Humpbacks are frequently covered in barnacles and other pesky hangers-on, and so possibly the whales are using the massive jump and slap back down into the water to remove these unpleasant hitchhikers.
The famous image of the breaching humpback whale (image from missionblue.org)
Marine biologists have described the haunting song of the Humpback Whale as ‘probably the most complex in the animal kingdom.’ Scientists were first alerted to these amazingly complex songs by a US government agent called Frank Watlington working at an underwater station using hydrophones to listen for Russian Submarines in the 1960’s. He kept recordings of these haunting songs but shared them with no one, afraid they would be used by whalers to locate and kill the whales, at a time when whaling was still big business. On a trip to Bermuda, he was introduced to two biologists, Katy and Roger Payne, by a mutual friend, and began discussing his recordings. As a researcher in acoustic biology, Katy was fascinated, and began to make spectrograms to visualise the calls. She saw patterns and structure in these spectrograms and realised these motifs were specific Humpback vocal patterns sung only by members of the same group.
Males are the only Humpbacks that vocalise, and they produce their most complex songs during the breeding season. To this day scientists are not entirely sure what the purpose of these songs is. Possibly they are used to attract females, like a cetacean Michael Bublé, but field playback observations have shown that females rarely if ever approach the source of the song. Other scientists have suggested it is a form of male-to-male communication to assert dominance or maybe even to team up to attract the ladies like a whale boyband. There is some suggestion that females may be attracted to a congregation of singing males, so it is beneficial for males to team up to croon out the classics. Additionally, some hypothesise that it is a way to recruit new whales to wintering grounds when established feeding areas become overcrowded. More recently, studies of Humpback songs recorded off Hawaii suggest that the songs might be being used to locate other whales, like a giant, oceanic version of Marco Polo.
An example spectrogram of a male Humpback song (image from https://www.fisheries.noaa.gov/national/science-data/sounds-ocean)
There are a range of other vocalisations less complex than these songs belted out by the males that are hypothesised to have a range of social functions. ‘Grumbles’, ‘snorts’ and ‘thwops’ have been recorded within groups of whales, suggesting inter-group communication. ‘Underwater blows’ and ‘cries’ were heard between competitive groups, whereas ‘groans’, ‘grunts’ and ‘barks’ were recorded as whales joined new pods, indicating some role in social integration. More studies are needed to pin down the exact roles of these diverse sounds, but one thing is certain, the oceans will never be silent blue expanses while Humpbacks are around.
A tragic past: the legacies of whaling
Whaling has long been a part of human history, but the development of steam powered engines and explosive harpoons in the 19th century industrialised hunting and allowed whalers to target faster whales. Whales were depleted across the globe, driving whaling ships into the Antarctic, where feeding aggregations of whales created rich hunting grounds. The vast and often brutal regime soon led to collapses in whale populations the world over as we raced to harvest their meat, blubber and oil to fuel the fires of industry. Many countries, such as Russia, Germany, Japan, South Korea, the US and Canada, had thriving whaling industries. For Humpback Whales alone, in the 20th Century, an estimated 200,000 whales were killed in the Southern Hemisphere. In the 1960’s, decades of sustained, uncontrolled whaling had left just 5000 Humpback Whales from pre-commercial whaling numbers of 125,000.
Some countries, the Soviet Union in particular, underreported catches by significant amounts, putting the whales in an even more dire position.
The history of whaling (from Encyclopaedia Britannica : https://www.britannica.com/topic/whaling)
By 1925, The League of Nations recognised that whales were overly exploited and set up the Bureau of Whaling Statistics to try and track and manage catches. Further steps were taken and in 1931 the Convention for the Regulation of Whaling was signed by 22 nations, although major whaling countries, like Germany and Japan, refused to sign and the slaughter continued. Throughout the 1940’s it was finally impossible to ignore the imminent extinction of multiple species of whale, and eventually in 1946 the International Whaling Commission was set up with 14 member states, aiming to set quotas and enforce protection on certain whale species. Unfortunately, the IWC was fairly useless for a time, lacking in law enforcement and focusing on the best quotas they could achieve and not on sustainable harvest and conservation of whales for the future. Countless species, including Humpback Whales, continued to be harpooned towards extinction.
However, as numbers plummeted, it became harder and harder for whalers to actually find any whales to harvest, and this, coupled with the formation of the World Wildlife Fund and ‘Save the Whales’ campaigns around the world, began a steady attitude shift. Eventually in 1982, a moratorium on commercial whaling was put forwards at the annual IWC meeting. With a majority of 25 to 7 members, the motion was passed and came into force in 1986. In 1994, after intense lobbying by scientists, charities and animal lovers, the Southern Ocean Whale Sanctuary, a 50 million square kilometre protected region, was set up. This sanctuary aims to protect feeding and breeding grounds for the historically worst exploited populations, ensuring the long-term recovery and survival of whales. For Humpbacks, 2004 heralded heavily restricted hunting, allowing only a few individuals taken a year off the coast of the Caribbean Islands. Whales have shown amazing resilience, and they are fortunately now a much more common sight than they used to be.
Unfortunately, whaling is not entirely consigned to bloody history. Japan, Norway and Iceland are still considered whaling nations, and use loopholes in the law to take around 1200 whales per year, often under the guise of ‘scientific research.’ Most often countries still have a demand for their meat as traditional dishes, and their oils are still used in some pharmaceuticals and cosmetics, despite the ban on whaling and the use of whale derived products. Japan has simply restarted commercial whaling and show no signs of changing their minds on that any time soon. Not only whales, but other cetaceans, most notably dolphins, are exploited in violent, brutal hunts, such as the infamous Taiji hunts and the traditional hunts of long finned pilot whales in the Faroe Islands. There is much debate about the best way to tackle commercial and cultural whale hunts, but the intelligence and awareness of these cetaceans must be considered. As a species, we must try to put this cruel, most often unnecessary practice behind us, not least because whales are facing other threats to their survival from our actions.
Although Humpback Whales are listed as least concern on the IUCN red list, it is still recognised that there are many threats against them. They are particularly vulnerable to fishing gear entanglements and ship collisions. All members of the IWC are encouraged to report strikes and by catch, but in reality, few do. Due to their gulp feeding techniques, Baleen Whales like Humpbacks are particularly vulnerable to the insidious threats of microplastics, as they swallow them in great mouths of seawater and can’t filter them out due to their small size. Like most whales, noise pollution from ships and submarines can cause them great stress and affect their ability to communicate and feed. With our actions, we are greatly testing the famed resilience of these ocean wonders.
Conservation Optimism and Organisations
There is still a lot of hope for Humpback Whales and their cetacean relatives. Once, looking at bloody oceans in the height of the whaling industry, it must have been hard to imagine that whales would ever recover. And yet, today, many whaling stations stand silent and rusting and we have seen amazing increases in numbers, thanks to recognition of our exploitation and campaigns to stop the slaughter. The Save the Whales campaign can be looked upon as one of the biggest and most successful conservation initiatives of recent years. Look what we can achieve when we pull together!
If you want to learn more about whale conservation, please check out:
- Whale and Dolphin Conservation (https://uk.whales.org/)
- This is a British Charity working for 30 years to conserve whales and dolphins across the world. Their main aims are to stop the captivity of cetaceans, end whaling, stop deaths from nets and create healthy seas by working alongside partners to clean up pollution from the ocean, as well as prevent it from entering the ocean in the first place. They also carry out a number of vital research projects across the globe.
- If you want to get involved you can:
- Adopt a whale or dolphin.
- Donate or fundraise.
- Volunteer in their offices or at events, campaign alongside the charity for policy to protect whales and dolphins.
We can all protect whales and their ocean habitat with one simple action: PICK UP YOUR TRASH! Cut back on your plastic use where you can, but where you can’t, take your rubbish with you, dispose of it correctly and keep the seas as pristine as the Whales want them to be.
Amazing videos!
References
Bryngelson, S.H. and Colonius, T. (2019) ‘Simulation of humpback whale bubble-net feeding models.’ The Journal of the Acoustical Society of America, 147(2)
Dunlop, R.A. Cato, D.H. and Noad, M.J. (2008) ‘Non-song acoustic communication in migrating Humpback Whales.’ Marine Mammal Science, 24(3)
Fossi, M.C. Panti, C. Geurranti, C. Coppola, D. Giannetti, M. Marsali, L. and Minutoli, R. (2012) ‘Are baleen whales exposed to the threat of microplastics? A case study of the Mediterranean fin whale.’ Marine Pollution Bulletin, 64(11).
Herman, L.M. (2016) ‘The multiple functions of male song within the humpback whale (Megaptera novaeangliae) mating system: review, evaluation and synthesis.’ Biological Reviews, 92(3)
https://wwf.panda.org/wwf_news/?13796/The-History-of-Whaling-and-the-International-Whaling-Commission-IWC#:~:text=Whaling%20as%20an%20industry%20began,Norwegians%20and%20many%20other%20nations.
https://uk.whales.org/our-4-goals/stop-whaling/
Mercado, E. (2021) ‘Intra-individual variation in the songs of humpback whales suggests they are sonically searching for conspecifics.’ Learning and Behaviour.
Reeve, L.L.N. (2001) ‘Of whales and ships: impacts on the great whales of underwater noise pollution from commercial shipping and proposals for regulation under international law.’ Ocean and Coastal Law Journal.
Werth, A.J. and Lemon, C.L. (2020) ‘Animal Behaviour: whale breaching says it loud and clear.’ elifesciences.org
