Deep dive...into Humpback whales

Humpback whales make one of the longest migrations of all animals, with some individuals travelling up to 8,000 kilometres between their feeding and breeding grounds.  

Part of the baleen whale group, humpback whales have the scientific name ‘Megaptera novaeangliae’. The first part translates to ‘big-winged’, in reference to the whale’s long pectoral fins. And ‘novaeangliae’ is the Latin word for ‘New England’, which refers to the location where European whalers first encountered the species.   

The descriptor ‘humpback’ comes, unsurprisingly, from a small hump in front of the whale’s dorsal fin. The hump becomes apparent when the creature raises and bends its back in preparation for a dive underwater.  

Humpback whales can grow to 18 metres long (females tend to grow slightly longer than males) and they can weigh in at a whopping 40 tonnes (40,000 kg).  

Their appearance is mostly grey or light black and individuals have different amounts of white on their bellies, the undersides of their flukes (tails) and on their pectoral fins. These markings help researchers to photo identify and track individual humpback whales over time.  

It’s known that Southern hemisphere humpbacks tend to have more white markings, particularly on their bellies and flanks, than the Northern hemisphere humpbacks have.  

The whale’s fluke is noticeably wide (up to 5 metres) so that’s often the part of the body that’s first spotted in the water by researchers and whale watchers. The fluke has a serrated pattern along its edge.  

Humpbacks spend most of their time near coastlines, which is where they find their food (tiny shrimp-like krill, plankton and small fish).  

The species has a life expectancy of 80 to 90 years. Females produce a single calf every two to three years on average, with their offspring staying with mum for up to a year after weaning. Mothers are protective of their calves, swimming very close to them and staying tactile through pectoral fin touch.  

These pectoral fins are amazing tools – they grow up to around a third of the whale’s body length and are highly manoeuverable. The species uses their fins for swimming, hunting (they slap the water) and researchers believe they may also use them to regulate body temperature.  

Humpbacks are found in oceans all over the world, with major populations found in the North Atlantic, North Pacific and in the Southern and Indian oceans.  

In the northern hemisphere, whales feed in the colder polar areas between June and October before heading south to breed in warmer waters in the months between December and April.  

In the southern hemisphere, the populations feed around the Antarctic between November and March and migrate north towards the equator where they mate and give birth between July and October.  

The migrations are long each year – up to 8,000 kilometres – and the whales can move with pace through the water. In the North Pacific, some humpback whales migrate from Alaska to Hawaii (4,800 kilometres) in as few as 32 days.  

Before the 1985 ban on commercial whaling, humpback whale populations were severely reduced (perhaps by as much as 90 to 95 per cent). In 1970, its population was so threatened that the U.S. listed all humpback whales in its territory as endangered.  

Thankfully, its numbers have improved since 1985 and it’s now listed as having ‘Least concern’ status according to the IUCN Red List of Threatened Species.  

Commercial whaling is no longer a major threat but humpbacks are still hunted in some places, such as the St Vincent and Grenadine islands in the Caribbean and Greenland which both use the Aboriginal Subsistence Whaling Quota permitted through the International Whaling Commission (IWC). Greenland, for instance, has a quota allowing for up to nine humpbacks to be killed each year.  

A recent IWC assessment of Southern hemisphere humpbacks estimated that overall numbers were at around 70 per cent of the number of whales thought to live in that region before hunting began.  

It’s estimated that there are currently between 120,000 and 135,000 humpback whales in waters around the world.  

Like many other large whales, the prey of humpback whales are tiny creatures. They feed on plankton, shrimp-like crustaceans (krill) and small fish. They sieve a huge amount of water through their baleen plates, which act as filters to separate food from liquid.  

Humpbacks have been observed using special techniques to help them herd and disorient their prey. Bubble net feeding is one of those techniques – the whales blow big waves of air bubbles to condense their prey. Once they have them where they want them, the humpbacks lunge upward through the circular bubble net and open up wide to take in their food.  

Humpback whales consume up to 1,360 kilograms (1.36 tonnes) of food every day though they tend to generally fast during migration and when spending time at their breeding grounds (when they dip into their fat reserves). However, researchers have tracked some individuals engaging in opportunistic feeding during migration and breeding periods.  

Humpbacks are famous for their ability to sing – letting out complex cries and noises, often for hours on end. Male humpback whales are particularly vocal during the mating season, which is thought to be their attempt to attract a potential female partner.  

These songs are studied by scientists to decipher their meaning.  

 A study published in September 2022 found that humpback songs easily spread from one population to another across the Pacific Ocean.   

Ellen Garland, author of the study and a marine biologist at the University of St Andrews, said it can take just a couple of years for a song to move several thousand miles. The study showed that whales in Australia were passing their songs to others in French Polynesia, who, in turn, gave songs to whales in Ecuador.  

One of the bestselling albums of all time captures some of these impressive songs – ‘Songs of the Humpback Whale’ was recorded in 1970 and released that same year by Dr Roger Payne, founder of Ocean Alliance. Listen to one of those songs here on YouTube. 

Humpback whales are a favourite of whale watchers which shouldn’t come as a massive surprise – their high levels of activity mean they put on a great display for anyone watching!  

They rise nose-first out of the water (spy hopping), slap the water with their pectoral fins and use their massive flukes to propel themselves through the water and sometimes completely out of it.  

This behaviour is called breaching. Exactly why whales breach is still not clear to us. There are a few different possibilities – including courting other whales, shaking parasites off their skin or simply to make a sound by splashing back in the water (they may be communicating to other whales, including signalling a warning). 

Baby whales that have lost their mothers have been observed breaching repeatedly – probably to send both a visual and audio signal to its mother.

The other strong possibility is that the whale is playing. There may not be any other reason apart from the explanation that jumping out of the water and splashing back down is fun! 

Take a look at a phenomenal breach below (this clip, recorded in Australia, went viral and has been viewed 76 million times to date!):  

Like other whales, humpbacks can become entangled in different types of fishing gear. This can cause injury, fatigue, compromised feeding and even death. 

Estimates from 1995 showed that entanglement was responsible for a five per cent annual mortality rate among humpback whales and it’s likely to have increased in recent years (with greater population numbers and more opportunities for fishing gear to come into contact with humpbacks).

A study in 2019 found that 25 per cent of humpback whales surveyed had entanglement scars. UK charity Whale Wise is currently investigating this matter with its Scars from Above project.  

Accidental vessel strikes can injure or kill humpback whales. Humpback whales are vulnerable to vessel strikes throughout their range, but the risk is much higher in coastal areas with heavier ship traffic. 

Climate change and pollution can lead to loss of habitat as waters become warmer. 

Humpback whales forage for food in higher latitudes (northern hemisphere) and lower latitudes (southern hemisphere). Climate change is causing our polar regions to lose sea ice, year on year, and this has a knock on effect on prey distribution for whales. This leads to changes in feeding behaviour, creates nutritional stress and reduced reproduction for humpbacks. 

Plastics and micro plastics in the ocean pose a threat to whales, along with all other marine mammals and fish. Chemical pollutants entering into the water ecosystem are also a serious threat to all creatures in our ocean. 

Humpback whales, like other whales, uses noise to communicate so increased noise pollution from vessels interferes with this ability.  

The only natural predator of the humpback whale is the orca. Orcas have been observed attacking and eating humpbacks (always calves).  

Humpback whales have been witnessed coming to the aid of grey whales under attack from orcas. Check out the video below filmed for BBC’s Planet Earth.