Magic comeback of the humpback by 10% a year

Humpback populaitons are recovering dramatically
A Humpback whale breaches off the coast of iSimangaliso on its journey north.

Thanks to the moratorium on whaling, Humpback whale populations in the southern hemisphere have staged a remarkable recovery. But now comes the new threat of seismic surveys.

Back home in the Antarctic feeding grounds

After a 6,000km round trip, said to be one of the greatest annual migrations on Earth, a large number of the southern hemisphere humpback whales are back in their summer feeding grounds in the Antarctic.  There, they’ll feed on krill for the next three or so months to replenish their stores of fat before heading north again to their equatorial breeding grounds, where warm waters provide a gentle entry to the world for the blubberless new-born calves.

Perhaps you were among the many people who, in the winter months, on tour boats or even from the shore, marvelled at the acrobatic feats – the breaching, lobtailing, spy hopping – of these charismatic mammals as they moved up and down our coastline following ancient routes embedded deep within their collective memories.   

Humpback tail
Tail slapping of a Humpback
Humpback spyhopping

Whaling moratorium

Perhaps too, their numbers amazed you if you were aware that commercial whaling between the 1900s and 1960s exploited Humpbacks to the point that they were endangered.  The population that migrates up our richly biodiverse East Coast lost about 200,000 animals to whaling during those years, the brutal harpoons seeking them out in their breeding grounds, during their migration, and in the Antarctic. But at last, relief came in the 1980s when the International Whaling Commission placed a moratorium on commercial whaling. In response, Humpback whale numbers have been increasing at an annual rate of 10%. “It’s the best conservation story yet,” said whale researcher, Chris Wilkinson of the University of Pretoria’s Mammal Research Institute and who, for several seasons tracked the Humpbacks migrating past Cape Vidal on the KZN North Coast between July and August.

I met Chris at the tail end of the 2019 monitoring period at his research site on top of one of a pair of watch towers on a high dune at Vidal.

Whale survey platform
One of the survey platforms at Vidal.
Whale researcher, Chris Wilkinson surveying whale numbers off Cape Vidal.

Up there, Chris and a team of volunteers had been observing whales from sunrise to sunset every day for six weeks. “It’s a great vantage point. We can see 15 kilometres out to sea and the continental shelf is narrow here so the whales often come in close”.  

The monitoring was carried out during the same period each year. It involved teams of two in each tower counting and tracking every group of whales that passed during shifts lasting ten hours. The survey replicated the study carried out at the same site thirty years previously, when observers struggled to find whales and had so much time they could draw the dorsal fins of individual whales for recognition. 

Whale fin
Dorsal fin patterns identify individual whales.

In contrast, Chris and his team only just managed to keep up with the sightings.

“We counted in excess of 1000 groups. On one day alone, we tracked 100 groups”.

Chris Wilkinson

Population trends

At the time of our meeting, Chris was yet to analyse the data but was confident the results would indicate some recovery of the population towards pre-whaling numbers, or the carrying capacity for the species. “We’re not looking at exact numbers – that’s not possible because we can only watch during daylight hours and we also don’t see the whales further out to sea. We’re looking at trends”.  

The rising trend is not unique to the KZN coastline. “Many countries that have Humpback whales are measuring their own populations and have also recorded an increase”.  Chris explained that there are seven Humpback populations in the southern hemisphere (A –G), each following a different migratory route.  Those relevant to South Africa are the B population that travels up our west coast and on to Angola and Gabon, and the C population that splits into four groups:  C1 Humpbacks migrate up our east coast, C2 up the Mozambique Channel to the Comoros or Seychelles, C3 to the waters of Madagascar, and C4 to the Mascarene Islands.  Chris‘s research concerned only C1, which means they were seeing only about a third of the C population.

Fasting en route

From the Vidal tower I spotted some C1s, or rather, the colossal splashes of breaching whales. It was astonishing to learn that the adults don’t feed while migrating. “It’s a long way and slow going when they’re heading north as they’re swimming against the current so they conserve their energy and use up their blubber to sustain themselves,” Chris explained. “The way back is easier as they sit in the current.”  (An interesting aside is that the Agulhas current that flows down the east coast is one of the fastest in the world.) The calves, though, feed voraciously – about 600 litres of milk a day –  to pile on blubber before they reach the icy southern ocean.

Whale tourism

Boat-based whale viewing is a bucket list experience.

The recovery of the Humpbacks is great news not only for the survival of a species but for whale tourism too with authorised boat-based whale-viewing adventures in Marine Protected Areas, such as the iSimangaliso MPA, an experience of a lifetime.

Whale poo is cool!

But perhaps the biggest benefit of the recovery of the humpback population is the impact this has on the planet, for, as we are at last discovering, whales are key to the health of ocean ecosystems. Their critical role starts at a rather basic level.  “The cool thing about whales is their poo,” Chris told me.  

In short, whales generally do not go to the loo deep down in the ocean but perform that function at the surface, triggering an astounding trophic cascade. The faecal matter is rich in micro-nutrients, particularly iron, which the whales release in the photic zone. These nutrients fertilise the plant plankton on which animal plankton, like krill, feed. In turn those tiny creatures are food to whales and other sea animals, like the fish you might be having for dinner tonight. But the benefits don’t end on the dinner plate. Plant plankton absorbs significant amounts of carbon from the atmosphere. When the plant dies, it takes that CO2 down to the ocean floor.

In sum then, the more whales, the more poo, the more iron, the more plant plankton, the more krill, fish, and other sea creatures, the more food security (for both people and animals), the less carbon in the atmosphere, and the healthier the climate. Putting this all in a nutshell, whales drive essential ecosystems and even have an important influence on the climate.  

Whales matter

And so, even if you live far from the ocean in Pofadder or Hotazel, whales matter to you. May they forever be spared the harpoon. But tragically, they now face a new hazard off our East Coast, and particularly within the renowned biodiversity hotspot that is the uniquely wonderful, endemic-rich Wild Coast

That hazard is acoustic pollution from seismic surveys that Shell, with the blessing of our government and contrary to the spirit of COP26, is carrying out in its search for offshore oil and gas deposits. Shell representatives insist that the exploration will not be detrimental to marine animals; that mitigation measures are in place; that an exclusion zone is put around the sound source. But, it must be asked, what about the animals trapped inside that exclusion zone? They argue too that the exploration is essential because oil and gas will still be needed well into the future, and that the project will benefit many.

“Blunt force weapon”

Marine scientists though, refute Shell’s claims that the surveys are harmless. They state that there is growing evidence pointing to unmitigable negative impacts of seismic disturbance on marine creatures, including tiny species such as the all-important zooplankton. The Centre for Biological Diversity describes the blasts as a ‘blunt-force weapon’ that can reach more than 250 decibels, be heard for miles, and can cause hearing loss, disturb essential behaviours like feeding and breeding, reduce catch rates of commercial fish, and mask communications between individual whales and dolphins. In regard to the humpback migration, though most that follow the East Coast passage are back in the Antarctic now, a number of individuals will still be en route.  

Concerned citizens have gathered, staging protests all along the coast and last week, an urgent interdict was brought by environmental groups to block Shell from proceeding. The High Court in Makhanda dismissed the application with costs, but another urgent interdict  has been launched.

Songs of the whales

So the gloves are off and we must hope that good sense and compassion for our wild ocean world will prevail.  Rather than the sound of seismic blasting, may the song of the humpback whale be heard for ever more.

A version of part of this story first appeared in November 2019 edition of the now closed SA Country Life magazine.

The views and opinions expressed in this article are those of the author and do not necessarily reflect the views of Safrea or its members.


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