'Supergroup' whale pods along SA's shoreline sign of population growth - marine researcher

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A humpback whale and its calf.
A humpback whale and its calf.
Auscape/Universal Images Group via Getty Images
  • The whale populations off the West Coast have been experiencing exponential growth.
  • Two whale carcasses, which recently washed ashore in Cape Town, could be a symptom of this growth.
  • South Africa experiences a unique phenomenon of large whale pods, called supergroups.

Two whale carcasses have washed up on Cape Town's shores in just under a month - and we're likely to see more, says a local marine researcher.

But they shouldn't cause alarm because the carcasses are a symptom of a growing whale population thriving off South Africa's coastline.

Marine researcher and founder of Sea Search, Simon Elwen, said after being nearly decimated around 100 years ago, the whale populations had started experiencing exponential growth.

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Supported by a vast, rich ecosystem, South Africa has started experiencing a unique phenomenon of large pods of humpback whales travelling along its coastline.

These pods can contain anything from 20 to 200 whales - prompting the name "supergroups", explained Elwen.

While most Western Cape residents might be familiar with Southern Right Whales, which breed off the south coast in winter, South Africa's waters are home to various breeds of whales all year, said Elwen.

Humpback whales were often found off the West Coast, especially in summer, where they feed while migrating to warmer waters for their breeding season.

"It happens offshore, miles out to sea, so people don't see them very often," added Elwen.

Darryl Colenbrander, head of Coastal Policy Development and Management Programmes at the City of Cape Town, said it's not unusual for whale carcasses to wash up on Cape Town beaches, especially when a large pod was in the area.

"It's not unusual to have a large pod of whales moving past and to get the odd mortality," he said.

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Both whales were large juvenile whales, which appeared to have died of natural causes, said Colenbrander.

"We usually examine the carcasses when they wash up. You can sometimes see if the whale has a clear cause of death like a propeller strike, but there was no evidence of this on the two whales that washed ashore," he said.

On Wednesday, there were pods off Scarborough and Sea Point, Elwen said.

Because of the growing population, many of the whales in the pods were juveniles.

The whale carcass washed up on Clifton fourth beac
The whale carcass washed up on Clifton 4th Beach on Tuesday morning, and was removed later that afternoon.
The whale carcass washed up on Clifton fourth beac
The whale carcass washed up on Clifton 4th beach on Tuesday morning, and was removed later that afternoon.

And scientists are starting to see more and more of these young whales beaching or their carcasses washing ashore.

Elwen said that several whale strandings had been recorded on the Namibian coast in recent months. Along with the carcasses washing up in Cape Town, this could indicate that the ecosystem was at carrying capacity.

These whales were likely young and hungry, making them more vulnerable to disease, propeller strikes or strandings.

Colenbrander said it's impossible to predict how many whale carcasses may wash ashore.

"We get several whale carcasses coming ashore every year, but that number varies. That's just the way mother nature operates. The whales could die from propeller strikes, entanglements or natural causes.

Elwen added: "We're more likely to see whale carcasses washing up. But, to put it into context, we have a lot of dead whales because we have a lot more alive ones. We're in a period of rediscovery. It's a very exciting time from a scientific point of view."

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