First it was the great white sharks who mysteriously vanished from the waters of Cape Town but now the coast is short of whales too, as marine biologists scramble to understand why.

A Southern right whale breaches near the shore of Muizenberg Beach in False Bay, Cape Town
Southern right whales are disappearing from Cape Town's coast and scientists are trying to determine why ©Jennifer Bruce/AFP/Getty

Sightings of whales and sharks in Cape Town have declined in the past 18 months. An aerial survey carried out by the University of Pretoria Whale Unit at the start of the month, recorded only 200 southern right whales in the area, the second-lowest count in 24 years. Scientists are trying to figure out why, though it's believed that food shortages related to climate change could be linked. 

"The decline in numbers is related to an incomplete migration of the non-calving component of the population (males and resting females), and the decreased frequency at which female right whales are calving," Dr Els Vermeulen, research manager of the University of Pretoria's Whale Unit, told Lonely Planet. "All our data points towards a decreased energy level, related to decreased food availability in the Southern Ocean, possibly related to climate change."

Right whales feed off krill and copepods but if not enough of these food sources are available due to warming waters, the whales can't store the energy they need to complete the migration from Antarctica.

A closeup of a curious juvenile Southern Right Whale in the water
A closeup of a curious juvenile southern right whale in False Bay, South Africa ©Catherine Withers-Clarke via Getty

Southern right whales, a protected species, mainly travel to South Africa to give birth to their young between July and October in sheltered bays. They don't feed in this region, nor are they being eaten by other animals so their impact on the local ecosystem is minimal. Still, it's worrying to note the decline of such a huge presence in these waters. It's especially puzzling because a record number of southern right species was counted last year. But right now, scientists aren't able to determine if the numbers will bounce back. "We simply do not know at this stage," Dr Vermuelen explained, as research continues.

The survey's results come as the city's tourism industry is trying to make sense of the mysterious disappearance of great white sharks from False Bay and Seal Island. This part of Cape Town is one of the best places in the world to spot great white sharks and shark diving is an incredibly popular tourist activity. But so far this year, none of the sharks have been counted.

Great white shark with open mouth breaches water
Great white shark sightings have plummeted in South Africa ©andreahumm/Budget Travel

Between 2010 and 2016, Shark Spotters, the safety and conservation group that monitors shark sightings, recorded an average of 205 white shark sightings per year at their operating beaches during the spring and summer period. By 2018, that number fell to 50, and this year there hasn't been a single confirmed sighting, according to Bloomberg.

In a statement on Facebook, Shark Spotters said: "While the exact reason for this is unclear, the arrival of a specific ecotype of Orca that predates on sharks appears to have had a significant effect on the distribution of white sharks in our area."

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