[imagesource: Dmitry Kokh]

South Africa’s great white shark population has been the subject of a number of recent studies.

We know that the presence of two orcas, Port and Starboard, has caused the sharks to stop visiting certain regions along the coast.

Since 2017, eight carcasses have washed up on the shores of the Gansbaai coast, with seven missing livers and the heart and testes of one carcass also torn out. The orcas are likely responsible for further great white deaths where the carcasses didn’t wash up on shore.

In Plett, where long-distance swimmer and stockbroker Bruce Wolov tragically lost his life after a shark attack last month, the results of another fascinating study have now been released.

Dr Lacey Williams, head field specialist at the Oceans Research Institute in Mossel Bay, spent hundreds of hours in 2019 watching interactions between sharks and seals from the cliffs of the Robberg Nature Reserve.

Her research has shown that seals will come together in ‘gangs’, known as mobbing, in order to “actively approach, harass and sometimes even attack” the apex predators.

The Daily Maverick below:

“What’s happening here at Robberg is ecologically incredible. It’s unlike anywhere else that we’ve been able to see, especially for white sharks and seals,” said Williams, explaining that the landscape allows us to observe a highly migratory species close to shore in shallow water, which is typically very difficult for scientists to do.

…South Africa is on the map because of the unique predator-prey dynamics between these two species and the prevalence of seal mobbing behaviour.

Image: David Jenkins / Specialist Stock / Barcroft Media

“It has been noticed elsewhere in the world, but nowhere else had it been observed with the intensity and the consistency … we saw here,” said Williams.

Researchers counted hundreds of interactions between the species from May to the end of July 2019 from a cliff vantage point. They also made use of drones for aerial footage.

What’s remarkable is that the seals didn’t only come together during or after an attack to protect themselves.

Williams found 70% of white sharks were mobbed before they attacked, and seals were three times less likely to be targeted and attacked if they were already mobbing the shark than if they were doing some other behaviour.

The seals were essentially engaging in preemptive strikes to avoid becoming prey.

Understanding how aquatic ecosystems works is important, says Williams, because  “we are of nature, not separate from it”.

Hear, hear!

National Geographic shared this footage of seals ‘mobbing’ a great white shark off our coast back in 2019:

[source:dailymaverick]