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This weekend saw another great white shark wash up dead along the coast near Gansbaai, meaning that the attacks that grabbed headlines back in May are far from over (HERE).

On Saturday a 4,2 metre male great white shark washed ashore, the fourth since May, with the tell-tale marks of having fallen victim to orca predation.

The liver had been removed, with these images below the Marine Dynamics Twitter account:

It turns out they know which orcas are behind the attacks, with this via Traveller24:

[Biologist Alison Towner said] that the attacks are largely being attributed to a pair of orca, nicknamed port and starboard due to the slanting of their dorsal fins, also see at Dangerpoint over the weekend.

She says the two orcas are known to be shark hunters, as they have apparently killed other shark in species in the area.

Towner says these two animals were also spotted in the bay, when the previous attacks took place.

We’ve covered just how effective orcas are are are at hunting but let’s tick that box once more:

Known as the “Wolves of the Sea”, orcas are the true apex predators of the ocean, and the only known predator of the great white shark.

They are extremely intelligent, specialised hunters, feeding above sharks on the overall oceanic food chain. They hunt in organised social groups, using echo-location, strategy, and teamwork to kill their prey, which can be anything in the ocean, from seals, to dolphins, dugongs, otters, turtles, birds, squid, and sometimes even land mammals.

According to the [Department of Environmental Affairs ] DEA statement, the orcas were targeting the squalene rich livers that assists sharks with their buoyancy. This substance is also highly nutritious pound for pound, compared with the muscle tissue. Although this type of selective feeding on livers is extremely rare in orca whales, seals have been known to predate sea birds where they often remove and consume only the stomach/abdominal content and not the rest of the carcass.

Shark cage diving has all but ground to a halt, with great white sightings few and far between, although the long term patterns or effects of the orca predation remain unclear:

The incidents have already affected the number of great white sightings, as the sharks leave the bay to avoid the orcas. The killings are a blow to the already struggling population of great white sharks in South Africa, a local population which some scientists say is facing extinction.

The DEA, along with various shark scientists and marine mammalogists, is currently collating all the scientific information about the incidents, and they are urging the public to be aware that this is a natural phenomenon, and might have to do with changes in seasons or temperatures and prey regimes of the orcas.

Here’s hoping the local great white shark population can bounce back, and not just from an economic standpoint, because our oceans are poorer off without this species.

You can find out additional information about this attack, and those from back in May, on Marine Dynamic’s Facebook page HERE.

[source:traveller24]