If you’ve been following the ongoing story of Port and Starboard, the orcas responsible for the precision-killing of a number of great white sharks over the past few years, then we have an update for you.

According to a Facebook post by Pete Oxford, they’ve been at it again, this time killing five cow sharks, also known as sevengill sharks, in Betty’s Bay.

Here’s some of the info from that post, along with the images:

After being alerted by a local resident, Michelle, last night that there were 5 dead sharks on Main Beach, Betty’s Bay we walked the beach looking for their corpses to try to figure out what might be the cause of their deaths.

Finding four of the five in the darkness – they all showed exactly, the same apparent cause of death. Namely that their throats seemed to have been ripped out…Our torch light examination revealed an almost surgical incision of the wound in each case.

We had heard the stories of how the two male orcas who frequent our coast (named Port and Starboard) had killed several great white sharks.

Pete then called on experts Meaghen McCord [pictured up top] and Pippa Ehrlich [pictured below], who came from Hermanus and Simon’s Town respectively to investigate:

[They] confirmed that the sharks had indeed all been killed by killer whales. It was a classic modus operandi where apparently, the orcas grab a pectoral fin each, flipping the shark over and tugging to split open the throat and chest cavity whereby they suck out the liver.

Indeed, the wounds were consistent with that theory and once opening the carcasses the livers were gone. – Mystery solved!

Pete added that the infamous duo of Port and Starboard, identifiable as each has a distinct, flopped-over dorsal fin, are known to be still in the area.

Recent research by the Save Our Seas Foundation had shown that the sevengill cowsharks had filled the void in False Bay, with great white shark numbers having dwindled, although that hasn’t slowed down the orcas.

Marine biologist Alison Kock shared this video two days ago:

The notorious shark-eating orcas, Port & Starboard, found the sevengill shark aggregation at Seal Island today @SANParks #orcas #sharks #liveyourwild To learn more about these orcas https://t.co/k3YQ6E6VF0 pic.twitter.com/nK8JMiqYAs

— Dr. Alison Kock (@UrbanEdgeSharks) May 26, 2019

That link above takes you to a research paper titled ‘Running scared: when predators become prey‘, co-authored by Kock, along with Tamlyn M. Engelbrecht and M. Justin O’Riain.

Here’s a small part of the abstract, dealing with “the increased presence of killer whales (Orcinus orca) in False Bay”:

These super predators are known to specialize on certain prey species, and up until 2015 were only documented preying on marine mammals within False Bay. However, in 2015 and 2016 we documented two events in which killer whales preyed upon broadnose sevengill sharks, using a specialized feeding method in which only the liver of each shark was consumed.

Although selective feeding on shark liver by killer whales is established, this is the first record of killer whale predations on sevengill sharks in False Bay, and the first documentation of a novel feeding technique, in which killer whales used force applied to the pectoral fins of each shark to rupture the pectoral girdle and thereby access the liver.

Whilst there are probably some people who would be relieved to have fewer sharks around our coastline, the knock-on effect of a change in the ecosystem could be far-reaching:

Both sevengill sharks and white sharks play an important role as apex predators in the ecosystems they inhabit. A reduction in their numbers due to direct predation from killer whales, combined with their prolonged absence from traditional aggregation sites, is predicted to have cascading effects throughout entire coastal ecosystems.

…ongoing research is needed to gain a better understanding of the drivers behind killer whale presence along the South African coast, and the impact on the long‐term behavior and movement patterns of apex shark species such as sevengills and white sharks.

You can read that full paper here.

All in all, it’s a pretty exciting time for those with a keen interest in our ocean’s ecosystems, with Port and Starboard really shaking things up.

[sources:facebook&esajournals]