Port & Starboard at Seal Island
Posted on Sunday, 26 May 2019
The notorious shark-eating orca duo of Port and Starboard need no introduction. Last weekend the carcasses of 5 Sevengill sharks washed ashore in the Betty’s Bay area showing the classic signs of an orca kill, a surgically clean removal of each shark’s liver. They were sighted in this area at that time and a day or so afte, they were then spotted further up the coast in Struisbaai. With the high number of Sevengill sharks we were currently seeing at Seal Island we felt as if we had dodged a bullet.
However, early yesterday morning we received a call from Ryan, our Skipper on White Pointer 2 .
Ryan had found Port and Starboard at Seal Island.
We were already in the car on our way to Simon's Town to go hiking, so plans were immediately changed and we managed to get out to the Island fairly quickly.
In our absence Ryan and our crew reported that the kelp gulls were busy feeding around what we classically observe as post predation events.
Port and Starboard, confirmed age at being over 30 based on the curled flukes, were patrolling around Seal Island at a pretty good pace and their breathing pattern was fast and regular.
They then proceeded with some social behaviour together on the surface.
By the time we arrived they had slowed down quite a lot and were doing patterns further away from the Island, but always returning back to the vicinity of the Island. They generally seemed to stay down for up to 2-5 minutes at a time and would most times surface fairly far from where they had last submerged.
We were able to observe them over a 4 hour period and during that time on one occasion Chris was alerted to a big splash and the fluke of one of them coming back down into the water. When we approached the area there was a small slick on the surface indicating a feeding event had just taken place.
We have spent a lot of time talking to Dr Ingrid Visser, world renowned for her extensive work with orca. She is the only person to observe and document clear cases of orca killing and feeding on sharks, including sevengill sharks in New Zealand from beginning to end, above and below the water.
She describes one method, where an Orca will use a “karate-chop” action using its fluke to ultimately kill its shark prey. We think this is what Chris may have witnessed but with no carcass or any other way of identifying what was eaten, it is not possible to say for sure.
Later in the morning, and after the orca had spent multiple 2 to 5 minute chunks of staying below in the same area, a larger slick appeared on the surface. This was the second sign of a kill we could observe but again there was no positive way of identifying what the prey item was.
We can assume they were sevengill sharks since there were high numbers present at Seal Island but I must stress that we cannot say this with 100% certainty.
What we do question was a piece of seal skin that Ryan and our Crew spotted and retrieved from earlier in the morning. This was a very fresh piece of only the outside skin and had classic Orca teeth marks on the upper fur surface. Ingrid confirmed this for us stating “ The spacing of the teeth marks are similar to those I've seen from confirmed Orca predation events, and similar to the spacing seen on Orca when conspecifics rake them withtheir teeth.” She added “I believe you now have a record of these two Orca feeding on seals, which fits with their previous behaviour of targeting high-reward prey such as sharks.” It appears to us that this was the work of an orca and perhaps the skinning took place during a food sharing event. So, were the orca also eating seals, or perhaps only eating seals?
On our last sighting of Port and Starboard they went down and looked to be heading in an easterly direction back to Seal Island. A few minutes later, about 500 meters in front of where we had last seen them, a Sevengill shark breached out of the water twice. In the aftermath there was no slick, no bird activity and no further sighting of Port and Starboard. Dr Visser has again related to us that the sharks go ballistic in trying to get out of the water to avoid hunting orca and use anything they can as possible cover. So again, the assumption we made is that this shark could have had an encounter with the orca.
We have never seen Sevengill sharks breach before and this seemed an extreme event to us.
Another co-incidence took place as we were heading back to Simon's Town. We were again alerted to a large slick on the surface just to the south west of Seal Island. Two giant petrels and some gulls were at the source. Upon arrival we found a very fresh seal carcass (young of the year size). We could not find any signs of how the seal had been killed but it was strange that with the north wind that was blowing we can say with certainty that it had not washed from the Island. The seal had just died/been killed upwind of the Island. So, again we are left wondering if this was the work of Port and Starboard?
In total we can defiantly say we saw two post predation slicks (excluding a number of slicks our crew observed before we arrived). Without seeing any carcasses we cannot confirm, although we assume, the prey items were Sevengill sharks.
There is however also the question of the two seal remnants…
It is not a surprise that none of the shark diving boats saw any Sevengill sharks around the boat yesterday. We have two days of bad weather ahead so it is a case of waiting to see what we will find on Wednesday. And perhaps in the meantime some evidence will wash ashore that will help to answer some questions.