Posted on Thursday, 30 September 2010
Dear Shark Lovers,
I am really excited to sit down and report our September shark news so I hope that you will all find time to sit down and enjoy this!
At the very end of the season we experienced a truly phenomenal event of Great white sharks feeding on a whale carcass in False Bay that was the ultimate end to a great 2010 season at Seal Island.
Whale Carcass Feeding Event
Our Great white shark season at Seal Island normally goes through to about 10 to 15 September. At this point the seasons start to change and with the arrival of spring warmer water currents bring a multitude of other shark species and gamefish to False Bay. The Great whites must prefer to feed on these prey items as at the soonest chance of a “choice of menu” the sharks depart Seal Island is search of their new choices inshore.
We had a good early September whereby we were seeing a good number of predatory events on the seals and then still a number of sharks around the boat when anchoring. As we got closer to 10 September there was a dramatic down turn in activity with only a couple of predatory events at the very start of the morning and nothing up at the boat. We were hosting a great group of shark fanatics with Alessandro De Maddalena over a 10 day period and as they had already had great encounters with the great whites the good weather gave us an opportunity to try a pelagic shark trip on the last day of their trip.
One of the singles biggest lessons in nature is to always be aware of the signs and signals the environment is constantly projecting. Over the last 10 years we have had the privilege of witness 4 events of sharks feeding on whale carcasses. Each time Giant Petrels, the great scavenging bird of the open ocean, have been prolific at these natural events.
Just as we were about to head out of False Bay Chris noticed a large amount of these birds concentrated in a small area. He instinctively knew what they had come across so made a 90 degree turn off course and we thus shortly stumbled onto a dead 12 meter Brydes whale. So followed a fascinating 9 day event as we witnessed a clean up job like no other.
On closer inspection it was evident that the whale had sadly either been hit by a large boat or had died in a trawl net (this was surmised from two deep lacerations down the length of her body). Although the carcass was only a few days old there were already a number of white shark bites as well as what we presumed were blue shark and mako shark bites. This made sense since the carcass had drifted into False Bay from the open ocean.
The Great Tow
Chris made a decision to tow the whale some 9 miles further into False Bay to Seal Island in the hope that the Great Whites could dispose of the carcass in the natural way. Judging by the prevailing weather conditions and current drift the carcass would have washed up onto a tricky bit of coast line making the clean up job a very difficult one. As the carcass would have weighed between 12 and 15 tons the towing mission was extremely slow going. Half way through the morning and only 2 miles into the journey we were able to enlist the help of the navy tug boat. (A big thank you to them!).
We eventually arrived around 3pm at Seal Island. Would you believe that over the 9 mile towing area across False Bay we did not have one single shark come to investigate? We found this unbelievable as the chum slick that was being created as we towed the whale was like a super highway of all things good for sharks. We firmly believed that upon arrival to the Island it could only be a maximum of 30 minutes before the first Great white arrived. As with so many times with sharks we were wrong!
We eventually departed the Island at 6.30pm having not had a single shark at the carcass. We all felt exceptionally dissapointed for the Italians that were so excited to see this event and who were flying out that evening.
The following day we headed out in very strong wind not knowing what to expect.
We knew that the sharks had already changed their movement pattern to the inshore area so it was very interesting to note what a dramatic affect a chum slick onshore had in the sharks being able to locate the carcass. The following few days would provide fascinating information about what our Great white sharks are doing this time of year when we normally struggle to find them.
Upon arrival it was evident that the sharks must have found the carcass in the early hours of the morning once the wind direction had changed onshore.
Large chunks of blubber had already been removed and one animal was busy gorging himself as we attempted to secure our boat onto the anchored whale.
Great white sharks need to consume high energy yielding food as they themselves require large amounts of energy to maintain their energy sapping lifestyles as well as be able to thermo regulate their own body temperatures. The tick layer of blubber on a whale is the ultimate energy source for this and must be irresistible to a hungry or even a not yet hungry shark. We had to cut a small chunk of blubber for samples for MCM and were really surprised at how tough it was to obtain this small piece and was certainly not the marshmallow like texture one would assume.
This knowledge makes the actual feeding event that more spectacular. Each time a shark comes in to feed it can take up to a 50 pound chunk of blubber as it vigorously saw’s away at its rich find. Each time its jaws clamp down a great whoosh of water is pushed through giving way to a very memorable sound given that this is the only time you will actually hear a Great white shark. The apparent ease with which they tear chunks from the carcass is spectacular. Once the chunk is obtained the shark will slowly and gently slide away before plotting its return in this all you can eat buffet.
One would think that a feeding opportunity such as this would give rise to a feeding frenzy but this is not the case at all.
In all 5 whale carcass feeding events we have now observed all feeding has been done in a pretty controlled manner and although they sharks are that much more excited than normal due to the over stimulus of the giant whale slick their behaviour is by no means out of control.
I guess the most interesting and memorable observation of this event was just how selective the sharks were. Once the best blubbery bits had been eaten off the side of the whale the sharks had to work a little higher up on the carcass to find the rest of the blubber. What remained on the side was the actual flesh of the whale. It was extremely evident of how selective the sharks were when they would bite into the flesh and then move on as soon as they could taste it was not the energy rich blubber they were after. Under such stimulated circumstances we all thought it was amazing that they were clearly able to make a decision on exactly what part of the whale they were after. I guess this pretty much puts to rest any claims of Great whites going into a feeding frenzy.
In one horrific moment a shark inevitably bit through the womb of the whale and out popped its already dead calf that was at just about full term. We all felt terribly sad at this terrible waste of life of this whale and its unborn calf …the fact that the sharks were able to benefit rather than the carcass being removed from a beach somewhere did at least mean that some good came of it.
Great whites are seldom comfortable with each others presence and a strict hierarchy of the bigger animals being dominant over the smaller animals exists. This did somewhat break down under this mass feeding event. Some of the sharks did have fresh bite marks from other sharks, probably having been derived from feeding too close to each other meaning that they would need to have been pretty tolerant of each other to get that close. This more relaxed behaviour was also observed when we had 2 to 3 sharks around the carcass together. I would imagine that since the “meal” was so large competition between the sharks was not high.
Numbers & Shark Sightings
On the day of the tow we observed no Great whites on the carcass at all. We started the tow from the mouth of False Bay with the slick being carried in WNW direction. I think it would be safe to say that due to the irresistibility of the slick there could not have been a single shark in this area and direction!
Even the first few hours at Seal Island brought no sharks at all.
Once the wind direction changed and thus took the slick directly onshore to the beach the sharks started to arrive once they obviously found the slick in that area.
We previously did not have a good idea of how many sharks are patrolling the inshore area once the sharks leave Seal Island but our observations here do give some insight.
After spending the entire day with the carcass on day 2 we recorded 23 different Great white sharks. The most feeding at one time were four individuals. On day 3 we recorded 9 different sharks and on day 4 another 5 different sharks. From day 5 the numbers of sharks started to drop until day 8 and 9 there were none at all. Chris & I had to leave for a trip to Guadalupe from day 6 but our crew and Alison Kock from Save our Seas kept us well informed with what was happening. It is possible that the same sharks were recorded on different days but I think we can safely surmise that there were 30 plus sharks at this mass feeding event. I would never have thought that this many sharks would be present in False Bay at this time of the year so it is very valuable information as to their movements in the Bay.
Interestingly many of the sharks where sharks that we had seen during the season including the famous Amber, Clover, Sicklefin and Nikita. All three of these sharks had not been seen at Seal island for some time prior to the whale carcass. Also interesting were the number of sharks that we had not seen before. There are so many sharks that we think are in the area but never feel comfortable coming up to the boats so this does give us some further insight.
In the past we had seen very large sharks arrive at carcasses including a massive 5.5 meter female in 2002. At this event these big sharks were worryingly absent. The largest female was about 4.4 meters and we had one large male of about 4.1 meters.
Throughout the whale carcass feeding event the sharks were still predating on seals with varying success. This is absolutely amazing to me but I guess when they happen to come across a seal natural instinct must kick in. Whatever the reason it is pretty unlucky for the seal that was killed by a completely over satiated Great white shark.
Isle Guadelupe, Mexico
Chris & I were really dissapointed to have the leave the whale carcass before it was over. This was an extremely rare event that we were privileged to come across and I don’t know if we will ever have the chance again. Never the less we had an amazing experience and learnt a great deal in the process.
We did however have another great privilege to spend some time with the Great whites at Isle Guadalupe off Mexico. Since we do not have any sharky plans for October I think I will save our Guadalupe events for then. It was a great trip so be excited for the news!
In the meantime we have completely revamped our website to include more detailed info on the trips and expeditions that we host and a new range of photographic prints have also been added.
Be sure to check out www.apexpredators.com as well as Photo’s of The Month for all the whale carcass and Guadalupe images.