July 2007 Shark Bytes
Posted on Tuesday, 31 July 2007
Dear Shark Lovers!
When I last wrote I had pretty quiet shark news to pass on but in the month of July I am pleased to report that Seal Island was a very different place compared to June and the shark activity has been very good.
On top of the good sharking we also had much calmer weather and managed to get to sea on 22 out of 30 days. We did have periods of bad weather but on the whole we also had a lot of good weather days.
We have been seeing good numbers of sharks around the boat and have been observing great interactions on the number of occasions when there have been more than 2 sharks around at the same time. Great white sharks do not like to be too close to each other and according to the hierarchy system that exists with great white sharks the bigger animals dominate over the smaller animals. Often we will have a shark around the boat that will suddenly bank off or shoot away with great speed. This indicates to us that another shark is close by, even if we cannot see it. These observations of ours played an interesting role in an active predation that I will talk about a little further on.
Although the predatory activity that makes Seal Island unique is probably one the most exciting spectacles in all of nature my favorite part of our trips is to be on anchor and observe the different great white sharks gently cruise around our boat at their own free will. Each shark is so different from each other and I particularly like to observe the different personalities and to try to get to know and recognize each individual shark. Chris & I try as best as possible to keep data on each shark and we record specifics such as size, sex, injuries, pigment markings and any identifying features. We also note down observations of any specific personality traits such as a shark being particularly relaxed or even noticeably excited.
Over the years it was been very rewarding to see the return of our better known sharks. The longest period of time that we have seen sharks return to Seal Island has been the famous shark, Rasta. I have written about her many times. Chris first recorded her in 1997 and we last saw her during the 2005 season. There have been many other sharks that we have being seeing for the last 5 years or so.
Cuz is another of our well known sharks. He is a 3,7 meter (12 foot) male and a particularly successful hunter. He re-appeared in June and we were still seeing him during the first third of July. We had one exceptional day with him where he stayed around our boat for a good hour with no other sharks around. Although he is a good hunter it is interesting to note that he is always very relaxed around the boat and will often put his head out of the water to look at us or perhaps the boat.
After mentioning all of the above Chris and I are very concerned about the number of our well known sharks that we have not yet seen this year. These are sharks that historically return to the Island each year and that are of varying sizes. So, in theory they should be here and for some reason they are not. We still have about another 6 weeks before the end of our season so we hoping that they will still arrive.
We are also noting that there has been a very quick turn around of “batches” of sharks at The Island. When I say batch I mean that we seem to see the same few sharks on and off for a few days at a time and kind of get to know who is around. In July we were finding that we were seeing different sharks on most trips and a lot of the sharks seem to be staying for only 2 or 3 days at a time. As a result we are not getting to know the sharks too easily.
The predation activity (sharks attempting to hunt seals) in June was virtually non-existent. It has picked up a little in July. We had a number of very busy days where we were seeing in the region of 20 different events but also had days were we did not see any at all. Two of the busiest days where when we had experienced sea-going guests with us and we were able to go out in pretty rough seas as the cold front was approaching. On these two trips we observed intense natural predation in a short space of time. We think this is due to a number of reasons. The bad weather means that the seals probably need to return to the shelter the Island offers them, so there is more seal movement and more opportunities for the sharks to hunt. We also think that the overcast skies and lower light levels coupled with the rough water make it more difficult for the seal to pick up on a shark approaching from the depths. Under these conditions the sharks are more successful than on calm days.
There were two highly unusual predatory events that I would like to mention. On one occasion we were watching a protracted chase by a 3,8 meter (12.5 foot) shark on a young seal. The surface chase was rather intense and the large shark lunged out of the water, exposing up to three quarters of its body a number of times. As the seal appeared to be moving off towards the Island a noticeably smaller shark breached almost the whole way out of the water, and although it was in the vicinity of the seal it missed it by a long shot. Chris & I discussed the event afterwards and theorized that perhaps all the noise created by the chasing on the surface attracted the smaller shark to the event. It might have gotten a little too close to the event and its breach might have been the reaction to some sort of social interaction between the larger and smaller shark. It was just such an unusual event that I am still trying to play the scene back in my mind to try and work out what happened.