In the last issue of Le Mag, we have already made three observations concerning the tiger shark. We will now continue these observations by analyzing the behavior of this shark, a rather delicate area, as we will see in our "observation N ° 4" ...
Observation N ° 4
Although having made more than fifty immersions with the tiger shark, it is difficult to define with certainty the behaviors and the codes of the interaction between this shark and the man, whereas it is not not for oceanic sharks and hammer. During a stay in South Africa, a tiger shark specialist who has been diving for more than 7ans for two dives a day with him, told me about his observations: "The only thing I know about the behavior this animal is that I do not know anything! Difficult, therefore, to build a behavioral record of the species. On the other hand, there are two significant approaches that we can explore. The tiger shark is a fish with which it is easy to interfere because, not very shy in the presence of the man, it is him who will approach the divers and who will decide the interactions. To date, two types of dives are feasible in the presence of this predator: on the one hand feeding and on the other unprovoked encounters. It is on the study of these two extremely different explorations that we will proceed to the analysis of their behavior.
Under food stimulation
As this article is not intended to be part of the debate that this practice constitutes, we will focus on shark approaches in two circumstances and places of "feeding".
In South Africa, this type of diving is done in drift, about thirty meters under our fins. A washing machine drum is filled with 20kg of sardine porridge at a depth of 6 to 8m and a second smaller can is arranged between 10 and 12m, the interest being to create an olfactory corridor allowing the shark to go up the flow to its source. In addition to attracting tiger sharks, odors also attract sharks (Carcharhinus limbatus) and sometimes bulldog sharks called there Zambian sharks (Carcharhinus leucas). Contrary to popular belief, tiger sharks are not the first on the zone and will leave the territory to smaller sharks. During this time, he (they) go (go) to swim at the level of the second can, below us, in arcs of circles, at the limit of our visual field which, because of the low visibility, is reduced. Very shy, this shark will first observe. Sometimes he disappears to reappear behind us, out of the eye contact that bothers him.
Photo © Gilles Di Raimondo
Little by little, the concentric circles around the baits will be reduced, its depth of evolution will decrease and its swimming will accelerate. The shark, wary, will have taken the time it needed to understand and analyze the scene and all its actors. Once all risk is removed, it becomes dominant and quickly takes possession of the territory by removing other sharks and divers in the area, provided that the said divers have not previously shown signs of intrusiveness. Then a ballet is set up, dancing through which the tiger sharks present on the zone will follow the same axes of approach. From blue to the bait box to disappear into the blue again and then return one after the other to the box. Playing with the limit of visibility they attract us and move us away from the group. If an individual more daring than others dares, he will sniff the box that only rarely resists the pressure of his jaws. It follows then a frantic struggle between sharks to engulf the porridge of sardines they all want and the meeting is over! This dramaturgy is played every day according to the same ritual. Sharks are used to it and tirelessly repeat their role as extras. They are as trained. They know the man, which is why the safety instructions issued by the guide are imperative and must be strictly adhered to.
Photo © Gilles Di Raimondo
In the Bahamas, the context is different. Turquoise waters, visibility of 30m, depth of evolution 6m, dive sites: sandy bottom under the boat. The bait technique remains essentially the same, namely a canister filled with carcasses plunged into the current to attract sharks. This area is a resting area for full females before giving birth, far from the open sea so that juveniles are safe from predators. Here, same fight. The scent attracts other sharks, lemon sharks (Negaprion brevirostris) as well as gray Caribbean sharks (Carcharhinus perezi) sometimes. The behavior of female tiger sharks is slow, relaxed and without any aggressiveness.
Photo © Charlotte Faulkner
Always under a certain axis, they approach in front of the box while going up the current, sometimes overhang the diver, but evolve most of the time along the sandy bottom at the same level as us. Territoriality is set up between the sharks because the larger, more experienced, approach the scent zone, unlike the young, more fearful, who are excited by the bait but too fearful to approach it. Once again, sharks are used to the presence of humans and completely indifferent to their signals. Here, the safety instructions are less, taking into account the environment and the experience of sharks facing humans.
Photo © Charlotte Faulkner
Some recommendations to interact safely with tiger shark diving feeding :
- Wearing a full suit is compulsory. The white color of our skin is reminiscent of the color of the muscle of a fish, therefore of a bait!
- To avoid panic, be prepared psychologically. Before each straight jump, you are briefed and you can see the sharks from the boat before launching, which reduces stress.
- Adopt an upright position to appear more imposing and allow the animal to know our intentions. If this is not possible because you are in the sand, avoid lying down.
- Make as few movements as possible, no sudden movements, no agitation so as not to excite the shark. Usually if the shark is hand fed, the feeder (feeder) shakes his hand, so keep his arms along the body.
- Make as few bubbles as possible (avoid shortness of breath and excitement).
- Never find yourself isolated. The story of the lost sheep.
- Do not lose eye contact. Constantly look behind you. Curious and stubborn, the shark will not hesitate to approach you from behind because you no longer react to its approach!
- If the shark becomes too insistent, too inquisitive, leave the area but always facing it. Do not retreat so as not to react like a prey. Wait for the instructions and the signal from the feeder.
- If not comfortable, leave the area calmly.
Photo © Charlotte Faulkner
Tiger sharks react neither to flash, or very little, nor to recharging batteries, nor do they attach importance to your presence on the surface.
Clearly, diving with this shark implies the strict respect of certain safety rules and if you remain calm while respecting these instructions, you will have the unique chance to experience a moment of intimacy with this majestic shark, unfortunately disappearing of our oceans. By dipping with him under food stimulation, the tiger shark is demystified.
Dating not provoked, fortuitous
These meetings are more commonly known as "wild". They occur mostly by chance, on a reef or a coral bottom, in a pass or on sandy bottoms. Although tiger sharks are highly migratory, they are nonetheless sedentary for part of the year, at depths too great for divers during the day. During short seasons, their behavior changes and they can gather around certain areas to mate, rest or give birth. And it is now proven, after scientific study, that large fish populations migrate and aggregate in specific areas, at particular times for breeding. The example of natural encounter presented below was found twice, in the Red Sea, a non-specific place of encounter with tiger sharks:
- In the Red Sea, in 2009, a curious gathering of eight tiger sharks on the Elphinstone reef, in Egypt, amazes divers. These sharks will populate and stir the life of the coral reef for more than two months, and for some females, almost a year.
At the same period, in 2013, still in the Red Sea but in Sudan, the same gathering of tiger sharks was observed along a drop off for several weeks. There are four, three females and a large male. The dates coincide with the gap between two gestations for a female tiger shark. You should know that they do not reproduce every year. The most likely hypothesis is that sharks come together for a specific purpose, that of reproducing, because females do not yet possess the marks inflicted by the violence of the reproductive act, which consists of biting the female above. gills the better to protrude it, and they are not yet full. This hypothesis, according to which they would come to the area to reproduce, is not to be ruled out even if no change is noticed in the level of the life of the coral reef.
- During the reproduction period, the most imposing females, the most mature, delimit areas and territories. The stress generated by the presence of several rivals makes them particularly aggressive towards each other. The latter seek to attract the attention of males by the release of pheromones and chemical stimuli. Stimulation of males can also be done by generating nerve electrical impulses underwater, through tonic attitudes and behaviors, but also by best protecting their territory by using intimidation, sometimes force and this, at all depths.
It is during unprovoked fortuitous encounters that it is essential to make the right decisions.
During a feeding, one or more tiger sharks are attracted by the smell of food. Their motivation is to feed themselves. No amalgam is made between the divers and the bait. Sharks will quickly accept the presence of men to the point of ignoring them. If the situation degenerates, the boats are always above.
At a gathering to breed or otherwise, tiger sharks are not attracted to odors. The mere presence of divers on their area stimulates stress and makes the females even more nervous towards each other. The incursion of a large animal, the diver, on a preciously guarded territory, excites the pretenders and favors, by sending signals, their status of dominant animal to appropriate the favors of the males.
The shark can also confuse the diver with a rival potential, even a real intruder, that must be hunted from its territory.
Faced with a diver, who clearly has no advantage against such an animal, the tiger shark will not hesitate to:
- Show yourself several times, at various depths, from near and far.
- Go up from the bottom at good speed towards the divers.
- Overlook the area for divers.
- Perform "sprints".
- Being seized with nervous spasms.
- Hit the reef with his head.
- Approach head-on and unhook at the last moment, slowly or quickly.
It is sometimes difficult to go back to the boat simply, because the meetings are made during underwater walks. This is why it is relevant to display the greatest caution in the presence of this shark under these conditions. The most judicious, if this kind of signs appears, is to:
- leave his area of development, his territory, and go up quietly, without getting excited as one of his prey would do because that could make him even more nervous.
- Stay together, do not isolate yourself as a "black sheep" would do because, like any good opportunistic predator, it will associate the diver detached from the group with a sick prey.
- Keep the animal in visual contact until it disappears. As a general rule, it will not persecute like an oceanic shark (carcharhinus longimanus) or silky shark (carcharhinus falciformis) with relentless inquisitive rounds. He will step back and leave when the divers have left his area.
- Finally, do not get agitated underwater, and always keep calm.
Diving with tiger sharks in such circumstances requires a lot of hindsight, control and self-confidence. It is necessary to be able to understand, to detect and to judge the codes sent by the animal and especially to respect well and the rules of security and the intimacy of the shark.
To deny this story and convince the most perplexed, do not forget that in the underwater animal kingdom, there are no rules! Thus, it is also possible to observe a classic passage of curiosity shark on the diver's area, before seeing it disappear completely from your field of vision.
As you will have understood, it is not easy to describe a line of conduct in an animal as complex as the shark and particularly the tiger shark. Any behavior will necessarily be the result of a combination of several factors: a food stimulation, or its absence, will be grafted to factors of intra and inter species sociability, to the experience of the shark, to the reasons for its presence in the area, to the excitement of other sharks, etc ... To be continued!