Oceanic Whitetip Shark (Carcharhinus longimanus) Silky Shark (Carcharhinus falciformis) Grey Reef Shark (Carcharhinus amblyrhynchos) Scalloped Hammerhead Shark (Sphyrna lewini) Pelagic Thresher Shark (Alopias pelagicus) Whitetip Reef Shark (Triaenodon obesus)

Species Information

Here you can find basic information for shark species in the Egyptian Red Sea. Visit our research pages to find more detailed information about Oceanic Whitetip Sharks, Silky Sharks and Grey Reef Sharks.

Behaviour and Sensory Systems

Understanding how sharks experience the world can give us an insight into their behaviour and how best to interact with them.

Understanding Shark Behaviour

Sharks may well be the most feared and misinterpreted of all predators on our planet. Fuelled by the movie 'Jaws' (1975) and its sequels, subsequent publications, movies and documentaries, the picture of sharks as blood thirsty monsters has been firmly rooted in our heads.

In real life, the majority of the about 500 shark species described today is not even physically capable of causing serious damage to a human in the water, let alone interested in approaching one.

On the contrary, attempting to closely encounter sharks in their natural environment can easily turn into a challenging and time-consuming quest, not only because of their declining numbers, but because they avoid humans and their activities whenever possible.

The Red Sea is home to some of the more tolerant or even inquisitive species; close encounters may occur e.g. with oceanic whitetip sharks (Carcharhinus longimanus), silky sharks (C. falciformis), scalloped hammerhead sharks (Sphyrna lewini), grey reef sharks (C. amblyrhynchos) and even the elusive pelagic thresher shark (Alopias pelagicus).

Observing these large predators in the open sea is a fascinating experience.

The key to understanding, interpreting and eventually predicting their behaviour is knowing how sharks perceive their world; what senses they have at their disposal and what signals they are prone to react to.

This basic knowledge can avoid some of the major misconceptions about shark behaviour, which are stubbornly clouding any objective assessment of these animals.

Sensory Overview

Different shark species or families may have specific adaptations or alterations to their sensory systems; given here is a general overview.

Objective assessments of shark behaviour throughout the last few decades have revealed surprising signs of social interactions and even cooperation; sharks have developed fascinating physiological solutions to be able to inhabit basically all available marine habitats; they learn and adapt their strategies to different environmental situations.

Hearing

The furthest reaching sense that will alert a shark to a potentially interesting situation is its hearing. The only external signs of this sense are two small pores behind the eye on either side of the head, leading into the inner ear. The hearing range is about 10 – 1500 Hz (humans: 20 – 20.000 Hz, dolphins: 200 – 150.000 Hz), with most responses shown to irregular pulsating sounds lower than 400 Hz. This enables predatory sharks to pick up, for example, sounds created by the erratic flapping movements of injured or dying fish. Depending on the strength of the signal, low-frequency sound waves might well travel several kilometers under water before being significantly attenuated.

Smell

Skin flaps are directing water into the paired nostrils on either side of the shark's snout, leading it past extensive olfactory epitheliums packed with chemoreceptors. These receptors will recognise a whole array of specific molecules in the water, allowing the brain to analyse the composition of the scent trail and identify the underlying source, especially if it belongs to its prey or indicates a conspecific's readiness to mate. The acuteness of the sharks sense of smell is legendary, under controlled conditions in pools they have responded to one part of tuna extract or blood in one million parts of water! Under natural conditions in the open sea, a lot of factors can cause a chemical trail to be diluted or break up, so the exact range of this sense is likely to vary with situation.

Vision

The eyes of sharks are complex, highly evolved vertebrate eyes, and about ten times better adapted to low light conditions than human eyes. Species living in clear or shallow water additionally have colour vision, with photo-receptors that are most sensitive to blue-green wavelengths. To protect the vulnerable lenses, some sharks have a third eyelid, the nictitating membrane, to be drawn over the eye just before attacking prey or closely approaching objects; others roll their eyeball under the tissue surrounding the eye away from potential injury.

Pressure

(Lateral line system). All along both sides of the body sharks have a system of water filled pores and connected canals, whose pressure-sensitive haircells detect differences in water pressure and acceleration. This information is related to the brain and allows the shark to identify and locate prey organisms and avoid potential predators. Depending on the strength of the water movement and pressure changes, the lateral line system is reported to function over a distance of about two body lengths to more than 100 m.

Electric & Magnetic

(Ampullae of Lorenzini). Little dark pores all over the sharks' snout and lower jaw mark the exit points of channels connected to small sacs, the so-called Ampullae of Lorenzini. They are filled with mucus and are sensitive to small electric currents, which helps to detect the minute electric activity any living organism produces, as well as allowing the sharks to use the magnetic field of the earth for orientation. Again, information on this sense's maximum range differs, in this case from 2 m to about 20-30 cm. Hammerhead sharks with their flattened, widened heads and enlarged sensory area are the most efficient in their use of this sense.

Touch

This contact sense relies on open nerve endings under the sharks' skin that react to direct physical pressure. Some sharks, especially bottom-dwellers, have barbels around their mouths giving them additional sensitivity when probing the sand for food.

Taste

This second contact sense is formed by taste buds in the sharks' mouth & gullet. They detect the same principal tastes as humans (sweet, salty, bitter & sour), and sharks tend to nudge and mouth objects to decide if they are edible.

Myths

With an understanding of basic facts on shark behaviour and their sensory systems, some of the more common misconceptions are easily corrected...

The explanations given here to debunk some of the most common shark myths are adjusted to the situation and the species in the Red Sea, with clear warm water, no river mouths or extensive surf zones, and laws to prohibit fishing or feeding activities at dive sites.

Depending on the location, the species and the kind of interaction, there will be other factors to be considered!

Sharks will attack and try to eat anything in their path, including humans.

Most of the about 500 shark species in the world's oceans are fairly specialised in their diet, proven by specific adaptations of their teeth and other morphological features. Only very few species are large enough and have such general and opportunistic feeding habits, that they would even theoretically consider something the size and shape of a human as potential prey.

The large oceanic sharks, e.g. oceanic whitetip sharks (Carcharhinus longimanus), mako sharks (Isurus sp.), silky sharks (C. falciformis), blue sharks (Prionace glauca) are most likely to take a closer interest in humans and their activities. After all, they do have very few natural enemies, and the open sea is a difficult environment; these sharks cannot afford to be picky or let a potential food source pass by, not knowing when the next one comes along.

Even if any of these sharks display any kind of interest in a human, e.g. a scuba diver, they generally approach carefully. Keep in mind that they are approaching something rather large, loud and unknown. As a predator, they need to stay healthy and avoid injuries, which explains their cautious behaviour. A lot of their subsequent behaviours will depend on the human's response to the approach.

Diving or swimming with sharks is suicidal.

All available statistics on shark attacks (or shark incidents) clearly contradict that statement. Actually scuba diving is probably the safest way to interact with sharks in their natural environment, while there is some reasonable concerns about swimming with them. The position on the surface is the most vulnerable one. For a marine predator, seeing a large 'something' on the surface probably leaves three main possibilities: an inanimate floating object (very often accompanied by a variety of smaller marine organisms underneath), the carcass of a marine animal, or an animal in trouble that is unable to leave the surface due to injury or sickness. All these situations invite a large predator to approach safely from underneath, and check this object for its food potential.

The minimum safety requirement for somebody swimming in an area where sharks are likely to occur is wearing a mask. This will at least allow you to be aware of an approaching shark and react to it. The reaction can be as simple as following its movement with your head and/or calmly changing your body position in relation to it. Again, sharks are very successful and efficient predators, they do register if they have been detected by their environment or not. Once they have been seen, they loose the element of surprise and stay cautious; they might even turn away and leave.

Where there are dolphins, there are no sharks.

For the open sea, the opposite is closer to the truth. Dolphins travelling or hunting over deep water in the tropics or subtropics are often accompanied by sharks, e.g. oceanic whitetip sharks (Carcharhinus longimanus) or silky sharks (C. falciformis).

A shark circling a human being is getting ready to attack.

Contrary to common beliefs, a shark that calmly circles a human in the water is by no means preparing for an attack. A more realistic explanation is that the shark is simply making use of its full range of senses, in this case especially the lateral line system, to explore and identify the unknown object it encounters. After one or two circles they normally turn away and disappear again, unless their attention is held by one of their other senses.

Bending down the pectoral fins is a sign of aggression in sharks.

Bent-down pectoral fins is one of the behaviours that have been identified from threatening displays shown by a variety of sharks in the presence of humans. Like many other agonistic displays in the animal kingdom, they consist of a sequence of stereotyped behaviours that evolved to avoid physical confrontations, which could result in injury for both opponents.

Because of the ritualistic and sequential nature of these displays, one cannot simply take one of the behaviours out of this complex context and assign the same meaning to it.

To qualify as part of an aggressive display, the bent down pectoral fins would have to be accompanied at least by stiff, exaggerated swimming movements, an arched back and a lifted head. By itself, bending down pectoral fins in an otherwise slow swimming, relaxed shark simply functions to steer this animal away from the object it approaches. The closer the approach, the more marked the angle of the pectorals (see images below). In some cases, the use of only one pectoral fin indicates in which direction the shark will turn away, as shown in image 4; the right pectoral is almost vertical, the animal turns away to its right side.

Longimanus Pectoral Fin Myth

On a personal note...

Statistics only take us so far in dealing with human phobias or anxieties. Knowing that the realistic chance of something (like e.g. a shark attack) happening to you is 0.000X % or less is inconsequential if your are facing a primary fear, like being dragged down into the abyss, being eaten alive, or – actually – if you should be the one in a million (or more) that is struck by this statistically almost impossible event...

Understanding shark biology as well as personal encounters with sharks have helped a lot of divers to overcome the horror-image that has been planted in our heads for decades by the media and numerous Hollywood productions.

Most myths regarding sharks are leftovers from an era, where behaviours were generally interpreted as being directed towards us, human beings. One look at the sharks evolutionary history is enough to correct that impression. The earliest shark ancestors have been identified to be about 400 million years old; most shark species living today are virtually unchanged in tens of millions of years. The period of time that they have coexisted with humans in their underwater realm equals no more than a tiny fraction of their existence. They have had no time for behavioural adjustments to our presence; equally, they have neither had enough time with nor exposure to humans to become familiar with us and classify us as a food source. Quite frankly and sadly, the millions of years it would take them to adapt they won't get, looking at the incredible speed we decimate their populations.

Having said all that, sharks still are large, effective predators. Pretending that there is absolutely no risks in closely interacting with them is wrong and unrealistic. The best approach is one of respect and caution, free of hysteria and sensationalism. Sharks are not out there to get us; aggression is rare and normally provoked by humans.

But everybody has his or her own personal comfort zone when it comes to sharks. Just make sure that you stay well within its limits when you enter the water with them.

Diving with sharks...

The Egyptian Red Sea offers great opportunities to meet sharks underwater, especially when diving the offshore islands and reef walls. The majority of sharks will avoid close encounters with humans in the water, they are careful, shy and easily intimidated by our presence. The best case scenario with these species is that they tolerate us in their vicinity, which generally only happens with divers that stay very calm and quiet.

In certain situations, or with certain species such as oceanic whitetip sharks and silky sharks, close approaches might occur and are something that divers should be prepared for.

Behavioural Rules

Remember, you are entering the realm of highly evolved and perfectly adapted open-ocean predators, who should be treated with respect and caution. And while the risks in diving with sharks are minimal, following certain behavioural rules helps to avoid potentially stressful or even dangerous situations.

  • Feeding sharks is illegal across the Egyptian Red Sea! Do not enter the water if there is any sign of feeding activity around the boat.

  • Insist on being properly briefed before a potential encounter.

  • Only enter the water if you are comfortable with the situation and confident that you can stay calm.

  • Avoid any quick, jerky or erratic movements.

  • Be aware that you are most vulnerable on the surface. So descend promptly after entering the water and watch your buoyancy throughout the dive.

  • Try to avoid quick ascents, especially with a shark right below you.

  • If you want (or need) to leave the water, do so in a calm and orderly fashion.

  • Most shark species that are inquisitive enough for close approaches are found in open water, not along the reef. Staying next or retreating to the reef should help avoid a close encounter. If conditions allow it, surface next to the reef and wait to be picked up by zodiac.

  • Do not try to touch or in any way harass any shark. This includes not closing off an escape route for sharks you find underneath overhangs, in caves or crevices in the reef wall.

  • Do not be alarmed by a shark calmly circling you; just make sure you turn with it and keep it in sight

  • Stay alert and look around you from time to time to see if another shark is approaching you from behind/underneath/above. As predators, sneaking up on unknown objects is part of their natural behaviour.

  • Generally, sharks are more reluctant to closely approach groups of divers than single ones.

This text is referring to diving only. Snorkelling in the Marine Parks, in St. Johns, and around reefs where oceanic whitetip sharks or silky sharks might be present, is forbidden until further notice following the unfortunate death of a french snorkeler on the St. Johns plateau in June 2009.

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