Latin name

Rhincodon typus

Other names

Rhincodon typus

Identification

The body is strong and thick, the head is relatively small. The shape of the head is strongly flattened, becoming flatter towards the end of the snout. There are 5 gill slits, which are extremely wide and long. The mouth is at the end of the snout, not underneath as in most other sharks. The jaw is very broad, up to a metre and a half wide. It can open very wide and when fully open is a broad oval. The corners of the mouth have leathery growths that look like small antennae. The body becomes thick behind the head and the back rises in the form of a hollow hump. The body is thickest behind the head and then becomes thinner. On the back of the body there are several longitudinal folds of skin in the form of long ridges on the sides and back, extending to the tail. These sharks have a much smaller liver than most other sharks. As a result, they often swallow air to regulate their body's buoyancy (in other sharks, the liver, which contains a large amount of fat and is less dense than water, increases buoyancy).

Whale shark eyes

The eyes are very small and deep set, close to the end of the snout, almost at the edge of the mouth. They lie on the line separating the dark colouring of the back and sides from the white belly. In the largest specimens, the eyes are barely 5 cm in diameter. The slit is absent, but the eye may be closed by a thick fold of skin that extends forward. If a large enough object gets too close to the eye, the shark will pull the eye back into its orbit and cover it with this fold. This is a unique feature of these sharks. Almost immediately behind the eyes are the round mudguards.

Whale shark teeth

The number of teeth is extremely large and can reach several thousand. For example, a shark with 3,000 teeth in its mouth had about 300 rows of teeth on each jaw. The teeth are small, even in the largest sharks not exceeding 6 mm in length.

The brain of a whale shark 

The brain of the whale shark is significantly smaller than that of other sharks in relation to body size. The cerebellum is more developed than in other cartilaginous fish. Other features of its brain may be an adaptation to a social lifestyle.

Whale shark skin

The skin is very tough and thick, reaching a thickness of 14 cm in large specimens. It is covered with very small placoid scales that look like sharp spines, about 0.75 mm high and 0.5 mm wide. The structure of the scales differs markedly from those of most sharks - the scales of the whale shark have a very strongly developed and curved posterior tip, and the lateral lobes of the scales are poorly developed. It is thought that the scales of this structure improve the hydrodynamic properties of the fish's body. The skin is about a third thinner on the belly, which is probably why the shark often instinctively turns its back, which is better protected than the belly, when approaching a diver.

Features of fish fins

There are two dorsal fins, both of which are set well back. The first fin is high and broad, in the shape of an almost equilateral triangle. The caudal fin, as in all sharks, is highly asymmetrical, with the upper blade about one and a half times longer than the lower. At the same time, the upper blade has no notch, which is characteristic of the caudal fins of most sharks. For example, a 12-metre fish has a tail fin width of 4.8 metres and a pectoral fin length of 2.4 metres.

Fish colouring

The back and sides of this fish are dark, usually grey with blue or brown tinges. On the dark background are fairly regular longitudinal and transverse narrow off-white stripes, interspersed with fairly regular rounded spots of the same colour. On the head and pectoral fins the spots are smaller, more frequent and randomly arranged. The underside of the body is dirty white. The skin of the body and fins usually has a large number of scratches, creating an individual pattern that allows observers to distinguish certain individuals. The pattern of spots on the skin of sharks is not known to change with age.

It is thought that this colouration is an inherited trait from their ancestors. Another hypothesis is that the anti-shadow colouration may be due to the fact that whale sharks, which usually swim near the surface, are heavily exposed to ultraviolet radiation from sunlight, the harmful effects of which are neutralised to some extent by the dark colouration.

Distribution

Whale sharks are most commonly found near Taiwan and off the Seychelles, where they are present throughout the year, with peak numbers in these waters in June-August and October-November. Higher numbers are found off the coast of East and South East Africa, where numbers also fluctuate seasonally, with some estimates suggesting that 19% of the world's population is found off the coast of Mozambique. Other areas where these sharks are common include the Gulf of Mexico, Philippine waters (where they are particularly abundant from December to May), the coast of Chile and parts of the Australian coast. Elsewhere in their range, whale shark sightings are relatively rare and always seasonal.

Habitat

It is found in warm waters at low latitudes and occurs almost everywhere in this belt, although it is rare everywhere. Its range is mainly limited to waters between 30° north and 35° south latitude, but sharks can go as far north or south as 40° north. Sharks have been found to prefer areas of the ocean with a surface water temperature of 21-25°C, with an influx of cooler (up to 17°C) water from the depths (these areas are likely to contain the greatest amount of plankton on which sharks feed) and a very high salinity of 34-35 ‰. Observations in the Gulf of California suggest that whale sharks in this area prefer warm water, with temperatures of 26-34°C. There is evidence that these sharks occasionally appear in fresh water, swimming into the mouths of rivers, especially when there are clusters of planktonic organisms. They are characterised by exceptional apathy and slowness. Fish prefer to stay in the surface layer of water, usually not deeper than 70 metres.

Sailing speed

They swim with undulating movements of the entire back of the body, not just the caudal fin like most other sharks; in these gentle oscillations the fish uses about 2/3 of its body length. Whale sharks swim very slowly, about 5km/h under normal conditions, and often even slower.

Size

The whale shark is the largest modern fish. There is scientific information about a whale shark that is 20 metres long and weighs 34 tonnes. In the wild, however, whale sharks larger than 12 metres are extremely rare. As with most sharks, females are larger than males.

Behavior

They make very long migrations. Populations of these sharks are segregated by sex and size. It is possible that juvenile sharks stay in different areas than adults, and that different age groups of adult sharks (both males and females) have different migration routes. It is also likely that they prefer to return to the same places year after year after migrating.

Whale sharks are active around the clock and sleep for short periods regardless of the time of day. They feed during the hours of darkness.

They are kept in small groups or, more rarely, individually, and very rarely in schools of up to 100 fish. In exceptional cases, groups of sharks can contain hundreds of fish.

Food and feeding habits

It feeds on practically anything that falls into its mouth and that it can swallow. These are mainly various planktonic organisms a few millimetres in size - crustaceans, small squid, jellyfish, etc. It also eats small gregarious fish - anchovies, sardines, small mackerel and even small tuna. 

When feeding, the shark moves very slowly - about 1 m/s, and often almost stops, hanging in the water and sucking up plankton, swaying up and down, moving its head to the side. Often the fish is held almost perpendicular to the surface, sometimes the head can be seen poking out of the water between waves. Feeding at the surface can be very long, with an average of about 7.5 hours per day.

Whale shark feeding method

The whale shark's sifter  consists of 20 cartilaginous plates that connect the individual gill arches like a grid (the side of the cells is only 1-3 mm) and on which the skin teeth are located. When feeding, a shark can pass up to 6 thousand cubic metres of water through its jaws per hour. After collecting water with plankton in the mouth, the shark closes it and the water is then filtered through the gill openings. The filtered food is then passed through a narrow oesophagus (no more than 10 centimetres in diameter) into the stomach. Due to this feeding method, the teeth of the whale shark are very small and numerous; they are not used for biting, but for "locking" the prey in the mouth. The feeding shark makes 7-20 swallowing movements per minute, with the jaw movements occurring simultaneously with the movements of the gill slits. When food is plentiful, the fish is so full that its belly bulges.

Reproduction

Viviparous - embryos develop in eggs and hatch from them while still in the womb. At birth, aculeates are very small, about half a metre long. They have considerable internal reserves of nutrients that allow them to survive for long periods without an external food source. The shark has an exceptionally long period of sexual maturation. It does not reach puberty until 30, 35 or even 50 years of age, and its life expectancy is long - up to 70 and, according to some reports, up to 100 years. Puberty occurs when the shark reaches a length of 4.4-5.6 metres, according to some sources, and 8-9 metres according to others. These sharks have an excess of males over females.

Fishing

Sometimes caught by recreational fishermen, rarely by commercial fishermen. The most common way to catch these sharks is with a harpoon. Their sluggish temperament makes them relatively easy to catch.

Relationship with a person

Not considered a threat to humans.

The skin of this shark is used for tanning. Its body parts are used in traditional Chinese medicine.