The whale shark, Rhincodon typus
(© Brad Norman)

What do they look like?
The whale shark (Rhincodon typus) is the largest shark in the ocean, reaching lengths of 20 metres and a weight of 20 tonnes. Whale sharks are closely related to the bottom-dwelling sharks, which include the wobbegongs. There is a pattern of lines and spots on the skin of each shark that enables them to blend into their surroundings.

The unique pattern does not appear to change over time and can be used to identify individual sharks (see photoid.whaleshark.org).

• What do they look like?
• Where are they found?
• What do they eat?
• How do they reproduce?
• What kind of environment do they live in?
• Are they migratory?
• What threatens the survival of Whale Sharks?
• Are Whale Sharks protected?

Where are they found?
Whale sharks (Rhincodon typus) have a broad distribution in tropical and warm temperate seas.They are thought to prefer surface sea-water temperatures between 21°–25°C. Sightings at Ningaloo Marine Park (NMP), however, are most common in water temperatures around 27°C.

They are known to live in both deep and shallow coastal waters and the lagoons of coral atolls and reefs. Australia is one of the most reliable locations to find whale sharks. They have been seen in India, the Maldives, South Africa, Belize, Mexico, the Galapagos Islands, Southeast Asia and Indonesia.

Whale sharks are widely distributed in Australian waters. They are most common in Ningaloo Marine Park, but have been seen at Christmas Island, off Queensland and near Eden, New South Wales.

What do they eat?
One of only three filter-feeding sharks (the other two being the basking and megamouth sharks), whale sharks feed on minute organisms including krill, crab larvae, jellyfish etc., and has been known to feed on larger prey such as sardines, anchovies, mackerels, small tunas and squid.

Although they have about 3 000 tiny teeth (each less than 6mm in length), these teeth are not used while feeding. Instead, the whale shark can sieve prey items as small as 1mm through the fine mesh of the gill-rakers. They are able to open their mouth wider than 1m to improve feeding and are occasionally sighted hanging vertically in the water to allow baitfish and other food items to be ‘sucked’ in.

The whale shark is widely distributed through tropical seas.
(© CSIRO)

Copepods and juvenile crabs are eaten by whale sharks ( © Brad Norman).

How do they reproduce?
Whale sharks have internal fertilisation and produce live young (ovoviviparity). They have the highest number of young of any shark – producing litters of around 300 pups, although these are very small at an average length of around 55 cm. The length of gestation, how often and where they breed remains unknown. The only pregnant female whale shark ever recorded was found off the coast of Taiwan. There have been very few juvenile whale sharks seen at any location in their range.

Studies of the whale sharks at NMP have established that male whale sharks do not usually mature before they reach a length of around 8 – 9 metres. Males can be distinguished by the presence of two claspers near the pelvic fin (absent in females). The size at maturity of female whale sharks cannot be determined through external observation.