whale sharks

Whale sharks (Rhincodon typus) are found in warm, tropical waters around the world. At certain times of the year they gather in areas that provide a rich food source, like the KwaZulu-Natal coastline of South Africa, where they are found in numbers towards the end of summer. (See more information on these mysterious creatures provided by the KwaZulu-Natal Nature Conservation Service. A marine Earth-Touch crew headed by Graeme Duane will be filming this event again this year, so look out for new footage on our website.

The name “whale shark” refers to the whale-like size of this shark, and the fact that it sieves the sea with its huge mouth for plankton and microscopic sea life, similar to the way that baleen whales do.

Whale sharks are huge animals that can grow up to about 18m (59ft) long and weigh around 34 tons (in comparison an adult elephant weighs less than one fifth of this weight, or about 6 tons, according to the KwaZulu-Natal Nature Conservation Service. Colouration is brown or dark blue-grey, with white spots and stripes on the upper body surfaces and white below. Whale sharks have massive, wide mouths and their eyes are positioned on either side of their mouths.

Riding this current, they travel in huge silvery shoals many kilometres long and several kilometres wide. As they make their way north, there’s guaranteed to be an amazing show of predatory sea life, from birds to seals, sharks and dolphins, which turn out in great numbers for the feast.

Whale sharks are filter feeders, consuming mostly plankton, which they sieve from the water, but they also eat small fish like sardines and anchovies, krill and squid, according to the Canadian Museum of Nature. Although they have many rows of small teeth, these are not used in feeding. Whale sharks feed by sucking seawater into their cavernous mouths and forcing it out through their gills. In the process, a fine sieve in the gills traps tiny plankton organisms, which the whale shark swallows.

Although whale sharks are mainly pelagic, seasonal feeding takes place at several coastal sites worldwide, like Ningaloo Reef in western Australia and Útila in Honduras. Whale sharks are also believed to be philopatric or site-faithful, which means they tend to return to the same seasonal feeding locations every year. (See the Australian Department of the Environment and Heritage’s factsheet on whale sharks).

Not much is known about the breeding of whale sharks, but evidence from captured species indicates that they are ovoviviparous (i.e. the female produces eggs that hatch inside her body, and then gives birth to live young.) According to the KwaZulu-Natal Nature Conservation Service’s whaleshark factsheet, the young measure about 60cm (2ft) in length when born, and are mature only at about the age of 30.

The whale shark is the only member of the genus Rhincodon, and is believed to have originated about 60-million years ago. The whale shark was first identified in April 1828, after one measuring 4.6 m (15ft) was harpooned in Table Bay, South Africa, according to Smiths’ Sea Fishes, edited by Margaret M Smith and Philip C Heemstra. Struik, Cape Town, 2003. ISBN: 0387168516

The meat and fins of whale sharks are still sought-after commodities by fishermen, which poses a serious threat to populations where such activity is not monitored. Threats posed by pollution, increased boat usage and overfishing on reefs also impact on whale sharks, directly and indirectly, particularly in terms of the destruction of their prey. It is also feared that migratory patterns may be disrupted due to noise pollution and habitat destruction. See the Whale shark project for more information about this.