Whale Shark

Biology and Behavior of the Largest Fish in the World

Whale Shark Whale Shark, Rhincodon typus
Borut Furlan/WaterFrame/Getty Images

Whale sharks are gentle giants that live in warm waters and have beautiful markings. Although these are the largest fish in the world, they feed on tiny organisms. 

These unique, filter feeding sharks appeared to evolve about the same time as filter feeding whales, around 35 to 65 million years ago. 

Identification

While its name may be deceiving, the whale shark is actually a shark (which is a cartilaginous fish).

Whale sharks can grow to 65 feet in length and up to about 75,000 pounds in weight. Females are generally larger than males.

Whale sharks have a beautiful coloration pattern on their back and sides. This is formed  of light spots and stripes over a dark gray, blue or brown background. Scientists use these spots to identify individual sharks, which helps them learn more about the species as a whole. The underside of a whale shark is light.

Scientists are not sure why whale sharks have this distinctive, complex coloration pattern. The whale shark evolved from bottom-dwelling carpet sharks that have noticeable body markings, so perhaps the shark's markings are simply evolutionary leftovers. Other theories are that the marks help camouflage the shark, help sharks recognize each other or, perhaps most interesting, are used as an adaptation to protect the shark from ultraviolet radiation. 

Other identification features include a streamlined body and broad, flat head.

These sharks also have small eyes. Although their eyes are each about the size of a golf ball, this is small in comparison to the shark's 60-foot size.

Classification

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Elasmobranchii
  • Order: Orectolobiformes
  • Family: Rhincodontidae
  • Genus: Rhincodon
  • Species: typus

    Rhincodon is translated from the Green as "rasp-tooth" and typus means "type."

    Distribution

    The whale shark is a widespread animal that occurs in warmer temperate and tropical waters. It is found in the pelagic zone in the Atlantic, Pacific and Indian Oceans.

    Feeding

    Whale sharks are migratory animals who appear to move to feeding areas in conjunction with fish and coral spawning activity. 

    Like basking sharks, whale sharks filter small organisms out of the water.  Their prey includes plankton, crustaceans, tiny fish, and sometimes larger fish and squid. Basking sharks move water through their mouths by slowly swimming forward. The whale shark feeds by opening its mouth and sucking in water, which then passes through the gills. Organisms get trapped in small, tooth-like structures called dermal denticles, and in the pharynx. A whale shark can filter over 1,500 gallons of water an hour. Several whale sharks may be found feeding a productive area.

    Whale sharks have about 300 rows of tiny teeth, totaling about 27,000 teeth, but they are not thought to play a role in feeding.

    Reproduction

    Whale sharks are ovoviviparous and females give birth to live young that are about 2 feet long. Their age at sexual maturity and length of gestation are unknown.

    Not much is known about breeding or birthing grounds either. In March 2009, rescuers found a 15-inch long baby whale shark in a coastal area in the Philippines, where it had been caught in a rope. This may mean that the Philippines is a birthing ground for the species.

    Whale sharks appear to be a long-lived animal. Estimates for the longevity of whale sharks are in the range of 60-150 years.

    Conservation

    The whale shark is listed as vulnerable on the IUCN Red List. Threats include hunting, impacts of diving tourism and overall low abundance.

    References and Further Information:

    • Associated Press. 2009. "Tiny Whale Shark Rescued" (Online. MSNBC.com. Accessed April 11, 2009.
    • Martins, Carol and Craig Knickle. 2009. "Whale Shark" (Online). Florida Museum of Natural History Ichthyology Department. Accessed April 7, 2009.
    • Norman, B. 2000. Rhincodon typus. (Online) 2008 IUCN Red List of Threatened Species. Accessed April 9, 2009.
    • Skomal, G. 2008. The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. Cider Mill Press Book Publishers. 278pp. 
    • Wilson, S.G. and R.A. Martin. 2001. Body markings of the whale shark: vestigial or functional? Western Australian Naturalist. Accessed January 16, 2016.
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    Kennedy, Jennifer. "Whale Shark." ThoughtCo, Aug. 29, 2016, thoughtco.com/whale-shark-profile-2291598. Kennedy, Jennifer. (2016, August 29). Whale Shark. Retrieved from https://www.thoughtco.com/whale-shark-profile-2291598 Kennedy, Jennifer. "Whale Shark." ThoughtCo. https://www.thoughtco.com/whale-shark-profile-2291598 (accessed September 26, 2017).