The whale shark (Rhincodon typus) is a large, slow-moving shark that feeds by filtration. It is the largest known fish species. The largest recorded specimen was 18.8 meters long. This shark holds several size records in the animal kingdom, most notably as the most massive non-cetacean animal. It is the sole member of the genus Rhincodon and the family Rhincodontidae within the subclass Elasmobranchii of the class Chondrichthyes. Before 1984, it was classified as Rhiniodon in the family Rhinodontidae.
Whale sharks live in open waters of all tropical oceans, rarely found in waters below 21°C. Their lifespan is estimated between 80 and 130 years, based on studies of their vertebral growth bands and growth rates of free-living specimens. These sharks have very large mouths and feed by filtration, similar to megamouth and basking sharks. Their diet consists mainly of plankton and small fish, and they pose no threat to humans.
The species was identified in April 1828 after a 4.6 m specimen was harpooned in Table Bay, South Africa. Andrew Smith, a British military doctor, described it the following year. The name "whale shark" refers to its size and appearance; however, it is a fish, not a mammal, and is not closely related to whales. Its filter-feeding habits are similar to those of baleen whales.
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Characteristics: What is the whale shark (Rhincodon typus) like?
Whale sharks have a broad, flattened head with a large mouth and two small eyes at the front corners. Unlike many other sharks, their mouth is located at the front of the head rather than on the underside. A 12.1-meter whale shark had a mouth 1.55 meters wide. This mouth can contain over 300 rows of tiny teeth and 20 filter pads for feeding. The spiracles are located just behind the eyes, and they have five large pairs of gills. Their skin is dark gray with a white belly and marked with pale gray or white spots and stripes, unique to each individual. The skin can be up to 15 cm thick, being very tough and rough to the touch. The shark has three prominent ridges along its sides, starting behind the head and ending at the caudal peduncle. It has two dorsal fins located towards the rear of the body, a pair of pectoral fins, a pair of pelvic fins, and a single medial anal fin. The caudal fin is heterocercal, with the upper lobe larger than the lower.
It has been discovered that whale sharks possess dermal denticles on the surface of their eyeballs, structured differently from those on the rest of the body. These denticles, along with the shark's ability to retract its eyes deeply into the sockets, protect the eyes from potential damage.
Evidence suggests that whale sharks can recover from severe injuries and regenerate small sections of their fins. Additionally, their spot patterns can reform over previously wounded areas.
The complete and annotated genome of the whale shark was published in 2017, forming part of the order Orectolobiformes and family Rhincodontidae.
Rhodopsin, the light-sensitive pigment in the retinal rods, normally green-sensitive, is adapted to low-light vision. However, in the whale shark and the cloudy catshark, two amino acid substitutions make the pigment more sensitive to blue light, predominant in the ocean depths. One of these mutations also makes rhodopsin vulnerable to high temperatures. In humans, a similar mutation causes congenital stationary night blindness due to pigment breakdown by body temperature. This pigment becomes unstable in shallow waters, where the temperature is higher, and the light spectrum is complete. To avoid this instability, the shark deactivates the pigment in shallow waters and reactivates it in the cold ocean depths. These mutations allow the shark to see well at both ends of its vertical range. The shark's eyes have lost all cone opsins except LWS.
Size and Measurements
The whale shark is the largest animal in the world after cetaceans. There is evidence suggesting sexual dimorphism in size, with females being larger than males. A 2020 study, which analyzed the growth of these sharks over a decade, determined that males reach an average length of between 8 and 9 meters. This same study predicted that females could reach an average length of around 14.5 meters, although this estimate is based on more limited data. These averages do not represent the maximum possible sizes. Previous research has estimated that whale sharks can measure between 14 and 21.9 meters in length. Limited evidence, primarily on males, indicates that sexual maturity is reached at approximately 8 to 9 meters, while females may mature at an equal or greater size. The maximum length of the species is uncertain due to the lack of detailed documentation of the largest reported individuals. Whale sharks around 18 meters long have been documented.
Accurately measuring large whale sharks is challenging, both on land and in the water. On land, the total length can vary depending on the position of the tail, whether it is at a natural angle or stretched to its fullest. In the water, historical techniques have included comparisons with objects of known size and knotted ropes, but these can be inaccurate. In 2011, laser photogrammetry was proposed to improve the accuracy of measurements in the water.
The Largest and Heaviest Whale Shark in the World
Since the 19th century, there have been accounts of large whale sharks. Some of these include:
In 1868, the Irish scientist Edward Perceval Wright obtained several small specimens in the Seychelles. Wright was informed of a whale shark measuring over 14 meters. He claimed to have observed specimens over 15 meters and was informed of individuals over 21 meters.
Hugh M. Smith described a huge animal caught in a bamboo fish trap in Thailand in 1919. The shark was too heavy to drag to shore and no measurements were taken. Smith learned from independent sources that it measured at least 10 wa (a Thai unit of length measuring between the outstretched arms of a person). Smith noted that a wa could be interpreted as 2 meters or the approximate average of 1.7 to 1.8 meters, according to local fishermen. Later sources claimed this whale shark measured approximately 18 meters, but the accuracy of the estimate has been questioned.
In 1934, a ship called Maunganui encountered a whale shark in the South Pacific Ocean and rammed it. The shark got stuck on the bow of the ship, reportedly with 4.6 meters on one side and 12.2 meters on the other, suggesting a total length of about 17 meters.
Scott A. Eckert and Brent S. Stewart reported on the satellite tracking of whale sharks between 1994 and 1996. Of the 15 individuals tracked, two females were reported to be 15 and 18 meters respectively. A 20.75-meter-long whale shark was reported stranded along the coast of Ratnagiri in 1995. A female individual with a standard length of 15 meters and an estimated total length of 18.8 meters was reported from the Arabian Sea in 2001. In a 2015 study analyzing the size of marine megafauna, McClain and colleagues considered this female to be the most reliable and accurately measured.
On February 7, 2012, a large whale shark was found floating 150 kilometers off the coast of Karachi, Pakistan. The specimen's length was said to be between 11 and 12 meters, with a weight of around 15,000 kg.
Classification of the Whale Shark (Rhincodon typus)
- Kingdom: Animalia
- Phylum: Chordata
- Class: Chondrichthyes (cartilaginous fish)
- Order: Orectolobiformes
- Family: Rhincodontidae
- Genus: Rhincodon
Habitat and Global Distribution
The whale shark inhabits tropical and warm temperate seas worldwide. Predominantly pelagic, it is found in both coastal and oceanic zones. Tracking studies have revealed that whale sharks have dynamic habitat use patterns, likely in response to food availability. In the northeastern region of the Yucatan Peninsula, these sharks swim in coastal surface waters from dawn to mid-afternoon, followed by vertical movements in oceanic waters during the afternoon and night. About 95% of this time is spent in epipelagic depths (less than 200 meters), although they also perform regular deep dives (more than 500 meters), often descending in "stepped patterns," likely in search of food. The deepest recorded dive reached 1,928 meters, making the whale shark the deepest diving fish ever recorded. They have also been observed staying at depths greater than 50 meters for three days or more.
The whale shark is a migratory species with two distinct subpopulations: an Atlantic subpopulation, ranging from Maine and the Azores to Cape Agulhas in South Africa, and an Indo-Pacific subpopulation, which hosts 75% of the entire population. They are generally found between 30°N and 35°S, where water temperatures are above 21°C, although they have been spotted as far north as the Bay of Fundy in Canada and the Sea of Okhotsk, north of Japan, and as far south as Victoria, Australia.
Seasonal feeding aggregations occur at various coastal sites, such as the Persian Gulf and the Gulf of Oman, Ningaloo Reef in Western Australia, Darwin Island in the Galapagos, Quintana Roo in Mexico, Mafia Island in Tanzania, Inhambane Province in Mozambique, and the Philippines, around Mahe in the Seychelles, the coasts of Gujarat and Kerala in India, Taiwan, southern China, and Qatar.
In 2011, a gathering of over 400 whale sharks was recorded off the coast of Yucatan, one of the largest documented concentrations. Aggregations in this area are some of the most reliably seasonal, with large numbers of whale sharks congregating most years between May and September. The associated ecotourism has grown rapidly, reaching unsustainable levels.
Growth, Reproduction, and Longevity
The growth, longevity, and reproduction of the whale shark are still poorly understood aspects. There was uncertainty about whether the growth bands in their vertebrae formed annually or every two years, which is crucial for determining the age, growth, and longevity of these sharks. A 2020 study compared the ratio of carbon-14 isotopes in the vertebral growth bands with the nuclear testing events of the 1950s and 1960s, revealing that the growth bands form annually. This study determined an age of 50 years for a 10-meter female and 35 years for a 9.9-meter male. Other studies have estimated their lifespan to be between 80 and 130 years.
Evidence suggests that males grow faster than females in the early stages of life but eventually reach a smaller maximum size. Whale sharks exhibit late sexual maturity, with males estimated to reach maturity around 25 years old.
Although no whale shark pups have been observed, mating has been recorded in Santa Elena. The first filmed record of the species mating was in 2019, off Ningaloo Reef in Australia, where a male unsuccessfully attempted to mate with an immature female.
In July 1996, a 10.6-meter pregnant female was captured with 300 pups, indicating that whale sharks are ovoviviparous. The eggs remain inside the body, and females give birth to live young measuring 40 to 60 cm in length. Evidence suggests that the pups are not born all at once, but the female retains sperm from one mating and produces a steady stream of pups over a prolonged period.
On March 7, 2009, marine scientists in the Philippines discovered what is believed to be the smallest living whale shark ever recorded. This young shark, 38 cm long, was found with its tail tied to a stake on a beach in Pilar, Sorsogon, and was released back into its natural habitat. This finding suggests that the area may be a birthing ground. Both young whale sharks and pregnant females have been seen in the waters of Santa Elena, where numerous whale sharks can be observed during the summer.
In August 2019, whale shark sightings were reported during photographic identification activities by WWF Philippines. There were a total of 168 sightings, 64 of which were re-sightings of previously registered whale sharks. WWF highlighted the identification of "very young whale shark pups" among the individuals sighted in the first half of 2019, suggesting that Ticao Pass could be a breeding ground for the species.
Feeding, What Does It Eat?
The whale shark is a filter feeder, being one of the three species of sharks that use this method, along with the basking shark and the megamouth shark. Its diet includes plankton, copepods, krill, fish eggs, red crab larvae from Christmas Island, and small nektonic creatures such as squid or small fish. It also consumes clouds of eggs during the mass spawning of fish and corals. The numerous vestigial teeth it possesses play no role in its feeding.
The whale shark employs two feeding methods: ram filtration, where it swims with its mouth open pushing water and food into its mouth, and active suction, where it opens and closes its mouth, sucking in water that it then expels through its gills. In both cases, the filter pads separate the food from the water. These unique sieve-like pads are modified gill rakers that separate food by cross-flow filtration, where water travels almost parallel to the surface of the filter pad. This method is extremely efficient, minimizing the clogging of the pads. Whale sharks have been observed "coughing" to clear the buildup of particles on the filter pads. They migrate both for feeding and possibly for reproduction.
The whale shark actively feeds and concentrates in areas with high concentrations of plankton or fish. It can filter feed while swimming or do so in a stationary position. A juvenile consumes approximately 21 kg of plankton per day.
Due to their feeding method, whale sharks are known to ingest microplastics, which have been confirmed in their feces.
Where to See It
Despite their size, whale sharks do not pose a danger to humans. They are docile and sometimes allow swimmers to hold onto them, though this practice is discouraged by scientists and conservationists due to the disturbance it causes the sharks. Juveniles are friendly and may interact with divers.
The Rhincodon typus shark is spotted by divers in many locations, including the Bay Islands in Honduras, Thailand, Indonesia, the Philippines, the Maldives, the Red Sea, Western Australia, Taiwan, Panama, Belize, Mozambique, South Africa, the Galapagos Islands, Saint Helena, Mexico, the Seychelles, Malaysia, India, Sri Lanka, Oman, Puerto Rico, and other parts of the Caribbean. Juveniles are found near the shore in the Gulf of Tadjoura, in the Horn of Africa.
It is common to book guided excursions to see the whale shark and even participate in swimming activities in Cancun, Isla Mujeres, Isla Holbox in Mexico, as well as tours in various regions of the world where it is present and has its natural habitats.
Is it Dangerous or Aggressive?
No, the whale shark is not aggressive. Despite its enormous size, it is a docile species and poses no threat to humans. They are known for their calm behavior and often allow swimmers and divers to approach them. Whale sharks are primarily filter feeders, consuming small organisms like plankton, which reinforces their harmless nature towards humans. However, it is recommended not to touch or disturb them, as it is important to respect their space and natural behavior like with any wild animal.
Conservation Status and Endangerment
There is no solid estimate of the global population of whale sharks. The IUCN considers the species endangered due to fishing, bycatch, and ship strikes, combined with their long lifespan and late maturation. In June 2018, the New Zealand Department of Conservation classified the whale shark as "Migrant" with the qualifier "Secure Overseas" under the New Zealand Threat Classification System.
It is included in the CMS Memorandum of Understanding on the Conservation of Migratory Sharks. In 1998, the Philippines banned all fishing, selling, importing, and exporting of whale sharks for commercial purposes, followed by India in May 2001 and Taiwan in May 2007.
The Gulf of Mexico oil spill in 2010 affected whale sharks, as they could not avoid the oil slick in their feeding area. Although no dead whale sharks were found, their habitat was severely impacted.
In Captivity
The whale shark is present in some public aquariums, though its large size requires a very big tank and specialized feeding needs. Its large size and iconic status have also generated opposition to keeping the species in captivity, especially after the early deaths of some captive sharks.
The first attempt to keep whale sharks in captivity was in 1934 in Izu, Japan. Since then, several aquariums have kept the species with varying survival rates. The record for a whale shark in captivity is an individual that has lived for over 26 years at the Okinawa Churaumi Aquarium.
Outside Asia, the only place that has kept whale sharks in captivity is the Georgia Aquarium in the United States. Georgia has two whale sharks: Taroko and Yushan, which arrived in 2007. Other whale sharks in Georgia died in 2007, 2020, and 2021. All whale sharks in Georgia were imported from Taiwan before Taiwan closed this fishery in 2008.
Common Names for Rhincodon typus by Country
In Madagascar, whale sharks are called "marokintana" in Malagasy, which means "many stars," referring to the markings on the shark's back.
In the Philippines, they are known as "butanding" and "balilan." The whale shark appears on the reverse of the 100-peso Philippine banknote. By law, divers must maintain a distance of 1.2 meters (4 feet) from the sharks, and there are fines and possible imprisonment for anyone who touches these animals.
In Japan, whale sharks are called "jinbei-zame" because their markings resemble the typical patterns of the jinbei, a traditional garment. In Indonesia, they are known as "gurano bintang," and in Vietnam as "ca ong," which literally means "sir fish."
In English-speaking countries like the United States and England, it is called "whale shark."
The whale shark also appears on the 2015-2017 edition of the 1,000-rufiyaa banknote of the Maldives, along with the green turtle.