Whale Shark
Scientific Classification: Rhincodon typus
Overview
Whale sharks are the gentle giants of the ocean! Not only are they the biggest sharks, but they are also the largest fish alive today. It is estimated that whale sharks can grow as large as 61.7 feet on average.
Despite the “shark” in their name, whale sharks are far removed from the bloodthirsty predators frequently portrayed on television. They are filter feeders. Gliding through the water, they draw in and sift through tiny sources of nourishment such as plankton, krill, schooling fish, and crustaceans with their wide mouths.
Whale sharks are known to have a gentle demeanor towards humans, though they may occasionally bump into boats inadvertently. Regions recognized for whale shark sightings benefit from tourists keen to dive or snorkel with these giants, thereby generating income for local communities and enhancing conservation efforts.
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Orectolobiformes
Family: Rhincodontidae
Genus: Rhincodon
Species: R. typus
Diet
Plankton and small pelagic animals like copepods, krills, and small fish
Size
Up to 61.7 feet in length. Weighing up to 92,000 pounds.
Lifespan
140+ years
Conservation
Endangered
Features
True Shark
The name “whale shark” might be confusing to some – the whale shark is not a whale but a fish. As a true shark, unlike mammals such as whales and dolphins, which must surface to breathe, whale sharks can remain submerged indefinitely, drawing oxygen from the water through their gills. They also possess a skeleton made of cartilage rather than bone.
The “whale” reflects its enormous size and similar filter-feeding behavior found in baleen whales, such as humpback or blue whales.
Coloration
Whale sharks display a blend of gray, blue, or brown hues on their backs with white spots and stripes that create a checkerboard design. Their bellies are white without any markings.
Similar to the unique fingerprint of each human, the spotted pattern of every whale shark is one-of-a-kind. These spots help researchers differentiate and identify each individual.
Electroreception
Whale sharks, like many other marine animals, have a sixth sense called electroreception. Electroreception refers to the ability to detect electric fields in their environment. This sensory capability is facilitated by specialized organs known as the ampullae of Lorenzini, which are gel-filled canals ending in pores on the skin’s surface, primarily around the shark’s head and nose.
While electroreception is well-documented in many shark species, enabling them to detect the weak electric fields generated by muscle contractions of prey or navigate by sensing the Earth’s magnetic field. It’s believed that electroreception in whale sharks may aid in navigating the vast oceans, locating swarms of plankton, and possibly in social interactions or detecting predators.
Filter Feeder
Whale sharks are filter feeders – a feeding method that involves swimming with their mouths open to collect and consume small organisms suspended in the water. As they swim, they take in water filled with plankton, small fish, krill, and microscopic plants and animals. Their gills are equipped with gill rakers – fine, bristle-like structures – that act as a filtration system. As water passes over these gill rakers, food particles are trapped, and water is expelled.
Whale sharks have thousands of tiny teeth, with estimates ranging from about 3,000 to over 4,500 teeth in 300 rows. These teeth are very small, often only a few millimeters in size. The teeth of whale sharks are considered to be vestigial, meaning they are remnants of an evolutionary past and do not serve a significant purpose in their current feeding behavior.
Distribution
Highly migratory
Whale sharks are known to wander the open sea. Recent research shows that they can make incredible journeys, reaching up to 8,078 miles over 37 months. That is nearly 7 miles per day!
Whale sharks are primarily pelagic, roaming the open tropical and warm temperate waters across the globe, with a preference for water temperatures between 70°F and 86°F. They are occasionally observed near coasts, lagoons, and coral reefs. Whale sharks are primarily observed in epipelagic zones, typically remaining above depths of 660 feet. However, the deepest recorded dive reached 6,325 feet.
Whale sharks are migratory and often return to the same spots to feed. They’re attracted to areas with abundant food sources, such as plankton blooms and spawning events. Australia’s Ningaloo Marine Park is a hotspot for whale sharks, especially from March to April, when they gather off the central western coast.
These sharks have a broad habitat range, from the Atlantic Ocean – stretching from New York to the Gulf of Mexico and the Caribbean, extending to parts of South America and West Africa. In the Pacific Ocean, they can be seen in the Philippines and Taiwan to parts of Indonesia, extending eastward to islands like Galápagos and even farther into the central Pacific. Occasionally, sightings are reported in the Red Sea.
Diet
The whale shark, alongside only two other shark species – the basking shark and the megamouth shark – is a filter feeder. They filter out water and capture small organisms ranging from microscopic zooplankton to small pelagic animals like copepods, krills, shrimps, crab larvae, jellyfish, squids, and various small fish and fish eggs. Some fish includes sardines, anchovies, and mackerel, as well as young tunas and albacore.
Did you know?
A juvenile whale shark can consume up to 46 pounds of plankton daily!
Reproduction
Growth Rate
As whale sharks age, their growth rate slows down. In the first year, whale sharks grow at a rate of 1.3 feet per year, which gradually declines to 0.87 feet per year by the age of 20.
Whale sharks take about 24 to 28 years to mature, usually at least 16 feet long before they’re considered adults. As they age, these sharks prefer the open sea, a big change from their younger days spent closer to the shore.
A mother whale shark can have more than 300 pups at once! They are born alive, a process known as ovoviviparity, where the eggs hatch inside the mother, and then she gives birth to her live young. Research has identified the waters southeast of Taiwan as a critical birthing area for whale sharks during the summer months. Upon entering the world, these baby whale sharks already measure about 22 to 25 inches in length.
Behaviors
Whale sharks exhibit a few different feeding behaviors:
- Ram filtration: This is where they swim forward with their mouths open, letting water flow in and over the gill rakers, trapping food as the water exits through their gills.
- Active suction feeding: In this method, whale sharks suck in volumes of water and prey by rapidly opening and closing their mouths, acting like a giant vacuum.
- Vertical feeding: Sometimes observed in a stationary, vertical position, whale sharks open and close their mouths to draw in water rich with food.
Feeding
Social
In spite of their massive size, whale sharks pose no significant threat to humans. In fact, whale sharks are often curious and even playful around divers and snorkelers, allowing close encounters without showing aggression. They have been known to allow swimmers to hitch a ride on their backs. However, experts in shark science and conservation advise against this practice, citing the stress it causes to the animal and concerns for people’s safety.
Their calm demeanor has made them a popular attraction for eco-tourism. However, as with any wild animal, it’s important to maintain a respectful distance to avoid disturbing them or altering their natural behaviors.
Importance to Humans
Ecotourism
Whale sharks significantly contribute to ecotourism, attracting snorkelers, divers, and educational tours to regions where these docile sharks gather, such as Ningaloo Marine Park in Western Australia. From March to July, the park becomes a feeding ground for hundreds of whale sharks converging to dine on zooplankton. Typically, 300 to 500 whale sharks gather annually, generating approximately AU$6 million (about $8 million USD) in 2006 for the local economy.
Nonetheless, there is a growing concern for the well-being of whale sharks. Incidents where whale sharks have been injured by boat strikes have been reported. Furthermore, conservationists and divers worldwide advocate for the protection of whale sharks and other large marine species by urging people to refrain from riding, chasing, or harassing them.
Aquarium
Whale sharks have become major attractions in the few public aquariums capable of accommodating them. Their substantial size necessitates expansive tanks and specialized care. The history of whale sharks in captivity began in 1934, when one was kept in a netted-off section of a natural bay in Izu, Japan, for approximately four months. There have also been many instances where whale sharks are kept in captivity in China. To date, the Georgia Aquarium in Atlanta, USA, is the only facility outside Asia that has successfully managed to care for whale sharks.
Concerns are mounting regarding the ethics of holding whale sharks in captivity, driven by their need for extensive roaming areas and the premature deaths of some individuals in such settings.
Trade
Although internationally protected as an endangered species, whale sharks are still targeted due to the high demand for their parts. In regions where regulations exist, enforcement might be weak, allowing illegal trade to flourish. Sometimes, whale sharks are caught accidentally as bycatch in nets targeting other fish. However, instead of being released, they might be retained because of the value of their parts.
Meat
Whale shark meat can be found fresh, frozen, dried, and salted for human consumption in some regions. In Indonesia, a 22-foot-long whale shark can yield 2,200 pounds of meat valued at $1,800 in the market.
Liver Oil
Liver oil from whale sharks can be processed and sold for use in cosmetics, supplements, and for industrial purposes.
Fins
One of the most lucrative parts of the whale shark is its fins. It is highly prized in the shark fin soup market, especially in some Asian countries, such as China and Taiwan. Whale shark fins are exceptionally large and can fetch a high price on the black market.
Danger to Humans
Whale sharks seldom cause any issues. On rare occasions, they have collided with fishing charters after being provoked. The most significant risk comes from accidental collisions with boats. Studies show that over 80% of the world’s goods are transported by sea, making maritime transport a backbone of global trade. However, whale sharks share much of their space with these large vessels – 92% horizontally and almost 50% vertically.
Ecological Interactions
Associations
Bottlenose dolphins, yellowfin tuna, blackjacks, hammerhead sharks, and tiger sharks are frequently observed swimming near whale sharks or feeding in proximity. Silky sharks and Galapagos sharks are known to rub against the bodies and heads of whale sharks.
Sharksuckers and common remoras adhere to whale sharks, particularly near the mouth, tail, and pelvic fins as a mode of transportation and feed on leftover food particles. Blue-streak cleaner wrasse and moon wrasse in the Philippines and king angelfish in Malpelo Island have also been documented to clean whale sharks.
Parasites
Whale sharks often play host to tiny hitchhikers called copepods. One specific type, the Pandarus rhincodonicus, is especially common on whale sharks in both the Pacific and Indian Oceans. Although these copepods feast on microorganisms found on the whale shark’s skin, they also feed on small bits of the skin itself and the mucous that whale sharks produce.
Predators
There are not many known predators for whale sharks. However, when they are small, the pups are vulnerable to blue sharks and blue marlins. There have been cases where young whale sharks were found inside the stomachs of these predators. At Ningaloo Reef in Australia, great white sharks and tiger sharks have been known to feed on whale sharks, especially when they gather in groups.
Conservation
In 2016, the International Union for Conservation of Nature (IUCN) labeled whale sharks as “endangered.” Due to their docile nature, whale sharks are over-exploited. These giants primarily face threats from human activities: they are illegally hunted for their meat by fishermen with harpoons and at risk of collisions with large ships. Although hunting, selling, and trading whale sharks have been outlawed in countries such as Malaysia, the Philippines, and India, the demand for their meat and fins continues to place them in jeopardy, particularly in Asia.
You May Also Like
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- Dove A. 2015. Foraging and Ingestive Behaviors of Whale Sharks, Rhincodon typus, in Response to Chemical Stimulus Cues. The Biological Bulletin 228(1): 65-74. https://doi.org/10.1086/BBLv228n1p65
- Fisher C., Slater M. 2010. Effects of electromagnetic fields on marine species: A literature review. Oregon Wave Energy.
- Green S., Hearn A., Green J. 2023. Species associated with whale sharks Rhincodontypus (Orectolobiformes, Rhincodontidae) in the Galapagos Archipelago. Biodiversity data journal 11, e97864. https://doi.org/10.3897/BDJ.11.e97864
- Moore G., Newbrey M. 2016. Whale shark on a white shark’s menu. Mar Biodiv. 46, 745–746. https://doi.org/10.1007/s12526-015-0430-9
- Nijman V. 2023. Illegal Trade in Protected Sharks: The Case of Artisanal Whale Shark Meat Fisheries in Java, Indonesia. Animals : an open access journal from MDPI 13(16): 2656. https://doi.org/10.3390/ani13162656
- Norman B., Reynolds S., Morgan D. 2022. Three-way symbiotic relationships in whale sharks. Pacific Conservation Biology 28:80-83. https://doi.org/10.1071/PC20043
- Perry C. 2017. Age and Growth of Whale Sharks (Rhincodon typus) near the South Ari Atoll, Maldives. Master’s thesis. Nova Southeastern University.
- Perry C. et al. 2020. St. Helena: An Important Reproductive Habitat for Whale Sharks (Rhincodon typus) in the Central South Atlantic. Front. Mar. Sci. https://doi.org/10.3389/fmars.2020.576343
- Perry C., Figueiredo J., Vaudo J., Hancock J., Rees R., Shivji M. 2018. Comparing length-measurement methods and estimating growth parameters of free-swimming whale sharks (Rhincodon typus) near the South Ari Atoll, Maldives. Marine and Freshwater Research 69: 1487-1495. https://doi.org/10.1071/MF17393
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