| Name | Whale shark | Diet | Carnivorous (filter-feeder) |
| Scientific name | Rhincodon typus | Weight | 15–20 tons (33,000–44,000 pounds) |
| Pronunciation | weyl shark | Length | 8–14.5 meters (26 to 48 feet) |
| Classification | Chondrichthyes, Orectolobiformes, Rhincodontidae | Location | Worldwide |
The Whale Shark
What do you call a shark that looks and feeds like a baleen whale?
That’s a whale shark!
True to its name, the whale shark is a large shark that grows as big as whales and feeds by filtering tiny prey out of the water.
The whale shark is the largest living shark species, which also makes it the largest fish species alive today.
Whale sharks have a widespread distribution.
They are found in virtually all warm tropical and temperate oceans in the world.
The gentle giant is easily recognizable thanks to its large flattened head and a “checkerboard” color pattern.
The whale shark is one of the most interesting shark species in the world.
It is massive but completely harmless, making it a popular species with snorkelers and divers who frequently visit sites where the shark aggregates to catch a glimpse of it.
In this post, we’ll explore all the fascinating facts about the largest non-mammalian animal swimming in Earth’s seas.
Taxonomy and Classification
The scientific name of the whale shark is Rhincodon typus.
It is the only living shark species in the Rhincodon genus and Rhincodontidae family.
The only other member of this shark family, Palaeorhincodon) went extinct during the Paleocene Epoch.
The whale shark is a type of carpet shark (order Orectolobiformes).
This is one of the oldest shark orders that is still living today.
Members of this order are characterized by primitive features such as possessing five gill slits instead of four and having two spineless dorsal fins.
Carpet sharks have been around since the Jurassic Period.
The whale shark itself evolved during the Oligocene, about 28 million years ago.
However, the closely related and similar-looking Palaeorhincodon evolved earlier during the Paleocene and was alive till the Early Eocene Epoch, about 56 million years ago.
Physical Characteristics
As the name suggests, the whale shark is reputed for its sheer size.
It is an enormous shark with a body as big as a school bus.
It’s uncertain how big this shark can grow, but a maximum length of about 18.8 m (61.7 ft) has been recorded.
Adult whale sharks can weigh up to 41,000 pounds.
Based on this size estimate, the whale shark is easily the largest shark species alive and also the largest non-mammalian animal in the world’s oceans.
Female whale sharks are generally larger than males.
The average male measures between eight and nine meters (26 to 30 feet), while females grow to a length of about 14.5 meters (48 feet).
Whale sharks have broad, flattened heads with a large mouth located at the front of their head instead of underneath like other shark species.
The shark’s two small eyes are at the front corners of its face.
Like other carpet shark species, the whale shark has short barbels protruding from its nostrils.
The bizarre appearance of this shark’s head makes it look like an oversized catfish.
Whale sharks have large mouths.
A 12.1 meter (39.7 feet) long individual has gaping jaws measuring up to 1.55 meters (5.1 feet) across.
The mouth of an adult whale shark contains up to 300 rows of teeth and 20 filter pads used for filter-feeding.
Like other carpet shark species, the whale shark has five large pairs of gills.
It also has two dorsal fins located relatively far back on its body compared to other sharks.
Whale sharks have two pectoral fins, two pelvic fins, and a single anal fin.
The tail fins are heterocercal, meaning the upper lobe is larger than the lower lobe.
The shark also has three prominent ridges on its sides.
These are known as keels, and experts think they help the fish create turbulence in the water as it feeds, which can enhance the efficiency of its filter-feeding.
The skin of a whale shark is typically dark gray with a pattern of pale gray or white spots and stripes.
These spots and stripes are unique to each individual and can be used for identification, similar to a fingerprint.
Habitat and Distribution
Whale sharks have a global distribution.
They are found in tropical and warm-temperate seas all over the world except for the Mediterranean.
In the places where they’re found, whale sharks are known to inhabit shallow and deep coastal waters.
They may also be found in lagoons of coral reefs or islets.
These sharks prefer warm water with surface temperatures of about 21 to 25 ºC (69.8 to 77 ºF).
In the western Atlantic Ocean, whale sharks live off the coast of the United States and Central Brazil.
They’re also found in the Caribbean Sea and the Gulf of Mexico.
Whale sharks living in the Eastern Atlantic are typically found on the coast of Senegal, Cape Verde, Mauritania, and the Gulf of Guinea.
Whale sharks also inhabit the Indian Ocean and parts of the Pacific Ocean.
Their range in these oceans covers the coast of South Africa and the coast of various Asian countries such as China, Pakistan, India, and Sri Lanka.
Whale sharks also live off the coast of Australia, Papua New Guinea, and New Caledonia.
These sharks spend a lot of time close to the surface at depths of about 50 meters (160 feet) or less.
They are also found at epipelagic depths of about 200 meters (660 feet).
Whale sharks have been known to take regular deep dives to depths of up to 500 meters (1,600 feet or more).
The deepest recorded dive for this fish is about 1928 meters (6,325 feet), making the whale shark the deepest diving living fish species on record.
Behavior and Social Structure
Whale sharks forage at or near the ocean surface.
They are not strongly territorial.
They frequent certain areas where food and other resources are more abundant but are not aggressive toward other whale sharks in the same area, which is why they’re often described as gentle giants.
They do not get aggressive or threaten humans, even when researchers or divers swim right next to them.
Whale sharks are highly migratory sharks.
They tend to cover vast distances in search of productive feeding grounds.
Scientists have recognized two distinct subpopulations of this shark.
The population of whale sharks in the Atlantic has a range that extends from Maine and the Azores all the way to Cape Agulhas in South Africa.
The second population lives in the Indo-Pacific seas and accounts for up to 75% of the total whale shark population.
They typically migrate between latitudes 30°N and 35°S in warm waters with temperatures higher than 21 °C (70 °F).
However, they have been spotted in locations further south, such as Victoria in Australia, and up north as far as the Okhotsk Sea in Japan and Canada’s Bay of Fundy.
Whale sharks are also known for their seasonal feeding aggregations in various coastal sites.
Some of these locations include:
- The Darwin Island in the Galapagos
- Persian Gulf
- Gulf of Oman
- Ningaloo Reef in Western Australia
- Quintana Roo in Mexico
- Mafia Island of Pwani Region in Tanzania
- Yucatan Coast
Yucatan Coast hosts the largest yearly aggregations of whale sharks and is one of the most reliable places to spot them since they tend to gather here in large numbers between May and September every year.
Despite forming these aggregations, whale sharks are largely solitary and do not interact significantly, even when hunting prey in groups like this.
Whale sharks are more active during the day between sunrise and midafternoon when they swim inshore.
They spend the afternoon and night oscillating vertically in the water.
Diet and Feeding
Whale sharks are carnivorous filter-feeders.
While this is an unusual feeding habit for a shark, they’re not the only sharks that feed this way.
Other sharks that feed this way include the megamouth shark and the basking shark.
Their diet mainly consists of plankton.
These are tiny organisms such as copepods, krill, shrimp, and other tiny marine invertebrates.
In addition to plankton, whale sharks may also prey on schools of small fish and fish eggs.
The fish has a wide mouth, which it opens wide while swimming.
Although it has several rows of teeth that number up to 3,000 in total, the teeth do not play any significant role in feeding.
Whale sharks have filter pads (modified gill rakers) in their mouth.
These comb-like structures help filter out prey from the large volumes of water that the fish ingests.
Whale sharks capture prey through ram filtration (swimming forward with the mouth open) or active suction feeding (sucking in large volumes of water).
Once the prey is separated from the water and ingested by the fish, the excess water is expelled through the gills.
Whale sharks consume large amounts of food this way, with juveniles eating as much as 21 kilograms (46 pounds) of plankton daily.
Reproduction and Life Cycle
The reproductive behavior of whale sharks is not well understood.
They have only been observed mating twice, and pupping has never been witnessed.
Scientists are not certain if they exhibit any elaborate mating behavior.
After mating, female whale sharks can retain sperm from the male for a long time and use them to fertilize their eggs at intervals over a prolonged period.
Whale sharks are ovoviviparous.
This means they give birth to live young that hatch in eggs within the mother’s body.
A pregnant whale shark was captured in 1996 with up to 300 pups, confirming the assertion that these sharks reproduce via ovoviviparity.
The calves are born at a length of about 40 to 60 centimeters (16 to 24 inches).
The exact pupping and nursery grounds of this shark species remain a mystery.
Experts are also unsure of their gestation period, but sharks generally have a long gestation period of about 11 to 12 months.
Whale sharks have a very long span and are among the longest-living fish species.
The oldest individual is about 50 years old, but experts think whale sharks may survive for up to 100 years in the wild.
Ecological Role and Interactions
As the largest fish in the ocean, whale sharks can have their pick of any food in the ocean.
However, they are predatory filter-feeders, which means they mainly feed on plankton and other microscopic animals that they scoop up in their wide mouth.
This means whale sharks feed at the very bottom of the aquatic food chain, aiding the transfer of energy from lower to higher trophic levels.
Their role as filter feeders also helps to control the population of these small organisms, preventing overpopulation and ensuring the balance of the marine food web.
They also feed on fish eggs and large schools of small fish, which helps to keep the population of fish within their ecosystem at a healthy level.
Due to their large size, whale sharks are not commonly attacked by other marine animals despite not having any significant defenses.
Their major predators include orcas, white sharks, and humans.
Conservation Status and Threats
The International Union for Conservation of Nature (IUCN) lists the whale shark as an endangered species.
While there isn’t robust data to estimate their population size and distribution accurately, the species faces a significant threat from commercial fisheries, who sometimes catch them as bycatch.
Habitat loss, pollution, and sea vessel strikes are among the major threats faced by this species.
All of these threats, combined with the late maturation and slow reproduction rate, make the species quite susceptible to population decline.
Many countries, such as the United States, Australia, India, Taiwan, and the Philippines, have established protected areas for this species.
They also have laws prohibiting the fishing, sale, importation, and exportation of whale sharks for commercial purposes.
A number of international treaties, such as the CMS Memorandum of Understanding on the Conservation of Migratory Sharks and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), regulate the internal trade of the species.
While these efforts have helped whale shark populations rebound over the years, hundreds of these sharks are still killed illegally for their fins, oil, and skin in various places.
Unique Adaptations and Survival Strategies:
One of the unique adaptations of the whale shark is their filter-feeding habit, made possible by the shark’s large mouth and filter pads.
Whale sharks exhibit active filter-feeding.
Unlike basking sharks and some other filter feeders that have to swim to pump water into their mouths, whale sharks swallow water actively to take in prey.
This allows them to feed without necessarily swimming forward.
As they take in large volumes of water, the specialized gill rakers help them filter plankton and other small organisms out of the water.
Whale sharks have large livers that contain low-density oils, providing buoyancy control.
This adaptation allows them to regulate their depth in the water column more effectively and move efficiently at different depths.
Whale sharks also exhibit a unique type of feeding behavior known as vertical suction feeding.
During such stationary vertical suction feeding, the shark remains in a relatively horizontal or near-vertical position and stops swimming entirely.
The shark’s mouth is positioned vertically just below the water surface, and it suctions food into its mouth periodically.
To do this effectively, whale sharks depend on their large liver, which contains low-density oils that help them control their buoyancy in the water.
The whale shark’s filter-feeding strategy is highly efficient for obtaining nutrition to support their massive size.
Cultural Significance and Human Interactions:
The whale shark is well-known by indigenous people, especially in areas where they’re quite common.
For instance, the Malagasy people of Madagascar call whale sharks marokintana, which means “many stars.”
This is a reference to their “checkered” appearance.
In the Philippines, the shark is one of the most recognized animals, and it’s even featured on one of the country’s currencies.
Other countries where this shark species is well-known include Indonesia, Vietnam, and Japan.
Whale sharks fuel ecotourism in many countries of the world, such as Mexico, Honduras, Thailand, Western Australia, Indonesia, the Philippines, the Maldives, and so on.
Many people visit these locations yearly to spot aggregations of whale sharks as they feed.
The whale shark’s gentle demeanor means people can approach the shark and get close without any danger.
Divers may even touch or ride whale sharks, but this is often discouraged because of the distress it causes to the shark.
In some countries, interactions with sharks that go beyond observing them are prohibited, with possible prison sentences for defaulters.
Future Prospects and Research
Despite being one of the most fascinating shark species, there’s still a lot we do not know about whale sharks.
Most significantly, there’s limited understanding of the population, distribution, and reproductive behavior of this shark species.
For instance, researchers have not been able to identify specific pupping grounds and nurseries used by this shark.
With advancements in tracking technologies, we may be able to learn more about the migration patterns of whale sharks and many of their other elusive behaviors.
Research on whale shark movements will also be valuable to conservation efforts as it will help identify critical habitats and migration corridors needing protection.
As a fish species with a very long lifespan, future research may also focus on understanding aging and cell regeneration in whale sharks.
Such studies may be valuable for future studies related to aging and cancer prevention in humans.
Conclusion
The whale shark is a species of carpet shark found in warm tropical waters all over the world.
This massive size can grow to lengths of up to 18 meters (over 60 feet), which makes it the largest shark species in the world.
It is also the world’s largest fish and third biggest marine animal.
Despite their size, the whale shark is a gentle giant.
This filter-feeder preys on plankton and small fish and does not get aggressive when humans swim close to them.
The whale shark is currently on the IUCN endangered list, which means more needs to be done to learn more about this species and protect it from going extinct.
Sources:
- https://en.wikipedia.org/wiki/Whale_shark
- https://en.wikipedia.org/wiki/Carpet_shark
- https://www.worldwildlife.org/species/whale-shark https://www.nationalgeographic.com/animals/fish/facts/whale-shark
- https://oceana.org/marine-life/whale-shark/
- https://www.wwf.org.uk/learn/fascinating-facts/whale-sharks
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