Whale Sharks: Size, Characteristics, Feeding Habits, Mating | Sea Life, Islands and Oceania

WHALE SHARKS

Flower Garden Banks National Marine Sanctuary off Texas in the Gulf of Mexico

Whale sharks (Scientific name: Rhincodon typus) are the largest fish in sea and the largest fish that ever lived on the planet, possibly reaching lengths of 20 meters (65 feet) and weighing up to 40 tons (36,290 kilograms) (See Size Below). Whale sharks are generally solitary creatures that live in tropical and subtropical seas all around the world. They have been spotted in the waters off 125 nations and prefer surface water temperatures in the 70s and low 80s primarily in the belt that circles the globe between 30̊ North latitude and 35̊ South. Sources: Steven Wilson, Natural History, April 2006; Eugenie Clark, National Geographic, December 1992]

Also known as Dámero and Tiburon ballena, whale sharks are migratory fish usually found in the open sea but often seen in coastal areas too. Jennifer S. Holland wrote in National Geographic, “Whale sharks can be as long as a school bus... They have a mouth that looks, head-on, wide enough to suck down a small car. ..The "whale" part of the name refers to size and how the animals eat. They are one of only three known shark species that filter feed, as baleen whales do, swimming slowly through plankton-rich water, maws agape. Water goes in carrying edibles of all sizes, and water sans food flows out.” [Source: Jennifer S. Holland, National Geographic, October 2011]

Whale sharks are docile, pose no risk to humans and are approachable. They are seen with regularity by humans in large numbers in Western Australia and the Gulf of Mexico near the Yucatan Peninsula in Mexico where they gather at certain times of the year to feed. In some places like the Philippines they attracted artificially with food hand-outs for the tourism trade. It is not known how many whale sharks there are and if their numbers are stable or declining. Little is known of their social behavior. No one knows where they breed of what their migration patterns are. Some tagged sharks migrate long distances. One individual was tracked migrating from the Sea of Cortez off Mexico 8,000 miles across the Pacific.

Fortunately for whale sharks their meat is not very tasty and they don't carry much oil. The Taiwanese call the animal the tofu shark" because its flesh is soft and gelatinous. The Japanese call it the "good luck shark" and rarely kill it. Fisherman in the Maldives harpoon the sharks and sometimes swim into their mouth and through one of the gills with a rope so the creature can be dragged into shore. Whalers from the village of Lamalera on Lembata in Indonesia hunt whale sharks, which they call the stupid fish,

Whale-shark-like creatures originated perhaps around 60 million years ago. Fossil records of ancestral species show that there were three species in the genus Palaeorhincodon dating from the Eocene Period (56 million to 33.9 million years ago).

Websites and Resources: Shark Foundation shark.swiss ; Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems

Whale Shark Habitat and Where They Are Found

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whale shark range
Whale sharks are found in all tropical and warm-temperate seas around the world, preferring water temperatures of 20 to 25̊Celsius (68-77° Fahrenheit). They are found mostly in tropical oceans in places like Brazil to Malaysia and Thailand. but have also been spotted in temperate waters off the U.S. They have been found in the open ocean, reefs, coastal areas and brackish water.

Whale sharks are highly migratory (make seasonal movements between regions, such as between breeding and wintering grounds) and generally pelagic (living in the open ocean, far from land). They are distributed throughout the world's tropical seas and typically found between 30°N and 35°S latitude and occasionally as far as 41°N and 36.5°S. Nearly every coastal nation within these latitudes has recorded whale sharks in its waters. This species can regularly be found in the offshore waters of Australia, Belize, Ecuador, Mexico, the Philippines, and South Africa. [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web (ADW) /=]

Whale shark are known to inhabit both deep and shallow coastal waters of subtropical zones and lagoons of coral atolls and reefs. They prefer surface waters between 21° and 30°C and often found in coastal zones with high food productivity. Evidence from tagged sharks indicate they have the ability to dive to depths exceeding 1700 meters (5,577 feet, almost a mile) and can tolerate temperatures as low as 7.8°C (46̊F).

Whale Shark Characteristics

Whale sharks have broad, flat heads with short snouts, conspicuous ridges along the sides of their bodies and interesting white, yellow, and grey checkerboard markings on their backs. The distinct markings — pale spots, grids of bars and stipes on top of the shark’s grey, blue and brown back and sides — are though to be some sort of camouflage, possibly mimicking the way light dances off the surface of the water. Some think their primary purpose is to shield juveniles from predators. Background colors can range from different shades of grey, blue or brown, with typical pelagic countershading. Coloration remains the same over the shark's lifespan, making it useful photo identification of individuals.

whale shark teeth

The mouth of a whale shark is so large four divers can swim into it simultaneously. The fish's hide is like elephants skin and the polka dots on its back are as large as a hand. Although creatures are for the most part docile and easy going, a gentle whip of its tail is enough to catapult a diver backwards and knock off their mask and fins. [Source: Eugenie Clark, National Geographic August 1981]

According to Animal Diversity Web: Whale sharks have spindle shaped, fusiform bodies, which are widest at the midsection and taper at the head and tail. There are three prominent longitudinal ridges (carinae) along the dorsal sides. The head is depressed, broad and flattened, with a large terminal mouth that can measure up to 1.5 meters across, containing up to 300 rows of hundreds of tiny, hooked, and replaceable teeth. The gill slits are very large and are internally modified into filtration screens that are used for retaining small prey. At the front of the snout they have a pair of small nares with rudimentary barbels; these nares lack the circumnarial folds and grooves present in other shark species. Like other pelagic (living in the open ocean, far from land) sharks, they have a large dorsal fin along with a smaller second dorsal fin and a semi-lunate caudal fin. Males have claspers, which are modified anal fins. The skin is studded with dermal denticles, which are tooth-like scale structures that are considered to be hydrodynamically important, reducing drag and functioning as a form of parasite repellent. [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web (ADW) /=]

The skeleton consists of thick flexible cartilage, and a rib cage is absent, which significantly reduces body weight. Body rigidity is provided by a sub-dermal complex of collagen fibers that act as a type of flexible "corset" that the locomotory muscles attach to from the backbone, to make a light and mechanically efficient system.

Whale Shark Swimming and Diving

Whale sharks move slowly through the sea, propelled forward by the back and forth motion of their tail. They are filter feeders like basking sharks and the megamouth shark but more closely related to nurse sharks than either of these two massive sharks. Little is known of why whale sharks dive deep into the ocean. Temperature and depth data from tagged whale sharks indicated most of them spend most their time on the surface but some dove to a depth of more than 3,200 feet, far deeper than it was though they traveled.

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whale shark gills
According to Animal Diversity Web:This species is a strong but typically slow swimmer. Adolescent and adult whale sharks typically cruise at speeds of 0.05–1.0+ meters per second and continue to do so for many hours at a time. Early satellite tracking studies showed that whale sharks could travel very long distances, over 13,000 kilometers in 37 months at speeds of up to 3.9 kilometers per hour. Data from tagging studies have given us a better understanding of their capability for ocean-scale movements as well as their ability to make deep dives and change their diving patterns relative to environmental or bathymetric conditions. Their diving patterns are believed to be regulated by circadian rhythms, which may be influenced by daily light and dark cycles. Whale sharks spend most of the day near the surface and dive during dark hours. The reason for undertaking dives to mesopelagic (living in the open ocean, far from land) and bathypelagic (living in the open ocean, far from land) depths is unclear, but may indicate foraging behavior, especially when the animals are crossing less productive open ocean surface waters. [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web (ADW) /=]

A research team led by Yuki Watanabe, an associate professor of marine zoology at the National Institute of Polar Research, compared the long-distance cruising speeds of 46 species of fish in a paper published in April 2016 on the Proceedings of the U.S. National Academy of Sciences. Sunfish and salmon were the slowest: An 87-kilogram sunfish swam at 2.2 kilometers per hour (kph) (1.4 miles per hour (mph)) and a 3.3-kilogram salmon at 2.7 kph (1.7). A 2.2-ton whale shark was measured going 3.1 kph (1.9 mph) of a 2.2-ton whale shark, a speed not unexpected considering its huge body. A428-kilogram great white shark swam the fastest at 8.1 kilometers per hour (kph (5 miles per hour (mph)), followed by a 240-kilogram bluefin tuna at 7.2 kph (3.5 mph). The scientists used small monitoring systems attached to fish. The high speeds of the sharks and tuna are attributed to their unique body system that has evolved to keep their body temperatures relatively high. [Source: Earth.com, January 16, 2017]

Whale Shark Size and Lifespan

Whale shark may grow up to 20 meters (65 feet) weigh as much as 40 tons by some estimates but specimens longer than 13 meters (40 feet) are uncommon. Their average length is around seven meters (23 feet) and their average weight is eight to ten tons, with big ones weighing around 20.6 tons. Really large ones have been documented weighing 30,844 kilograms (31 tonnes, 34 tons, 67938 pounds). [Sources: Steven Wilson, Natural History, April 2006; Eugenie Clark, National Geographic, December 1992]

The largest individual reported to date was a Tawainese specimen in 1987 that was described — but not scientifically verified — as being 20 meters (65 feet) long. The largest whale shark ever recorded was 18.8-meters (61.7 feet) long. Based on local fisherman observations the largest ones have been estimated to weigh 37 tonnes (37,000 kilograms, 41 tones, 81,500 pounds) or even 43 tonnes (43,000 kilograms, 47 tons, 94,800 pounds), but the accuracy of these estimate has been questioned. [Source: Wikipedia, Olivia Munson, USA TODAY, March 21, 2023]

According to the Guinness Book of Records, a whale shark captured off the coast of Pakistan was 12.6 meters (41½ feet) long, and weighed an estimated 16½-to-23 tons. There are claims of 59-foot-long whale sharks that weigh 37 tons.

It is unknown how long whale sharks can live, however, scientists believe they can live approximately 60-100 years. Information on the lifespan of whale sharks is scarce. Studies based on the growth rings found in the shark’s vertebra suggest that whale sharks reach sexual maternity when they are between 20 and 30 years old. Due to their advanced age at sexual maturity, it is believed that they may have lifespans exceeding 100 years or maybe even 150 years. Their lifespan in captivity is much shorter than this. [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web (ADW) /=]

Whale Sharks Regulate Their Body Temperature

Four whale sharks were outfit with time-depth recorders by a team led by Michelle Thums of the University of Western Australia to study their vertical movement in the water column. Their research, published in Biology Letters in October 2012, provided evidence that the world’s largest fish visit the surface to warm up after diving deep, suggesting they engage in behavioural thermoregulation (searching out cold or hot habitats that allow the organism to alter its rate of heat loss or gain). [Source: By Paul Robinson, Earth Times, October 17, 2012]

Earth Times reported: With negative buoyancy, most pelagic fish species swim towards the surface quite often, but elasmobranchs (eg. sharks and rays) spend long periods at the surface following dives. Whale sharks spend an average of 49 percent of its time at the surface between its diving stints (of over 1000 meters). Analysing the dives resulted in the discovery of three dive-types.
Type 1) From 0400 to 1600 hours was the commonest dive-type, occupying 44 percent of the animal's diving behaviour
Type 2) From 1800 to 0600 hours, type 2 dives were almost as common as type 1.
Type 3) From 0300 to 1800 hours, with peaks at 0500 and 1200h, type 3 dive bouts had the longest post-dive surface duration. A shark at Christmas Island was used for a longer period and illustrated more type 3 dives than others over 88 days. This shark travelled to Indonesia during this time, using deeper waters up to 3482 meters at least! However the other individuals had a maximum of nine percent of their diving as type 3. Individual preferences could have had something to do with these dives.

Results supported the idea that thermoregulation took place by using warm surface waters as a heater for the body. Fish physiology demands these higher body temperatures for optimal performance. In warm waters, above 25°C (77̊F) , no relationship exited and it's perhaps necessary to get rid of excess heat at some temperatures by diving deep to cooler water. It wouldn't have been ethical but measuring internal temperatures would have been useful, despite the fact that whale sharks are pure ectotherms. The external sensors should have indicated both ocean temperature and the approximate body temperature, especially after time at depth.

Overall, the research indicated a positive correlation between time spend at the surface and depth of dives at temperatures below 25°C (77̊F). Other factors such as feeding, especially for a filter feeder, come into play. This animal however, recycles so much water that it would need to replace lost heat energy after a deep feeding "bout." More fish and especially large, non-filter-feeders could be usefully tagged now that this technology has been successfully employed. We look forward to the discovery of more intriguing information on our fish and other species.

Whale Shark Behavior, Senses and Perception

whale shark eye

Whale sharks are generally solitary, diurnal (active mainly during the daytime), motile (move around as opposed to being stationary), nomadic (move from place to place, generally within a well-defined range) and migratory (make seasonal movements between regions, such as between breeding and wintering grounds). [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: Whale sharks show the ability to learn. Individuals in captivity show changes in behavior; when their keepers appear with food, the sharks swim in tight circles near the feeding point. They are also known to investigate the nets of local boats targeting small fishes. At Ningaloo Reef in Western Australia, whale sharks have been observed accepting handouts of fish from the fishermen.

Whale sharks sense using vision, touch, sound. vibrations, electric signals and magnetism. According to Animal Diversity Web: Whale sharks have small, circular eyes that are positioned laterally on the head, creating a wide field of vision. The broad, blunt shape of the head and the position of the eyes suggest that they may have binocular vision. Whale shark eyes are able to follow swimmers at distances of three to five meters away, suggesting that they are capable of picking out objects and movement at close range. [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web (ADW) /=]

Most sharks have ampullae of Lorenzini, which are pit-like organs clustered around the head that detect weak electric and magnetic fields and may help with navigation. The inner ear of this species is the largest known in the animal kingdom, and the diameter of the semicircular canals is near the theoretical maximum dimensions for such structures. With such large hearing structures, it is likely that whale sharks are most receptive to long wavelength and low frequency sounds, suggesting that some sort of auditory communication between conspecifics may exist. The olfactory capsules in whale sharks are spherical and rather large, so it is likely that they would have similar chemo-sensory detection abilities to those of other orectolobiform species, such as nurse sharks (Ginglymostoma cirratum).

Whale sharks possess a mechanosensory lateral line system, but its capabilities are unknown. The lateral line enables sharks to react to water currents (rheotaxis). Whale sharks show a similar response to currents and can register their movement across the lines of force of the earth’s magnetic field, which is believed to assist in navigation. The lateral line also helps with prey detection, feeding, and prey capture.

Whale Shark Behavior and Migrations

20120518-whale shark -2006_March_15_jason2.jpg Not only are whale sharks the largest fish they also hold the record for the farthest migration. In 2018, researchers reported in the journal Marine Biodiversity Records that a female tagged off of Panama showed up near the Marianas Trench, after traveling a distance estimated to be 20,142 kilometers (12,515.7 miles) 842 days later. [Source: Stephanie Pappas, Live Science, July 25, 2022]

As whale sharks migrate across oceans, they do not maintain a home range, nor defend territory. Different geographic locations appear to be preferred at various times of the year. Whale sharks can stay in fairly localized areas or undertake large-scale transoceanic migrations. It is believed that their migratory movements might be strongly related to the location’s productivity, which is frequently associated with schools of pelagic (open ocean) fish that are possibly searching for the same prey. It is believed that migratory patterns are also related to breeding behaviors. /=\

Smithsonian magazine reported: “Rachel Graham, a conservation scientist at the Wildlife Conservation Society, was the first to attach a depth tag to one of the giants, in Belize in 2000. One of the 44 satellite tags she eventually deployed told her that a whale shark had dived 4,921 feet — nearly a mile. A marine biologist named Eric Hoffmayer recorded the deepest dive yet: in 2008, he monitored a shark in the Gulf of Mexico that descended 6,324 feet. “Their ability to adapt to all sorts of different environments is an important part of their survival,” says Graham, who’s tracking whale sharks in the Western Caribbean, Gulf of Mexico and Indian Ocean. Scientists don’t know why the animals go so deep. Sharks lack a swim bladder that keeps other fish buoyant, so one idea is that whale sharks free-fall toward the seafloor to rest. [Source: Juliet Eilperin, Smithsonian Magazine, June 2011]

“In 2007, Robert Hueter tagged a pregnant 25-foot-long female he nicknamed Rio Lady. Over the following 150 days, she traveled nearly 5,000 miles, from the Yucatán Peninsula through the Caribbean Sea to south of the Equator east of Brazil, ending up north of Ascension Island and south of St. Peter and St. Paul Rocks, roughly halfway between Brazil and Africa. No one is certain where whale sharks breed or give birth, but Hueter believes this area may be one of their elusive pupping grounds.

Whale Shark Food and Eating Behavior

20120518-Walhai shark.jpeg Although whale sharks weigh several tons they feed mainly on algae, plankton, shrimp, fish spawns, crab larvae and krill. In addition to these small organisms they also consume jellyfish, squid schooling fish such as sardines, anchovies and mackerels, which they strain from the water as they swim with their meter-long mouths and specialized teeth. Occasionally they eat small tuna and albacore. Whale sharks can sift prey as small as one millimeters through the fine mesh of their gill rakers. Muscle tissue shows a positive relationship with the size of the fish, suggesting that as they increase in size, their diets change to include prey items of a larger size. A comparison of the diets of juveniles and larger individuals indicates that as whale sharks get older they switch from pelagic (open ocean) prey species to coastal prey species

Whale sharks are filter-feeders, meaning they feed passively by swimming through the water, often near the surface, with their mouths open, straining food from the water seawater and filtering it using their gill slits. Basking sharks and megamouth sharks also filter feed — the only other shark species that do so. Whale shark purposely seek out food, going after dense concentrations of small marine life, rather than straining the open see like basking sharks. Whale sharks have 27,000 tiny little teeth that serve little purpose but are similar to teeth found in 400-million-year-old fossil sharks. Research has shown that whale sharks primarily eat zooplankton in nutrient-rich coastal waters. But in other areas they seek out fish eggs, especially those of the little tunny. If they take in something too big, they spit it out.

Whale sharks are regarded as “suction filter feeders.” Food-filled seawater flows through their jaws — which can be over a meter across — and is strained with 20 porous sieve-like gill plates, with the prey that remains in the mouth being directed towards the digestive system. Channels behind the gill plates direct the filtered water over its gill filaments, which extract oxygen for respiration. The filtered water is then released though the whale sharks gill slits. In this way the shark can generate suction to draw in its food, perhaps by expanding the oral cavity and depressing the tongue-like structure on the floor of its mouth.

When feeding whale sharks sometimes lifts their head above the surface and then sinks quickly to draw water into their mouths to create a suction effect allowing for the intake of much larger amounts of prey than if they solely drifted through the sea. There have been reports of whale sharks feeding in a vertical position, with their head up and tail down, pumping water through their gills. Sometimes they drop their tail to anchor themselves in position on the sea floor and suck fish in by creating a vacuum with the opening and closing of their mouth.

Whale Shark Feeding Methods

feeding in the Maldives

Whale sharks use their mouths like giant buckets to trap food. Their mouth is at an unusual position for a fish. Sometimes whale sharks collect a lot of garbage. A bucket, boot and wallet were found in the stomach of one. Accidently swallowed large objects are expelled when the fish turns its stomach inside out and thrusts the object out of its mouth. Whale shark filtration pads sometimes become blocked with particles which the sharks clear them by back-flushing. When they do this they appear to cough underwater, ejecting a stream of debris..

According to Animal Diversity Web: Whale sharks are able to feed by suction, ram-feeding, and active surface ram-feeding. In ram filter feeding, the fish swims forward at constant speed with its mouth partially or fully open, straining prey particles from the water by forward propulsion. This is also called ‘passive feeding’, as there is little if any pumping of the gills. This type of feeding usually occurs when prey is present at low density. [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web (ADW) /=]

At Ningaloo Reef, ram filter feeding is associated with the presence of copepods and chaetognaths. Suction feeding is achieved by opening the mouth forcefully, sucking or gulping in prey. Water is ejected through the gills when the mouth is closed, filtering out the trapped prey. Whale sharks often do this while stationary, in a vertical or horizontal position. This type of feeding is associated with medium-density prey.

Active surface ram-feeding occurs when an individual is at the surface with the top of its mouth above the waterline. The shark swims strongly, often in a circular path, collecting neustonic prey. This behavior is usually associated with dense plankton conditions. Planktonic prey is captured by filtering seawater through a filter-like device containing five sets of porous pads on each side of the pharyngeal cavity. The backmost pair is nearly triangular in shape, and leads into a narrow esophagus. The pads are interconnected by a tissue raphe (ridge), so that water entering the pharyngeal cavity has to pass through the pads prior to passing over the gills and out through the external gill slits.

Whale Shark Group Feeding Behavior

Feeding of La Paz, Mexico

Whale sharks are generally solitary but sometimes they gather in large groups where large amounts of food are present. Otherwise little is known about their movements across the sea.

Every year whale sharks gather in large numbers at Ningaloo reef in Western Australia to a feast on spawning of coral. This is the largest known gathering of whale sharks in the world. It is not unusual for divers to see 20 or 30 of them in a single day, and manta rays, minke whales and mobula rays also show up at the 160 mile long reef for the mass spawning which only occurs once every year. Groups at Ningaloo tend to be immature males.

Aggregations of whale shark have been reported in several different areas. The largest known is the ‘afuera’ aggregation off Isla Contoy in the Mexican Caribbean. Aerial surveys there recorded up to 420 individuals in an area of 18 square kilometers, and aerial photographs have shown 68 whale sharks in an area of one square kilometers, of which an average of 74 percent were males. Some whale shark feed on plankton blooms, which are spawned by fierce desert winds and cold-water upwelling. Each winter, great numbers of whale sharks gather in the Gulf of Tadjoura off the Horn of Africa. In the Indian Ocean they feast on clouds of egg roe and small fish, which in Indonesia are called “ikan teri”. [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web]

Whale sharks on rare occasions feed on fish in packs. One researcher observed a 100 of them or so with a large school of feeding tuna. The sharks, who were also feeding, hung vertically, and did a marine version of chin-ups, in and out of the water, scooping up fish with each thrust. [Source: Eugenie Clark, National Geographic August 1981]

Sarah Keartes wrote in National Geographic: Video taken at Australia’s Ningaloo Reef shows that whale sharks can hunt baitfish in tandem with other predators. Whale sharks are known to chase fish on their own, but they’re relatively slow swimmers. When speedier animals, such as tuna and diving birds, force prey into a defensive ball, the largest mouth gets the most fish. This behavior, rarely documented, may be a way for the giant sharks to save energy while foraging. [Source: Sarah Keartes, Cynthia Barnett, Nadia Drake, and Hicks Wogan, National Geographic, July, 14, 2022]

Whale Shark Mating and Reproduction

Whale sharks are ovoviviparous (young are produced from eggs that hatch within the body of a parent) and iteroparous (offspring are produced in groups such as litters). They engage in internal reproduction in which sperm from the male fertilizes the egg within the female and employ sperm-storing (producing young from sperm that has been stored, allowing it be used for fertilization at some time after mating). As is the case with other ovoviviparous species, female whale sharks provide protection to their internally developing young until they hatch from their eggs and are born. Like all sharks, there is no parental care shown by the females — or males — towards pups after they are born. [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web (ADW) /=]

Little is known about whale shark breeding behavior. For a long time only one whale shark egg had been described in the scientific literature. No one has ever seen them mate or give birth. The female whale shark has a twin uterus and gives birth to embryos that have emerged from eggs within the body before birth. For a long time about everything that was known about whale shark reproduction was gleaned from a 10-meter (35-foot) specimen harpooned by a Taiwanese fisherman in 1995 that contained 301 embryos between 40 and 64 centimeters (16 and 25 inches) long in various stages of development. Biologist Eugenie Clark said that 300 embryos "far exceed the largest number reported for any shark." The sex ratio was 50:50. The largest embryos were free of their egg cases, with no external yolk sacs, indicating they were ready to be released. This proved that whale shark give birth to live offspring after aplacental viviparous development (in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch)..

Information regarding the frequency with which whale sharks reproduce, and when and where they do it, is currently unknown. Juveniles found in coastal waters of Taiwan, the Philippines, and India suggest that these places may be important breeding areas. Based on the Taiwanese specimen, scientists have deduced that whale sharks give birth to live pups when they are about 70 centimeters (two feet) long. The pups are born from eggs that hatch in their mother’s uterus.

Whale sharks are polygynandrous (promiscuous), with both males and females having multiple partners. According to Animal Diversity Web: Genetic data from one set of embryos suggested that they were all sired by the same father. This indicates that a single male can fertilize an entire litter, suggesting that females utilize a form of sperm storage to fertilize the eggs in successive phases. If this reproductive behavior is typical for this species, it would suggest that they mate rarely with a single individual, and that breeding or mating areas with large numbers of adults will not be found in this species. Observations of sex and age segregation in tagged individuals, compared with this genetic data, lead researchers to believe that females may exhibit natal philopatry (returning to their birthplace in order to breed). /=\

Whale Shark Development

Young whale sharks less than three meters (10 feet) are rarely seen, leading researchers to speculate that they inhabit deep, offshore habitats where they are safe from predators during a vulnerable period of their lives. Infant whale sharks have been recovered from the stomachs of blue sharks and blue marlins. There is currently limited information to accurately determine the age of sexual maturity in whale sharks, but it is suggested that it can take up to 30 years. Their development and life cycle is characterized by indeterminate growth (they continue growing throughout their lives). /=\

According to Animal Diversity Web: There is no maternal nutrient transfer to the pups, which are sustained by egg yolk sacs while carried inside the mother. Many of the embryos in the whale shark harpooned in Taiwan in 1995, were still within their egg cases and had external yolk sacs. The egg capsules were amber with a smooth texture and had a respiratory opening on each side. [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web (ADW) /=]

Whale sharks are born at an average length of 55 centimeters (21.6 inches). The smallest recorded live specimen was found in the Philippines, measuring 38 centimeters (15 inches). Growth in whale sharks is believed to be higher during the younger stages of life, gradually slowing after maturity. Growth rates of whale sharks that were measured in aquaria show that pups grow faster than larger juveniles and females grow faster and even larger than males. In juveniles, the upper lobe of the caudal fin is considerably longer than the lower lobe, but this changes to a semi-lunate form as the juveniles mature into adults. Studies based on the growth rings found in the shark’s vertebra suggest that whale sharks reach sexual maternity when they are between 20 and 30 years old.

Whale Shark Predators and Ecological Niches

Whale sharks have very few natural predators due to their large size when mature. Among the species that have been observed preying — or trying to prey — on whale shark have been orcas (killer whales), blue sharks, blue marlin, great white sharks and humans. Juvenile whale sharks are vulnerable to attacks from blue marlin and blue sharks since they haven’t gotten really large yet. There is evidence of orcas attacking and consuming whale sharks up to eight meters in size. A whale shark was sighted off Australia in 2002 with a missing fin and large bite marks, presumably made by a great white shark. The whale shark’s best defense is its skin, which is covered in dermal denticles and a thick layer of cartilage, which make it very tough. Numerous individual whale sharks have been found with bite marks and scars from predators, indicating they have survived attacks from these predators. [Source: Paulina Calleros and Jessica Vazquez, Animal Diversity Web (ADW) /=]

As large, filter-feeding fish, whale sharks affect populations of zooplankton, small nekton and fish by consuming them Certain kinds of copepods are uniquely hosted by whale sharks: Prosaetes rhinodontis is found on the surface of the filtration pads and is thought to be parasitic, while Pandarus rhincodonicus feeds on bacteria on the surface of the skin. Most whale sharks are hosts to sharksuckers and common remora. Smaller species of sharksucker, such as white suckerfish, can be found living in the mouth and gill slits

Whale sharks are often followed by an entourage of other fish — attracted by the offer of free meals, protection and an easy ride. Cobia often swim along with whale sharks. Whale shark followed by groups of juvenile golden trevallies roam the western reaches of the Indian Ocean. Some small fish pick off bits of organic material that clings to the shark’s tiny teeth, Others hang around its tail and go through it excrement. Sometimes so many remoras cling around a whale shark's mouth it looks as if the massive shark is growing a goatee. The remoras attach themselves on this part of the shark so they can feed on small fish that doesn't penetrate the whale shark's filtering system. [Source: Nathaniel Kenney, National Geographic, February 1968]

Image Source: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023