Whale sharks are a highly migratory, pelagic species distributed throughout the world's tropical seas, typically being found between 30°N and 35°S latitude and occasionally as high as 41°N and 36.5°S. Nearly every coastal nation within these latitudes has recorded whale sharks in its waters. They are known to inhabit both deep and shallow coastal waters of subtropical zones and lagoons of coral atolls and reefs. This species can regularly be found in the offshore waters of Australia, Belize, Ecuador, Mexico, the Philippines, and South Africa. (Demetrios, 1979; Wolfson, 1983; Wolfson, 1986)
This species prefers surface waters between 21° and 30°C. These giant zooplanktivores are usually found in coastal zones with high food productivity. Data collected from archival tags demonstrated that this species has the ability to dive to depths exceeding 1700 meters and can also tolerate temperatures as low as 7.8°C. (Colman, 1997; Graham, et al., 2006; Gudger, 1915; Iwasaki, 1970; Norman, 1999; Rowat and Brooks, 2012; Tyminski, et al., 2008)
This species is the largest known fish, with the largest specimen recorded at 20 meters long. 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 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. The integument has distinct markings and patterns that resemble a checkerboard, composed of light spots and stripes over a dark body, creating a disruptive coloration pattern. Color 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 an ideal character for photo identification of individuals. 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. (Bigelow and Schroeder, 1948; Compagno, 2001; Gudger, 1915; Muller, 1999; Myrberg Jr, 2001; Rowat and Brooks, 2012; Wilson and Martin, 2003)
Whale sharks are obligate lecithotrophic livebearers, a reproductive mode where eggs are fertilized internally, and develop in the female until the end of the embryonic phase or later. There is no maternal nutrient transfer to the pups, which are sustained by egg yolk sacs while carried inside the mother. In 1995, a 10.6 m female was harpooned off the eastern coast of Taiwan. She had an approximate number of 304 embryos, ranging in length from 42 to 63 cm. Many 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. The largest embryos were found free of their egg cases, with no external yolk sacs, indicating they were ready to be released. This proved that the species is a livebearer with aplacental viviparous development. The litter was the largest recorded in any shark species, with a sex ratio of 50:50. Whale sharks are born at an average length of 55 cm. The smallest recorded live specimen was found in the Philippines, measuring 38 centimeters. Growth in whale sharks is believed to be higher during the younger stages of life, gradually slowing after maturity. The largest individual reported to date was a Tawainese specimen in 1987 at 20 meters, while the next largest specimen was 18.8 meters in total length from the Indian fishery. 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. (Borrell, et al., 2011; Chang, et al., 1997; Chen, et al., 1997; Joung, et al., 1996; Kitafuji and Yamamoto, 1998; Leu, et al., 1997; Uchida, et al., 2000)
Genetic data from the previously mentioned 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). (Joung, et al., 1996; Leu, et al., 1997; Rowat and Brooks, 2012; Schmidt, et al., 2010)
There is currently limited evidence to accurately determine the age of sexual maturity in whale sharks, but it is suggested that it can take up to 30 years. Information regarding the frequency with which they can reproduce, and when and where this may happen, is currently unknown. Juveniles found in coastal waters of Taiwan, the Philippines, and India suggest that these locations may be important breeding areas. (Norman, 2004; Taylor, 1994; Wintner, 2000)
Due to their ovoviviparous reproductive strategy, 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 towards pups after they are born. (Chang, et al., 1997)
Information on the lifespan of whale sharks is very limited. Due to their advanced age at sexual maturity, it is believed that they may have lifespans exceeding 100 years. (Rowat and Brooks, 2012; Taylor, 1994)
Whale sharks are the only pelagic orectoloboids. They are usually solitary animals, although aggregations have been reported from 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 km^2, and aerial photographs have shown 68 whale sharks in an area of 1 km^2, of which an average of 74% were males. (Clarke and Nelson, 1997; Compagno, 2001; Gunn, et al., 1999; Rowat and Brooks, 2012)
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. (Gunn, et al., 1999)
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 km in 37 months at speeds of up to 3.9 km 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 and bathypelagic depths is unclear, but may indicate foraging behavior, especially when the animals are crossing less productive open ocean surface waters. (Carey, et al., 1990; Finstad and Nelson, 1975; Gunn, et al., 1999; Rowat and Brooks, 2012)
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 fish that are possibly searching for the same prey. It is believed that migratory patterns are also related to breeding behaviors. (Gunn, et al., 1999; Rowat and Gore, 2007)
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 3 to 5 meters away, suggesting that they are capable of picking out objects and movement at close range. 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. (Clarke and Nelson, 1997; Dennison, 1937; Martin, 2007; Norman, 1999; Peach, 2002; Rowat and Brooks, 2012; Rowat and Gore, 2007; Wilson, et al., 2006)
Whale sharks are known to prey on a range of planktonic and small nektonic organisms that are spatiotemporally patchy. These include krill, crab larvae, jellyfish, sardines, anchovies, mackerels, small tunas, and squid. 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. 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 sharks can sift prey as small as 1 mm through the fine mesh of their gill rakers. They also have several rows of small teeth, but these seem to play little if any role in feeding. In all methods of feeding, the filtration pads will at some time become blocked with particles and the shark will clear them by back-flushing, where they appear to cough underwater, ejecting a stream of debris. 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 and higher trophic level. A comparison of the diets of juveniles and larger individuals indicates an ontogenetic transition from pelagic prey species to coastal prey species. (Borrell, et al., 2011; Colman, 1997; Compagno, 1984; Gudger, 1915; Hoffmayer, et al., 2007; Motta, et al., 2010; Nelson and Eckert, 2007; Sims, 1999; Taylor, et al., 1983)
Whale sharks have very few natural predators due to their large size when mature. Human activities and poaching have considerably reduced their number. Small individuals are vulnerable since they haven’t fully developed and their size makes them an easy prey for blue marlin and blue sharks. Orcas are known to attack and consume whale sharks up to 8 m in size. Evidence of a whale shark being attacked by a larger shark was recorded off Australia. This individual was sighted in 2002 with a missing fin and large bite marks, most likely inflicted by a great white shark. (Arzoumanian, et al., 2005; Meekan, et al., 2006; Norman, 2002; Rowat and Brooks, 2012; Rowat and Gore, 2007; Taylor, 1989)
A whale shark’s best defensive adaptation is its skin, which is covered in dermal denticles that makes it very tough, along with a thick layer of cartilage. Numerous individuals have been seen with bite marks and scars from predators, indicating they have survived those attacks. (Norman, 2002; Taylor, 1989)
As large, filter-feeding fish, whale sharks affect local populations of zooplankton and small nekton by consuming these organisms. Two siphonostomatoid 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 varieties of sharksucker, such as white suckerfish, are often found living in the mouth and peribrachial cavity, as well as in the spiracle. (Colman, 1997; Norman, et al., 2000; Rowat and Brooks, 2012; Wright, 1877; Yamaguti, 1963)
Whale sharks are considered food in many countries, with their soft meat being known as "tofu shark". The flesh is a delicacy in the Taiwanese restaurant trade. Although the cartilage fibers in the fins are not good for making soup, they are sold as display or trophy fins in Asian restaurants and the perceived values of their fins appear to have increased over the years. There are recent reports of live individuals being finned in the Maldives and Philippines. Hunting has significantly decreased their numbers. In Pakistan, the flesh is traditionally consumed either fresh or salted, and Whale shark liver oil has been used for treating boat hulls, and as shoeshine. Ecotourism industries based on snorkeling and viewing Whale Sharks are now established in several locations, including Mexico, Australia, Philippines, southeastern Africa, Seychelles, Maldives, Belize and Honduras. In some areas tourism has developed and has become a significant source of income, due to laws that protect and ban the whale shark fishery. In these areas, monitoring must continue to ensure that high levels of tourism do not have a negative effect on the behavior of the species at their aggregation sites. ("Proposal to include the Whale Shark (Rhincodon typus) in Appendix II of the Convention on International Trade in Endangered Species (CITES)", 2002; Chen and Phipps, 2002; Chen, et al., 1997; Norman, 1999; Riley, et al., 2009; Rowat and Brooks, 2012)
Whale sharks can become tangled in nets and damage fishing equipment. (Colman, 1997)
Due to their docile lifestyle and very limited defenses, whale sharks have become prone to exploitation. Currently, their global conservation status is "vulnerable to extinction", because populations are decreasing in many locations as a result of reduction by unregulated fisheries. Whale sharks can also be injured by boats and propeller strikes. This species is legally protected in Australian Commonwealth waters and the states of Queensland, Tasmania and Western Australia, the Maldives, Philippines, India, Thailand, Malaysia, Honduras, Mexico, in US Atlantic waters, and in a small sanctuary area off of Belize. Full legal protection is under consideration in South Africa and Taiwan. In 1999 the whale shark was listed on Appendix II of the Bonn Convention for the Conservation of Migratory Species of Wild Animals. This identifies it as a species whose conservation status would benefit from the implementation of international cooperative agreements. This regulation has been enforced since February 2003, and requires fishing states to demonstrate that all exports are from a sustainably managed population, along with monitoring exports and imports. In Western Australian waters, Whale sharks are fully protected under the Wildlife Conservation Act of 1950. ("Proposal to include the Whale Shark (Rhincodon typus) in Appendix II of the Convention on International Trade in Endangered Species (CITES)", 2002; Fowler, 2000)
Fossil records of ancestral species show that there were three species in the genus Palaeorhincodon dating from the Eocene period, 35–58 million years ago. (Rowat and Brooks, 2012)
Paulina Calleros (author), San Diego Mesa College, Jessica Vazquez (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
areas with salty water, usually in coastal marshes and estuaries.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
uses electric signals to communicate
union of egg and spermatozoan
a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.
A substance that provides both nutrients and energy to a living thing.
Animals with indeterminate growth continue to grow throughout their lives.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
(as perception channel keyword). This animal has a special ability to detect the Earth's magnetic fields.
makes seasonal movements between breeding and wintering grounds
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
generally wanders from place to place, usually within a well-defined range.
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
an animal that mainly eats fish
an animal that mainly eats plankton
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.