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By Michael Salmonowicz
Geographic Range
Rhincodon typus are found in all warm temperate and tropical seas around the world, except the Mediterranean. They occur circumglobally from about 35 degrees north to 35 degrees south latitude.
Biogeographic Regions:
indian ocean (native 
); atlantic ocean (native ); pacific ocean (native ).
Habitat
R. typus inhabit ocean waters with surface temperatures between 70-77 degrees Fahrenheit. Whale sharks spend the majority of their time deep underwater, although it is unknown exactly how deep they go. (National Geographic 1992)
Physical Description
(65.6 ft; avg. 39.36 ft)
Whale sharks are the largest sharks in the world, reaching maximum lengths of 12 to 20 meters. They have broad, flat heads, and are primarily dark gray, bronze, or greenish gray on the upper-side of the body and a cream color on the under-side. The random white dots and lines along their backs are distinguishing features, and their pattern has helped scientists identify individuals during research. The terminal mouth (located at the front of the head) is another defining characteristic, as most sharks have mouths that are found beneath and behind their snouts. (National Geographic 1992 and The Natural History of Sharks 1969)
Some key physical features:
ectothermic ; heterothermic ; bilateral symmetry .
Reproduction
It appears as though whale sharks take part in copulation, but details beyond that are scarce. There is also uncertainty regarding the birth process. In 1953, an egg containing a whale-shark embryo was found in the Gulf of Mexico, leading to the claim that whale sharks are oviparous, meaning the young hatch from eggs outside the mother's body. However, many believe that the embryo was aborted (and subsequently expelled from the mother's body), and that R. typus are viviparous. The smallest free-living whale sharks to be found have been 55 cm long. Sexual maturity is thought to be reached, in both sexes, after they have attained a length greater than 9 meters. (National Geographic 1992 and The Natural History of Sharks 1969)
Key reproductive features:
iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (internal ).
Behavior
Whale sharks seem to be solitary, as large groups have only been observed occasionally. These sharks are mild mannered and usually indifferent or cautious when encountering humans. (National Geographic 1992 and The Encyclopedia Brittanica Online 1998)
Key behaviors:
natatorial ; motile .
Food Habits
R. typus feed on an array of planktonic and nektonic organisms. These include krill and squid, and small fish such as sardines, anchovies, and mackerel. (National Geographic 1992)
Economic Importance for Humans: Positive
Whale sharks are caught commercially around the world for food purposes when tuna, marlin, or other high-priced fish aren't in abundance. (National Geographic 1992)
Other Comments
R. typus are not whales, but sharks. The whale portion of their name was included to express the magnitude of their size. It is hypothesized that whale sharks have a maximum life span of around 100-150 years. Scientists still know relatively little about them, which accounts for the lack of detailed information above. (National Geographic 1992 and The Natural History of Sharks 1969)
Contributors
Michael Salmonowicz (author), University of Michigan.
