Reproduction

    There does not exist enough research to determine when a whale shark becomes

sexually mature.  Although some studies have been able to suggest that it takes

thirty years until an individual is mature enough to reproduce. Almost exclusively,

juveniles are found in regions such as coasts of Taiwan, the Philippines, and India.

These areas are hypothesized to be significant to mating (Norman, 2004).

    Rhincodon typus is a viviparous animal, although little has been observed when it

comes to reproduction in these animals because of their solitary lifestyle. Viviparous

means that an organism does not lay eggs, but rather offspring are born within the

mother's body and out of egg capsules (Ritter, 2009). A female may hold up to 300

embryos in the uterus, and it is possible that the embryos will be at different stages

of development. This type of development is similar to that found in the nurse shark,

where lecithotrophic embryos are also found in different stages and are able to hatch

at different times. (Lecithrotropic, as defined by encyclopedia.com, is

a mode of embryonic development in which the yolk of an egg provides all of the

nourishment.) Through similarities between the whale shark and the nurse shark

we can get a glimpse into reproduction of the whale shark.

   

    Genetic research on R. typus embryos has shown that up to all 300 offspring share

a father, indicating that a male shark can father an entire litter. The different rates of

development and the single father suggests that females may only need to mate once

and may store sperm from the single father (Joung, et all, 1996). Successful taggings

of whale sharks reveal that females will return to their birthplace to breed with the

single father, this is known as natal philopatry (Rowat and Brooks, 2012). While it

appears that females have one specific breeding place, they give birth at different

times throughout the year.

    Whale sharks are born at a size anywhere from 55 to 64 centimeters, but research

shows that R. typus has a higher growth rate during these early years of life. Growth

gradually slows down once a specimen reaches maturity, which is estimated at 30

years. When measured, growth rates are shown to be higher in pups rather than in

juveniles, and females grow faster than males (Borrell, et all, 2011).

 

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