Skip navigation
Go to home page > News > Our blog > How do whale sharks reproduce?
Whale shark in Galapagos
02/01/2014 Research

How do whale sharks reproduce?

One of the most significant questions that remain unanswered about the ecology of whale sharks is: Where do they give birth?

Photograph of Pete Haskell

Pete Haskell

Former Communications Officer at Galapagos Conservation Trust

Finding the answer to this question may be critical in successfully conserving the species because if we are able to protect and monitor “ground zero” we can at least be confident that whale sharks are still reproducing and that there are new generations emerging.

Preliminary findings from the Galapagos Whale Shark Project suggest that as many as 98% of the individuals that pass through the marine reserve are female, the vast majority of which are not only mature but appear pregnant. This observation is truly unique among the known whale shark populations worldwide and could indicate that their birthing grounds are relatively close by: a very exciting and important discovery.

But how do whale sharks reproduce? This is a question that we do know the answer to, but let’s first look at reproduction in sharks as a group. Uniquely, three different modes of reproduction have evolved in sharks and rays (the elasmobranchs), namely oviparity, viviparity and ovoviviparity.

Juvenile whale shark
Juvenile whale shark © Simon Pierce

Oviparous species, like many other fish, lay eggs. Eggs are typically brown in colour and have a leathery case protecting the embryo. If you have ever taken a stroll along the beach and found a “mermaid’s purse”, this is the empty egg shell from an elasmobranch. Whilst inside the egg case the embryo gets all the nutrients that it requires from the yolk of the egg. Oviparous species include the Port Jackson shark and the lesser spotted dogfish.

Viviparous species give birth to live young. This form is similar to reproduction in mammals in that there is a placental link between the developing embryo and the mother through which nutrients are transferred (similar to an umbilicus in humans). Species that have evolved to use this method include hammerhead and blue sharks.

Finally, there are ovoviviparous species which also give birth to live young but have a different method of internal nourishment. An embryo’s initial development occurs within an egg, gaining nutrients from the yolk, but the embryo emerges from the egg whilst still inside the mother. Once out of the egg, it is nourished by secretions from special glands within the mother until it is ready to be born. This method is the most common among elasmobranchs and is used in species such as sand tiger, great white and basking sharks.

Over 300 whale shark embryos were found in a single female in Taiwan.

If you find a mermaid’s purse on the beach and want to be a part of UK shark research, visit the Shark Trust’s Great Eggcase Hunt webpage.

Whale sharks are ovoviviparous. This is known from a single pregnant female that was caught in 1995 off the coast of Taiwan. Inside the uterus of this female, which was nicknamed “megamamma supreme”, scientists found over 300 embryos, far exceeding the highest number found in any other shark. Interestingly, many of these embryos were at different stages of development – some were still in their egg cases whilst others had emerged but were still in the uterus. This may signify that females are able to store a male’s sperm, selectively fertilising her eggs over a prolonged period.

It is thought that whale sharks are born between 40 – 60cm but strangely there are very few recorded sightings of individuals below 3m and it is not known where they spend their time before reaching this size. One notable exception to this is a whale shark that was found by fishermen in the Philippines in 2009. The shark measured just 38cm.

38cm long whale shark found in Philippines
38cm-long whale shark found in the Philippines © WWF Philippines

The fact that so little is known about where whale sharks are born and spend their first few years of life highlights the importance of the research being conducted in Galapagos. If their pupping grounds can be located, protected and monitored, the long-term conservation of this species will be much more secure.

Our whale shark adoption pack, featuring a soft toy, certificate and fact file

Adopt a whale shark

Support our marine conservation work by adopting a whale shark. Our adoption packs include a certificate, factfile and adorable soft toy.

Adopt today

Related articles

Whale shark in Galapagos
5th Nov 2024
Ocean protection Research

Tracking whale sharks from the air

The third article in our series from Dr Alex Hearn sees perseverance pay off thanks to an innovative new approach tracking whale sharks from the air.
Read more
Whale shark in Galapagos
9th Oct 2024
Ocean protection Research

When whale shark research goes wrong

In the second of his series of articles on whale shark research in Galapagos, Dr Alex Hearn reveals some of the frustrations and difficulties tracking whale sharks in the south of the Archipelago.
Read more
Dr Alex Hearn tagging a whale shark
28th Aug 2024
Ocean protection Overfishing

A decade of tracking whale sharks

In the first in a series of articles, Dr Alex Hearn reflects on the past ten years of work tracking whale sharks in Galapagos.
Read more
Diving with hammerhead sharks in Galapagos
20th Jun 2024
Events Ocean protection

Underwater Wonders of Galapagos Webinar 2024

Shark scientist Dr Alex Hearn joined us on 19 June for a fascinating ocean webinar, revealing his latest findings on the health of marine life around Galapagos.
Read more

Get the latest news from Galapagos

Join our mailing list to receive our monthly email newsletter, bringing you the latest news on Galapagos and our work to protect the Islands.

Hidden
Share This Page