Shark Reproduction

Sharks are complex animals that go through a unique process of reproduction. While a few shark species lay eggs, the great majority have offspring that undergo some development in the mother before being pushed out into the ocean.

How Do Sharks Reproduce

When time comes for sharks to reproduce, it is the females that begin the process. Female sharks secrete a substance called pheromones; in other words, a signal that lets male sharks know where they are. Following up to this event, the male’s role is to produce and store his sperm so that he’s ready when the time comes. Once the male reaches the female, the whole goal is to fertilize the egg. How that happens is a difficult, complicated, and invariably painful process that requires an in depth look. For the sharks to mate, the male has to get in the proper position behind the female, but this can be sometimes impossible with ocean currents pushing and pulling them around. As a result, the male has to bite the female in order to assume a fixed position behind her. Once in position, the male can finally insert his clasper into the female’s cloaca (sounds pretty familiar, right?). A clasper is not a separate body part but an extension from a male shark’s pelvic fin. Finally, the male releases his sperm into the female and fertilizes the egg, and from there the egg develops.

What Sharks Lay Eggs

As mentioned earlier, most sharks give birth to live young — it is actually the minority of sharks that lay eggs. These sharks are called oviparous, and include bamboo sharks, wobbegong sharks, carpet sharks, bullhead sharks, swell sharks, Port Jackson sharks, zebra sharks, and most catsharks. Among the oviparous shark species, some provide biological protection for their eggs by enclosing them in a leathery case, known by many children and beachgoers as a Mermaid’s Purse.

The eggs are filled with a nutrient-rich yolk, necessary for the development and sustenance of viable shark pups. Other fish eggs that lack this yolk have poorly-developed babies, many of which die before maturing. In contrast, shark pups are hatched strong, healthy, and independent of their mothers. While we don’t know exactly how long it takes between fertilization and hatching, we do know that this period is extended to allow for sufficient maturation. Once hatched, the pups each go their own direction and will begin their life of hunting, mating, and migrating.

A Shark Egg (Mermaid’s PurseProduced By Oviparous Reproduction

How Long Are Sharks Pregnant

The vast majority of sharks, however, do not go through this process. They do not lay eggs, they are not oviparous. These sharks are called viviparous, and they give birth to live young. Viviparous shark species can be differentiated by their process of reproduction: some species’ embryos are connected to the uterus while other species’ embryos are not. The former group goes through placental viviparity, where a placental connection is established with the mother and the offspring. The latter group goes through ovoviviparity, where this placental connection does not exist and offspring get sustenance from a yolk sac. However, the yolk sac has only a certain amount of nutrition, and if it runs out, shark young may turn to their siblings for food. When the mother gives birth to her batch of offspring, they come out completely developed, able to swim and feed and do everything their parents can do — just smaller. This entire process, from conception to birth, takes longer than expected. Sharks are actually known for their ridiculously long periods of gestation, and on average, these last anywhere between five months and two years!

How Many Babies Do Sharks Have

Knowing how long sharks carry their babies now leaves us with one question: How many babies do they eventually give birth to? For such lenghty gestation periods, you would expect there to be a lot of babies at the end. This is the case for some sharks, but from species to species litter size varies tremendously. On one end of this spectrum we have sand tiger sharks, whose litter size is capped at two. On the other end of this spectrum we have whale sharks, who can give birth to up to 300 pups! As you can tell, there is much variation in how many babies shark have and it’s one of those things that depends on the species of shark.