Do Sharks Lay Eggs? Surprisingly Not a 'Yes or No' Question

Yes, sharks lay eggs — at least some of them. These are known as oviparous species, and they include types like cat sharks, horn sharks and carpet sharks.

These sharks lay tough, leathery egg cases (often called mermaid’s purses) on the ocean bottom. The female shark produces fertilized eggs, each containing a developing embryo that consume yolk filled sacs during growth.

The egg capsule offers limited protection against predators and harsh environments. Inside, embryos rely primarily on the yolk sac inside to develop until hatching. These eggs are often anchored to rocks or plants in areas with low current.

On the flip side are viviparous species — such as bull sharks, hammerhead sharks and blue sharks — which give birth to live young.

In these species, the developing pups are nourished through a maternal and embryonic tissue connection via something like an umbilical cord attached to the uterine wall. This method resembles how mammals reproduce and is common among placental shark species.

Viviparity allows for the birth of live baby sharks that are relatively well-developed and able to survive independently. This strategy provides positive results in species that dwell in predator-heavy environments.

Many shark species fall into this hybrid category. Ovoviviparous species such as tiger sharks, mako sharks and mackerel sharks carry their embryos inside the mother's body, but the developing embryo feeds on a yolk sac rather than a placenta.

In some extreme cases, like Carcharias taurus (the sand tiger shark), the embryo displays intrauterine cannibalism, where the strongest pup consumes unfertilized eggs or weaker developing pups. It's a brutal but effective reproductive strategy that ensures survival of the fittest.

Angel sharks and other bottom-dwelling species often have fewer offspring but benefit from being near the ocean bottom, where eggs or pups are more protected. Some sharks produce unfertilized eggs (not full egg capsules) that serve as food for developing young, a process known as oophagy.

Sharks are different from other animals in that their reproductive organs are internal. The male inserts sperm via claspers, and the fertilization process begins inside the female's reproductive tract. The resulting baby sharks, or pups, can number in the dozens depending on species.

Understanding how many sharks reproduce helps scientists and conservationists protect vulnerable species. Since sharks generally have fewer offspring than other fish, overfishing can severely reduce populations.

The fact that only a few sharks lay eggs — and that the oviparous species lay eggs in lower numbers than bony fish — means each egg is important for the species' survival.

Whether it’s live birth, egg laying or something in between, shark biology is filled with surprises. The next time you hear someone ask, "Do sharks lay eggs?" you'll know the answer isn’t just yes or no — it’s a whole slew of possibilities.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.