Ovoviviparous animals represent a strange sort of hybrid. Their young develop in and hatch from eggs like oviparous animals, but they give birth like viviparous animals. So what’s going on? Let’s look at some examples of ovoviviparous animals.
But first a bit more about this category of animal.
With ovoviviparous animals, the young are indeed grown and developed in eggs, but the eggs are never laid. Instead, the eggs remain inside the mother’s reproductive tract. In some species, the eggs hatch there and the newly hatched young are either born immediately after hatching or they spend a bit more time developing inside their mothers before they’re born. In some species, the eggs are laid and then hatch immediately after being laid.
11 examples of ovoviviparous animals
1. Frogs
Most frogs lay eggs, but some don’t. Specifically, a few species of frogs, mostly native to Indonesia, are ovoviviparous. The females don’t ever lay the eggs, and instead the tadpoles hatch inside the mother. If you time it right, you can actually observe the tadpoles moving around in the mother’s reproductive tract before she gives birth.
In at least one South American species, Darwin’s Frog, the young develop in the vocal sac, while in some Australian frogs they develop inside the stomach.
2. Flies
Some species of fly, especially the carrion flies, the larva hatch before being laid. This is most common in flies whose larva depend on being immersed in a food source immediately. By hatching the eggs before they’re laid the mother fly can ensure that she deposits the larvae on a fresh food source.
3. Sharks
Sharks are one of the rare groups that has species in all three reproductive categories- oviparous, viviparous, and ovoviviparous. Tiger sharks and sand tiger sharks are just two examples of the many ovoviviparous shark species.
Sand tiger sharks, also called ragged tooth sharks, have a well-studied reproductive process. The eggs hatch inside the mother, but then things take a bloody turn. The first shark to hatch will almost always eat the others, either as eggs or as soon as they hatch. So, while they typically have multiple eggs, usually only one will survive to be born.
4. Rays
Unlike sharks, which exhibit a wide array of birthing strategies, almost all ray species are ovoviviparous. This is remarkable, because there’s a huge array of ray species and it’s highly unusual for such a large group to be so dominated by ovoviviparity. Only the skates and a small number of true rays are oviparous.
5. Guppies
Guppies are extremely popular as aquarium fish, because their small size and bright colors make keeping them both easy and enjoyable. They are also prolific breeders, which makes them affordable to buy and easy to breed.
Guppies are ovoviviparous, but unlike most ovoviviparous fish, which give birth to a handful of young at a time, guppies can sometimes give birth to as many as 200 fry at once. A female guppy can store the males sperm for months, fertilizing multiple broods of eggs.
6. Vipers
Most vipers are ovoviviparous. Rattlesnakes are famous for giving birth to live young, but as with most reptiles it isn’t true viviparity (though there are some snakes which give birth that way). The mother incubates the eggs inside her body, they all hatch at once, and then she gives birth to the hatchlings.
Most vipers will have 4-5 young in one brood, but that number will vary depending on the species. When they give birth, they often all come out at once, encased in what looks like an amniotic sac, which they have to break. Some species of rattlesnake have been observed keeping their newly hatched young in nests for several weeks, and even engaging in cooperative parenting with other mothers.
7. Anaconda
The world’s heaviest snake is ovoviviparous. Because of their huge size, anacondas give birth to much bigger litters than other ovoviviparous snakes. Females routinely give birth to 20-40 young after the eggs hatch, but broods of over 100 are not unheard-of.
In fact, it’s common for breeding females to lose half their body weight after giving birth, because of the size of their broods. The newly hatched snakes are less than three feet long, and they receive no parental care at all. Instead, they head off on their own.
8. Slow Worm
A misleading name for legless lizards, these animals are easily confused with snakes. The young are actually born while still in the egg, which has a very thin, transparent shell. They break the shell immediately after the egg is laid, which indicates that they have developed extensively before being laid.
9. Garter Snakes
Garter snakes are a large group of harmless colubrid snakes in North America. Almost all of them are ovoviviparous. They breed in massive groups in the spring, and sometimes the ground will be covered in breeding clumps of garter snakes near the areas where they brumate (reptilian hibernation) during the winter months. It’s the first thing they do when they wake up in spring.
Female garter snakes will give birth to 20-40 newly hatched little snakes sometime around the end of the summer or in early fall.
10. Seahorses
Seahorses are the only animals where the eggs are incubated and hatched by the father, not the mother. Once the eggs are fertilized they’re embedded in the male’s belly pouch, where they’re incubated and nourished before hatching. After the hatch, it will still take some time before the newly born seahorses leave the pouch.
This is because it takes some time for the baby seahorses to adjust to the salinity of seawater, and the male’s pouch actually regulates the salinity for them.
11. Chameleons
These color-changing reptiles are oviparous, like typical lizards. But some species are ovoviviparous. In these species, there’s typically a five to six month gestation period. When the time comes, the mother will deposit the eggs onto a branch, at this point the eggs are little more than the sticky membrane of the yolk sac surrounding the young chameleon.
The mother will press them down onto the branch so that stick, and then the young chameleon immediately breaks out of the egg.
