Crocodile Gives Birth Despite Living Alone For 16 Years

By: Catherine Cai

We all know about the birds and the bees. Mommy bee finds a daddy bee and together they make a baby bee. But what if the mommy bee can also be the father? This seems impossible scientifically, but there’s one tiny caveat: it just happened.

In January 2018, at the Costa Rican zoo, a female crocodile laid eggs. This was puzzling because the crocodile had been living alone for sixteen years. While crocodiles can lay eggs that are sterile, like hens with eggs, “some of this clutch looked quite normal. And one of them…continued to mature in an incubator” (Scientists Discover a Virgin Birth in a Crocodile - NYT). Unfortunately, the baby crocodile was eventually stillborn. Nevertheless, scientists were intrigued and wondered how this could have happened.

“Virgin birth”, or parthenogenesis, is when an embryo “[contains] only genetic material from its mother” (Scientists Discover a Virgin Birth in a Crocodile - NYT). In vertebrates, a parthenogen is formed when the egg cell rapidly divides, forming half of the genetics required. However, sometimes the organism will fuse with the byproduct of this process, called a polar body. When they fuse, the polar body donates the other half of the genetics, therefore creating a baby.

This baby may not be the healthiest, but it “might live long enough for a mate to arrive, thus allowing sexual reproduction, which tends to produce hardier offspring” (Scientists Discover a Virgin Birth in a Crocodile – NYT). As surprising as this may seem, parthenogenesis is common in plants. Shockingly, it has even been documented in certain species of snakes, birds, and fish, but never crocodiles.

If parthenogenesis is so common, why are scientists making a big fuss about it with crocodiles? In an interview for the New York Times, Dr. Warren Booth states that “crocodiles evolved long before many other modern parthenogenetic animals…what this tells us is it’s very likely that this also happened in pterosaurs and dinosaurs” (Scientists Discover a Virgin Birth in a Crocodile - NYT). This can be assumed, because “of where crocodilians…sit in the larger family tree. Birds and crocodiles are part of this ancient lineage called archosaurs.

Within the archosaurs, crocodilians are the oldest group, with pterosaurs and dinosaurs diverging later, and then birds descending from dinosaurs. If both crocodilians and birds…are capable of parthenogenesis, those in the middle, such as pterosaurs and dinosaurs, would likely have had the trait, too” (American Crocodiles can have 'virgin births' - here's what that means, National Geographic).

If scientists can successfully pinpoint where this happens in crocodiles, perhaps we’ll get to see real dinosaurs in the next Jurassic Park.

Source: Scientists Discover a Virgin Birth in a Crocodile – New York Times