National Geographic describes an Australian aquarium’s wonderment at a shark that just gave birth despite being alone for three years:
Aquarium keepers in Australia realized that this week, after a captive zebra shark (Stegostoma fasciatum) gave birth to three pups—without having had any contact with a male for years. (Zebra sharks are often called leopard sharks in Australia, but they are a different species from the leopard sharks found off the west coast of North America.)
The 20-something shark at Reef HQ Great Barrier Reef Aquarium in Townsville laid 41 eggs without a father. Three of them hatched into healthy pups, all female.
The pups were named Cleo, CC, and Gemini. Their mother is called Leonie.
“We have seen this process, called parthenogenesis, in a number of shark species, particularly in aquaria,” says George Burgess, a shark expert with the Florida Museum of Natural History.
At first, scientists thought the pregnancies were due to females storing up sperm from past mating encounters, something they can do for years. But that was disproven after several sharks gave birth with no access to males at all. The females reproduced without mating.
“I think it happens when they get pushed into an evolutionary corner, like in an aquarium with no males around,” says Burgess.