Shark Dads Lose Babies to Unborn Cannibal Siblings

Inside its mother’s womb, an unborn sand tiger shark is busy devouring its brothers and sisters. It’s just 10 centimetres long but it already has well-developed eyes and a set of sharp teeth, which it turns against its smaller siblings. By the time the pregnant female gives birth, it only has two babies left—one from each of its two wombs. These survivors have already eaten all the others. They’re the bloody victors of a pre-birth battle.

The arched back, upturned snout and protruding teeth of a sand tiger shark give it a particularly brutish look. Its reproductive habits don’t help. After sex, any fertilised eggs settle in one of the female’s two uteri. Like a quarter of shark species, the

DON'T MISS THE REST OF THIS STORY!
Create a free account to continue and get unlimited access to hundreds of Nat Geo articles, plus newsletters.

Create your free account to continue reading

No credit card required. Unlimited access to free content.
Or get a Premium Subscription to access the best of Nat Geo - just $19
SUBSCRIBE

Go Further

Subscriber Exclusive Content

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet