A new documentary by Nat Geo WILD called Cannibal Sharks is both disturbing and interesting in its revelations about sand tiger sharks — particularly what happens before they are born. According to Newsweek, the movie features Demian Chapman from Florida International University, who has spent over six years studying the unique species.
Chapman claims that scientists noticed something strange about sand tiger sharks as far back as the 1970s, when researchers first began examining their reproduction, In particular, the subtropical species always gave birth to two offspring, even though there were typically anywhere from 12 to 14 embryos early on in pregnancy.
“So the big question was, what was happening to all those other embryos?”
According to Chapman, one of the earliest clues for the disappearing embryos came when a researcher stuck his fingers into a sand tiger womb and was bitten by an embryo. It was this event that foreshadowed the disturbing revelation that before birth, sand tiger sharks cannibalize each other.
“What happens is the oldest of those embryos is actually a little bit ahead in terms of development of the others—develops teeth and eyes a bit earlier,” Chapman said.
“And once it’s got those things it actually starts hunting and killing all of its siblings. So they’re cannibals before birth which is really wild.”
The process is called “intrauterine cannibalization,” which means taking place in the womb, and it decreases the number of embryos from the initial group of 12 or 14 to just two.
"They're cannibals before birth": Sand tiger sharks eat one another in the womb https://t.co/156MPBcQGl
— Newsweek (@Newsweek) July 15, 2019
Outside of their cannibalistic nature, there are many other unique things about sand tiger sharks. Per Mental Floss, they are known to creep around shipwrecks, including those in North Carolina’s outer banks — also known as the “Graveyard of the Atlantic.” These unique sharks are attracted to shipwrecks because of the smaller fish that often transform them into faux reefs, making them ideal hunting locations.
When it comes to hunting, sand tiger sharks sometimes hunt cooperatively in groups of over 100. They use their numbers to push their prey into shallow waters or tight clusters — making them more vulnerable — before going in for the kill.
But when it comes to humans, Mental Floss reports that violent encounters are rare. Sand tiger sharks tend to keep their distance from people, although they sometimes steal fish from spear- and net-hunters. In these cases, the sharks may bite out of self-defense if they feel threatened. Outside of these situations, only 29 unprovoked sand tiger shark attacks on humans have been recorded since 1580.