If the popularity of Carin Bondar’s web series Wild Sex is a good indicator, animal reproduction is an endlessly fascinating subject. Unfortunately, great white sharks don’t have much to offer to the conversation, largely because:
White sharks have only been observed mating once.
They were observed mating by a New Zealand Department of Conservation employee in 1991. Why haven’t white sharks been seen mating again?
It’s not because they are prudes, but because scientists haven’t been able to observe them at the right place, at the right time. The migration patterns of tagged white sharks show that they may use mating grounds off Guadalupe Island in Mexico, among other places.
However, we can infer the details of how white sharks reproduce from the behavior of other species.
White sharks become sexually mature between 8 and 15 years old.
Male white sharks are thought to be sexually mature earlier than females.
Like mammals, white sharks reproduce internally.
Male sharks have two external reproductive structures, called claspers, which they use to transfer sperm to females.
Male sharks bite females to hold them down during mating.
Ouch. It seems cruel, but remember that white sharks need to keep moving all the time. It would be difficult for both of them to stop to mate, so one of them has to hang on to the other. Luckily, females have tougher skin than males to accommodate this.
Only 10 pregnant females have been ever been dissected.
So few females means that scientists have a small sample size to draw conclusions from.
White sharks are pregnant for 18 months.
This is scientists’ best estimate for how long their gestation takes – no one knows for sure.
To stay alive, white shark embryos eat the unfertilized eggs in their mothers womb before they are born.
This practice is called oophagy.
No one has ever seen white sharks giving birth.
We don’t know how large white shark litters are, and we don’t know how often they reproduce. Not knowing this makes it hard to estimate how fast white shark populations can grow, which is essential for conserving them.
If you’d like to learn more about great white shark reproduction, the Florida Museum of Natural History has a summary. It was published in 1997, and thanks to tagging and increased research, we know even more today.