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Is it true that with seahorses, males give birth? - JJ, age 9, Brisbane.
Great question! It sounds crazy, but it is true.
Seahorses and their close relatives the pipefish and the seadragons are very unusual, because it is the males that get pregnant and give birth to the babies. Instead of growing the baby seahorses inside their belly in a uterus, like human mums do, the seahorse dads will carry the babies in a pouch, a bit like a kangaroo’s pouch.
To produce babies, seahorses have to mate first. Seahorse mating is really beautiful. Males and females dance around one another and flutter their fins, and they may dance together over several days before they actually mate.
When they’ve decided they like each other, the seahorse females swim towards the surface of the water, and the males follow. The females then put their bright orange eggs into the pouch of the males through the hole at the top of the pouch. Once the eggs are safely inside, the males will add their sperm and shut the opening. The eggs are fertilised by the sperm, and then start developing into baby seahorses.
With that, the job of the seahorse mum is done! She swims off, and leaves the father to take care of the growing babies. Inside the pouch, the babies grow eyes, tiny snouts, and little tails. It takes about 20 days for the babies to develop, safely tucked away from other animals that might want to eat them.
When male seahorses give birth, it is very dramatic. You can watch a cool video of seahorse birth here:
The male will open the hole in his brood pouch, and violently jerk around to squeeze all of the babies out. They shoot out very quickly, and it looks spectacular. In fact, some species of seahorse can give birth to more than 1,000 babies at once!
After he has given birth, the seahorse dad does nothing more for his babies. They must look after themselves and hide from predators, as they have no parents to protect them. The seahorse father does not eat until several hours after he has given birth. However, if the babies are still hanging around him after that, they may become a tasty meal. That’s right, males sometimes eat their own babies.
It’s tough being a baby seahorse. Of the hundreds of babies that the male gives birth to, only one or two will survive to become adults and have babies of their own.
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Authors: Camilla Whittington, Research Fellow / Lecturer, University of Sydney