Male seahorses carry the babies because of a unique evolutionary adaptation. They have a specialized pouch on their abdomen lined with blood vessels that provides a safe, protected environment for developing embryos.
The female deposits her eggs into the male's pouch. The eggs are fertilized in the water before entering the pouch, and the male incubates them, supplying oxygen and nutrients. After gestation, the male gives birth to live, fully formed young.
This role reversal likely evolved due to intense competition for mates. It allows the female to quickly produce a new batch of eggs while the male cares for the current brood, increasing offspring survival.