We’re used to thinking of the male as hit-and-run participant in reproduction, while the female does the heavy lifting. Roles are reversed in seahorses, so the social dynamics are also different from almost all other species. This creates an opportunity for polyandry — a single female keeps a “harem” of males.
Despite their size, these animals live rich, dramatic lives that you might expect to find in a telenovela, rather than a scientific journal.
Through daily courtship rituals, bonded pairs of male and female seahorses can synchronise their reproductive cycles. By communicating through these elaborate dances, a female will know when to prepare a clutch of eggs to coincide with the male as he prepares his brood pouch. When they’re both ready, the pair will rise through the water column, and the female will pass her unfertilised eggs into the male’s pouch. He fertilises the eggs as they enter the pouch, and it is this quirk of their reproductive cycle that has resulted in another: due to the eggs entering the male’s reproductive system unfertilised and him subsequently fertilising them, he can be certain that each offspring is his. This is extremely rare in the animal kingdom. As a result, males have evolved to take better care of the developing offspring than perhaps any other male in the animal kingdom, due to the assurance of paternity. This was the behaviour I expected to see, repeated on a miniature scale.