Seahorses may be graceful and elegant but the idea that they are monogamous and mate for life is just a myth, according to research.

A study indicates that the sea creatures are promiscuous, flighty and more than a little bit gay — none more so than the Australian seahorse. And unlike human rules of attraction, it was the members of the Hippocampus genus with the biggest bellies that attracted the most partners.

The results also suggested that of 3,168 recorded sexual encounters, 37 per cent were same-sex liaisons.

Scientists at fifteen Sea Life Centre aquariums around Britain studied ninety seahorses of three species from Australia, the Caribbean and the Channel.

Until now many marine biologists had believed that seahorses were monogamous, and that theirs was one of the few species in which the male becomes pregnant and carries the eggs.

However, individual seahorses were recorded flirting with up to 25 potential partners a day.


The Australian bigbellied seahorse was the most indiscriminate, mating with both females and males several times a day. Caribbean slender seahorses were also promiscuous. Of the three species studied, only some of the British spiny seahorse were faithful to one partner. Out of those, five pairs remained faithful, while twelve did not.

Paul Bullimore, a Sea Life Centre marine curator, said: “The results of the survey came as a revelation to all of us. The fabled monogamy of the seahorse really has been exposed as a myth. We were pretty sure there was far more promiscuity among seahorses than is generally acknowledged, but we hadn’t picked up on the same-sex liaisons.

“This bisexual activity was both a great surprise and a shock to many of us that work with the creatures. The observations of big-bellied seahorses suggest that neither males nor females of this species had any preferred partner. They really are indiscriminate and shameless creatures.”

The scientists were looking for signs of courtship, including colour changes, knotting of tails and synchronised swimming. The information was studied at the national seahorse breeding centre in the Sea Life Park, Weymouth.

A total of 1,986 “contacts” were recorded between males and females, and another 836 between females and 346 between males.

Mr Bullimore said: “The big-bellied seahorses showed the keenest propensity for fooling around. They appeared happy to engage in courtship and fool around with any other member of the same species in the same tank. Only in the case of the spiny seahorses were there clearly pairs that remained faithful to each other.”

“Perhaps the naturalists who first reported monogamy in seahorses had observed it in one or two species and assumed it would be universal.

“Another possibility is that the sexual behaviour is different in aquarium conditions to that in the wild.”

Weymouth’s Sea Life breeding programme began in 1995 when a fisherman off the Dorset coast accidentally caught seven long-nose spiny seahorses. Until the capture of this group the species was thought to be almost entirely extinct in British waters as a result of crude Victorian oyster fishing techniques.

• The spiny seahorse and short-snouted seahorse live in British coastal waters
• The female transfers eggs to the male, who fertilises them in his pouch and gives birth
• Their eyes can work independently, so they can look backwards and forwards at once
• Less than one in 1,000 fry become adults
• They can change colour quickly to match their surroundings; males and females also change colour during courtship

See also
On the smells of sex
Gay pride for animals
More on seahorses