Seahorses at a marine centre are being tagged with tiny necklaces to see if they stay faithful to their mate.

The creatures - long famed for their fidelity - are being put to the test at Birmingham's National Sea Life Centre. The couples are being fitted with colour coded necklaces and then having their mating behaviour recorded.

Marine experts at the National Seahorse Breeding and Conservation unit at Weymouth Sea Life Park in Dorset have long had their doubts about the famed faithfulness of seahorse partners.

Marine biologist Robin James said only limited research had been carried out on this previously. "We had a small-scale investigation seven years ago after casual observations suggested some female seahorses were a bit promiscuous," he said.

Visitors to the centre are being asked to look out for amorous behaviour with signs including colour-changing, twining tails and leaning towards each other and quivering.

Vicky Griffiths, from the Sea Life Centre in Birmingham, said: "We will collect data over a month then send it to Weymouth for analysis along with the results from all the other Sea Life centres. We think there probably is a bit of 'playing away from home' among some species of seahorse." The study is also being carried out at eight Sea Life centres in Germany, as well as seven other UK the centres.

Stefan Inselmann, Sea Life's senior marine biologist in Germany, said: "Besides the fact that it is the males that give birth, the alleged fidelity of seahorses is probably the thing most people know about them. When they hear this may not be true they seem happy to watch for quite long periods to see if there's any hanky panky."