Fishy mating behaviour not limited to primates, scientists find

Jan 4, 2011, 0:10 GMT

Frankfurt - Some male fish species are able to judge the sex appeal of their rivals and display mating behaviour more commonly associated with highly developed primates, scientists in Germany said on Wednesday.

Male fish of the Poecilia Mexicana species feign a lack of interest in their preferred mating partner if they spot a sexually active rival nearby, according to observations by a research team at Frankfurt University.

'They fear that their preferred female could be snatched away from them, so they lay a false trail,' said biologist David Bierbach.

Attractive mating partners are deemed to be larger male fish, bearing particularly bright markings.

'This type of behaviour has been seen mostly amongst primates and more developed animals,' Bierbach added.

The discovery, by a team led by Bierbach and Martin Plath, is to be published in the Biology Letters journal of the British Royal Society.

The behaviour was seen after the research team allowed the fish to get to know each other for a week, keeping some males apart from the females and placing others in the vicinity of females.

The latter group were assumed by rivals to be sexually active. Whenever one of these fish approached a male courting a female, the courting male distanced itself from the desired female fish.

'The males reacted more strongly to these (sexually active) rivals,' Bierbach said.

The scientists explained that males saved their energies to fend off sexually active rivals, rather than waste efforts on those that were ill, injured or underfed.

This complex behaviour was necessary as female fish of the Poecilia Mexicana species moved in swarms, contrasted with lone male stalkers. The male fish have to approach the female to ascertain its suitability as a mating partner, a process which could tip off other males seeking partners.

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