May 2009


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Fresh Fish

If you can imagine the implications of a 1994 study showing that female guppies “may experience up to one forced copulation attempt (a sneaky mating) from males every minute” and how it makes them miss out on feeding opportunities, you might understand why researchers delved even deeper into the sexual behaviour of guppies.

The latest study now reveals the extent to which sexual harassment from males can damage relationships between females. This study, carried out by the Universities of Exeter, Bangor and Bath, in collaboration with The University of the West Indies (UWI), was published in Proceedings of the Royal Society B, in April 2009.

The research, led by the Centre for Research in Animal Behaviour at the University of Exeter and funded by the Natural Environment Research Council (NERC), uncovers the effect of sexual harassment on the ability of female fish to form social bonds with each other.

Guppies, a popular aquarium fish, had been observed to display a very high level of sexual harassment from males towards females. The researchers found that male harassment not only breaks down female social structures but also affects females’ ability to recognise one another. The research provides an insight into the effect of male sexual harassment on female social networks and social recognition. According to researchers, the findings could have relevance to other species.

Lead author, Dr Safi Darden of the University of Exeter, explains the link, “Sexual harassment is a burden that females of many species ranging from insects to primates suffer and the results of our work suggest that this harassment may limit the opportunities for females to form social bonds across a range of species.”

The research team, which included Prof Indar Ramnarine of the Department of Life Sciences at UWI, worked with a population of wild guppies taken from the lower portion of the Turure River in Trinidad. They isolated the females and introduced males to change the sex ratio so they could identify the effect of males on female social behaviour. Monitoring the guppies kept in semi-natural pools at the Department’s orchid enclosure, they tested the females’ ability to recognise their peers and form bonds with other members of the group. The study showed that, after experiencing a high level of sexual harassment, females were less able to recognise the other females in the group. They were also more likely to form bonds with new females, introduced from outside their network. “This is an extremely interesting result as it appears that females that experience sexual harassment actually prefer to avoid other females with whom they associate the negative experience,” said co-author Dr Darren Croft of the University of Exeter.

“The health and well-being of an individual is dependent, in part, on having strong social bonds with others and females that have weakened social bonds may be less likely to survive in the wild, said Dr Safi Darden. “This makes the effect of male harassment quite significant, but it is an area that has not previously been studied.”

The researchers do not know exactly why sexual harassment from males has such a marked effect on female social interaction. They speculate it is possible that the sheer amount of time spent by females dealing with unwanted male attention prevents them from forming relationships with other females. They believe females from groups with more males may have bonded with females from outside in order to try to establish themselves in a more favourable environment.