A species of owl tries to sound macho by lowering the pitch of its hoots, scientists have learned.

Researchers from Brighton who studied European scops owls on a French island found that the hooting of males reflected their body weight. Heavier owls had deeper hoots than lighter ones.

Tests in which recorded hoots were played back to owls showed they had a big effect on behaviour.

When hoots were modified to sound higher, they produced a more aggressive response from territorial males.

Surprisingly, owls responded to calls mimicking heavy males by lowering their own hoots.

The British and French scientists believe they were trying to make themselves sound heavier to scare off the competition.

David Reby, an expert in mammal vocal communication from the University of Sussex and co-author of the research, said: "The vocal communication of owls has interesting similarities to that of terrestrial mammals where the information is typically encoded in acoustic components of the calls, rather than in the diversity of the vocal repertoire, as it is in songbirds."

The European scops is one of the smallest species of owl.

During the study, carried out on the island of Oleron off the west coast of France, several hundred hoots were recorded from 17 territorial males.

A series of playback experiments were conducted to monitor the reaction of owls to broadcast hoots.

Several hoots were altered in pitch so that they mimicked the calls of males with a range of body weights.

The findings appear in the April issue of the journal American Naturalist.