“The distress call is a very clear, rather loud vocalisation, so there is a risk that it could attract predators in the surroundings. That’s why the hens only call if it benefits them in the mating,” says Hanne Løvlie, researcher in Ethology at Linköping University and leader of a study now being published in the journal Animal Behaviour.
Løvlie and her colleagues conducted an experiment where hens were subjected to mating attempts by a low-ranking rooster. In half the attempts there was a higher-ranking rooster in the next aviary; in the other half, there were no roosters at all nearby.
“We saw that in most cases, the hens resisted and tried to avoid mating, and many of them let out the distress call. The most fascinating thing was that they were clearly more willing to call when there was a high-ranking rooster in the next cage. This shows that the hens select which situations they use the vocalisation in, and that they do so to attract a rooster who can help her disrupt a forced mating,” Ms Løvlie says.
Similar mating calls have been observed in other vertebrates, but they seem to have varying functions. The hens’ vocalisations and patterns are reminiscent of those in certain mammals. For example, elk cows let out a wail if they are being courted by smaller bulls, more rarely if the suitors are large and handsome.
“Our study, which is a collaboration between Linköping and Stockholm Universities, shows that hens have been selected in order to try to regain control over who they mate with, even in situations they can’t themselves control. By resorting to the distress call when a “hero” is on hand, they can get help in avoiding an unwanted mating,” Ms Løvlie says.
Article: A cry for help: female distress calling during copulation is context dependent by H Løvlie, J Zidar, J and C Berneheim . Animal Behaviour, vol. 92, 2014. http://dx.doi.org/10.1016/j.anbehav.2014.04.002