Sex in the morning or in the evening?

In the animal kingdom, males more often than females can increase their reproductive success by being promiscuous. This in turn can result in males imposing high numbers of copulation attempts and sexual harassment on females.

In the promiscuous feral chicken, males initiate more than 90 per cents of all copulation attempts; most of them in the evening after hens have laid their eggs and are most fertile. In female-dominated groups hens are also interested in sex in evenings. However, as shown in a new study published in American Naturalist, in male-dominated groups hens rather initiate sex in mornings.

'Sexual harassment in evenings in male-dominated groups may just be too much for the hens', says Hanne Løvlie from Stockholm University, one of the researchers of the study. 'Hens were exposed to more intense sexual harassment in male-dominated group. By initiate sex in mornings when the cockerels are less amorous and the free-ranging chickens also are more spread out foraging, hens may avoid the intense sexual harassment in evenings.'

The study shows that changes in the intensity of sexual harassment trigger a plasticity in the hens' sexual behaviour not before shown. A plasticity that in turn may enable hens to mate without suffering sexual harassment.

'The sexes therefore not only fall out on how much sex they want, but also when at day to have it', says Hanne Løvlie.

Contact Information
Hanne Løvlie, Department of Zoology, Stockholm University, tel +46 73 6394497, +46 8 16 48 96, e-mail hanne.lovlie@zoologi.su.se.