My undergraduate research: why blood is thicker than water for mating roosters

Conducted as part of an undergraduate placement year project at The University of Manchester, a study published in the journal Behavioural Ecology has shown that male domestic fowl are less aggressive towards related males than they are to unrelated males when competing for mates. Recently-graduated BSc Biology with Industrial/Professional Experience student, Charlotte Rosher, was interested in evolutionary biology and its implications for animal behaviour. She spent her placement year at the Linkoping University, Sweden, doing research with Associate Professor Hanne Løvlie. Here, Charlotte explains her research…

Domestic fowl form social hierarchies in which one individual is dominant over the others. Cockerels are in competition with each other to mate with hens, as a successful mating allows them to pass their genes to the next generation. Dominant males commonly interrupt the mating attempts of lower ranking males, which prevents them from transmitting their genes.

However, if the lower ranking male and the higher ranking male are related, then they actually share genes. Our research asks whether cockerels not only attempt to produce offspring themselves, but also help other cock relatives to do so.

Are dominant cockerels more permissive towards the mating attempts of subordinate relatives than to those of unrelated lower-ranked cockerels?

Aggressive male cockerel behaviour. Photo credit: Hanne Løvlie

What did we do?

To answer our research question, birds were divided into groups with one dominant cockerel and two cockerels of lower rank, one of which was the brother or son of the dominant cockerel. The three cockerels were released with four hens, which is natural is a natural group size in these birds, and we observed the mating behaviour that took place.

What did we find?

The results showed that dominant males interrupted matings of relatives less frequently than those of unrelated males. Through the preferential directing of aggressive behaviour, these males were favouring the matings of their relatives.

This means that domestic fowl can determine the kinship between members of their group, and this affects their behaviour in a mating situation. It has previously been determined that some birds such as the red junglefowl, the wild ancestor of the domestic fowl studied here, can recognise their relatives.

Nonetheless, questions remain as to how birds determine whether an individual is related to them, but it is possible that they use their sense of smell. Animal behaviour is shaped by evolutionary processes, and the results from this study highlight how finely tuned this behaviour can be.

I very much enjoyed spending my placement year doing hands-on research that tackled key questions in the field of behavioural ecology. This study shows that males interrupted the matings of relatives less frequently, and from an evolutionary perspective this is a means by which that individual’s shared genes could be passed on to the next generation.

The study was carried out at the Tovetorp Research Station in collaboration with Stockholm University, The University of Manchester and University College London, and Monash University in Australia. The work received financial support from Linköping University, ERASMUS, the Zochonis Enterprise Fund, the Australian Research Council and Marie Curie Actions.

Relatedness and age reduce aggressive male interactions over mating in domestic fowl, Charlotte Rosher, Anna Favati, Rebecca Dean, Hanne Løvlie (2017), Behavioral Ecology, published online on 28 February 2017,

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