Hens with bigger ‘hairdos’ get more sex

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Hens with bigger fleshy crests on their heads get more sex and larger quantities of sperm from dominant male roosters, according to a new study.

While many studies have shown that males with more visible ornamentation have a mating advantage, this is the first to show that large ornamental body parts can give female animals a mating advantage, the researchers claim. 

Charlie Cornwallis at the University of Oxford, UK, demonstrated that looks matter to male chickens by running a series of tests in which he presented each of them with pairs of hens.

In the first part of the experiment, he and his colleagues covered the eye-catching red crests, known as “combs”, on the females’ heads with small hoods. This made it impossible for the male birds to size up the hens’ combs. As a result, in this part of the study, the males apparently picked their mate at random.

Next, the researchers removed the hoods from the hens and repeated the tests. The team found that 80% of the time males went after the hen with a larger comb.

The hens also wore a harness that held a plastic sack in place to collect the sperm males favoured them with. An analysis of collected samples revealed that large-combed hens received 50% more sperm from dominant males than their counterparts with relatively small combs. This is important because hens often compete for sex with dominant males, explains Cornwallis.
Visibility to predators

The exact reason that males prefer hens with larger combs remains unclear. But Cornwallis suspects that the body part indicates the fertility of female fowl: hens with larger combs lay larger eggs.

The size of the comb can also vary over time, and is probably dependant on the hens’ hormonal balance. Cornwallis says that having a smaller comb can also have its advantages: “This can not only reduce sexual harassment [from male chickens] but also reduce visibility to predators.”

Some of the female turkeys that do not end up on a dinner plate this Thanksgiving might tell a similar story, he says. While these birds do not have combs, they do have red, fleshy flaps known as “snoods” that hang near their eyes.

But the turkey on your plate this holiday will have been born through artificial insemination, whatever the quality of its mother’s snood, notes Tom Klopfenstein, farm manager of Kauffman Turkey Farms in Waterman, Illinois, US.

Journal: Proceedings of the Royal Society B (DOI: 10.1098/rspb.2006.3757)

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