Old males win sex battle

Jun 25, 2010
Old males win sex battle
Old males can still dominate the pecking order

(PhysOrg.com) -- Old roosters can still dominate the sexual pecking order even when their ability to fertilise eggs drastically declines, new Oxford University research has shown.

A study of feral chickens, reported in this week’s , suggests an evolutionary battle between what’s good for old roosters and what’s good for their hens - which would benefit from sex with younger, more potent males.

The team, led by Oxford University researchers, studied the relationship between the status of male birds, their reproductive performance, and female , in a feral population of chickens in Sweden.

‘We found that roosters decline in a number of key reproductive traits as they age - from libido to sperm quality - and, in groups where there’s intense competition, tend to lose out to younger males,’ said Dr Tommaso Pizzari of Oxford University’s Department of Zoology, an author of the report. ‘However, old males remain capable of dominating the pecking order: When this happens they can monopolise access to females but, because of their sexual decline, they fail to fertilise all the eggs available. This implies an evolutionary conflict between ageing roosters and fertile hens.’

The researchers used four different experiments to separate out the influence of male and female factors on reproductive success - something that is difficult to study in wild animals. It is only recently that scientists have started to understand the significant role that age-related ‘sexual decline’ (reproductive senescence) plays in natural animal populations.

‘In evolution there are many battlegrounds, but nothing is more important than successfully reproducing. So, for hens, being monopolised by an impotent old rooster who will cause them to lay many infertile eggs is a disaster and amounts to a declaration of war. Our study shows that this sort of sexual decline is an engine driving in animals,’ said Dr Rebecca Dean of Oxford University’s Department of Zoology, also an author of the report.

Explore further: Orchid named after UC Riverside researcher

More information: A report of the research, ‘Male reproductive senescence causes potential for sexual conflict over mating’, is published in the 13 July issue of Current Biology.

Related Stories

Sex in the morning or the evening?

Jun 26, 2007

Most research on sexual conflict ignores the fact that the fitness pay-offs of mating may change drastically over a short timescale, for example over a single day.

The cost of keeping eggs fresh for mother cockroaches

Feb 26, 2007

One of the defining differences between the sexes is in the size of their gametes. Males make many tiny sperm while females make only a few large eggs. This suggests that sperm are cheap while eggs are expensive. ...

Small But Mighty Female Lizards Control Genetic Destiny

Apr 05, 2010

(PhysOrg.com) -- "Be faithful in small things because it is in them that your strength lies." Mother Teresa's words echo throughout the world. They ring particularly true in the biological kingdom among brown ...

Parents seeking sex abandon 1 in 3 offspring

Jul 30, 2007

The eggs of the penduline tit Remiz pendulinus are frequently abandoned as both parents go in search of new sexual conquests, a study published in the Journal of Evolutionary Biology has found.

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

4 hours ago

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

21 hours ago

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

23 hours ago

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

23 hours ago

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Researchers develop new model of cellular movement

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

Under some LED bulbs whites aren't 'whiter than white'

For years, companies have been adding whiteners to laundry detergent, paints, plastics, paper and fabrics to make whites look "whiter than white," but now, with a switch away from incandescent and fluorescent lighting, different ...