Rainfall linked to skewed sex ratios

April 22, 2010

An increased proportion of male African buffalo are born during the rainy season. Researchers writing in the open access journal BMC Evolutionary Biology collected data from over 200 calves and 3000 foetuses, finding that rain likely exerts this effect by interaction with so-called sex ratio (SR) genes, which cause differences in number, quality or function of X- and Y-bearing sperm.

Pim van Hooft, from Wageningen University, The Netherlands, worked with a team of researchers to study animals in the Kruger National Park, the scene of the famous 'Battle at Kruger' wildlife video. He said, "Here we show temporal correlations between information carried on the male and foetal sex ratios in the buffalo population, suggesting the presence of SR genes. Sex ratios were male-biased during wet periods and female-biased during dry periods, both seasonally and annually".

The researchers studied data collected between 1978 and 1998 to investigate the associations between rainfall, birth rates/ratios and . Ejaculate volume, sperm motility and proportion of normal-shaped sperm decrease significantly during the dry season. This decline in quality is likely due to decreasing availability and quality of food resources. According to van Hooft, "These observations may point towards a general mechanism in mammals whereby semen-quality related variation is driven by SR genes".

Explore further: Does promiscuity prevent extinction?

More information: Rainfall-driven sex-ratio genes in African buffalo suggested by correlations between Y-chromosomal haplotype frequencies and foetal sex ratio, Pim van Hooft, Herbert HT Prins, Wayne M Getz, Anna E Jolles, Sipke E van Wieren, Barend J Greyling, Paul D van Helden and Armanda DS Bastos, BMC Evolutionary Biology (in press), www.biomedcentral.com/bmcevolbiol/

Related Stories

Does promiscuity prevent extinction?

February 25, 2010

Promiscuous females may be the key to a species' survival, according to new research by the Universities of Exeter and Liverpool. Published today (25 February) in Current Biology, the study could solve the mystery of why ...

A sex-ratio meiotic drive system in Drosophila simulans

November 6, 2007

If you met a person who had 10 children, all of whom were girls, you would probably find this surprising. Yet this kind of distorted sex ratio does occur in groups as diverse as mammals, insects, and plants, where some parents ...

A boy for every girl? Not even close

September 10, 2009

In a perfect world, for every boy there would of course be a girl, but a new study shows that actual sex ratios can sometimes sway very far from that ideal. In fact, the male-to-female ratio of one tropical butterfly has ...

Recommended for you

Mammal long thought extinct in Australia resurfaces

December 15, 2017

A crest-tailed mulgara, a small carnivorous marsupial known only from fossilised bone fragments and presumed extinct in NSW for more than century, has been discovered in Sturt National Park north-west of Tibooburra.

Finding a lethal parasite's vulnerabilities

December 15, 2017

An estimated 100 million people around the world are infected with Strongyloides stercoralis, a parasitic nematode, yet it's likely that many don't know it. The infection can persist for years, usually only causing mild symptoms. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.