Rainfall linked to skewed sex ratios

Apr 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: Wolves susceptible to yawn contagion

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/

add to favorites email to friend print save as pdf

Related Stories

Does promiscuity prevent extinction?

Feb 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 my ...

A sex-ratio meiotic drive system in Drosophila simulans

Nov 06, 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, ...

A boy for every girl? Not even close

Sep 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

Wolves susceptible to yawn contagion

13 hours ago

Wolves may be susceptible to yawn contagion, according to a study published August 27, 2014 in the open-access journal PLOS ONE by Teresa Romero from The University of Tokyo, Japan, and colleagues.

User comments : 0