Science - April 29, 2010
More sons after sex in the rain
Quality of buffalo sperm is better in rainy periods.

'The obvious explanation is that this excess of males in rainy periods has to do with variations in physical condition', explains Van Hooft. 'Their physical condition improves during rainy periods and the quality of their sperm is also better then than in dry periods.' According to Van Hooft, the buffalos' physical condition affects the activity of the so-called sex-ratio genes on the Y chromosome.