The new science cartoon presents the results of research on the influence of red deer female condition on foetus sex ratio. The survey revealed that maternal body mass affects foetus sex ratio –  the probability of having male offspring increased with increased with growing female body mass. Full version of the article “Heavier females produce more sons in a low-density population of red deer” is available at: http://onlinelibrary.wiley.com/doi/10.1111/jzo.12430/full