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Updated: Jul 9, 2026

Determination of Reproductive Competence by Confirming Pubertal Onset and Performing a Fertility Assay in Mice and Rats
Published on: October 13, 2018
Experimental alteration of litter sex ratios in a mammal
Elissa Z Cameron1, Patrick R Lemons, Philip W Bateman
1Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria 0002, Republic of South Africa. ezcameron@zoology.up.ac.za
Abstract:
Adaptive theory predicts that mothers would be advantaged by adjusting the sex ratio of their offspring in relation to their offspring's future reproductive success. Studies investigating sex ratio variation in mammals, including humans, have obtained notoriously inconsistent results, except when maternal condition is measured around conception. Several mechanisms for sex ratio adjustment have been proposed. Here, we test the hypothesis that glucose concentrations around conception influence sex ratios. The change in glucose levels resulted in a change in sex ratios, with more daughters being born to females with experimentally lowered glucose, and with the change in glucose levels being more predictive than the glucose levels per se. We provide evidence for a mechanism, which, in tandem with other mechanisms, could explain observed sex ratio variation in mammals.
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