University Of Tasmania

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Extreme sex ratio variation in relation to change in condition around conception

journal contribution
posted on 2023-05-17, 04:46 authored by Elissa Cameron, Linklater, WL
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 have produced notoriously inconsistent results, although recent studies suggest more consistency if sex ratio variation is related to maternal condition at conception, potentially mediated by changes in circulating glucose level. Consequently, we hypothesized that change in condition might better predict sex ratio variation than condition per se. Here, we investigate sex ratio variation in feral horses (Equus caballus), where sex ratio variation was previously shown to be related to maternal condition at conception. We used condition measures before and after conception to measure the change in condition around conception in individual mothers. The relationship with sex ratio was substantially more extreme than previously reported: 3% of females losing condition gave birth to a son, whereas 80% of those females that were gaining condition gave birth to a son. Change in condition is more predictive of sex ratio than actual condition, supporting previous studies, and shows the most extreme variation in mammals ever reported.


Publication title

Biology Letters








School of Natural Sciences


The Royal Society Publishing

Place of publication

United Kingdom

Rights statement

Copyright © 2007 Royal Society Publishig

Repository Status

  • Restricted

Socio-economic Objectives

Terrestrial biodiversity

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    University Of Tasmania