Signals of fertility in female animals are of increasing interest to evolutionary biologists, a development that coincides with increasing interest in male mate choice and the potential for female traits to evolve under sexual selection. We characterized variation in size of an exaggerated female fertility signal in baboons and investigated the sources of that variance. The number of sexual cycles that a female had experienced after her most recent pregnancy (“cycles since resumption”) was the strongest predictor of swelling size. Furthermore, the relationship between cycles since resumption and swelling size was most evident during rainy periods and was not evident during times of drought. Finally, we found significant differences in swelling size between individual females; these differences endured across cycles (i.e., were not explained by variation within individuals) and persisted in spite of ecological effects. This study is the first to provide conclusive evidence of significant variation in swelling size between female primates (controlling for cycles since resumption) and to demonstrate that ecological constraints influence variation in this signal of fertility.

中文翻译：

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女性生育信号的变异来源：狒狒自然种群中过度的发情肿胀

进化生物学家对雌性动物的生育信号越来越感兴趣，这一发展与对雄性配偶选择的兴趣增加以及雌性特征在性选择下进化的潜力相吻合。我们描述了狒狒中夸大的雌性生育信号大小的变化，并调查了这种变化的来源。女性在最近一次怀孕后经历的性周期数（“恢复后的周期数”）是肿胀大小的最强预测指标。此外，恢复以来的周期与膨胀大小之间的关系在雨季最为明显，而在干旱时期则不明显。最后，我们发现个体女性之间肿胀大小存在显着差异；这些差异跨越周期（即，不能用个体内部的变异来解释）并且尽管有生态影响，但仍然存在。这项研究首次提供了关于雌性灵长类动物肿胀大小显着变化的确凿证据（控制自恢复以来的周期），并证明生态限制影响了这种生育信号的变化。