Data from: Baby on board: olfactory cues indicate pregnancy and fetal sex in a non-human primate

Olfactory cues play an integral, albeit underappreciated, role in mediating vertebrate social and reproductive behaviour. These cues fluctuate with the signaller's hormonal condition, coincident with and informative about relevant aspects of its reproductive state, such as pubertal onset, change in season and, in females, timing of ovulation. Although pregnancy dramatically alters a female's endocrine profiles, which can be further influenced by fetal sex, the relationship between gestation and olfactory cues is poorly understood. We therefore examined the effects of pregnancy and fetal sex on volatile genital secretions in the ring-tailed lemur (Lemur catta), a strepsirrhine primate possessing complex olfactory mechanisms of reproductive signalling. While pregnant, dams altered and dampened their expression of volatile chemicals, with compound richness being particularly reduced in dams bearing sons. These changes were comparable in magnitude with other, published chemical differences among lemurs that are salient to conspecifics. Such olfactory ‘signatures’ of pregnancy may help guide social interactions, potentially promoting mother–infant recognition, reducing intragroup conflict or counteracting behavioural mechanisms of paternity confusion; cues that also advertise fetal sex may additionally facilitate differential sex allocation.

嗅觉信号（olfactory cues）虽未得到充分重视，却是介导脊椎动物社会与繁殖行为不可或缺的核心因素。这类信号随信号发出者的激素状态波动，其变化与个体繁殖状态的关键特征同步，且能传递相关信息，包括青春期启动、季节更替，以及雌性的排卵时间。尽管妊娠会显著改变雌性的内分泌特征，且胎儿性别可进一步影响这一过程，但目前学界对妊娠与嗅觉信号间的关联仍知之甚少。为此，我们以环尾狐猴（Lemur catta）——一种具备复杂繁殖信号嗅觉机制的原猴亚目灵长类——为研究对象，探究了妊娠与胎儿性别对其挥发性生殖器分泌物的影响。研究发现，妊娠雌性会改变并抑制其挥发性化学物质的表达水平，其中产雄性幼崽的妊娠雌性的化合物丰富度下降尤为显著。此类变化的幅度与已发表文献中记载的、狐猴种内对同种个体具有显著性的其他化学差异相当。这类妊娠相关的嗅觉‘特征信号’或可调控社会互动，具体可涵盖促进母婴识别、减少群体内部冲突，或是抵消父权混淆的行为机制；而能够传递胎儿性别的信号，还可进一步辅助性别差异化分配。