Data from: Alloparenting is associated with reduced maternal lactation effort and faster weaning in wild chimpanzees

Alloparenting, when individuals other than the mother assist with infant care, can vary between and within populations and has potential fitness costs and benefits for individuals involved. We investigated the effects of alloparenting on the speed with which infants were weaned, a potential component of maternal fitness because of how it can affect inter-birth intervals, in wild chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Uganda. We also provide, to our knowledge, the first description of alloparenting in this population and present a novel measure of the contribution of milk to infant diets through faecal stable nitrogen isotopes (δ15N). Using 42 mother–infant pairs, we tested associations of two alloparenting dimensions, natal attraction (interest in infants) and infant handling (holding, carrying), to the proportion of time mothers spent feeding and to maternal lactation effort (mean nursing rates and mother–infant δ15N differences). Neither natal attraction nor infant handling was significantly associated with feeding time. Infant handling was inversely associated with both measures of lactation effort, although natal attraction showed no association. Alloparenting may benefit mothers by enabling females to invest in their next offspring sooner through accelerated weaning. Our findings emphasize the significance of alloparenting as a flexible component of female reproductive strategies in some species.

异亲抚育（Alloparenting）指除生母之外的个体参与幼崽照料的行为，其在种群间及种群内部均存在差异，且会对参与个体产生潜在的适合度成本与收益。我们针对乌干达恩戈戈（Ngogo）种群的野生黑猩猩（Pan troglodytes schweinfurthii）展开研究，探讨异亲抚育对幼崽断乳速度的影响——由于断乳速度会影响产间隔时间，因此该因素是母方适合度的潜在组成部分。据我们所知，本研究还首次对该种群的异亲抚育行为进行了描述，并提出了一项通过粪便稳定氮同位素（δ15N）量化母乳在幼崽饮食中占比的全新指标。我们以42对母幼对子为研究对象，检验了异亲抚育的两个维度——新生儿吸引（对幼崽的兴趣）与幼崽抚触（握持、携带幼崽）——与母方觅食时长以及母方泌乳投入（平均哺乳频率以及母幼间δ15N差值）之间的关联。研究结果显示，新生儿吸引与幼崽抚触均与母方觅食时长无显著关联；而幼崽抚触与两项泌乳投入指标均呈负相关，新生儿吸引则未表现出此类关联。异亲抚育或可通过加快幼崽断乳进程，帮助雌性更早投入下一胎后代的繁育，从而使母方获益。本研究结果凸显了在部分物种中，异亲抚育作为雌性繁殖策略的灵活组成部分所具有的重要意义。