Data from: Alternative reproductive tactics in female striped mice: heavier females are more likely to breed solitary than communally

1. Alternative reproductive tactics (ARTs) are discrete reproductive phenotypes governed by decision rules called strategies. ARTs are fixed for life in species with alternative strategies, while tactic expression is plastic in species with a single strategy. ARTs have been investigated in males of many species, but few studies have tested whether the same theoretical framework applies in females. 2. Female striped mice (Rhabdomys pumilio) employ three ARTs: communal breeders give birth in a nest shared with female kin and a breeding male and show allo-parental care; returners give birth away from the shared nest and later return to it; and solitary breeders give birth away from the shared nest and do not return to the group. 3. Here, studying free-living female striped mice over six breeding seasons, we tested whether ARTs arise from alternative strategies or a single strategy. 4. We also asked to what extent stochastic extrinsic factors explain whether individuals become solitary rather than group living. 5. Females switched tactics, consistent with a single strategy, so we tested whether this represented a mixed or conditional single strategy. Only the latter predicts differences between ARTs in traits indicating competitive ability, such as body mass or age, before individuals adopt a tactic. We weighed females at conception when they were still group living to eliminate potential confounding effects of gestation and subsequent social tactic (solitary versus group living) on body mass. 6. Females that went on to use a solitary ART were heavier than those that became communal breeders and returners, in support of a conditional strategy. 7. Solitary breeders also arose through extrinsic factors (mortality of all adult female group members). They weighed less than females that became solitary while relatives were alive, but did not differ in body mass from communal breeders and returners. 8. We conclude that ART theory applies to both sexes, with female striped mice following a conditional single strategy. Future studies should consider the possibility that phenotypes that superficially resemble evolved tactics might also arise through non-adaptive extrinsic causes.

1. 替代繁殖策略（Alternative Reproductive Tactics, ARTs）是由被称为策略的决策规则所调控的离散繁殖表型。在采用替代策略的物种中，ARTs终生固定不变；而在仅采用单一策略的物种中，策略表达则具有可塑性。目前已有诸多研究针对多个物种的雄性个体开展了ARTs相关探究，但鲜有研究检验同一理论框架是否同样适用于雌性个体。
2. 条纹小鼠（*Rhabdomys pumilio*）的雌性个体存在三种ARTs：社群繁殖者会在与雌性亲属及繁育雄性共享的巢穴中产仔，并表现出异亲抚育行为；回归者会在远离共享巢穴的区域产仔，之后再返回该共享巢穴；独居繁殖者则会在远离共享巢穴的区域产仔，且不会返回社群群体。
3. 本研究针对6个繁殖季内的野生条纹小鼠雌性个体展开探究，以此检验ARTs究竟源自替代策略，还是单一策略。
4. 我们同时还探讨了随机外在因素在多大程度上可以解释个体为何会选择独居而非社群生活。
5. 雌性个体的策略切换现象与单一策略假说相符，因此我们进一步检验了该现象究竟属于混合型单一策略，还是条件型单一策略。唯有后者可预测：个体在采用某一繁殖策略之前，不同ARTs对应的个体在诸如体重或年龄这类体现竞争能力的性状上存在差异。我们在雌性个体仍处于社群生活阶段时，于受孕阶段对其进行称重，以消除妊娠期及后续社会策略（独居vs社群生活）对体重产生的潜在混杂效应。
6. 后续采用独居ART的雌性个体体重，高于最终成为社群繁殖者及回归者的雌性个体，这一结果支持了条件型单一策略假说。
7. 独居繁殖者的产生同样也会受到外在因素的影响（例如群体内所有成年雌性个体全部死亡）。这类因群体雌性全部死亡而成为独居繁殖者的个体，体重低于那些在亲属尚存时便选择独居的雌性个体，但它们的体重与社群繁殖者及回归者并无显著差异。
8. 我们的研究结论表明，ART理论同样适用于雌雄两性，条纹小鼠的雌性个体遵循条件型单一策略。未来的研究应当考虑到：那些表面上看似演化而来的繁殖策略表型，也可能由非适应性的外在因素所引发。