Data from: No apparent benefits of allonursing for recipient offspring and mothers in the cooperatively breeding meerkat

1. Cooperative behaviours by definition are those that provide some benefit to another individual. Allonursing, the nursing of non-descendent young, is often considered a cooperative behaviour and is assumed to provide benefits to recipient offspring in terms of growth and survival, and to their mothers, by enabling them to share the lactation load. However, these proposed benefits are not well understood, in part because maternal and litter traits and other ecological and social variables are not independent of one another, making patterns hard to discern using standard univariate analyses. 2. Here, we investigate the potential benefits of allonursing in the cooperatively breeding Kalahari meerkat, where socially subordinate females allonurse the young of a dominant pair without having young of their own. 3. We use structural equation modelling to allow us to account for the interdependence of maternal traits, litter traits and environmental factors. 4. We find no evidence that allonursing provides benefits to pups or mothers. Pups that received allonursing were not heavier at emergence and did not have a higher survival rate than pups that did not receive allonursing. Mothers whose litters were allonursed were not in better physical condition, did not reconceive faster and did not reduce their own nursing investment compared to mothers who nursed their litters alone. These patterns were not significantly influenced by whether mothers were in relatively good, or poor, condition. 5. We suggest that allonursing may persist in this species because the costs to allonurses may be low. Alternatively, allonursing may confer other, more cryptic, benefits to pups or allonurses, such as immunological or social benefits.1. 合作行为从定义上来说是指能为其他个体带来一定益处的行为。异亲哺乳（allonursing），即对非后代幼崽进行哺乳的行为，通常被视作一种合作行为，学界一般认为其可通过分担泌乳负担，为接收哺乳的幼崽带来生长与存活层面的益处，同时也能为幼崽的生母提供帮助。然而，这类被提出的益处尚未得到充分阐明，部分原因在于母体性状、窝仔性状以及其他生态与社会变量之间并非相互独立，这使得通过标准单变量分析难以辨清其中的关联模式。 2. 本研究以合作繁殖的喀拉哈里狐獴为研究对象，探究异亲哺乳的潜在益处。在该物种中，处于社会从属地位的雌性个体即便自身未生育幼崽，也会为优势繁殖对的幼崽进行异亲哺乳。 3. 本研究采用结构方程模型（structural equation modelling），以考量母体性状、窝仔性状与环境因素之间的相互依赖关系。 4. 本研究未发现异亲哺乳能为幼崽或母兽带来益处的证据：接收过异亲哺乳的幼崽在出巢时体重并未更高，存活率也并未高于未接收异亲哺乳的幼崽；与仅自行哺乳幼崽的母兽相比，其幼崽接受过异亲哺乳的母兽身体状况并未更佳，也并未更快再次受孕，亦未减少自身的哺乳投入。母兽自身的身体状况（良好或较差）并未对上述关联模式产生显著影响。 5. 本研究推测，异亲哺乳行为在该物种中得以留存，可能是因为实施异亲哺乳的个体所需承担的成本较低；抑或是异亲哺乳能为幼崽或实施异亲哺乳的个体带来其他更为隐蔽的益处，例如免疫学层面或社会层面的益处。