MacLeod Kirsty J, McGhee Katie E, Clutton-Brock Tim H
Large Animal Research Group, Department of Zoology, University of Cambridge, Downing Street, CB2 3EJ, Cambridge, UK.
Behavioural Ecology Research Group, Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK.
J Anim Ecol. 2015 Jul;84(4):1050-8. doi: 10.1111/1365-2656.12343. Epub 2015 Mar 3.
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. 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. We use structural equation modelling to allow us to account for the interdependence of maternal traits, litter traits and environmental factors. 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. 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.
从定义上来说，合作行为是那些能给其他个体带来某种益处的行为。异亲抚育，即对非亲生幼崽的抚育，通常被视为一种合作行为，并且假定它能在幼崽的生长和存活方面给接受抚育的后代带来益处，同时通过让母亲们分担哺乳负担，也能给母亲们带来好处。然而，这些假定的益处并未得到很好的理解，部分原因在于母体特征、窝仔特征以及其他生态和社会变量并非相互独立，这使得使用标准的单变量分析很难辨别其中的模式。在此，我们研究了在合作繁殖的喀拉哈里狐獴中异亲抚育的潜在益处，在这种动物群体中，处于社会从属地位的雌性会对占主导地位的一对狐獴的幼崽进行异亲抚育，而它们自己并没有幼崽。我们使用结构方程模型来考虑母体特征、窝仔特征和环境因素之间的相互依存关系。我们没有发现证据表明异亲抚育能给幼崽或母亲带来益处。接受异亲抚育的幼崽在出窝时体重并不比未接受异亲抚育的幼崽更重，存活率也没有更高。与独自哺育幼崽的母亲相比，其幼崽接受异亲抚育的母亲身体状况并没有更好，再次受孕也没有更快，并且没有减少自己的哺乳投入。这些模式并没有受到母亲身体状况相对较好或较差的显著影响。我们认为异亲抚育可能在这个物种中持续存在，是因为异亲抚育者的代价可能较低。或者，异亲抚育可能会给幼崽或异亲抚育者带来其他更隐蔽的益处，比如免疫或社会方面的益处。
