Hodge Sarah J
University of Cambridge Large Animal Research Group, Department of Zoology Downing Street, Cambridge CB2 3EJ, UK.
Proc Biol Sci. 2005 Dec 7;272(1580):2479-84. doi: 10.1098/rspb.2005.3255.
Helpers in cooperative and communal breeding species are thought to accrue fitness benefits through improving the condition and survival of the offspring that they care for, yet few studies have shown conclusively that helpers benefit the offspring they rear. Using a novel approach to control for potentially confounding group-specific variables, I compare banded mongoose (Mungos mungo) offspring within the same litter that differ in the amount of time they spend with a helper, and hence the amount of care they receive. I show that pups that spend more time in close proximity to a helper are fed more, grow faster and have a higher probability of survival to independence than their littermates. Moreover, high growth rates during development reduce the age at which females breed for the first time, suggesting that helpers can improve the future fecundity of the offspring for which they care. These results provide strong evidence that it is the amount of investment per se that benefits offspring, rather than some correlate such as territory quality, and validate the assumption that helpers improve the reproductive success of breeders, and hence may gain fitness benefits from their actions. Furthermore, the finding that helpers may benefit offspring in the long-term suggests that current studies underestimate the fitness benefits that helpers gain from rearing the offspring of others.
在合作繁殖和群居繁殖的物种中，帮手被认为是通过改善它们所照顾的后代的状况和存活率来获得适应性益处的，然而很少有研究能确凿地表明帮手会使它们抚养的后代受益。我采用一种新颖的方法来控制潜在的混淆性群体特定变量，比较同一窝内带状猫鼬（Mungos mungo）幼崽，它们与帮手相处的时间不同，因此得到的照顾量也不同。我发现，与帮手近距离相处时间更长的幼崽比它们的同窝幼崽喂食更多、生长更快，独立生存的概率更高。此外，发育期间的高生长率降低了雌性首次繁殖的年龄，这表明帮手可以提高它们所照顾的后代未来的繁殖力。这些结果提供了有力证据，即正是投资量本身使后代受益，而不是诸如领地质量等一些相关因素，并验证了帮手能提高繁殖者繁殖成功率的假设，因此它们可能从自己的行为中获得适应性益处。此外，帮手可能长期使后代受益这一发现表明，目前的研究低估了帮手从抚养其他个体的后代中获得的适应性益处。
