Abstract

Cooperative actions are beneficial to the group, but presumably costly to the individual co-operators. In cooperatively breeding species, helping to raise young is thought to involve important energetic costs, which could lead to elevated exposure to reactive oxygen species, resulting in oxidative stress. However, identifying such costs can be difficult if individuals adjust their investment in helping in relation to environmental conditions or their own physiological condition. Experimental approaches are therefore required to quantify the costs of helping but, to date, these have been infrequent. Here, we combined correlational and experimental data to investigate the oxidative cost of helping-at-the-nest and how this affects helping decisions in wild sociable weavers Philetairus socius, a colonial cooperatively breeding bird. At the correlational level, we found that the probability of helping was influenced by the interaction of an individual’s oxidative state and age: compared to younger birds, older individuals were more likely to help when they had higher oxidative damage, and the opposite trend was found for younger individuals. After experimentally increasing the energetic cost of flight, manipulated helpers in breeding colonies decreased nestling feeding rates and incurred an increase in oxidative damage, which was not present in manipulated helpers in non-breeding colonies. This indicates that individuals decreased their helping behavior to minimize the associated costs. These results suggest that oxidative stress can influence helping decisions and underlie a trade-off between cooperation and self-maintenance, which is central to understanding when helping might take place in this and other species.

中文翻译：

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合作育种者帮助的氧化成本及其最小化

摘要

合作行动对集体有利，但对个体合作者来说可能代价高昂。在合作繁殖的物种中，帮助养育年轻人被认为涉及重要的能量成本，这可能导致接触活性氧的增加，从而导致氧化应激。然而，如果个人根据环境条件或他们自己的生理状况调整他们在帮助方面的投资，那么确定这些成本可能会很困难。因此，需要实验方法来量化帮助的成本，但迄今为止，这些成本并不常见。在这里，我们结合相关数据和实验数据来研究在巢中帮助的氧化成本以及这如何影响野生社交织布工的帮助决策Philetairus socius，一种殖民地合作繁殖的鸟类。在相关层面上，我们发现帮助的概率受个体氧化状态和年龄相互作用的影响：与年轻的鸟类相比，年龄较大的个体在氧化损伤较高时更有可能提供帮助，而发现相反的趋势对于年轻人。在实验性地增加飞行的能量成本后，繁殖群落中的操纵助手降低了雏鸟的摄食率并导致氧化损伤增加，而非繁殖群的操纵助手中不存在这种情况。这表明个人减少了他们的帮助行为以最小化相关成本。这些结果表明，氧化应激可以影响帮助决策，并成为合作与自我维持之间权衡的基础，