Social immunity refers to any immune defence that benefits others, besides the individual that mounts the response. Since contributions to social immunity are known to be personally costly, they are contributions to a public good. However, individuals vary in their contributions to this public good and it is unclear why. Here we investigate whether they are responding to contributions made by others with experiments on burying beetle (Nicrophorus vespilloides) families. In this species, females, males and larvae each contribute to social immunity through the application of antimicrobial exudates upon the carrion breeding resource. We show experimentally that mothers reduce their contributions to social immunity when raising large broods, and test two contrasting hypotheses to explain why. Either mothers are treating social immunity as a public good, investing less in social immunity when their offspring collectively contribute more, or mothers are trading off investment in social immunity with investment in parental care. Overall, our experiments yield no evidence to support the existence of a trade-off between social immunity and other parental care traits: we found no evidence of a trade-off in terms of time allocated to each activity, nor did the relationship between social immunity and brood size change with female condition. Instead, and consistent with predictions from models of public goods games, we found that higher quality mothers contributed more to social immunity. Therefore our results suggest that mothers are playing a public goods game with their offspring to determine their personal contribution to the defence of the carrion breeding resource.

中文翻译：

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家庭的社会免疫：父母对公共物品的贡献受育雏大小调节

社会免疫是指任何有利于他人的免疫防御，除了引发反应的个人。由于众所周知对社会豁免的贡献是对个人的昂贵，因此它们是对公共物品的贡献。然而，个人对这一公共利益的贡献各不相同，原因尚不清楚。在这里，我们调查他们是否对其他人通过埋葬甲虫（Nicrophorus vespilloides）家族的实验做出的贡献做出反应。在这个物种中，雌性、雄性和幼虫都通过在腐肉繁殖资源上应用抗菌渗出物来促进社会免疫。我们通过实验表明，母亲在养大窝时会减少对社会免疫的贡献，并测试两个相反的假设来解释原因。要么母亲将社会免疫视为一种公共物品，当她们的后代集体贡献更多时，对社会免疫的投资就会减少，要么母亲正在对社会免疫的投资与对父母照顾的投资进行权衡。总体而言，我们的实验没有提供证据支持社会免疫与其他父母照顾特征之间存在权衡：我们没有发现在分配给每项活动的时间方面存在权衡的证据，社会免疫之间的关系也没有发现和育雏大小随雌性状况而变化。相反，与公共产品游戏模型的预测一致，我们发现质量更高的母亲对社会免疫力的贡献更大。