Data from: Threat sensitive adjustment of aggression by males and females in a biparental cichlid

Defending offspring provides fitness benefits to parents, but is costly. To moderate costs, parents should adjust aggressive responses to the threat posed by different species entering their territory. However, few studies have experimentally tested behavioral adjustments in response to the threat posed by different types of intruders, particularly in the field, and in environments with an array of heterospecific intruders. Here, using a biparental cichlid, the poor man’s tropheus (Hypsophrys nematopus), we investigated whether males and females in the wild invest equally into offspring defense and what impact the absence of a partner might have on the quality of offspring defense provided by a solitary parent. In a separate experiment, we assessed responses of breeding pairs to three common heterospecific intruders that pose different levels of threat to the breeding pair and their brood. We found that both paired and unpaired females invested significantly more into territorial aggression than males. However, unpaired females were unable to fully compensate for the absence of their partner, with intruders left to venture closer to their offspring. Furthermore, we show that breeding pairs can readily discriminate between heterospecific intruders, with pairs responding quicker and more aggressively towards species that posed a greater potential threat. Our results demonstrate that biparental species can have extensive behavioral flexibility in their aggressive responses towards intruders, even in environments with a high frequency of territory incursion. The quality of territorial defense can nevertheless be compromised if one parent is left to defend the brood alone.

抚育子代可为亲代带来适合度收益，但同时需付出相应代价。为平衡此类成本，亲代应当针对进入其领地的不同物种所构成的威胁，灵活调整攻击响应策略。然而，目前鲜有研究通过实验探究亲代针对不同类型入侵者威胁的行为调控机制，尤其是在野外环境以及存在多种异种入侵者的场景中。本研究以双亲抚育的慈鲷——贫民丽体鱼（Hypsophrys nematopus）为实验对象，旨在探究野外环境中雌雄亲代对子代防御的投入是否均等，以及配偶缺失对单亲抚育子代的防御质量会产生何种影响。在另一组独立实验中，我们评估了繁殖配偶对三类常见异种入侵者的响应行为——这三类入侵者对繁殖亲代及其子代的威胁程度各不相同。实验结果显示，无论是否有配偶陪伴，雌性亲代的领地攻击投入量均显著高于雄性。但单亲雌性无法完全弥补配偶缺失带来的防御缺口，入侵者得以更接近其子代。此外，本研究证实繁殖配偶可有效区分不同异种入侵者：相较于低威胁物种，繁殖亲代会对潜在威胁更高的物种做出更快、更猛烈的攻击响应。研究结果表明，即使在领地入侵频率较高的环境中，双亲抚育物种仍可对入侵者展现出极强的行为调控灵活性。但倘若仅剩单亲独自抚育子代，领地防御的质量仍会受到损害。