Data from: Task-dependent workload adjustment of female breeders in a cooperatively breeding fish

Parental investment affects the future survival and reproductive success of breeders. Therefore, breeders should optimize the amount of care they invest into the current offspring. In cooperative breeding systems, the amount of breeders’ parental care is influenced by the behavior of brood-care helpers. Such workload adjustment is expected to depend on the task that needs to be fulfilled. While investment rules of breeders in respect to single tasks are well investigated in many bird and mammal species, little is known about behavioral adjustment of breeders when dealing with multiple tasks. Here, we examined the workload adjustment in multiple tasks of female breeders in the cooperatively breeding fish Neolamprologus obscurus. By combining behavioral observations with helper removal experiments in a wild population, we found that female territory defense and offspring care significantly decreased with increasing helper number. Furthermore, the workload invested in these tasks significantly increased after the removal of a helper, suggesting load-lightening effects in territory defense and offspring care. On the other hand, female territory maintenance behavior (i.e. excavating sand from the breeding shelter) did not correlate with helper number. While sand excavation significantly increased after the helper removal experiment, the size of the excavated stone area decreased after the helper removal in the recent study, suggesting that sand excavation may have additive effects for the breeders. These results demonstrate and underline the importance of task dependent workload adjustment in cooperative breeders.

亲本投资（parental investment）会影响繁殖者未来的存活与繁殖成功率，因此繁殖者应当优化其对当前子代的抚育投入总量。在合作繁殖系统（cooperative breeding systems）中，繁殖者的亲本抚育量会受到育幼帮手（brood-care helpers）行为的调控。此类工作量调整理应取决于具体需要完成的任务类型。尽管诸多鸟类与哺乳类物种中，繁殖者针对单一任务的投资规则已得到充分研究，但目前学界对繁殖者应对多重任务时的行为调控机制仍知之甚少。本研究以合作繁殖鱼类暗带矛丽鱼（Neolamprologus obscurus）为对象，探究了雌性繁殖个体在多重任务中的工作量调控模式。通过结合野生种群的行为观察与帮手移除实验，我们发现：随着帮手数量增加，雌性的领域防御与育幼行为显著减少；而在移除帮手后，个体在这两类任务中的工作量均显著上升，表明领域防御与育幼行为存在减负效应（load-lightening effects）。另一方面，雌性的领域维持行为（即从繁殖庇护所中挖掘砂石）则与帮手数量无显著关联。尽管帮手移除实验后砂石挖掘行为显著增强，但本研究中挖掘出的砂石区域面积却有所下降，提示砂石挖掘可能对繁殖者存在附加效应。上述结果证实并凸显了合作繁殖者依据任务类型进行工作量调控的重要性。