Savage James L, Browning Lucy E, Manica Andrea, Russell Andrew F, Johnstone Rufus A
Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ UK.
Behavioural Ecology Group, Department of Animal Sciences, Wageningen University, De Elst 1, 6708 WD Wageningen, The Netherlands.
Behav Ecol Sociobiol. 2017;71(11):162. doi: 10.1007/s00265-017-2391-4. Epub 2017 Oct 17.
For individuals collaborating to rear offspring, effective organization of resource delivery is difficult because each carer benefits when the others provide a greater share of the total investment required. When investment is provided in discrete events, one possible solution is to adopt a turn-taking strategy whereby each individual reduces its contribution rate after investing, only increasing its rate again once another carer contributes. To test whether turn-taking occurs in a natural cooperative care system, here we use a continuous time Markov model to deduce the provisioning behavior of the chestnut-crowned babbler (), a cooperatively breeding Australian bird with variable number of carers. Our analysis suggests that turn-taking occurs across a range of group sizes (2-6), with individual birds being more likely to visit following other individuals than to make repeat visits. We show using a randomization test that some of this apparent turn-taking arises as a by-product of the distribution of individual inter-visit intervals ("passive" turn-taking) but that individuals also respond actively to the investment of others over and above this effect ("active" turn-taking). We conclude that turn-taking in babblers is a consequence of both their individual provisioning behavior and deliberate response rules, with the former effect arising through a minimum interval required to forage and travel to and from the nest. Our results reinforce the importance of considering fine-scale investment dynamics when studying parental care and suggest that behavioral rules such as turn-taking may be more common than previously thought.
Caring for offspring is a crucial stage in the life histories of many animals and often involves conflict as each carer typically benefits when others contribute a greater share of the work required. One way to resolve this conflict is to monitor when other carers contribute and adopt a simple "turn-taking" rule to ensure fairness, but natural parental care has rarely been studied in sufficient detail to identify such rules. Our study investigates whether cooperatively breeding chestnut-crowned babblers "take turns" delivering food to offspring, and (if so) whether this a deliberate strategy or simply a by-product of independent care behavior. We find that babblers indeed take turns and conclude that part of the observed turn-taking is due to deliberate responsiveness, with the rest arising from the species' breeding ecology.
对于共同养育后代的个体而言，有效地组织资源供给是困难的，因为当其他照料者承担了更大比例的总投资时，每个照料者都会从中受益。当投资以离散事件的形式进行时，一种可能的解决方案是采用轮流策略，即每个个体在投资后降低其贡献率，只有在其他照料者做出贡献后才会再次提高其贡献率。为了测试轮流策略是否发生在自然的合作照料系统中，我们在这里使用连续时间马尔可夫模型来推导栗冠鸫鹛（一种澳大利亚合作繁殖鸟类，照料者数量可变）的供给行为。我们的分析表明，轮流策略在一系列群体规模（2 - 6只）中都会出现，个体鸟类在其他个体拜访之后更有可能去拜访，而不是进行重复拜访。我们通过随机化检验表明，这种明显的轮流策略部分是个体拜访间隔分布的副产品（“被动”轮流），但个体也会在这种影响之外，积极地对其他个体的投资做出反应（“主动”轮流）。我们得出结论，鸫鹛的轮流策略是其个体供给行为和刻意反应规则的结果，前者是由于往返巢穴觅食和旅行所需的最短间隔时间产生的。我们的结果强化了在研究亲代照料时考虑精细尺度投资动态的重要性，并表明轮流等行为规则可能比以前认为的更为普遍。
照顾后代是许多动物生命历程中的关键阶段，并且通常涉及冲突，因为每个照料者通常在其他照料者承担了更大比例的所需工作时受益。解决这种冲突的一种方法是监测其他照料者何时做出贡献，并采用简单的“轮流”规则来确保公平，但自然亲代照料很少得到足够详细的研究以识别此类规则。我们的研究调查了合作繁殖的栗冠鸫鹛是否“轮流”为后代提供食物，以及（如果是这样）这是一种刻意策略还是仅仅是独立照料行为的副产品。我们发现鸫鹛确实会轮流，并得出结论，观察到的轮流行为部分是由于刻意的反应，其余部分则源于该物种的繁殖生态。
