Abstract
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 (Pomatostomus ruficeps), 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.Significance statementCaring 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.
Highlights
Individuals cooperating to rear offspring face several problems when attempting to share provisioning effort efficiently
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 (Bpassive^ turn-taking) but that individuals respond actively to the investment of others over and above this effect (Bactive^ turn-taking)
We found strong evidence that chestnut-crowned babblers respond to other carers visiting the nest by modifying their own visit rate, beyond the apparent turn-taking arising from combination of group size effects, unequal visit. Both our run tests and Markov analyses suggested that some of the tendencies for individuals to take turns could not be explained by group size effects alone
Summary
Individuals cooperating to rear offspring face several problems when attempting to share provisioning effort efficiently. Models have typically adopted either Bsealed bid^ (Houston and Davies 1985; Savage et al 2013) or Bnegotiation^ (McNamara et al 1999; Johnstone 2011; Lessells and McNamara 2012) approaches to determine the optimum investment level (or response rule, in negotiation models) for each carer during a breeding attempt Both methods produce qualitatively similar results, generally predicting incomplete compensation to changes in investment by other carers (McNamara et al 1999), additional considerations such as asymmetric information about the offspring among carers (Johnstone and Hinde 2006), maternal tactics (Savage et al 2013), or threshold effects such as partner desertion (Jones et al 2002) can lead to alternative predictions. Empirical work supports incomplete compensation as the usual strategy adopted in biparental species ( with substantial variation, reviewed in Harrison et al 2009), but results are more mixed in cooperative species where nonbreeding individuals contribute to care (Hatchwell 1999)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
