Task partitioning increases reproductive output in a cooperative bird
ABSTRACT Parents often face a trade-off between the quality and quantity of young produced because terminating investment in current young could result in lower survival and future reproductive success, whereas initiating new breeding attempts could result in greater production of young. In cooperatively breeding species, helpers may alleviate this trade-off by assuming the role of primary caregivers to first broods, liberating breeders to initiate subsequent breeding attempts without compromising the level of care offspring receive. Here, we investigate the occurrence and consequences of brood overlap in the cooperatively breeding pied babbler (Turdoides bicolor). Brood overlap occurred only in groups and resulted in breeders primarily investing in second broods while helpers continued to provide care to first broods, resulting in dependent young from overlapping broods being raised simultaneously. Interbrood partitioning of care during brood overlap resulted in a greater production of young per season in groups (cf., pairs) without any effect on offspring survival, thus representing a reproductive benefit of task partitioning in cooperatively breeding species. Copyright 2008, Oxford University Press.
Full-textDOI: · Available from: Amanda R Ridley, Jul 04, 2015
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ABSTRACT: Eavesdropping behaviour can increase the total amount of information available to an individual and therefore has the potential to provide substantial benefits. Recent research has suggested that some species are ‘information givers’, particularly social species with cooperative vigilance systems, and that these species may consequently affect community structure by influencing the behaviour and niche utilisation of other species. Here, using behavioural observations and playback experiments, we compared the behavioural change in a solitary species (the scimitarbill) and a social species (the pied babbler), to the presence and alarm calls of one another. Our results revealed that scimitarbills underwent significant behavioural changes in the presence of social pied babblers: they reduced their vigilance rate by over 60%, increased their foraging efficiency, and expanded their niche by moving into open habitat and excavating subterranean food items. In contrast, pied babblers – who have an effective intraspecific sentinel system - did not show significant behavioural changes to the presence or alarm calls of scimitarbills. These results suggest that interceptive eavesdropping can provide significant benefits, influencing the behaviour and habitat utilization of eavesdropping species.Functional Ecology 07/2013; DOI:10.1111/1365-2435.12153 · 4.86 Impact Factor
- Behaviour 01/2013; 150:691-712. · 1.40 Impact Factor
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ABSTRACT: Understanding the social organization of group-living organisms is crucial for the comprehension of the underlying selective mechanisms involved in the evolution of cooperation. Division of labour and caste formation is restricted to eusocial organisms, but behavioural asymmetries and reproductive skew is common in other group-living animals. Permanently, social spiders form highly related groups with reproductive skew and communal brood care. We investigated task differentiation in nonreproductive tasks in two permanently and independently derived social spider species asking the following questions: Do individual spiders vary consistently in their propensity to engage in prey attack? Are individual spiders' propensities to engage in web maintenance behaviour influenced by their previous engagement in prey attack? Interestingly, we found that both species showed some degree of task specialization, but in distinctly different ways: Stegodyphus sarasinorum showed behavioural asymmetries at the individual level, that is, individual spiders that had attacked prey once were more likely to attack prey again, independent of their body size or hunger level. In contrast, Anelosimus eximius showed no individual specialization, but showed differentiation according to instar, where adult and subadult females were more likely to engage in prey attack than were juveniles. We found no evidence for division of labour between prey attack and web maintenance. Different solutions to achieve task differentiation in prey attack for the two species studied here suggest an adaptive value of task specialization in foraging for social spiders.Journal of Evolutionary Biology 11/2012; 26(1). DOI:10.1111/jeb.12024 · 3.48 Impact Factor