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.
SourceAvailable from: Amanda R Ridley[Show abstract] [Hide abstract]
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
[Show abstract] [Hide abstract]
ABSTRACT: Size has profound consequences for the structure and function of biological systems, across levels of organization from cells to social groups. As tightly integrated units that vary greatly in size, eusocial insect colonies, in particular, are expected to exhibit social scaling relations. To address the question of how social organization scales with colony size, we quantified task performance in variably sized colonies of the harvester ant Pogonomyrmex californicus. We found a positive scaling relationship between colony size and division of labor in 2 different contexts. First, individual workers were more specialized in older, larger colonies. Second, division of labor increased with colony size, independently of colony age. Moreover, the proportional allocation of workers to tasks shifted during colony ontogeny--older, larger colonies performed relatively less brood care--but did not vary with colony size among same-aged colonies. There were no colony-size effects on per capita activity or the distribution of activity across workers. Size-related changes in task performance were correlated with changes in the rate of encounter between nest mates. These results highlight the importance of colony size for the organization of work in insect societies and raise broader questions about the role of size in sociobiology. Copyright 2011, Oxford University Press.Behavioral Ecology 08/2011; 22(5):90-96. DOI:10.1093/beheco/arr075 · 3.16 Impact Factor