Carer provisioning rules in an obligate cooperative breeder: prey type, size and delivery rate
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ORIGINAL PAPER
Carer provisioning rules in an obligate cooperative breeder: prey type, size and delivery rate L. E. Browning & C. M. Young & J. L. Savage & D. J. F. Russell & H. Barclay & S. C. Griffith & A. F. Russell
Received: 25 June 2012 / Revised: 24 September 2012 / Accepted: 24 September 2012 / Published online: 9 October 2012 # Springer-Verlag Berlin Heidelberg 2012
L. E. Browning : J. L. Savage : H. Barclay Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
examined the provisioning strategies of breeders and nonbreeding helpers in obligate cooperative breeders, wherein reproduction without help is typically unsuccessful. We investigated these components of provisioning in obligately cooperative chestnut-crowned babblers (Pomatostomus ruficeps). Prey type was associated with size, and delivery rate was the best predictor of the overall amount of food provided by carers. As broods aged, breeders and helpers similarly modified the relative proportion of different prey provided and increased both prey size and delivery rate. Breeding females contributed less prey than male breeders and adult helpers, and were the only carers to load-lighten by reducing their provisioning rates in the presence of additional carers. While our results suggest that breeders and helpers follow broadly comparable provisioning rules, they are also consistent with the idea that, in obligately cooperative species, breeding females benefit more from conserving resources for future reproduction than do helpers which have a low probability of breeding independently.
C. M. Young : S. C. Griffith Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia
Keywords Additive care . Allo-parental care . Costs of helping . Helper effort . Load-lightening
D. J. F. Russell Department of Animal & Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
Introduction
Abstract Providing food to developing offspring is beneficial for offspring but costly for carers. Understanding patterns of provisioning thus yields important insights into how selection shapes (allo-) parental care strategies. Broadly, offspring development will be influenced by three components of provisioning (prey type, size and delivery rate). However, all three variables are rarely considered simultaneously, leading to suggestions that the results of many studies are misleading. Additionally, few studies have Communicated by P. A. Bednekoff L. E. Browning (*) Fowlers Gap Arid Zone Research Station, School of Biological, Earth & Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia e-mail: [email protected]
D. J. F. Russell Sea Mammal Research Unit, University of St Andrews, Fife KY16 8LB, UK A. F. Russell Centre for Ecology & Conservation, College of Life & Environmental Sciences, University of Exeter, Penryn, Cornwall TR10 9EZ, UK A. F. Russell Station d’Ecologie Expérimentale du CNRS, USR 2936, 09200 Moulis, France
In iteroparous organisms, fitness is maximised in large part by optimis
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