Maternal effects in the highly communal sociable weaver may exacerbate brood reduction and prepare offspring for a competitive social environment
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Maternal effects can influence offspring phenotype with short- and long-term consequences. Yet, how the social environment may influence egg composition is not well understood. Here, we investigate how laying order and social environment predict maternal effects in the sociable weaver, Philetairus socius, a species that lives in massive communal nests which may be occupied by only a few to 100+ individuals in a single nest. This range of social environments is associated with variation in a number of phenotypic and life-history traits. We investigate whether maternal effects are adjusted accordingly. We found no evidence for the prediction that females might benefit from modifying brood hierarchies through an increased deposition of androgens with laying order. Instead, females appear to exacerbate brood reduction by decreasing the costly production of yolk mass and antioxidants with laying order. Additionally, we found that this effect did not depend on colony size. Finally, in accordance with an expected increased intensity of environmental stress with increasing colony size, we found that yolk androgen concentration increased with colony size. This result suggests that females may enhance the competitive ability of offspring raised in larger colonies, possibly preparing the offspring for a competitive social environment.
KeywordsBreeding density Competition Egg composition Hatching asynchrony Maternal investment
We are grateful to De Beers Consolidated Mines Ltd and Morné du Plessis for the opportunity to work at Benfontein Game Farm, to the Northern Cape Province’s Department of Tourism, and Environment and Conservation (especially Mark Anderson) for research permits, and to Eric Herrmann for his assistance in the field. The androgen assays were carried out at the University of Groningen by kind permission of Ton Groothuis. Nick Davies, Rebecca Kilner, Jane Reid, Indrikis Krams and two anonymous referees provided helpful comments on earlier drafts of the manuscript. R.E.v.D. was supported by a grant of the Natural Environment Research Council (NERC) to B.J.H., and C.N.S. by St John’s College, Cambridge (UK) and the University of Cape Town (South Africa). Our research complied with the current laws of the countries in which it was performed.
Conflict of interest
The authors declare that they have no conflict of interest.
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