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Does the presence of helpers affect maternal investment in cooperative breeders?

last modified Nov 24, 2017 01:29 PM

As part of their degree third year undergraduate Zoology students have to complete one or two projects that have been devised by researchers in the Department.   One of the exciting things that can lead from the projects is the possibility of having the results of the work published.  Papers of former students are displayed on the wall of the lecture theatre and on our project work webpage.

One such paper has come out in PeerJ today:  The relationship between egg size and helper number in cooperative breeders: a meta-analysis across species by Dixit T., English S., Lukas D.  The Part II Zoology student was Tamnay Dixit (St John’s) who graduated in June 2017.

The initial project was devised by Dr Sinead English (now at the University of Bristol) and Dr Dieter Lukas (now at Max Plank Institute for Evolutionary Anthropology) and was framed as such: 

Sociable Weaver (credit Jessie Walton)

Does the presence of helpers affect maternal investment in cooperative breeders? There is increasing evidence in species-specific studies that mothers adjust offspring size in response to helper presence. This project will extract data from online life history databases and the published literature to investigate if, across species, mothers produce smaller offspring in cooperative compared to non-cooperative species, controlling for phylogeny and other aspects of ecology.

From the work done by the authors the results of the study found that cooperatively breeding birds and fish may have evolved the adaptive ability to reduce the size of their eggs when helpers are available to lighten the parental load, a new study suggests. The findings indicate that in some species, the social environment may influence female reproductive decisions even prior to the birth of offspring. Dixit went on to say: “While this paper does not provide conclusive evidence as it is based on a small sample of studies and species, it suggests that it is at least possible that the females of certain cooperatively breeding species may be able to adapt their reproductive decisions to changes in the social environment by reducing investment in current broods to prioritise future survival and reproduction.”

One of Dixit’s supervisors said “Tanmay did an amazing job, and he is the first and corresponding author on the manuscript. We were always inspired by the papers from undergraduates hanging in the Part II lecture theatre and being listed on the website.”

Dixit is currently on a year abroad studying avian brood parasitism in South Africa and Zambia. He hopes to return to the UK to study for a PhD in 2018.

Dixit T, English S, Lukas D. (2017The relationship between egg size and helper number in cooperative breeders: a meta-analysis across speciesPeerJ 5:e4028  https://doi.org/10.7717/peerj.4028