Food passage time through animal guts is a critical parameter for constraining an animal’s ability to act as an agent of nutrient, seed, microbe, or pathogen dispersal in its ecosystem. Current methods to estimate food passage do not measure food directly, are impractical for many species, and often require unnatural conditions to administer. This new method directly measures the transit and retention times of plant foodstuffs by tracking isoptically-tagged greens from ingestion to plant biomarker excretion. In this project, you will take advantage of a newly piloted method to compare food transit time across a diverse array of plant eaters, focussed primarily on primates housed at the Twycross Zoo.
This project is intentionally flexible: The research questions this method can address are numerous and varied, depending on your background and interests. We envision a first thesis chapter which builds a comparative database of food transit times across primates of various sizes with different feeding strategies that stem from different phylogenetic lineages, all to develop generalised empirical scaling rules about food transit and retention times within — and potentially beyond — primates. Follow-on work could include international fieldwork on wild primates, capitalising on established collaborations between the supervisory team (e.g. Wildtracks in Belize and/or MadaGap in Madagascar) to observe the dispersal potential of particular focus species important for ecosystem function, reforestation and other other conservation measures. In Belize, a key question could be understanding the role of focal howling and spider monkeys in ecosystem regeneration, as seed dispersers and nutrient cyclers being reintroduced to areas from which they have been absent for decades. In Madagascar, a key question could be investigating the role of focal sifakas and dwarf lemurs as seed dispersers and nutrient cyclers whose territories span multiple forest fragments, both natural and anthropogenic, in the central highlands. Projects in both biodiversity hotspots can influence decisions around long-term management, future reintroductions, and wider rewilding efforts. Observational data gathered in the lab and/or field, could also be used to underpin numerical models, quantifying the potential contributions of focal species to dispersal and/or reforestation at local, regional, or global scales.
This project is not suitable for CASE funding
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This project integrates approaches from organic geochemistry and organismal ecology, with experimental, observational, and potentially computational components, in zoo, lab, and potentially field settings. Measuring gastrointestinal food transit time will involve growing isotopically-labelled greens in greenhouse conditions, feeding these to zoo-housed primates, sequential faecal collection, and follow on lab work including column chemistry and mass spectrometry. As outlined, these approaches could be complemented with international field work to observe sample wild primates and/or computational work to model dispersal potential across geographic scales.
Because this project is so interdisciplinary, it could suit applicants interested in ecology from a variety of backgrounds including biology, environmental science, conservation, or geochemistry. What is essential is a desire and/or willingness to undertake extensive zoo and lab work during the PhD.
DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.
The supervisory team is well placed to provide the training essential to undertake all aspects of this PhD. Between us, we have expertise in organic and isotope geochemistry, primate ecology and conservation, zoo science, and numerical modelling. In addition to access to animals at Twycross Zoo, at Birmingham we have access to greenhouse space to grow isotopically-tagged plants and an organic geochemistry lab to analyse faecal samples. There are also opportunities to develop skills in science communication, public engagement, and community organising by getting involved in ongoing projects in the lead supervisor’s lab group as well as opportunities to work with collaborators leading efforts in (international) biodiversity conservation outside of academia by getting involved in ongoing projects with the Twycross Zoo and NGO MadaGap.
The supervisory team includes Prof Sarah Greene and Dr James Bendle at the University of Birmingham, Dr Lydia Greene, co-founder of the NGO MadaGap, and Dr Stuart Young, Conservation Programmes Manager at the Twycross Zoo.
The timeline here is only indicative, as there is scope for the student to help shape the direction of the project in later years to suit their interests and future career goals.
Year 1: Growing isotopically-labelled plants, feeding experiments/faecal sampling at Twycross Zoo, and begin geochemical lab work, to build a foundational database about gastrointestinal food transit time across plant-eating (primate) species. Alongside, literature review to decide and refine questions for subsequent chapters.
Year 2: Continued labwork, manuscript preparation, and enacting follow-on research plans developed in year 1 (e.g., applied field and/or computational studies).
Year 3: Finish labwork, data analysis, and writing.
We would also strongly urge the candidate to consider doing a placement during the PhD to gain experience outside of an academic setting, potentially with one of the listed project partners.
Abraham, A.J., Prys-Jones, T.O., De Cuyper, A., Ridenour, C., Hempson, G.P., Hocking, T., Clauss, M., Doughty, C.E., 2021. Improved estimation of gut passage time considerably affects trait-based dispersal models. Functional Ecology 35, 860–869.
*Baker, G., Greene, L.K., Bendle, J., Allison, M., Seki, O., and Greene, S.E., submitted. Novel isotopic-tagging approach reveals threefold extension of animal gut-retention times.
McGrosky, A., Meloro, C., Navarrete, A., Heldstab, S.A., Kitchener, A.C., Isler, K., Clauss, M. Gross intestinal morphometry and allometry in primates. Am. J. Primatol. 81, e23035 (2019).
*Available upon request.
Prospective applicants please contact me (Sarah Greene – [email protected]) in advance of applying. You are very welcome to ask questions about the project, to discuss whether working with me on this project at the University of Birmingham is a good fit for you, or to ask advice about putting together a strong application. I am also happy to put you in contact with my current and former students to ask questions about their experiences.
To apply to this project:
Applications must be submitted by 23:59 GMT on Wednesday 7th January 2026.