A two-year post-doc position is available at the LBBE in Lyon to investigate whether chronic expsoure to low doses of toxic trace metals affect reproductive performance in roe deer.
Context and research question
Due to the raising number of chemicals that are released in the environment by anthropic activities, most organisms are likely exposed to low doses of numerous contaminants throughout their lives (Saaristo et al., 2018). The multiplicity of exposures contributes to the exposome, a concept which encompasses all exposures of an individual from conception till death (Wild, 2005). While short-term effects of acute exposure to diverse contaminants are relatively well understood, long-term effects of chronic exposure to low doses are far less documented, in particular in wildlife. Such exposure could nevertheless have lasting consequences for individual fitness, and ultimately for population demography (Rattner et al., 2023). Among hazardous contaminants, metals such as lead, cadmium or mercury do not exert any biological function, et can be toxic event at low doses. Several studies reported their deleterious effects on reproduction, but data come mostly from experimental approaches conducted in the lab (e.g. Goutam Mukherjee et al., 2022). However, the consequences of exposure to toxic metals for wildlife fertility remain largely unknown.
In this context, it is essential to explore whether chronic exposure to low doses of contaminants affect fitness-related traits in wildlife. This project thus aims at evaluating the implications of chronic exposure to low doses of toxic trace metals for reproductive performance in a wild ungulate, the roe deer (Capreolus capreolus).
The project will take advantage of the longitudinal monitoring of two roe deer populations through a capture-mark-recapture (CMR) program that has been carried out for 48 and 50 years (Chizé in the west of France and Trois-Fontaines in the North-Eastern France, respectively ; Gaillard et al., 1993). In females, the reproductive effort is estimated through the fecundity (number of embryos and/or fawns), as well as through fawn viability and condition. In males, the allocation to reproduction is mainly measured through antler size, a sexual character that is involved in competition for female access (Cambreling et al., 2023). For the past 3 years, a protocol for sperm collection has been implemented in Trois-Fontaines, offering a unique opportunity to assess ejaculate quality (sperm concentration, motility and morphology), an important driver of fertility in mammals (Snook, 2005). In addition, a large set to trace metals has been measured in hair samples collected on 430 individuals between 2016 and 2019 in both populations (Herrada et al., 2024).
Tasks and feasibility
The recruited person will be in charge of evaluating the consequences of exposure to various toxic trace metals (e.g. lead, cadmium, mercury, arsenic, aluminum, chromium) on female reproductive success on the one hand, and on male allocation to reproductive traits on the other hand. She/he will test whether individuals exhibiting the highest levels of metal exposure suffer from a reduced reproductive success (i.e. reduction in fecundity and/or in fawn viability and condition for females), or from a lower allocation to primary and secondary sexual characters (i.e. reduction in sperm quality and/or in antler size for males). A first study conducted on roe deer that were shot by hunters suggests that testicular mass and cadmium exposure are negatively related (Vuarin et al., 2025), but the present project will enable to verify whether such a relationship actually translates into a negative impact on male fertility. Additionally, the analyses will take into account individual (e.g. mass, age) and environmental (e.g. cohort, habitat) factors that may modulate the relationships between metals and reproductive traits.
Most of the data have already been collected, ensuring the feasibility of the project. To the best of our knowledge, there is no existing database combining life histories and measures of metal exposure levels on known-age individuals for wild mammals, hence representing the main strength of the project. Only part of the data on ejaculate quality remains to be acquired. This innovative aspect of the project will be tested on a subset of data limited to the males from whom semen has already been collected, to which will be added those captured during the summer of 2026 (for a total of a hundred of individuals). Trace metal measurements for these males will be performed by the Chrono-environment laboratory (UMR 6249 CNRS-University of Franche-Comté), with whom a collaboration has already been initiated.
Desired profile
The recruited person must have a PhD in evolutionary ecology, ecophysiology or ecotoxicology. Specialization in reproductive biology/physiology or in wildlife toxicology could be an asset, but is not a prerequisite for the position. The successful candidate will need to demonstrate rigor, critical thinking and autonomy, in particular in the handling and analysis of large datasets. She/he should master statistical approaches classically used in biology and ecology (e.g. linear mixt effects models, multivariate analyses), ideally with R. She/he will also be required to participate in field work to capture roe deer in winter (CMR program) and in summer (sperm collection), representing 6 to 8 weeks of field work through the year in total. A keen interest in fieldwork and teamwork is therefore essential. As such, candidates must undergo training in animal experimentation at the level of experimental procedure designer (level 1), if they are not already qualified.
Application and admission procedures
Applications must be submitted by the 15th of February 2026 at the latest to Pauline Vuarin (pauline.vuarin@univ-lyon1.fr) and Jean-François Lemaître (jean-francois.lemaitre@univ-lyon1.fr), and should include a CV with the contact details of at least 2 referees and a cover letter detailing the interest in and suitability for the project. Interviews will take place in late February/early March, with a starting date set for mid-May at the latest.
The successful candidate will be based at the Biometry and Evolutionary Biology Laboratory (LBBE, UMR 5558 CNRS-University of Claude Bernard Lyon 1) in Lyon (La Doua campus in Villeurbanne) and will work closely with all LBBE members of the roe deer program and with colleagues from the French Office for Biodiversity (the institution that co-supervises the roe deer program). She/he will join the Evolutionary Biodemography team of the Evolutionary Ecology department. This department runs various long-term monitoring programs for vertebrates (roe deer, marmots, dippers), brings together researchers with diverse skills (evolutionary biology, demography, ecophysiology, epidemiology, ecotoxicology), and has recognised expertise in statistics and modelling. It also welcomes several interns, PhD candidates and post-docs each year, provides technical and logistical support for fieldwork, and hosts various social and scientific events. The net monthly salary will be €1,864 (recruitment up to 3 years post-PhD).
References
Cambreling, S., Gaillard, J.M., Pellerin, M., Vanpé, C., Débias, F., Delorme, D., Garcia, R., Hewison, A.J.M., Lemaître, J.F., 2023. Natal environmental conditions modulate senescence of antler length in roe deer. Front. Ecol. Evol. 11, 1–12. https://doi.org/10.3389/fevo.2023.1139235
Gaillard, J., Delorme, D., Boutin, J., Van Laere, G., Boisaubert, B., Pradel, R., 1993. Roe deer survival patterns: a comparative analysis of contrasting populations. J. Anim. Ecol. 62, 778–791.
Goutam Mukherjee, A., Ramesh Wanjari, U., Renu, K., Vellingiri, B., Valsala Gopalakrishnan, A., 2022. Heavy metal and metalloid – induced reproductive toxicity. Environ. Toxicol. Pharmacol. 92, 103859. https://doi.org/10.1016/j.etap.2022.103859
Herrada, A., Bariod, L., Saïd, S., Rey, B., Bidault, H., Bollet, Y., Chabot, S., Débias, F., Duhayer, J., Pardonnet, S., Pellerin, M., Fanjul, J.B., Rousset, C., Fritsch, C., Crini, N., Scheifler, R., Bourgoin, G., Vuarin, P., 2024. Minor and trace element concentrations in roe deer hair: A non-invasive method to define reference values in wildlife. Ecol. Indic. 159, 111720. https://doi.org/10.1016/j.ecolind.2024.111720
Rattner, B.A., Bean, T.G., Beasley, V.R., Berny, P., Eisenreich, K.M., Elliott, J.E., Eng, M.L., Fuchsman, P.C., King, M.D., Mateo, R., Meyer, C.B., Brien, J.M.O., Salice, C.J., 2023. Wildlife ecological risk assessment in the 21st century: Promising technologies to assess toxicological effects. Integr. Environ. Assess. Manag. 00, 1–24. https://doi.org/10.1002/ieam.4806
Saaristo, M., Brodin, T., Balshine, S., Bertram, M.G., Brooks, B.W., Ehlman, S.M., McCallum, E.S., Sih, A., Sundin, J., Wong, B.B.M., Arnold, K.E., 2018. Direct and indirect effects of chemical contaminants on the behaviour, ecology and evolution of wildlife. Proc. R. Soc. B 285, 20181297. https://doi.org/10.1098/rspb.2018.1297
Snook, R.R., 2005. Sperm in competition: Not playing by the numbers. Trends Ecol. Evol. 20, 46–53. https://doi.org/10.1016/j.tree.2004.10.011
Vuarin, P., Rey, B., Herrada, A., François, D., Crini, N., Scheifler, R., Lemaître, J., Saïd, S., 2025. Exposure to toxic trace metals is negatively associated with testis mass in wild male roe deer. Environ. Pollut. 383, 126825. https://doi.org/10.1016/j.envpol.2025.126825
Wild, C.P., 2005. Complementing the genome with an “exposome”: The outstanding challenge of environmental exposure measurement in molecular epidemiology. Cancer Epidemiol. Biomarkers Prev. 14, 1847–1850. https://doi.org/10.1158/1055-9965.EPI-05-0456
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