MASTER 2 INTERNSHIP: Variations in interbirth intervals in non-seasonal breeding mammals: a case study on the Asian elephant
Which factors determine the duration between two reproductive events in a long-lived non-seasonal breeder? In this project, we aim at providing insights into the drivers of female elephant reproductive fitness by investigating how interbirth intervals are influenced by environmental, individual, and demographic factors using an extensive longitudinal data on Asian elephants.
Interbirth intervals (IBIs) are a key metric of female reproductive success. After giving birth, most female mammals delay their next reproduction to invest in their current offspring (Gesquiere et al. 2018). In non-seasonal breeders, females must make a physiological ‘decision’ about when to resume reproduction in the absence of specific seasonal cues (Dezeure et al. 2021). The timing of this physiological decision reflects the tradeoff between three energetic demands: investment in the current offspring, investment in the next offspring, and investment in maternal somatic maintenance and growth. Life history theory predicts that the evolutionarily optimal IBI differs for different individuals whose fitness is affected by how closely a female spaces her offspring (Haig 2014). Trade-offs over birth spacing may be widespread in long-lived species with slow life histories, for which development from birth to independence spans several months.
The Asian elephant is a long-lived non-seasonal breeding species. Previous work has shown that Asian elephant fertility rate varied upon the age of the female but also according to environmental factors and across generations. The capture of wild elephants for working purposes can reduce their survival and fecundity rates compared to captive-born elephants (Jackson et al. 2019). Offspring born to older mothers display reduced overall survival but higher reproductive success, and reduced survival of their own progeny (Reichert et al. 2020a). Early-life conditions, specifically harsh environmental conditions, could also affect progeny’s life history (Nussey et al. 2008). Among the three components of fertility, age at first reproduction and reproductive senescence are the subject of extensive research, while IBIs are still poorly understood.
The student will use an extensive multigenerational demographic database on semi-captive Asian elephants from Myanmar. Successive Myanmar governments have practiced selective logging of teak using elephant draught power in timber extraction. Traditionally, wild elephants were captured to supplement the working population (Jackson et al. 2019). Today, half of the captive elephants in Myanmar (N ~2700) are government-owned and used in forest camps as riding, transport and draft animals. At night all elephants forage in forests, as part of their family groups unsupervised. Breeding rates are natural and not managed by humans with many captive-born calves thought to be sired by wild bulls (Lahdenperä et al. 2018). Therefore timber elephants are considered semi-captive. They have been monitored by the state for over a century through annual census reports as well as individual logbooks including detailed information on date of birth, reproduction, death, etc. This unique multigenerational dataset of more than 8000 individual life histories covering the period from 1960 to 2014 has been studied by the Timber elephant project from Turku University to investigate a large range of research subjects (see https://elephant-project.science). This long-term, individual-based dataset enables to accurately capture variation in individual life histories over several decades and across several generations.
Building on previous work (Lahdenperä, Mar, and Lummaa 2014; 2016; Lahdenperä et al. 2019; Robinson, Mar, and Lummaa 2012; Mumby et al. 2013; Chapman et al. 2019; Berger et al. 2021; Reichert et al. 2020b), the student will first analyze variations in IBIs and test potential determinants including female traits (e.g captive or wild born, age, parity), infant traits (sex) and environmental factors (e.g. across decade differences). He or she will then investigate potential trade-offs existing between reproductive pace and offspring survival.
The student will be co-supervised by Sarah Cubaynes (CEFE) and Gilles Maurer (CEFE). The internship will benefit from close collaboration with Virpi Lummaa (Turku Uni) and colleagues from the Elephant Timber project who have previously worked on the longitudinal dataset.
The student will be based at the CEFE (Center for Functional and Evolutionary Biology) in Montpellier for an internship of 5-6 months preferably.
We are looking for a highly motivated student, who has already completed their first year of Master in ecology, evolutionary biology, or demography, with a strong interest in biostatistics (proven experience of using R is required) and background in life history theory. Knowledge of English is required since the project will involve strong collaborations with international researchers.
CONTACT: If you wish to apply, please send your CV and cover letter to
gilles.maurer@cefe.cnrs.fr and sarah.cubaynes@cefe.cnrs.fr
APPLICATION DEADLINE: 20/10/2024
BIBLIOGRAPHY
Berger, Vérane, Sophie Reichert, Mirkka Lahdenperä, John Jackson, Win Htut, and Virpi Lummaa. 2021. “The Elephant in the Family: Costs and Benefits of Elder Siblings on Younger Offspring Life-History Trajectory in a Matrilineal Mammal.” Journal of Animal Ecology 90 (11): 2663–77. https://doi.org/10.1111/1365-2656.13573.
Chapman, Simon N., John Jackson, Win Htut, Virpi Lummaa, and Mirkka Lahdenperä. 2019. “Asian Elephants Exhibit Post-Reproductive Lifespans.” BMC Evolutionary Biology 1:1–11.
Dezeure, Jules, Alice Baniel, Alecia Carter, Guy Cowlishaw, Bernard Godelle, and Elise Huchard. 2021. “Birth Timing Generates Reproductive Trade-Offs in a Non-Seasonal Breeding Primate.” Proceedings of the Royal Society B 288 (1950). https://doi.org/10.1098/RSPB.2021.0286.
Gesquiere, Laurence R., Jeanne Altmann, Elizabeth A. Archie, and Susan C. Alberts. 2018. “Interbirth Intervals in Wild Baboons: Environmental Predictors and Hormonal Correlates.” American Journal of Physical Anthropology 166 (1): 107. https://doi.org/10.1002/AJPA.23407.
Haig, David. 2014. “Interbirth Intervals: Intrafamilial, Intragenomic and Intrasomatic Conflict.” Evolution, Medicine, and Public Health 2014 (1): 12–17. https://doi.org/10.1093/EMPH/EOU002.
Jackson, John, D.Z. Childs, Khyne U Mar, W. Htut, and V. Lummaa. 2019. “Long-Term Trends in Wild-Capture and Population Dynamics Point to an Uncertain Future for Captive Elephants.” Proceedings of the Royal Society B: Biological Sciences.
Lahdenperä, Mirkka, John Jackson, Win Htut, and Virpi Lummaa. 2019. “Capture from the Wild Has Long-Term Costs on Reproductive Success in Asian Elephants.” Proceedings of the Royal Society B: Biological Sciences 286 (1912). https://doi.org/10.1098/RSPB.2019.1584.
Lahdenperä, Mirkka, Khyne U. Mar, Alexandre Courtiol, and Virpi Lummaa. 2018. “Differences in Age-Specific Mortality between Wild-Caught and Captive-Born Asian Elephants.” Nature Communications 9 (1). https://doi.org/10.1038/s41467-018-05515-8.
Lahdenperä, Mirkka, Khyne U Mar, and Virpi Lummaa. 2014. “Reproductive Cessation and Post-Reproductive Lifespan in Asian Elephants and Pre-Industrial Humans.” Frontiers in Zoology 11:54. https://doi.org/10.1186/s12983-014-0054-0.
———. 2016. “Nearby Grandmother Enhances Calf Survival and Reproduction in Asian Elephants.” Scientific Reports, no. May, 1–10. https://doi.org/10.1038/srep27213.
Mumby, Hannah S, Alexandre Courtiol, Khyne U Mar, and Virpi Lummaa. 2013. “Birth Seasonality and Calf Mortality in a Large Population of Asian Elephants.” Ecology and Evolution 3 (11): 3794–3803. https://doi.org/10.1002/ece3.746.
Nussey, D. H., T. Coulson, M. Festa-Bianchet, and J. M. Gaillard. 2008. “Measuring Senescence in Wild Animal Populations: Towards a Longitudinal Approach.” Functional Ecology 22 (3): 393–406. https://doi.org/10.1111/J.1365-2435.2008.01408.X.
Reichert, Sophie, Vérane Berger, John Jackson, Simon N. Chapman, Win Htut, Khyne U. Mar, and Virpi Lummaa. 2020a. “Maternal Age at Birth Shapes Offspring Life‐history Trajectory across Generations in Long‐lived Asian Elephants.” Edited by Sandra Bouwhuis. Journal of Animal Ecology 89 (4): 996–1007. https://doi.org/10.1111/1365-2656.13049.
———. 2020b. “Maternal Age at Birth Shapes Offspring Life‐history Trajectory across Generations in Long‐lived Asian Elephants.” Edited by Sandra Bouwhuis. Journal of Animal Ecology 89 (4): 996–1007. https://doi.org/10.1111/1365-2656.13049.
Robinson, Matthew R, Khyne U Mar, and Virpi Lummaa. 2012. “Senescence and Age-Specific Trade-Offs between Reproduction and Survival in Female Asian Elephants.” Ecology Letters 15 (3): 260–66. https://doi.org/10.1111/j.1461-0248.2011.01735.x.
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