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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SOCIAL COST (Differential costs of social living in nature)

Teaser

Summary

Group living is a common phenomenon in nature in a wide range of taxa. While benefits, such as reduced predation risk, and costs, such as increased pathogen transmission, are well documented for some species, many other effects of group living are still poorly understood especially in natural populations. As such, there is a need for more work in wild study systems investigating links between stressors associated with group living and its costs. In particular, how group size and composition, reproduction, and individual social status might affect the level of social stress. Social stress can cause physiological stress in group living animals, including humans, leading to poor health or fitness reduction. Telomere dynamics and oxidative stress are linked to the occurrence of stressors and fitness. However, to date the association between telomere dynamics and oxidative stress/antioxidant defences in wild vertebrates is poorly understood. The aim of this study was to examine the direct links between social status, group size, sex and ecological stressors occurring in the wild and the associated physiological and molecular effects under natural conditions in Cape ground squirrels (Xerus inauris). Overall, this Marie Curie Fellowship was a success, as the substantial samples and behavioural data that have been collected will contribute significantly to our understanding of the cost of sociality.

Work performed

During this fellowship, I conducted three field seasons in free living Cape ground squirrels at the unique field site of the Kalahari Research Centre (http://www.kalahari-meerkats.com/index.php?id=krr) at the Kuruman River Reserve, South Africa, which is maintained and managed by the University ZÃ¼rich. This project is embedded in a long-term study where up to three volunteers are recording behavioural data, habituating and maintaining groups all year round. Due to my collaborator Prof. Manser, University of ZÃ¼rich, I have direct access of this unique dataset that will allow investigating group stability by modelling the hierarchy within groups and obtaining information on paternity.

During the first field season I optimized trapping and adapted protocols for blood collection with a team of volunteers and field site manager. Trapping was very successful and almost all present and non-pregnant individuals were caught. While animals were anaesthetised to reduce handling stress, I collected small blood samples, blood smears, and morphological measurements, such as weights, skull, tarsus lengths, etc., which will provide insight into individual body condition. For most individuals I have samples for several field seasons, which will allow me to compare data points between winter/summer and among years. However, the initially planned collection of sperm was omitted due to logistic reasons (i.e. to minimise the length of anaesthesia) and remains a potential project for the future.

The blood samples were shipped to the hostâ€™s lab in Glasgow where I conducted DNA extractions, as well as molecular assays to measure markers related to the ageing process including telomere length. The collected blood smears were analysed by a postgraduate volunteer, who counted white blood cells, which provide details on health status of individual animals.
In addition, I performed oxidative stress assays at my collaboratorâ€™s lab at the University of NeuchÃ¢tel, Switzerland and measured damage to lipids using malondialdehyde in plasma and red blood cells and the ratio of oxidized to reduced glutathione concentrations in the plasma using assays on the high-performance liquid chromatography. Further, a subset of the samples collected have been sent to my collaborator at the University of Pretoria in order to measure testosterone in plasma.

Analyses of these physiological and molecular data are still on-going. However preliminary results suggest that telomere shortening is affected by age i.e. subadults have longer telomeres compared to older individuals, which is in line with the expectations based on other species. Adding information on individual behaviour, group sizes and composition, hierarchy, and the associated physiological changes, will complete the picture about the costs of sociality.

The preliminary results of this project have been presented at several meetings including one symposium on the diversity of telomere dynamics organized in Edinburgh in 2017 to a broad audience (from ecologists to epidemiologists) interested in telomeres and ageing. In addition, I will present my research at the Conference on Behavioural Biology in Liverpool in 2018, all of which enables me to reach a broad audience and will open new perspectives for collaborations.

Final results

By opening up a new mammal study system for examining social stress under natural conditions, this fellowship yielded unprecedented data about the impact of different aspects of sociality on behaviour, physiological, and molecular processes, such as telomere shortening, oxidative stress. Such findings pave the way to test strategies associated with social stress in the future, for instance by manipulating dominance hierarchy, group size, or using antioxidant supplementation and examining how controlled social stress affects oxidative stress and telomere shortening. Another important achievement of this fellowship was the establishment of fruitful and important collaborations and networks that will be beneficial for future work.