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Stressed lemurs have worse chances of survival

High levels of hair cortisol – a sign of long-term stress – are associated with reduced survival in wild grey mouse lemurs (Microcebus murinus), according to a study published in the open access journal BMC Ecology

Researchers at the German Primate Centre and Georg-August University Göttingen, Germany found that grey mouse lemurs with high levels of the stress hormone cortisol in their fur were less likely to survive both long-term and over the reproductive season. 

Dr Josué Rakotoniaina, the corresponding author said “Despite the wide use of stress hormone levels as an index of health and condition, this study is among the first to correlate an index of chronic stress with survival in a wild population of lemurs. This was only possible by combining hair cortisol levels with several years of life history data that was gathered from a long-term monitoring project of mouse lemurs.”

Lemurs with low hair cortisol levels had on average a 13.9% higher chance to survive than those with high levels of hair cortisol. Lemurs with very good body condition – that is optimal body mass and size – survived on average 13.7% better than lemurs with poor body condition and females survived, on average, better than males. Variations in parasitism, such as the number of parasite infections, were not linked to survival.  

Dr Rakotoniaina added: “Our findings indicate that hair cortisol concentrations are a much better predictor of survival, and thus a better index of health, than other commonly used health indicators. Cortisol is taken up by hair as it grows so its concentration in a hair sample allows assessment of overall cortisol levels over time rather than – as single samples of blood, saliva or urine do – at one time point.” 

To test their hypothesis that high hair cortisol concentration as a measure of long-term stress is related to individual survival, the researchers studied a population of grey mouse lemurs in Kirindy Forest, Madagascar from 2012 to 2014. They assessed the relationship between hair cortisol concentration and long-term survival in 171 lemurs, while the effect of body condition on long-term survival was assessed in a sub-sample of 149, and the link between all health indicators (hair cortisol level, body condition and parasitism) and survival during the mating season was assessed in a group of 48 lemurs. 

The researchers suggest that the benefits of having low stress levels may be even more pronounced prior to the mating season. Individuals that are more affected by challenging conditions may not be able to cope with the additional stress during mating season which is particularly challenging for male mouse lemurs. 

Although the exact mechanism by which cortisol is built into hair is not yet fully understood and the observational nature of the study does not allow conclusions about the causes of mortality, the findings suggest that hair cortisol concentration may be a valid indicator of health in wild lemur populations. 
Dr. Rakotoniaina said: “This important information could facilitate conservation decisions as it provides conservationists with an essential tool that could be used to detect issues emerging at the population level and ultimately predict wild populations’ responses to environmental challenges.”


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Notes to editors:

1.    Images of the grey mouse lemurs can be found here.
Please credit Anni Hämäläinen in any re-use.

2.    Research article:
Hair cortisol concentrations correlate negatively with survival in a wild primate population
Rakotoniaina et al. BMC Ecology 2017
DOI: 10.1186/s12898-017-0140-1

The article is available at the journal website

Please name the journal in any story you write. If you are writing for the web, please link to the article. All articles are available free of charge, according to BioMed Central's open access policy.

3.    BMC Ecology is an open access, peer-reviewed journal that considers articles on environmental, behavioral and population ecology as well as biodiversity of plants, animals and microbes.

4.    A pioneer of open access publishing, BMC has an evolving portfolio of high quality peer-reviewed journals including broad interest titles such as BMC Biology and BMC Medicine, specialist journals such as Malaria Journal and Microbiome, and the BMC series.
At BMC, research is always in progress. We are committed to continual innovation to better support the needs of our communities, ensuring the integrity of the research we publish, and championing the benefits of open research. BMC is part of Springer Nature, giving us greater opportunities to help authors connect and advance discoveries across the world.

5.    Springer Nature Data Support Services
The Springer Nature Data Support Services help authors enhance their peer-reviewed publications and comply with funder and journal policies by preparing their data files for deposition in a repository and improving associated metadata.

For the present study, the dataset and basic contextual metadata were uploaded by the author, and initial checks were undertaken by a Data Support Services Research Data Editor to make sure that the data were complete and uncorrupted. A Research Data Editor also rewrote the title of the dataset to support discoverability, and added a comprehensive description and research method to provide context for the data. To further enhance discovery and to allow granular search of the data, categories from the Australian Fields of Research classification system and relevant keywords were added to the metadata. The dataset’s author list was cross-referenced with the associated manuscript to ensure accurate citation of the data, and a DOI was generated to provide a persistent link. The dataset was linked to the author’s manuscript and the publication date was coordinated for release with the publication of its associated article in BMC Ecology. All checks and enhancements were approved by the author, and the dataset will be made available through the Springer Nature section of the figshare repository.

6.    Dataset:
Capture-mark-recapture data modelling survival rates of Microcebus murinus in relation to glucocorticoid level, parasite infection and body condition
Rakotoniaina et al. 2017
DOI: 10.6084/m9.figshare.5259415. 

After the embargo lifts, please reference the dataset here.