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High stress during pregnancy decreases offspring survival, according to mongoose study

Pups born to females that experienced elevated stress hormones are much less likely to survive

University of Exeter

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IMAGE: High stress during pregnancy decreases offspring survival, according to this mongoose study. view more

Credit: Harry Marshall

Researchers studying banded mongooses in Uganda have discovered that pups born to females that experienced elevated stress hormones during the later stages of pregnancy are much less likely to survive their first month.

Dr Jennifer Sanderson, now a science teacher at Bedminster Down School in Bristol, spent four years observing wild banded mongooses to understand the effects that maternal stress may have on the survival of mongoose pups.

She discovered that female mongooses at the bottom of the social hierarchy experience an increase in circulating stress hormones, or 'glucocorticoids', and these high stress levels decrease the likelihood that pups will survive. The findings of the study are published today in the Royal Society journal Biology Letters.

Females often have to compete for access to the right resources to breed successfully, even in the most cooperative animal societies. Such female competition is widespread in animal populations but this study is the first to investigate if there is a link between socially induced stress and offspring survival in a wild cooperative mammal.

According to Dr Sanderson: "We all think of stress as a bad thing and it's easy to imagine that high stress levels during pregnancy can have negative effects on a baby's development. Our study has shown that pups born to females with high circulating glucocorticoids in the third trimester are much less likely to survive the first weeks of life and are unlikely to emerge from their burrows."

Banded mongooses are close relative of the famous meerkat and are found living in stable social groups across Central and Eastern Africa. They are highly social and breed communally with all females within a group commonly giving birth on exactly the same day.

The Banded Mongoose Research Project, led by Professor Michael Cant from the Centre for Ecology and Conservation at the University of Exeter's Penryn Campus in Cornwall, has been observing the mammals' breeding behaviour for over 20 years.

Professor Cant added, "Banded mongooses are almost unique because most females within the group commonly become pregnant together and then give birth on exactly the same day. On first glance it seems that the females are working together to produce and care for a huge communal litter. However, these results suggest that dominant females may be stressing out their female group mates during pregnancy - a strategy which decreases the survival chances of pups born to their competitors while potentially increasing their own pups' chances of making it to adulthood."

Dr Sanderson used an ultrasound machine to count the number of foetuses carried by banded mongooses in Uganda and then used genetic analyses to find out which females were the mothers of the pups which survived. Dr Sanderson also collected hundreds of faecal samples from the Ugandan mongooses which were then taken to a special Wildlife Endocrinology Lab at Chester Zoo where they were analysed for concentrations of hormones by the zoo's experts.

In social species such as banded mongooses dominant females may use aggressive tactics to induce a hormonal response in subordinates and prevent them from breeding. While previous studies have shown a link between socially-induced stress and conception rates, this is the first to show that elevated stress levels experienced during pregnancy can have negative effects on the survival of offspring.

These findings provide new insight into the subtlety of female competition within even the most cooperative animal societies and provide a better understanding of how stress associated being a subordinate female can affect offspring development.

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This study was funded by the Natural Environoment Research Council (NERC) and European Research Council (ERC).

'Elevated glucocorticoid concentrations during gestation predict reduced reproductive success in subordinate female banded mongooses' by J Sanderson, HJ Nichols, HH Marshall, EIK Vitikainen, FJ Thompson, SL Walker, MA Cant, AJ Young is published in the journal Biology Letters.

Image credits: Harry Marshall

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About the University of Exeter

The University of Exeter is a Russell Group university and in the top one percent of institutions globally. It combines world-class research with very high levels of student satisfaction. Exeter has over 19,000 students and is one of the global top 100 universities according to the Times Higher Education World University Rankings 2015-16, positioned 93rd. Exeter is also ranked 7th in The Times and The Sunday Times Good University Guide 2016, 9th in the Guardian University Guide 2016 and 10th in The Complete University Guide 2016. In the 2014 Research Excellence Framework (REF), the University ranked 16th nationally, with 98% of its research rated as being of international quality. Exeter was named The Times and The Sunday Times Sports University of the Year 2015-16, in recognition of excellence in performance, education and research. Exeter was The Sunday Times University of the Year 2012-13.

The University has four campuses. The Streatham and St Luke's campuses are in Exeter and there are two campuses in Cornwall, Penryn and Truro. The 2014-2015 academic year marks the 10-year anniversary of the two Cornwall campuses. In a pioneering arrangement in the UK, the Penryn Campus is jointly owned and managed with Falmouth University. At the campus, University of Exeter students can study programmes in the following areas: Animal Behaviour, Conservation Biology and Ecology, English, Environmental Science, Evolutionary Biology, Geography, Geology, History, Human Sciences, Marine Biology, Mining and Minerals Engineering, Politics and International Relations, Renewable Energy and Zoology.

The University has invested strategically to deliver more than £350 million worth of new facilities across its campuses in the past few years; including landmark new student services centres - the Forum in Exeter and The Exchange at Penryn - together with world-class new facilities for Biosciences, the Business School and the Environment and Sustainability Institute. There are plans for further investment between now and 2016. http://www.exeter.ac.uk/cornwall

About the University of Exeter's Centre for Ecology and Conservation (CEC)

Staff at the Centre for Ecology and Conservation, based on the Penryn Campus, undertake cutting-edge research that focusses on whole organism biology. The CEC has three interlinked research groups: Behaviour, Ecology and Conservation, and Evolution which constitute 40 academics and over 100 early career researchers. It engages widely with businesses, charities and government agencies and organisations in Cornwall, the Isles of Scilly and beyond to translate its research into societal impact. Staff at the CEC deliver educational programs to some 500 undergraduate and 100 postgraduate students.

A new £5.5 million Science and Engineering Research Support Facility (SERSF) is currently under construction at the Penryn Campus. The facility will bring pioneering business, science and engineering together and will provide space for the growing CEC alongside the University of Exeter Business School, which is expanding into Cornwall, and the University's Marine Renewables team.

The University of Exeter and Falmouth University are founding partners in the Combined Universities in Cornwall (CUC), a unique collaboration between six universities and colleges to promote regional economic regeneration through Higher Education, funded mainly by the European Union (Objective One and Convergence), the South West Regional Development Agency and the Higher Education Funding Council for England, with support from Cornwall Council.

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