Conflict over reproduction in a cooperative mammal: an experimental approach

Lead Research Organisation: University of Exeter
Department Name: Biosciences

Abstract

Animals that live in cooperative societies face inherent conflicts of interest which must be resolved in some way for the society to function. The most fundamental conflict concerns the distribution of reproduction. Animal societies vary enormously in the degree of 'reproductive skew', which measures the evenness with which reproduction is distributed among group members. A large number of evolutionary models have been proposed to account for why societies vary in this way. These models are based on different principles but nevertheless make similar or overlapping predictions, with the consequence that even the best attempts to test the models have up to now been uninformative. The best way to distinguish the models and provide a much richer understanding of reproductive conflict is to manipulate the degree of skew experimentally. We will carry out the first experiment of this kind large-scale on a free-living population of banded mongooses that we have studied for the last eleven years. This species is unusual because nearly all adult females (up to ten) in each group give birth together in the same den, and offspring are cared for by adults of both sexes. We have shown in a pilot study that we can use short-acting contraceptive injections to block pregnancy in breeding females for a single breeding attempt, thereby temporarily increasing the degree of skew while keeping group size and other variables constant. The behavioural responses to the manipulation, combined with genetic analyses of maternity, reproductive success and the kin structure of the group, will enable us to measure the costs of co-breeding, determine which individuals exert control over the distribution of reproduction, and provide information on the behavioural mechanisms employed in reproductive conflict. Moreover, our experiment will test for the first time the direction of causality between variation in the distribution of reproduction and variation in individual social behaviour, a important but untested assumption of models of skew and cooperation.

Publications

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Cant MA (2014) Policing of reproduction by hidden threats in a cooperative mammal. in Proceedings of the National Academy of Sciences of the United States of America

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Cant MA (2008) Reproductive conflict and the separation of reproductive generations in humans. in Proceedings of the National Academy of Sciences of the United States of America

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Field J (2009) Social stability and helping in small animal societies. in Philosophical transactions of the Royal Society of London. Series B, Biological sciences

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Johnstone R (2010) The evolution of menopause in cetaceans and humans: the role of demography in Proceedings of the Royal Society B: Biological Sciences

 
Description This project involved a large scale experiment to test how conflict over the profits of teamwork at resolved in cooperative mammals. The main findings were that socially dominant female banded mongooses use the threat of infanticide to deter reproduction by younger subordinates; but that these younger females can escape this threat by synchronising birth to the same day as older females. The results suggest that conflicts within cooperative groups may often be resolved by threats of infanticide or aggression, which remain hidden until they are triggered experimentally. We have also shown (in 2019) that females respond to the threat of infanticide by spontaneously aborting their litters. Coercion may therefore be widespread in animal societies, even those in which acts of aggression are rarely observed. Our theoretical development of this idea revealed the conditions where threats can be effective as a method of coercion, with wide applicability to social and cooperative vertebrates and insects.
Exploitation Route The evolution of cooperation is a topic of interdisciplinary interest and underlies many evolutionary, economic, and political issues such as global climate change, the stability of public goods, and human conflict. Understanding how conflicts are resolved to promote cooperation is a key step along the path to a full understanding of how altruism and cooperation can be favoured in the face of self-interest. The key finding took several years to pin down using our experimental method, but was published in PNAS in January 2014. This represents the culmination of the grant outcomes. However, we are currently using the long-term data collected over the 7 years of the experiment to test new hypotheses about the effect of reproductive competition (which was experimentally manipulated during the grant period) on behaviour and life history. We anticipate further important outputs as we analyse this long-term dataset.
Sectors Environment,Other

URL http://www.socialisresearch.org
 
Description Our findings contributed to an understanding of the lack of reproductive suppression in banded mongooses, and, by extension, other social vertebrates. Our research attracted the interest of film companies and led to a four part BBC TV Documentary entitled, Banded Brothers: The mongoose mob. This attracted an audience of 1.5 million in the UK and an estimated 20 million worldwide. The TV series contributed to an improved public understanding of science, and helped to promote Uganda's Queen Elizabeth National Park as as an eco-tourism destination.
First Year Of Impact 2010
Sector Other
Impact Types Societal

 
Description European Research Council Consolidator's Grant
Amount € 1,500,000 (EUR)
Organisation European Research Council (ERC) 
Sector Public
Country Belgium
Start 01/2013 
End 12/2017
 
Title Banded mongoose long term database 
Description A continuous database of behaviour and life history of the banded mongoose population since 1995. This will be deposited with NERC within the next three months. It provides valuable demographic and life history information about schedules of growth, fertility, survival and dispersal in a wild mammal population stretching over 6 generational lengths. 
Type Of Material Database/Collection of data 
Provided To Others? No  
Impact The creation and maintenance of this database allows very powerful analyses of social influences on health and life history in wild mammals. It formed the foundation for my successful ERC grant application in 2012, and underpins research on early life influences on cooperation, the topic of my current NERC grant. 
 
Description Mongoose genetics 
Organisation Liverpool John Moores University
Country United Kingdom 
Sector Academic/University 
PI Contribution We provide all tissue and blood samples for genetic analysis of parentage. We also provide the long term life history database, and collaborate on a range of publications investigating the genetic population structure of our field population.
Collaborator Contribution Developed microsatellite library for analysis of parentage. Currently working on construction of a full genetic pedigree, which will open up new lines of research.
Impact Numerous papers co-authored with HJ Nichols have investigated the genetic structure of the population, reproductive success, and inbreeding.
Start Year 2007
 
Description Banded brothers 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact My research on banded mongooses inspired a prime-time BBC2 series which was screened in February and March 2010. The BBC spent six months at the Uganda study site filming the mongooses, resulting in four one-hour documentaries which each drew an audience of 2 million in the UK, and over 30 million worldwide. I provided critical logistical support in Uganda, scientific background and consulted on scripts to ensure the effective communication of the science behind the programmes. This media impact of my NERC-funded research project was chosen as the number 1 'Knowledge Transfer Highlight' in NERC's 2010 Annual Report.

This series greatly raised the profile of the banded mongoose and our research project. It resulted in a surge of enquiries from the public at the field site, and stimulated me to set up an 'Mongoose Adventure Walk' tourism package at the site. This is a collaboration between the banded mongoose project and Uganda WIldlife Authority. We have trained two interpretive guides who communicate our research to tourists, and inform about the wider relevance of the research, the importance of Uganda's wildlife, and broader conservation aims.
Year(s) Of Engagement Activity 2010