Laboratory mouse aggression study

The NC3Rs is leading a data crowdsourcing project for animal technicians to collect data on the prevalence and potential triggers of cage aggression in group-housed male mice. The project is open to all technicians working within licensed facilities across the world.

Mice are used extensively for the purposes of scientific research, with over 2.8 million mice being used in the UK in 20161 alone. Increasing understanding of the potential triggers of mouse aggression could have a big welfare impact on a significant number of laboratory animals.  

The study is now closed. Thanks to all the technicans who participated in data collection. 

How technicians can participate in the study:

  • Technicians are asked to observe group-housed male mice during daily routine cage checks and to record information on incidents of aggression over a consecutive four-week period. 
  • Technicans can claim up to ten hours Continual Professional Development (CPD) credits from the Institute of Animal Technology.
  • We have created an Excel spreadsheet for recording your data - download it here.
  • A video tutorial which provides background information on the aims of the study, together with step-by-step instructions on how to collect and submit data can be viewed below. A written version of the instructions is given here. A summary of answers to frequently asked questions is given here.
  • Discuss and co-ordinate with your Facility Manager and other participating colleagues to ensure that the data collection tasks are shared and that there is no duplication in data entry.
  • You are advised to start data collection by 23 October 2017 to ensure that you can complete the data collection tasks in full. 
  • Thank you in advance for your contribution and we hope you enjoy participating in this important study.




The tutorial slides, which provide guidance on how to complete the information required for each section of the study, are detailed in the table below.

Section Slides
A1 - Consent 12-13
A2 - Questionnaire 14-16
A3 - Injuries log 17-25
A4 - Total male mice numbers 26-30

Online catalogue of aggression-related injuries

If, during the course of the study, you take pictures of any injured mice and would like to contribute to an online resource which will catalogue the range of aggression-related injuries that can arise, please attach your images along with the mouse identifier and date the image was taken when you submit your study data to the NC3Rs. All images will be anonymised when uploaded online. Please note that you should not take pictures of injured mice if in doing so you are likely to cause additional stress to the mice.

Background reading

There are many publications on the subject of mouse aggression in the literature and a few notable papers are set out below. You may wish to familiarise yourself with some or all of these papers throughout the course of the study.  


  1. Bussell J, Wells SE (2015). Talking welfare: the importance of a common language. Mamm Genome 26: 482-485. DOI: 10.1007/s00335-015-9591-x
  2. Charles River (2012). Reducing aggression in mice. Technical sheet. (accessed 29 August 2017).
  3. Gaskill BN (2014). Aggression in laboratory mice: potential influences and how to manage it. The Enrichment Record Winter 2014: 22-25. (accessed 29 August 2017).
  4. Hurst JL (2005). Making sense of scents: reducing aggression and uncontrolled variation in laboratory mice. (accessed 29 August 2017).
  5. Weber EM et al. (2017). Aggression in group-housed laboratory mice: why can't we solve the problem? Lab Animal 46: 157-161. DOI: 10.1038/laban.1219
  6. Van Loo PLP et al. (2003). Male management: coping with aggression problems in male mice. Lab Animal 37: 300-313. DOI: 10.1258/002367703322389870

Research papers

  1. Annas A et al. (2013). Group housing of male CD1 mice: reflections from toxicity studies. Lab Animals 47: 127-129. DOI: 10.1177/0023677213476278
  2. Gaskill BN, Prichett-Corning KR (2015). The effect of cage space on behaviour and reproduction in Crl:CD1(Icr) and C57BL/6NCrl laboratory mice. PLoS One 10: e0127875. DOI: 10.1371/journal.pone.0127875
  3. Gaskill BN et al. (2017). The effect of early life experience, environment, and genetic factors on spontaneous home-cage aggression-related wounding in male C57BL/6 mice. Lab Animal 46: 176-184. DOI: 10.1038/laban.1225
  4. Lockworth CR et al. (2015). Effect of enrichment devices on aggression in manipulated nude mice. J Am Assoc Lab Anim Sci 54: 731-736. PMCID: PMC4671788


The NC3Rs is grateful to the Mary Lyon Centre, Harwell Institute, the Laboratory Animal Science Unit, AstraZeneca, Alderley Park and the Sanger Institute for their contributions to the pilot phase of the study.


1Home Office report - Annual Statistics of Scientific Procedures on Living Animals Great Britain 2016 (accessed 29 August 2017).