Skip to main content

International 3Rs Prize now open for applications. £30k prize (£2k personal award) for outstanding science with demonstrable 3Rs impacts.

NC3Rs | 20 Years: Pioneering Better Science
Office-led project

Laboratory mouse aggression study

At a glance

Current contacts
A technician in a green gown, mask and hair net can be seen alongside racks of mouse cages. He can be seen reaching into one of the cages to check on the health of a mouse.


Aggression in group-housed mice is a serious welfare concern. Mice are used extensively for the purposes of scientific research, with over 2.7 million mice being used in the UK in 2017 alone [1]. Further understanding of the factors influencing mouse aggression could have a significant positive welfare impact on a large number of animals.

The NC3Rs led a crowdsourcing data project to collect data on the prevalence of and potential triggers for aggression in group-housed, male laboratory mice. In total, 44 facilities from nine countries participated in the study and data was collected by 143 animal technicians. A total of 788 incidents of aggression-related injuries were reported across a sample population of 137,580 mice.

Many thanks to all those who participated in the study. The results have now been published in Scientific Reports – read our news story for an overview. 

For further information, please email

How technicians participated in the study:

  • Technicians observed group-housed male mice during daily routine cage checks and recorded information on incidents of aggression.
  • Technicians claimed ten hours of Continual Professional Development (CPD) credits from the Institute of Animal Technology.
  • Participants were invited to view a video tutorial that provided background information on the aims of the study, together with step-by-step instructions on how to collect and submit data. A written version of the instructions is given here. A summary of answers to frequently asked questions is given here.
  • Data was collected over a consecutive four-week period between 1 September and 30 November 2017 and recorded using an Excel spreadsheet. 
  • The data was submitted to the NC3Rs, anonymised, checked and queries cleared with participants. It has now been analysed and is currently being prepared for publication in a peer-reviewed journal.

Video tutorial

The tutorial slides provide guidance on how to complete the information required for each section of the study. The different sections of the video 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

Background reading


  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. NC3Rs invited article. (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. Journal of the American Association for Laboratory Animal Science 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.