3Rs Information - Rodents


Welfare and scientific considerations of tattooing and ear tagging for mouse identification

A study has outlined the welfare and scientific considerations of tattooing and ear tagging mice and concluded that the total welfare costs of tattooing are not greater than for ear tagging.


Laboratory mouse housing conditions can be improved using common environmental enrichment without compromising data

A study, published in PLOS Biology investigated the effect of commonly used environmental enrichment on 164 physiological parameters in mice. The researchers found that environmental enrichment can successfully be added to the cages of mice without interfering with or compromising scientific data. We strongly advise that rodent researchers concerned about the use of environmental enrichment should read this paper.

Variation between inbred and outbred mice

paper published in Nature Methods comparing the phenotypic variation between inbred and outbred mice. These researchers have concluded that even though inbred mice are assumed to display less trait variability, there is no evidence for this and outbred mice, contrary to popular belief, may actually be better for most biomedical research. We recommend that researchers read this paper before planning a study to ensure that the correct mouse model is chosen for their particular needs.

Breaking up is hard to do: does splitting cages of mice reduce aggression?

study, published in the journal of Applied Animal Behaviour Science, evaluated best practices in separating mice following aggression-related behaviours and the likely outcomes of cage separation. This paper is an essential read for those working with rodents where aggression tends to be an issue.

Self-organising ‘gastruloids’ mimic early development of mouse embryos

Researchers from the University of Cambridge, the University of Geneva and the Federal Institute of Technology Lausanne (EPFL) have developed a 3D embryonic stem cell culture system capable of self-organising into the three major axes of the body. This has potential to replace the use of mice to study the early development of the human embryo. The NC3Rs has released a set of videos where Dr David Turner of the University of Cambridge discusses the research group’s publication on the work.


Housing temperatures in mice

Elsevier data scientists have used data mining, NLP and neural networks to discover that researchers are not keeping mice at the best temperatures for accurate results. This research corroborates a 2015 study where researchers confirmed that mice become resistant to certain cancer therapies at lower temperatures. The vast majority of researchers house their mice between temperatures of 20-22 degree Celsius which is too cold for mice, who respond better to a thermoneutral 30 degrees Celsius.


Mouse Cubby to reduce aggression in group housed male mice

An editorial in ALN magazine (a resource for the design and operation of research animal facilities globally) describes the Mouse Cubby, a refinement designed to reduce aggression in group-housed male mice. This insert allows complete visualisation of the mice in the cage, while dividing the cage from floor to ceiling. This appeals to the thigmotactic nature of mice and provides them an opportunity to manipulate their environment. As there are burrows and a large shared space, mice do not need to compete for limited territory and resources. The HPRA strongly advises all personnel involved in the housing and husbandry of mice to review this and the above resources in relation to mice.


Webinar on refined handling techniques in mice

webinar outlining refined techniques for handling and picking up mice is now available to watch online. This webinar outlines the evidence base supporting refined handling techniques in mice as well as practical advice and tips that can be implemented within institutions.


Group housing male laboratory mice 

An interesting review investigating whether to group-house male laboratory mice, given the welfare concerns relating to territorial behaviour and aggression, has been published. The conclusion is that group or single housing is highly context-dependent according to several factors (e.g. strain, age, social position, etc.) and should be evaluated on a case-by-case basis. The open-access paper can be accessed at the following link:



Results of mouse studies affected by the way the animals are handled

A study, funded by the NC3Rs, has shown that how mice are picked up can substantially change their behaviour in cognitive tests, with the benefits of non-aversive tunnel handling highlighted. This paper should be of interest to anyone working with mice. 


The NC3Rs has expanded the information available on its website on the subject of handling mice. There is now a webpage specifically dedicated to this topic that includes a video tutorial, frequently asked questions document, posters, relevant research papers and a webinar.

Home cage aggression in mice

An interesting article has been published in Lab Animal, regarding a series of experiments testing potential explanations and interventions for post-shipping aggression related injuries in C57BL/6 mice:



NC3Rs neonate assessment

The NC3Rs have published a useful article on the assessment of the welfare of neonatal mice in breeding programmes and provides tips on how to do this with minimal disruption to the litters.

Minimising aggression in group housed male mice

The results of a large NC3Rs study carried out across 44 facilities on aggression-related injuries in mice has been published in Scientific Reports. The report compares the prevalence of aggression across strains as well as the effects of housing and husbandry variables, and makes a number of practical recommendations.

Ageing animals in scientific research

A review article has recently been published on the care, husbandry and management of ageing mice used in scientific studies. The global population of older persons is growing at a rapid rate, and this is increasing the need for aged animals in scientific research. Many systems (e.g. musculoskeletal, cardiovascular and digestive) researched in rodents can become adversely affected as a result of ageing. This paper outlines considerations to mitigate potential adverse effects, including enhanced welfare monitoring, supplementary bedding, different food or alternative food placement, etc. This is essential reading for establishments that use aged rodents.



Tickling rats: a social enrichment to improve rodent welfare

Designed to mimic the play activity of juvenile rats, tickling has been shown to be an effective means of generating a positive affect (a positive mental state) in these animals. Rats that are tickled by their handler have reduced anxiety to handlers and new environments. Tickling rats prior to undergoing a stressful procedure (such as blood sampling) reduces the impact of the procedure on the animal. Tickling has also been demonstrated to increase brain levels of reward hormone dopamine - similar to humans who are tickled. The Gaskill lab also has a useful handout on rat tickling that may be of interest.


PREPARE - Group housing of rodents with cranial implants

Norecopa have added a page to the PREPARE guidelines on group housing of rodents with cranial implants. As there are very few publications on this topic, Norecopa have collected anecdotal evidence from members of the CompMed discussion forum. They would welcome any input to this and any other resources on the website. These can be sent to post@norecopa.no. In the spirit of the 3Rs, we would like to encourage researchers to get involved and share their expertise on this and other topics.


Refined scruffing technique in small laboratory animals

The scruffing technique is an essential immobilisation technique used with small animals to allow for proper implementation of certain procedures, such as oral gavage, and to prevent the operator from being bitten. Norecopa, in collaboration with the Norwegian University of Life Sciences, has produced a short video illustrating a refinement of the scruffing technique in mice. This technique uses three fingers, as opposed to the usual two. It creates a transverse skin fold on the animal, relieving any pressure on the throat and trachea that has the potential to cause the animal stress. This resource would be useful for any technicians or researchers who use small rodents such as mice.


Guidelines on severity assessment of genetically altered rodents

Detailed guidelines on how to perform welfare assessments on genetically altered mice and rats in order to determine the presence of a harmful phenotype, and its severity, have been produced by the Working Group of Animal Welfare Officers in Berlin and published in Laboratory Animals. These guidelines should provide a structured approach to welfare assessment of genetically modified lines, and thus will be beneficial to scientists, veterinarians and animal care staff.


Asepsis in rodent surgery

World renowned laboratory animal veterinarian, Prof Paul Flecknell, has written a blog for the NC3Rs about ensuring asepsis in rodent surgery. This is interesting reading for anyone undertaking surgery. 


Rodent infrared thermometers

We have recently been made aware of a non-invasive method of measuring rodent body temperaturewhich is the use of infrared thermometers. If relevant, please highlight this potential refinement to the users in your establishment.


Alternative to metabolic caging for rodent urine collection – hydrophobic sand

Hydrophobic sand has been developed as an alternative to restraining laboratory rodents in order to obtain a urine sample. The use of this sand is not considered a procedure by Directive 2010/63/EU, and so users are legally obliged to implement this refinement.


Mouse and Rat Grimace scales

Free A3 posters of the grimace scales can be ordered here. 


Refining arthritis models

There is an interesting report published by the RSPCA on refining rheumatoid arthritis research using mice and rats. If arthritis models are used in your establishment, this link should be circulated to the relevant researchers and technicians as well as the animal welfare body and the ethics committee.


Rodent handling

Although it is common knowledge that picking up rats by the tail is stressful and should be avoided, recent research has shown that picking up mice by the tail induces aversion and anxiety and should also be avoided. The NC3Rs website has been updated to provide information on non-aversive methods for picking up mice. We encourage establishments to become familiar with these methods and use them where possible.



Through this website you are able to link to other websites which are not under the control of the HPRA. We have no control over the nature, content and availability of those sites. The inclusion of any links does not necessarily imply that the HPRA recommends or endorses the views expressed within these linked websites.