A group of baby rats in a house
04 Nov 2019

Minimum Requirements for the Ethical Housing of Rats

This is a science-based checklist defining minimum requirements to house rats ethically. Please note that the checklist is an ABSOLUTE MINIMUM of what is reccomended in a lab setting, not a reccomendation, and the standard expected for pet owners is much higher. The guidelines are to provide an easy to read line in the sand for what is and isn't ethical treatment of rats, based not on personal opinion but on science and fact. TL;DR I'd never send an animal into a home or buy from a breeder that exactly fits this description, but it's a bar.

Rats don't just need food and water to experience a life that can be defined as humane, there are other vital welfare requirements that are recognised worldwide as being required by ALL animals no matter what their purpose. These are known as the Five Freedoms, and are as follows:

  1. Freedom from hunger or thirst by ready access to fresh water and a diet to maintain full health and vigour
  2. Freedom from discomfort by providing an appropriate environment including shelter and a comfortable resting area
  3. Freedom from pain, injury or disease by prevention or rapid diagnosis and treatment
  4. Freedom to express (most) normal behaviour by providing sufficient space, proper facilities and company of the animal's own kind
  5. Freedom from fear and distress by ensuring conditions and treatment which avoid mental suffering

The guidelines below are adapted from a set of ethics requirements written based on decades of research into rats in labs. In it's original form, it is used to ensure that lab animals are housed ethically and that good animal welfare is maintained in all the vital aspects of animal care. The full guidelines are referenced at the end of this article, but the checklist can be considered an adaptation of the guidelines into an easy to follow checklist that can be used by breeders to ensure that their housing is meeting acceptable animal welfare standards.


  • Rats are not overcrowded and the cage space is sensible for the size of all individuals and the number of animals. As a guideline, ten adult rats is considered appropriate for half a ‘Ferret Kingdom’, or two in a basic ‘PetOne rat cage’. (The minimum floor area for a group of up to 5 rats of up to 250- 300gm body weight should be 1,500cm2 and preferably 1,800cm2 . For larger rats, group size should be decreased or cage floor area increased.)
  • Nursing mothers (up to 21 days) are kept in a quiet cage or tub with no wire floor. 50L tub cages are considered appropriate. Mothers are not kept with intact males during the final week of pregnancy or while feeding. (For a nursing mother and litter (up to weaning at about 21 days), the floor area should be a minimum of 1,500cm2.)
  • Baby rats over weaning age have appropriate space to play and interact. (For juvenile rats (from weaning to about 50 days), for a maximum group of 12 juveniles, the floor area should be a minimum of 2,000cm2)

Cage design:

  • The height of cages allows rats to stand on their hind legs and stretch up fully. 
  • Food and water is available at all times and accessible at a level that allows rats (especially juvenile rats) to sit while eating and drinking, to avoid bony and cartilaginous damage. Scatter feeding in addition to hoppers is recommended to promote foraging behaviours and good posture.
  • Cages or tubs are well ventilated but kept out of direct drafts. 
  • The ambient temperature is kept at a safe level both day and night and the rats are not in direct sunlight.
  • Cages should be cleaned regularly to prevent ammonia buildup (kept below 25 ppm), rates vary based on cage size and rat numbers but as a guide, bedding is commonly replaced about once a week. 
  • A relative humidity at the level of rat cages of 40-70% is recommended as a guideline for optimal respiratory health and comfort, but is not enforced.
  • Where wire floors are used, the main floor area (not including ladders or additional shelves) should be covered with a stable flooring or cover (thick newspaper is sufficient) to enable animals to stand correctly.


  • Substrate should be provided in rat cages and should be in sufficient quantity to cover the whole floor. The depth of substrate required will vary with factors such as the type of substrate used, the number of rats in the cage and the frequency of cleaning. As a guide, the depth of substrate should be at least a minimum of 2cm. 
  • Substrate should be free of dust, microbial, parasitic, or chemical contaminants, non-traumatic, moisture absorbent and ammonia binding. The properties of substrate provided should also include that its particles can be manipulated and/or that it is suitable for digging/burrowing. 
  • Vermiculite or other substrates with small particles should not be used where they will come into contact with the animals


  • All rats should be provided with nesting material in addition to substrate, enough for all rats to nest comfortably and regulate temperature for sleeping.
  • Nesting material should be loose, manipulable and light enough to be carried. Suitable materials include shredded paper or straw.
  • There are sufficient enclosed, opaque shelters to allow all animals to simultaneously withdraw from light and activities outside their cage. 

Enrichment and social requirements:

  • Rats should be provided with items to enrich their environment. Items that assist rats to perform each of the following five categories of behaviours should be provided: 
    • Social interaction 
    • Chewing/gnawing (hides, food hoppers)
    • Locomotion (including climbing, exploring and playing), 
    • Resting/hiding, and 
    • Manipulating, carrying and hoarding food and objects. (Food hoppers, toys, nesting material.)
  • All housing for all animals allows the opportunity for social interaction, the opportunity to carry out normal behaviours and the opportunity to rest and withdraw from each other, UNLESS there are medical or behavioural circumstances which requires different circumstances AND it is clear that measures have been taken to meet the behavioural and psychological needs of the animals as closely as possible.
  • Rats should not be housed individually unless there is compelling evidence for the need to house the individual in this way. In such cases, rats should be able to see, hear and smell other rats.


​Article by Rachel Greenfield on 04/11/2019
Image by Rachel Greenfield


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