How animal enclosures are designed to meet the needs of laboratory animals

Having worked in animal research for over 14 years now I have not only gained a comprehensive knowledge of the requirements for animals used in research but have also seen significant improvements in this field. Currently, I work at King’s College London as a Site Manager where I oversee three animal units.

The role of an animal technologist varies dependent on experience but all are there to provide the best possible life to animals in research. Trainee animal technologists will often perform general husbandry duties such as cleaning cages, feeding, and watering, whereas senior technologists may be involved in colony management, scientific procedures etc.

During my career, and the many tours of research labs I’ve given, one of the common discussion is the type of cages used and how they vary so much between species.

Requirements for housing research animals in the UK are stipulated by Home Office and Animals (Scientific Procedures) Act, 1986 as well as any additional institutional requirements beyond this law. Providing the correct type of environment is essential for species to exhibit their natural behaviour.

Example of UK minimum cage sizing for M. mulatta

Housing requirements vary between species but here are some examples of why cages are designed in such a way:


Primate caging is typically tall as this enables the animals to feel more secure, as in the wild they would use the trees to climb high and get away from prey. Providing higher cages also allows for a more complex environment. Bars are often horizontal to allow the animal to climb the cage and maximise this as much as possible. Cages are normally made out of steel to ensure the animals are safely contained and also withstand potential damage in what are often a strong and intelligent species.

Cages are often multi-tiered to allow primates better utilisation of cage height and enable primates to get away from each other when necessary.  Environmental enrichment such as mirrors and perches provide further security to primates.

Primates are socially housed in multi-tier caging. The perches allow the primates to watch what is going on around the room.


Rodents have much smaller cages which are normally made up of a plastic, such as polysulfone. These plastics can withstand high temperatures during cleaning and have been shown to last a long time. Traditionally, animals were kept in open top caging but in recent years there has been a movement towards individually ventilated cages (IVCs). IVCs provide a more stable environment by having sealed caging and using air handling units for filtration; this has, in turn, provided a better environment for animal welfare and research. Controlling for the environment can both help control experimental variables, and prevent risks to animal health from external pathogens.

While the caging appears to be relatively small for rodents it is designed around the need of the animals. Rodents are often social species and in some cases larger spaces can cause anxiety due predator/prey relationships.

Environmental enrichment is used to encourage natural nesting behaviours which can be seen in the wild. In recent years red boxes have been implemented in some cages, humans can see through these but animals don’t see through this colour in the same way, therefore this allows better monitoring while making animals feel safe and secure.

Individually Ventilated Cages


Rabbits are often housed in floor pens as this provides space to exercise and express their social behaviour. Rabbits which are kept grouped housed tend to show less stereotypic behaviour and greater activity. Previously, rabbits were predominantly housed in single cages which caused more stress to the animals.  Enclosures are normally made up of wood frame with metal bars or completely metal frame with very small holes to prevent animals escaping.

Environmental enrichment such as cardboard boxes, hay/straw and raised areas can also provide more security and natural behaviours therefore reducing any abnormal behaviour which may be seen otherwise.  As albino rabbits are often used in research, boxes also provide a darker place to prevent damage to the retina of the eye.

Final thoughts

As humans we often believe that larger housing is better, just look at people who often want a huge home, but this doesn’t mean that an animal will be comfortable with this. The key is to tailor this to each species/individual’s needs for the highest welfare standards. Animals which naturally live in holes, or nests, often feel comfortable with less space compared with other animals. Other additions to accommodation such as environmental enrichment can enable expression of natural behaviour further and have significantly increased in recent years, no more barren cages!

In my 14+ years working with research animals, I have seen a huge amount of change. Improvements in caging and enrichment benefit not only the animals, but the pursuit of good science as well, and we should welcome it. I am also a strong believer that this has also improved the morale of staff, after all we all want the best for animal welfare which in turn will lead to good science.

Stephen Woodley

7 thoughts on “How animal enclosures are designed to meet the needs of laboratory animals

  1. Living in the wild is pretty much a horrible experience, fraught with starvation, predation, fighting amongst conspecifics, stress associated with constant high-level vigilance of their surroundings (think PTSD from extended periods in a war zone), etc.

    Living in the laboratory, while they are not natural settings, carries many benefits such as constant access to food, no predation, medical care for disease, pain management, etc. Of course, one couldn’t deny that there are stressors and/or anxiety associated with being caged, having less social activity, etc. But, when people talk about how it’s much better for animals to be in their natural settings, they are typically more than happy to dismiss (or remain ignorant of) the fact that the “wild” is certainly no picnic.

  2. Speaking as someone that has worked with NHPs, rodents and rabbits, we strive to ensure ALL animals are provided the best care and conditions feasible without affecting research. As a regulation, all social species are required to be housed socially (two or more), as long as it doesn’t negatively affect the research. The USDA would never approve that standard.

    It really concerns me that a person claiming to work in a US facility don’t understand this distinction. Probably not a good source of information.

    It is probably good to note we are always striving to improve conditions and explore reliable non-animal models for the medical advances from which each and every one of us benefit, not to mention our pets.

  3. There is, of course, extensive literature on this, and it shows over and over that this article is dishonest. Specifically, it disingenuously fails to note that “enriched” cages reduce chronic stress somewhat, but nonetheless lead to lives of misery even before experimentation begins (inevitably increasing stress; Balcombe J Am Assn Laboratory Animal Science 2004).

    There’s social isolation (Zimmermann Behavioural Brain Research 2001) or else intractable aggression (Weber Nature 2017); endless stereotypies showing clear evidence of poor psychological health (Novak Applied Animal Behaviour Science 2016), and distress caused by lack of variety, control, and adequate shelter (Van de Weerd J Applied Animal Welfare Science 2002).

    It is irrational and unethical to inflict such unpleasant lives on others, when all our own actions are ultimately grounded in our recognition of the fact that a good and pleasant life is an objectively good end.

  4. You’ve got to be sh***ing me! I work with nhp’s in research (united states), I work with wild caught rhesus put into a steel 3 foot by 3 foot cage that has one steel platform to sit on, a mirror and some old dog chew toy. And they are single housed, but technically according to regulations they are social housed since they can see another monkey (ask anyone with half a brain if they consider that social housing). I’ve been in other facilities owned by the same company working with african greens, all wild caught, they are single housed in 2×2 cages. Why are cages designed a certain way? Easy, it’s all about space and money. Rodent cages are designed around the needs of the animal? Mice in the wild, I forget the numbers told to me by experts who sell enrichment designed to allow the mouse to run, but mice run a surprisingly long distance every day. Most facilities provide no was to allow the animal to run except for running in circles around the cage (I have seen many times). All of our rabbits are single housed with no boxes, no raised platforms.

    1. This post is written by a UK-based animal technologist about the UK standards. The UK regulations prohibit wild caught animals, demand actual social housing (two animals in one enclosure). In my experience, many US labs are increasingly building new facilities and caging in line with European facility standards – which I think is positive. Perhaps you should consider pushing for some better facilities for your NHPs!

    2. Hi, AF.

      Thanks for your comments. Out of curiosity, do you work at an academic institution? I’m interested in differences/similarities in animal wellbeing between different types of institutions. Thanks!

    3. @AF
      Your description lacks all manner of context and is clearly comprised of leading statements.

      For the NHPs, it would be interesting to know the sex of the animals, previous history of attempts at social housing, whether this led to aggression and whether the mirrors do afford some degree of sociability in these animals that would otherwise not be possible.

      I fail to see what wheel running has to do with mouse wellbeing. Mouse territory can range from the size of a standard laboratory cage to as much as a few kilometers. This depends on available resources, temperature and many other factors. More space is not better. The affordances of the available space are perhaps a more useful metric.

      Rabbits also display aggressive behaviour – and the same argument presented above for the NHP also applies. They are not cute cuddly bunnies – do a quick google search or better yet read the guidelines of your institution — they are there for a reason.

Comments are closed.