On this page

• Which monkeys are used in scientific research?
• Why are monkeys used in research?
• Why do some monkeys have cranial implants?

• Where do research monkeys come from?

• How are the monkeys looked after?

• The future of research in monkeys

• What the experts think

• What types of research are monkeys used in?
• Areas of research that have relied on monkeys

 

Which monkeys are used in scientific research? 

The most commonly used monkeys in medical research are: Rhesus macaques (Macaca mulatta); Cynomolgus macaques (Macaca fascicularis); and Common Marmosets (Callithrix jacchus).

The order of primates can be broken down into three groups: apes; Old-World monkeys; and New-World monkeys. Macaques belong to the Old-World monkeys and are native to South and Southeast Asia. Marmosets are New-World monkeys, native to South America. Although the great apes (Orangutans, Chimpanzees, Bonobos, Gorillas) are our closest relatives, using a great ape in any regulated procedure is banned under UK legislation.

The next-closest ape species to humans are the Old-World monkeys. Humans share around 94% of their genetic code with macaques, and 91.7% with marmosets. This is compared to 85% genetic similarity between humans and rodents, making primates both physically and genetically the most useful comparison to humans in the animal kingdom.   

 

Why are monkeys used in research?

Each year, around 2,000 – 3,000 primates are involved in experiments in Great Britain. This makes up 0.1% of the animals used in research.  

Because Old-World monkeys are anatomically, physiologically, and genetically so similar to humans, they can be useful models for human disease.  Macaques and marmosets have similar brains, muscle structure and reproductive and immune systems to humans. This means research with monkeys can provide results which are more relevant to humans compared to information obtained from mice or rats. 

Roger Lemon, retired Professor of Neurophysiology at the Institute of Neurology, UCL, goes even further and says:

“I am absolutely certain that our knowledge of the human motor system would be very poor indeed without the wealth of neuroanatomical and neurophysiological studies carried out in monkeys.” 

Monkeys are complex animals with complex needs, for example needing larger enclosures, additional enrichment, and social housing.  Monkeys are very intelligent and sensitive animals, which is why they are protected by stricter regulations than other species and can only be used when it is absolutely necessary.

 

Why do some research monkeys have cranial implants?

Cranial implants, sometimes known as head posts, are required for monkeys which are used in some neurological research. The implants serve a dual purpose, providing easy access to the brain if needed, and providing a safe and low-stress method of stabilising the position of the monkey's head.

Cranial implants or head posts are implanted into the monkey's skull whilst the animal is under anaesthetic. Implants must be monitored daily to ensure that wound healing is not impaired and no infection has arisen. Surgical aftercare such as pain relief is always given when needed.

 

Where do research monkeys come from? 

In Great Britain, it is prohibited to conduct experiments on wild-caught monkeys due to the impact that capture and subsequent experiments have on their wellbeing, as well as the increased risk of disease transmission. 

As a result of this, all monkeys involved in experimental procedures in Great Britain are either F1 generation (captive offspring of wild-caught individuals) or F2+ (offspring of captive individuals). Where possible, F2+ generation individuals are used instead of F1 individuals. You can see the numbers of F1 and F2+ individuals used in animal research in Great Britain in 2022 in the Statistics of scientific procedures on living animals, Great Britain: 2022 (Section 3.1.3).  

A key source of cynomolgus macaques for research is breeding centres in Asia and Africa, including colonies in Mauritius, where macaques are non-native and are considered an invasive species and agricultural pest. Macaques that would otherwise be culled to control the population are bred to produce offspring that can be used in research.

In Great Britain, there are several establishments which are licensed to breed macaques solely for research purposes, for example, the Medical Research Council’s Centre for Macaques (CfM). 

 

How are the monkeys looked after?

Animal welfare is a legal and ethical responsibility for everyone who works with research animals. In the UK, lab animals are cared for by animal technicians who have undergone extensive training on the care and welfare of animals in a laboratory setting.

Within the lab, senior animal technicians and Named Animal Care and Welfare Officers (NACWOs) are responsible for each animal’s health and wellbeing and are not involved in the research. Animal technicians spend every day with the animals observing them, ensuring they are experiencing as little suffering as possible, and enriching their lives with activities that mimic the natural behaviours that would be displayed in the wild, for example foraging.

All research establishments in the UK must have a veterinarian on call 24 hours a day in case of emergencies.

 

Housing 

Primates are highly intelligent and social animals, and require large enclosures that allow individuals to walk, climb, swing and leap. Housing is designed to suit the unique biology of each species. For example, wild marmosets spend most of their time in trees and so their housing is made with this in mind: complex vertical structures like bridges, swings and perches above human head height are key to ensuring that marmosets can express their natural behaviours. To learn more about marmoset housing, click here. 

Macaques, however, use floor space more, so ground-based structures are important as well as vertical spaces. To learn more about macaque housing, click here. 

Both macaques and marmosets are highly social, living in multi-male, multi-female groups in the wild. To allow for natural social interactions, macaques are housed in pairs or social groups, and marmosets are housed in family groups. Animals may be isolated under rare circumstances, for example, if they are recovering from an illness or surgery and need to be quarantined or if being in a social group poses a danger to them.

 

Enrichment 

As well as ample space, primates need a complex and stimulating environment. In captive settings such as zoos and laboratories, these needs are met through enrichment activities. Enrichment includes anything that stimulates the animals psychologically or through physical activity. The best enrichment activities are based around natural behaviours that the animals would exhibit in the wild and they are usually centred around most animals’ favourite activity; foraging for food.

Enrichment can also be structural (e.g. swings, climbing apparatus and water tanks), food-related (e.g. food puzzles and foraging) or other sensory stimuli (e.g. smells and sounds).  

A prime example of enrichment for monkeys is spreading food, such as grains or dried fruit, around the home cage. (see video). This encourages the monkeys’ natural foraging behaviour and keeps them occupied for long periods of time.  

Learn more about the enrichment used for marmosets on the University of Stirling’s marmoset care website. 

Learn more about the enrichment used for macaques on the NC3Rs macaque website or head to the macaque holding room 1 of the University of Oxford lab tour to find out more about enrichment. Visit the food preparation room to find out more about how food is prepared for macaques. 

 

Training 

In order to minimise the stress caused by captivity and research procedures, monkeys need to have a good relationship with their keepers. One of the ways that this is achieved is through positive reinforcement training. Training helps to reduce stress by putting the ball in the animal’s court. By rewarding desired behaviours, the animal learns to associate those behaviours with rewards, and is therefore more motivated to complete those tasks. 

“We are finding that these monkeys can learn these tasks very quickly within their natural environment. It’s sort of like enrichment. It’s an interesting, fun game for them to play,” explains Professor Andrew Jackson, of Newcastle University. 

Training also removes the need for some procedures to be performed. For example, taking blood used to require the animal to be anaesthetised, but now animals are trained to present their arms or legs for injections (see video). This is much less stressful for the individual animal and the animal carers. 

Prof Jackson describes how this is approached at Newcastle University: “We want to see how much of the training we can actually do within the animals’ natural environment, so within the home cage where the monkeys live. We have developed a system that we can attach to the front of the cage, and the animals are free to come into this system and perform a simple task.” 

Check out the training pages of the NC3Rs website for more information about training research animals. 

Head to the Main Corridor Exit of the University of Oxford lab tour to hear more about how they train macaques for experiments. 

Learn more about training animals to move to desired locations at the MRC Centre for macaques. 

 

The future of research in monkeys

The use of monkeys in research remains controversial and has been the subject of vigorous campaigning by animal rights groups in the past. Many independent and expert enquiries such as the Weatherall Report have concluded that there is a strong case for using monkeys to advance scientific and medical knowledge and to assess the safety of new medicines. The use of monkeys, like other animals, should only be undertaken when there is no alternative, and should be subject to careful regulation. 

Most research monkeys are macaques or marmosets. They are used in relatively small numbers (they make up around 0.1% of research animals) but they have been important in many major medical advances, for example, the polio vaccine, life support systems for premature babies, and deep brain stimulation for Parkinson’s disease.

Currently, the main areas of primate study are infectious diseases to develop vaccines and treatments for HIV/AIDS and malaria. Monkeys are also used in neuroscience to better understand the brain and treat conditions ranging from Alzheimer’s disease to schizophrenia. They are important in research into reproduction, fertility and foetal development, and they are also used in the safety testing of new medicines and vaccines. 

 

What the experts think

In 2017, the Scientific Committee on Health, Environmental and Emerging Risks (SCHEER) released an updated opinion on the use of primates in research. Here is what they said: 

“The use of non-human primates remains necessary for certain types of research, but when their use is required to be determined on a case to case basis and only if no viable alternatives are available it is essential to adopt the highest standards of non-human primates housing and husbandry and to follow best practice in the conduct and refinement of scientific procedures.”

The topic of using monkeys was the subject of the Weatherall Report in 2007. At the time the government’s Chief Scientific Advisor, Sir David King FRS, said: 

"Although rare, the use of primates in medical research and testing is invaluable, as an essential aspect of work which provides the best hope for breakthroughs in important areas such as neurodegenerative disorders and for aspects of immune and reproductive functions."  

MRC press release responding to the Weatherall Report, June 2007. 

"There is a strong scientific case for the carefully regulated use of non-human primates where there are no other means to address clearly defined questions of particular biological or medical importance."  

Weatherall Report: The use of non-human primates in research, December 2006: 

"Primates have been used in research aimed at understanding how complex brains work, as their neurological development and higher cognitive functions are very similar to humans … Animal [primate] disease models were also used for research on hepatitis C, and polio."  

Nuffield Council on Bioethics, The ethics of research using animals, May 2005:

"... for certain experiments there are no alternatives to the use of non-human primates. Such experiments may be needed, for example, during the development of drugs and vaccines for prevention and cure of disease such as AIDS, TSE1, malaria, and influenza".  

European Commission Scientific Steering Committee (SSC), The Need for Non-Human Primates in Biomedical Research, April 2002: 

"Many significant advances in modern medicine have been based on research involving primates."  
 

What types of research are monkeys used in?  

Monkeys have been used to study many different areas of human and animal disease. They have been essential in research into neurological disorders such as Parkinson’s disease, reproductive disorders, understanding how vision works, and the development of vaccines.  

Like humans, monkeys see in colour and have binocular vision, which is why they have been used to better understand how humans process visual information from the 3D environment. 

Rhesus macaque monkeys were vital in the race to develop an effective vaccine against SARS-COV-2, the virus that causes COVID-19. Monkeys were used to identify the most promising candidates for vaccines and ensure that they were safe enough for human volunteers to take in the large-scale clinical trials that took place. 

Marmoset monkeys are predominantly used for research into Parkinson’s disease. Since the accidental discovery of MPTP, a substance that destroys a part of the brain and causes the symptoms of Parkinson’s, MPTP is used to induce the symptoms of Parkinson’s in marmoset monkeys. This has helped scientists explore new treatments for Parkinson’s disease.

More examples of how monkeys are used in research are listed in our iBook: Primates in Medical Research. 

 

Areas of research that have relied on monkeys

 

 

Watch our videos 

Parkinson's disease patient demonstrates his brain implant 
 
Marmosets in medical research 
 
Macaques in medical research 

 

Related Links 

Weatherall Report The use of non-human primates in research    
EC SSC Report: The Need for Non-Human Primates in Research  
Nuffield Council on Bioethics report: The ethics of research using animals  
NC3Rs guidance: Non-human primates    
European Scientific Committee on Health and Environmental Risks (SCHER) opinion on primate research (January 2009)