For primates and people: The benefits of researching stress in non-human primates

Jennah Green, a PhD student from Newcastle University’s Institute of Neuroscience and based at the MRC’s Centre for Macaques, is trying to develop new ways to assess the psychological wellbeing of rhesus macaques in research environments. Here she explains why it is so important to monitor monkeys’ welfare, and how improving animal welfare can lead to better science.

Macaques and a staff member at the MRC Centre for Macaques
Macaques and a staff member at the MRC Centre for Macaques

My interest in captive primate welfare was first sparked when I became involved in the Monkey Sanctuary in Cornwall. As I helped to build enrichment equipment for the rescued monkeys’ enclosures, I learnt about their varying psychological states, and was inspired to work on improving the lives of animals in captivity.

I’m now bringing my background in conservation into studying how we can use animal behaviour to interpret and assess the psychological wellbeing of these animals, particularly primates.

In the UK, primates are kept in a variety of captive settings including breeding centres, university laboratories, contract research organisations, zoos and rescue centres.

Improving methods used to assess the psychological wellbeing of the animals is a key goal for animal welfare researchers. My research aims to investigate aspects of behaviour that have not previously been studied in this context, with the aim of applying any new behavioural indicators of stress we find to new methods of monitoring and improving welfare across captive environments.

Replacement, reduction, refinement

Jennah Green
Jennah Green

The first and most important question to ask is: why are we interested in the first place?

Macaque monkeys are highly sentient creatures — it’s their similarity to humans that makes them such good animal models for some types of research. Primates are also particularly susceptible to psychological stress because they possess a cognitive sophistication close to that of humans.

This brings with it a host of ethical concerns for using animal models for research purposes. Whichever side of the animal research argument you fall on, no one would dispute that research animals should have the highest possible standard of welfare. If we are using animals for our own medical advancement, it is our moral duty to make sure they have the highest standard of living possible and that we don’t inflict any unnecessary suffering on them.

The scientific community has developed a code of ethics to achieve scientific advancement whilst minimising animal discomfort, based on the ‘3Rs of animal welfare’ philosophy. These are: reduction (reducing the number of animals used per experiment), replacement (finding experimental alternatives to animals) and refinement (minimising pain, suffering and distress in animals).

The refinement part of the philosophy is really important to me, because even while we work to reduce and replace animals, primates will continue be used for some types of research. Giving those individuals a high standard of living and reducing their suffering as much as possible is paramount. The first step is to ensure we can quickly detect and mitigate any suffering they are experiencing.

In addition to our moral duty to look after these animals, ensuring the monkeys are in good health will lead to better quality science. Poor welfare can change an animal’s biological function; stress has been known to reduce immune competence, modify brain structure and contribute to poor coronary health. Individuals with poor welfare therefore might not respond in the same way as a healthy individual would during experiments, so results may not be reliable or reproducible.

This is particularly significant when working with macaques, where only the smallest possible number of individuals is used in each study, so the data is more vulnerable to being skewed by unreliable results.

Current measures

There are a variety of different methods for monitoring welfare in non-human primates. These include physiological markers such as cortisol levels and heart rate, behaviour markers such as stereotypies (repetitive movements such as rocking) and general markers of health including weight and coat condition.

But most of these aren’t implemented routinely due to cost (both in terms of time and money), invasiveness (in the case of blood samples) and the specialist training needed. In some cases the measures are challenging to interpret (for example cortisol may increase during stress but also when the animal is excited).

So for most establishments, personal observations from staff and physical check-ups from veterinarians are the only measures routinely used.

Nocturnal behaviour

A night time shot of sleeping macaques
A night time shot of sleeping macaques

The vast majority of research on primate behaviour has been focused on daytime behaviours, meaning that half of the lives of these captive animals are essentially being ignored.

We know that sleep disruption can be related to stress and depression in humans, so it’s plausible that monitoring nocturnal patterns could provide insight in to the psychological wellbeing of laboratory primates, and be a new way of measuring welfare that has not yet been explored.

There are three main areas that I cover. The first is understanding what constitutes ‘normal’ sleep for captive macaques. Once this is established, the next step is to determine if there is a relationship between sleep patterns and stress, and what the consequences of poor sleep are for the mental wellbeing of the animals.

The third area is developing an automated system, using infra-red recording equipment and custom-written software, so that laboratory staff can conduct routine surveillance of night-time activities.

I have collected nocturnal footage at two different UK locations (a laboratory facility and a breeding centre) since February 2015.

To determine ‘normal’ sleep I am looking at patterns of behaviour throughout the night over a period of two years in the breeding colony. I am studying what variables might affect the patterns we see, for example the time of year (do they sleep less when the days are longer?), the day of the week (do they sleep differently at the weekend when there are fewer people and less activity in the unit?), and the composition of the group (do they sleep less if there are more infants or pregnant mothers in the group?).

To investigate if sleep patterns change after stressful events, I have filmed the monkeys in the weeks prior to, and after, undergoing a blood sampling procedure and their annual health check-ups. Both of these events require interaction with veterinary staff, separation from the rest of the group and sedation, all of which could be perceived as stressful to the monkeys. I then analyse the footage to see if the nocturnal patterns of activity differ before and after, particularly looking at how long it takes the group to go to sleep and how much movement there is in the enclosure overnight.

My aim is for the monitoring to be completely automatic so it requires no specialist training or time-consuming input of data. The custom written software detects movement levels on recorded footage, and uses ‘thresholds’ to distinguish unusual levels of movement throughout the night. Although I am developing this system based on a breeding colony of Rhesus macaques, it could be expanded to other non-human primates in other captive settings such as zoos, laboratories and rescue centers.

In that way, we’ll be able to improve the mental wellbeing of captive non-human primates, and those that are used in research will contribute to better quality science.

Jennah Green


Originally published at insight.