Why Do Zoo Animals Pace Back And Forth (Explained By Zoologist)

tiger pacing back and forth in the zoo

Imagine a life of solitary confinement.

No one to speak to. No one to interact with. Not even a book to occupy your mind.

A pretty lonely existence, right?

Your mental wellbeing would, most likely, decline quite significantly. Distressing thoughts may come into your head. Your physical behaviors may change.

Unfortunately, this is a common occurrence for animals living a caged existence within zoos across the globe. Coined the term zoochosis, pacing back and forth is often associated with animals suffering from extreme stress, often due to poor welfare, in captive environments. However, aimless pacing isn’t the only symptom of zoochosis. 

If you have ever visited a zoo, you may have noticed elephants rocking back and forth, polar bears swimming in circles or primates biting their tails. These are all tell-tale signs of an animal suffering from zoochosis.

But why do captive animals display these characteristics?

What Is Zoochosis?

Before we take a look at the why’s, let’s first discuss what zoochosis really is.

Yes, I know I said it stems from stress, but there really is a lot more to it than just stress alone. In fact, it is a form of psychosis – a mental health concern affecting perception with reality.

Zoochosis often becomes apparent in animals that are held captive in environments that do not fully cater to needs of an individual species.

For example, African elephants have a home range of approximately 11,000 square kilometers in the wild and walk around 30 miles per day. No zoo, no matter how ethically friendly it claims to be, can provide such a vast amount of space. In reality, most elephants are kept in enclosures a mere fraction of the size.

An environment may also cause unnatural stress and boredom for an animal. For example, nocturnal animals being forced to be active during opening hours, or the hordes of visitors that bang on glass partitioning, climb on fences or try and touch the animals. This will almost always lead to the deterioration of an animal’s mental and physical health.

As a response, a captive animal may develop abnormal behaviors. Referred to as stereotypic behaviors, these abnormal behaviors are highly repetitive, obsessive, invariant and serve no purpose.

Why Do Animals Suffer From Zoochosis?

Life on Earth has existed for 3.7 billion years.

That’s a whole lot of time for evolution to work its magic.

And so it has. Over millennia, animals have evolved a range of physical, physiological and behavioral traits to help them adapt to their natural environment.

Some adaptations rely on a symbiotic relationship with another species. This is evident in meerkats and the drongo bird. Other adaptations, such as the hunting techniques of endangered orcas, are specific to specific sub-populations of species.

A captive setting, or a zoo, cannot replicate the natural environment of a specific non-native animal. Space is restricted, social interactions are limited, diet is regulated, climate is different and there are humans practically everywhere. Noisy, smelly humans.

Every aspect of the landscape an animal has evolved to has drastically changed.

“But animals get food, medication and shelter in zoos” I hear you blurt. “How bad can it really be?”

Yes, animals within zoos do lead a sheltered life and their medical needs catered to. However, they are simply not adapted to life in captivity. A monkey should not be fed bananas every day. An elephant should not be kept alone. A dolphin should not be forced to perform for food.

When these stressful situations become too much, an animal may display signs of zoochosis. Pacing back and forth becomes a common occurrence, as does a range of other physical and behavioral actions, such as self-mutilation, neck twisting, rocking and vomiting.

A study, looking into the effects of captivity on large cetaceans, concludes that captivity can cause physical changes to the structure of the brain, causing significant health problems. The cerebral cortex, essential for memory, thought, learning, decision-making and intelligence, shrinks considerably.

Capillaries, responsible for pumping blood around the brain, also shrink. This, in turn, decreases the amount of oxygen the brain receives, again affecting cognitive abilities.

The study goes on to suggest that some of these physical changes are a direct result of animals not getting enough exercise through enclosures being too small, as well as a lack of stimulation through the use of enrichment.

What Is Stereotypic Behavior?

As we just discussed, stereotypic behaviors are abnormal, monotonous behaviors displayed by an animal suffering from zoochosis.

There are many types of stereotypic behaviors, such as:

Pacing and Circling

Pacing back and forth or circling are perhaps some of the most common symptoms associated with animals suffering from zoochosis in captivity. This behavior is particularly prevalent in carnivorous species, such as felines (big cats), canids (wild dogs) and ursines (bears).

Pacing is defined as a repetitive movement in a fixed pattern. It can be continuously walking up and down the same spot or circling in a specific area, often following the same path.

In captivity, it is relatively easy to spot the signs of an animal pacing, not just from the physical movements, but from the trails dented into the ground.

Tongue Playing and Bar Biting

This is one of those behaviors that looks cute but is in fact an abnormal behavior. Ask yourself, how many wild animals would go up to a metal post and start sucking on it?

Not many, should be the answer.

So why should this be any different to animals in captivity? In captive settings, it is relatively common to see both giraffes and non-human primates licking, sucking or biting poles, bars and walls in their enclosures.

Neck Twisting

For most mammals, neck twisting is an abnormal behavior which, if performed incorrectly, can cause serious damage.

Certain species in captivity, such as bears, giraffes and primates, are prone to twisting, rolling and flicking their heads in a non-natural way.

This is often a sign of distress and frustration and can cause irreversible damage, such as broken necks.

Swaying and Head-Bobbing

Motionless and expressionless, besides monotonous swaying, is another symptom of zoochosis.

Primates, bears and elephants have been recorded displaying this behavior. Sometimes, it is just the head and shoulders. Other times, it is the whole body swaying from side to side.  Head-bobbing may also be associated with swaying.


Sometimes, in times of extreme crisis (or after an intense exercise class), all you want to do is grab your legs and rock back and forth.

It’s an almost comforting feeling from the stress and discomfort happening around you.

That’s exactly what some great ape species, such as chimps and gorillas, do in captivity. This behavior  has been directly associated with poor welfare standards.

Over-Grooming and Self-Mutilation

We all know monkeys like to groom themselves one another. It is an important aspect of non-human primate social living.

But what happens if a typical tree-dwelling monkey is kept in isolation or if they’re highly stressed? Well, they may begin to over-groom.

This doesn’t sound too bad, right?

Unfortunately, over-grooming can lead to self-mutilation, such as pulling out clumps of hair. This can lead to patches of red, broken skin, which can cause infections.

Unfortunately, in our digital world, these behaviors are almost encouraged. What looks cute and funny to us, is an animal in high distress.

Humans have a tendency to anthropomorphize things – that is, relating non-human behavior to human behaviors.

A bear twisting its neck in circles, a giraffe seductively sucking a pole, or a monkey biting their nails. They seem funny on face value, because we can relate to their behavior. Afterall, how many of you have bitten your nails?

Consequently, videos are taken and shared online, where they can amass thousands, if not millions, of views. More videos circulate, as more and more people want the opportunity to capture a funny animal clip.

But, what we’re really doing is promoting the suffering of captive animals further.

How Can A Zoo Prevent Zoochosis?

Zoochosis can happen to any animal, in any captive setting.

However, there are preventative steps wildlife institutions can take to minimise the risk of animals developing zoochosis.

Replicate Natural Environments

Of course, an institution will never fully be able to replicate an animal’s natural environment 100% – there are too many variables to factor in.

However, with the right amount of talent and knowledge of an animal’s life-histories and physiology, enclosures can be designed to mimic the natural environment as closely as possible.

Some of the best wildlife exhibits will feature areas with climate control, to replicate a natural environment. This should be implemented in areas housing animals from the extremes, such as polar bears in the Arctic, to reptiles in the deserts.

Alongside climate control, natural features such as waterfalls, lakes, vegetation and rockwork can help replicate natural environments, promoting a healthy lifestyle in captive species.

Introduce A Varied Diet

A poor diet can have devastating consequences on captive animals. Couple this with a lack of exercise from inadequate space, we have some serious health problems on our hands.

Let’s take capuchin monkeys, for example. These New World primates are omnivores, and eat a wide range of plant and animal protein. Fruits, nuts, eggs, buds, insects, small vertebrates. You name it, a capuchin will most likely try and eat it.

But what happens if it is just fed fruit?

Well, we start to see a range of health problems that are comparable to humans consuming too much sugar – Type II Diabetes.

A varied diet will not only keep an animal healthy, but it will also keep them intrigued and interested, adding mental stimulation.

This also extends to herbivorous animals. Sloths, for example, can eat over 90 different species of leaves. However, individual personal preferences means that they tend to eat around just 7 varieties. This is why it is important to change diets  to see what food item is most favorable.

Mental Stimulation (Enrichment)

Do you ever go into an empty room and just sit there? You don’t turn on the TV. You don’t pick up a book. You don’t even get a snack. You just sit there.

Probably not.

We need some form of entertainment to stimulate our mind – whether it comes from simple, low-level cognitive stimulants, such as the TV, or advanced cognitive stimulants, such as puzzles.

Animals are the same.

They need enrichment!

Enrichment is the introduction of novel items or scents to stimulate natural behavior. Zoos, and other wildlife institutions, can achieve this by using an array of objects with differing tactile and sensory qualities, or create challenging puzzles that require high-cognitive abilities.

But, for enrichment to be effective, you need to know the life-histories of each animal. For example, you can’t give an animal with low dexterity, such as a wild boar, a food-related puzzle. However, give the same puzzle to a raccoon or monkey, and they will be entertained for as long as it takes them to retrieve the food reward

Enrichment can even extend to the regular feeding time of captive animals. Instead of presenting the animal food in a bowl from it to eat out of, staff should spread food around in different locations of the enclosure. This encourages foraging behaviors to replicate wild techniques.

Does This Mean All Zoos Are Bad?

Well, this very much depends on your personal standpoint.

If done correctly, zoos can be an incredibly powerful asset to aid in conservation – both indirectly and directly.

Many zoos have both in-situ and ex-situ conservation strategies that can aid in research and population increases in the wild. Zoos also attract a large range of audiences, and help inspire a positive change by informing the general public on how they can help support species across the globe.

In “good” zoos, detailed reports should be kept on each and every individual under their care. Staff should do routine checks to record behavior’s, social interactions and physical and mental well-being. With such detailed reports and assessments, staff are able to react quickly should an animal change their behavior and a cause can be addressed.

And, as we discussed above, a range of mental and physical stimulation should be included daily. This shouldn’t be the same every day, rather a novel stimulant, whether it is a food sensory, to keep an animal entertained.

Closing Thoughts

I wanted to hold off from using the analogy of prison for as long as possible.

But, how different are they?

An animal, trapped in a captive setting against its will, with no mental stimulation, will almost always develop some form of trauma.

More often than not, it is zoochosis.

Animals suffering from zoochosis have been recorded displaying a wide range of stereotypical behaviors, such as rocking and self-mutilation. However, one of the most common symptoms associated with zoochosis is pacing back and forth with no true purpose.

It is a sad existence, and certainly not a life worth living, just for the sole purpose of human entertainment.

Avoid institutions that exploit animals, keeps them in cramped conditions or in unnatural enclosures.

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