Confined, hot and lonely, no wonder Arturo the depressed polar bear is shaking his head

Polar bears are intelligent animals and need company and stimulation. Ahodges7, CC BY-SA

When my six-year-old daughter is stressed she bites her fingernails. Children in maths lessons often respond to the anxiety that doing mathematics causes by swinging their legs. Arturo the polar bear at Mendoza Zoo in Argentina responds to stress by pacing up and down whilst swinging his head from side to side.

So why does Arturo’s abnormal behaviour lead to outcries concerning his psychological well-being? The difference between Arturo and my daughter or reluctant children in maths lessons is that that the stress-related behaviour is no longer related to its triggers.

What does this expression of abnormal behaviour from Arturo tell us about his psychological state? Such behaviour in animals is indicative of a state of poor welfare. In effect, his behaviour tells us there is something wrong. It is common to see such behaviour in animals kept in un-stimulating environments such as barren cages in poor quality zoos. Referred to as stereotypic behaviour, defined by its repetitive movements, unvarying and with no apparent function, it may indicate that the animal is depressed. Studies have shown that changes in the brain chemistry of certain animal species performing such behaviours are similar to those observed in the brains of depressed humans. Infamously, in the 1990s the Calgary Zoo tried to treat its stereotypic polar bears with Prozac.

Stereotypic animal behaviour often looks like obsessive compulsive behaviours in humans, and certain types of abnormal behaviour such as body rocking, pacing, skin picking and hair plucking are common to distressed animals and humans. In fact, Kathy Carlstead at the Honolulu Zoo once made a documentary on abnormal behaviour in captive bears and afterwards received letters from American prisoners saying they did the same thing when locked in their cells.

Some anti-zoo protesters have tried to claim that such abnormal behaviour shows that animals are going mad. This is going too far. These animals are using a strategy to cope with a situation that has negatively affected their sense of well-being. In fact there is behavioural and physiological evidence that this is, in fact, a coping strategy, possibly mediated through the release of neurotransmitters that make creatures feel better.

For example leg swinging by children in class is a natural beta-blocker, reducing heart rate and making them feel less anxious. Thus, some argue the animal is coping with its environment. A university professor and the father of two small children, I can cope with lots of stress over prolonged periods of time, but no-one – least of all I – would argue that such a situation is good for my well-being (whether or not I mitigate the sense of the walls closing in by pacing around my office).

A lot of my sense of well-being is highly dependent on how I see my situation. Is the glass half empty or half full? This is something easy to ask a human, but we cannot ask an animal. Mike Mendl at the University of Bristol came up with a simple method to find out animals’ attitudes. He trained animals that if they went to a point on one side of a room they would get a reward from a bucket, and if they went to the other side the bucket would contain something unpleasant. Placing the bucket in the middle of the room between the two points creates an ambiguous situation. An animal that runs quickly towards the bucket therefore feels there will be something worth having, despite the lack of evidence either way – an optimistic outlook.

Mendl found that animals from enriched, stimulating environments run more quickly towards the bucket than those from barren environments. Dogs that wreck their owner’s home when left alone only slowly approach the ambiguous option compared to those that are not home-wreckers. The test gives an opportunity to sense an animal’s outlook, whether optimistic or pessimistic.

The well-being of animals is not a simple thing to measure or define, and so it is very difficult to encapsulate in law. In the UK, animal welfare laws are based on the Five Freedoms, which require that animals must be free from hunger and thirst; discomfort; pain, injury or disease; fear and distress; and should be free to express their natural patterns of behaviour. Should any of these freedoms be restricted, it’s fair to say the animal’s well-being is eroded.

I run 8km every morning because prevention is better than cure; the same applies to animal welfare – we need to avoid animals developing problems, and this can be done by applying the Five Freedoms and by ensuring rich environment for them to inhabit. Animals with welfare problems like Arturo can be helped by this approach, but it may be that their view of the world is too dark to fully recover.