Challenge at the zoo, or why puzzles are good for zoo animals

Challenge at the zoo, or why puzzles are good for zoo animals
Students had a unique opportunity to learn about the zoo keeper profession at the Moscow Zoo on St Tatyana Day. But if they thought nothing could be easier than cleaning enclosures and feeding the animals, they were in for a surprise, because the keepers also have to create the illusion that the animals in captivity have control over their lives. How do specialists manage to do that and why do zoologists have to make the animals’ lives more complicated?

Ponies chew on paper, a tiger plays with a large plastic barrel, Arctic wolves attack a bright traffic cone and monkeys mess around with a rubber hose. Polar bears sport a bright football and foxes investigate puzzle feeders. “They playabsolutely ,” we think when looking at them, “because what else can they do when they don’t need to hunt and avoid predators?”

However, it’s not all fun and games. Animals whose genes tells them to hunt, battle for territory and survive in a constantly changing environment, suffer from monotony in the captivity. They know the exact time when the food will come and the exact place it will be put, so why make any effort? They can just wait.

Their concerns in the wild and in captivity are different. Once researchers released tamarins that were born in captivity and tried to adapt them to the wild. But the experiment absolutely failed. It turned out that the tamarins could not find food, fell from trees and even did not know how to make sleeping nests because they had never done it before. The first generation of tamarins died. Then experts came to realise that the animals needed to be taught not only to climb trees and search for food, but also to avoid predators.

An interesting experiment was conducted on squirrel monkeys. A model of a bird of prey was installed above their enclosure. In the wild, predators hunt these small monkeys, and the latter always try to hide when they see a large bird shadow. The silhouette appeared above the enclosure regularly, and the monkeys who were afraid at first, began acting more coordinated as a group. They communicated more to each other and made more connections.

So researchers are now thinking of making the enclosure interior more complex and making the search for food harder, so the species would retain its traits in captivity and the animals’ lives would be more interesting.


Wheels aren’t just for hamsters

Seven Indian palm squirrels have received a bar with a toilet paper roll on it and a treat inside. “The animals have to find a way to hold onto the tube and get the treat,” says Irina Voshchanova, a research adviser at the Moscow Zoo. However, the squirrels are cautious about the roll and are not used to it yet.

Ирина Вощанова, научный сотрудник Московского зоопарка

But they like a wheel were they can run. Even in large enclosures, animals lack mobility, and this exercise machine is important to them. They also enjoy a hammock and a papier mache piñata with a treat inside. To reach the food, the squirrels have to find a way in.

A bright coloured fabric house hangs from a corner of the enclosure, similar to those bought for pet hamsters. The squirrels love it. “Animals need to have many shelters,” says Irina Voshchanova. The zoo keepers also try to make the interior pretty (for the sake of the visitors, as the animals do not care much).

Monkey world: Sack cloth, a box with hay and red rugs

Monkeys might not be beauty connoisseurs but bright legos and orange-and-white traffic cones are something they do enjoy. “Monkeys have colour vision, and colours are important to them,” said Moscow Zoo researcher Irina Voshchanova. “They are quite psychologically advanced animals who are attracted to objects with new shapes and new tactile sensations. They examine them, bite them, but, like in other cases, if they discover they cannot find any use for the object, they lose interest.” And indeed, the weeper capuchin appears more interested in food at the moment.

Meanwhile, a group of mandrills are happily tearing the bark off a pine-tree branch. They are very good at manipulating objects, and they must have something to apply this skill to. This is why they have lots of small objects for peeling in their enclosure. Pine-trees are perfect for this activity, while fir-trees do not seem to interest the mandrills. They also seem to be amazed by the blue pen cap that the keeper is holding in his hand. One of them is totally absorbed with a piece of hose: rubber is not only nice to chew on but also has hidden treats.

There is a box with hay in the corner of the eastern colobus monkeys’ enclosure. The monkeys root around in it to find food. Voshchanova said, “This way each animals has the chance of finding its own delicious treat. And there is nothing to guard.” Squirrel monkeys have a tricky food dispenser: three cups placed on a plastic tube. If they want to get their food, they have to be clever enough to lift the cup, put their paw into the tube and take out the food.

Tamarins have bits of sack cloth hanging in their enclosure, and there is a reason for it. For one, their babies like to climb on the the cloth. The cloth also functions as a screen for hiding. A monkey that grew up in a complex environment would guess that if their partner goes behind the screen on the one end, he will come out on the other and can be met there. “An animal that never had such obstacles will be unable to understand it,” said Voshchanova.

Monkey enclosures in general have quite intricate interiors. They have nets that can be weaved or used as a hiding place, climbing ropes, shaky platforms, ladders fixed at the top end only, hanging bridges, swinging snags, hammocks for resting and swings. It is important for monkeys to keep practicing their ability to move on unsteady surfaces and keep their balance.

In summer, Moscow Zoo gibbons move to their “country home” – an island in the middle of the pond with trees and special structures for climbing. The only way to get here from their warm feeding and sleeping house is across a hanging bridge. Zoo staff once noticed that the animals preferred to climb only strong sturdy branches and were scared of this shaky bridge, though in the wild gibbons soar from tree to tree at breath-taking heights. Since then, the hanging bridge together with numerous ropes and tree branches have also been used in the gibbons’ winter enclosure 

Large plastic barrels or balls are used as special rolling food dispensers. Mandrills find such dispensers too heavy to shake to get the food out, but large orangutans love it. A male who saw our group as a rival made a racket with the swings and then took out his irritation on the poor barrel.

“In the wild, females keep away because a male can be dangerous. Here they have fewer opportunities to hide than is advisable. We are trying to address this problem by structuring the space in a complex way. A male is normally big, heavy and less agile and therefore he cannot move around so quickly using ropes, for example,” Voshchanova said.

There are bits of rug scattered on the floor, and a teenaged orangutan is hiding behind a piece of cloth at the second level of the enclosure. In the wild, these animals also love to cover themselves with various objects, including leaves in the rain, which makes them feel safe. “If a young monkey receives a new object and it makes the animal worried, the monkey sometimes takes a piece of rug or sack cloth, covers itself and watches the object for some time until it has enough courage to cautiously approach the unknown object,” the zoo researcher said.

They also use the rugs to directly check how safe the new object is. Orangutans, for example, have no worries using the green food ball dispenser now but when it was first brought to them, the animals tried to hit the ball with a sack cloth to see if it was alive and could run.

The monkeys (anthropoids) regard the zoo visitors with interest. Voshchanova said, “We used to come to this hall for aerobic classes after it closed. Throughout the two hours that we exercised, a female monkey would be glued to the window. She knew when it was going to start, made herself comfortable at her favourite place near the window, and sat there and waited, all but propping her head on her hand.” The animal did not try to repeat the aerobics movements as she was not sure what they meant.

Tiger quest

The Amur tiger is not paying attention to the few visitors at the zoo. He is too busy chewing on a large plastic barrel. There are several of these barrels in the enclosure; some of them have already been taken down by the tiger, and another one with a tire on it is hanging above the floor. “These barrels contain treats, and the tiger has to struggle a lot to take the barrel down. Then it can carry it around and take treats from it,” says Alexei Podturkin, research fellow at the zoo.

The large cat has its own training programme that was developed by the zoo staff. They began developing it after they saw that the tiger pointlessly circled the enclosure, was afraid of everything new and avoided any new item it received.

At first they hung a big bag with food inside, but the tiger quickly learned to take it down. The tasks got more complicated, and now the tiger has to work at getting to the heavy barrels. “It has to figure out how to take the barrel down using both physical strength and brains to find a way to get the food,” Irina Voshchanova said.

Activities like this improve the animal’s physical and emotional condition. “It became more active and is interested in what is around it. For instance, in a month since the new programme, we noticed that the tiger was walking on the edge of the ditch and was watching something intensely. It turned out he had begun noticing his neighbors, a Père David's deer and a camel.”

Mats and portion control for Przewalski's horse

In the Przewalski's horse enclosure, Irina Voshchanova points out the plastic mats nailed to the walls. The animals rub against them to shed moulted hair. This is a decorative element which at the same time makes the lives of animals more comfortable.

The special feeder promotes normal feeding behavior for the horses. Horses wander and spend most of their day foraging and will eat an entire portion of food if they receive it. When there is nothing to eat, they will start chewing on the fence or the bars of the enclosure, and even start to suck air which leads to digestion problems and shortens their lives.

“The simple way to deal with this is to only allow them to eat small portions all day. For instance, this could be a barrel with small holes in it or a welded wire fabric so the horses can take one straw at a time, or a hollow plastic ball which the horses have to roll around to get food from,” Irina Voshchanova said.

The new life of a fearful jackal

A female jackal looks out from her den, walks the steps, fools around the enclosure and seems to be enjoying the attention. Pieces of cardboard lay scattered on the floor. These are the remains of cardboard boxes where keepers hid food. Some boxes were put on the floor, some hung, but the animal has opened and done away with them all by the time we approached her.

It is hard to believe that this female was so afraid. She used to hide or run around in circles showing her discomfort. Jackals are very shy animals. “They know that if they don’t watch, something will attack,” Irina said. To let the animal get used to its home, the zoo staff had to experiment a lot. They offered the jackal hanging barrels and boxes with food, but it was scared and didn’t know what to do with them. “This shows that what works for more experienced animals, doesn’t necessarily work with the animals that don’t have much experience at solving problems,” Irina said.

The keepers had to go slowly in their attempt to adjust the animal to changes. For instance, she had to get used to having to search for hidden food. “The animal learned where the food was and knew that she would be able to get it. After that, her behavior changed, she began roaming the enclosure and stopped circling the same route over and over,” said Alexei Podturkin. The project has ended, and now the developments learned by the researchers are used by zoologists.

Animal Psychotherapy

Why does an animal demonstrate unnatural behaviour? Zoo workers do not always know the reason. “It happens a lot because of difficulties when young,” said Moscow zoo researcher Irina Voshchanova. “Just like with people, those who grew up in poverty, are undeveloped and usually don’t came across difficulties when they are young.” It could be some unhappy life experience, for example, if an animal was kept in conditions where it was unable to change anything. Care takers need to correct unnatural behaviour and find a way to make an animal’s life fuller and more comfortable.

A zoologist’s job is to make an animal’s life more difficult 

The enclosure’s interior has to be changed from time to time to encourage the animals to be more proactive, to explore a familiar area anew, and make their behaviour more varied. Some zoos change the interior completely, for example, once every six months. But radical changes can upset the animals, which is why gradual change is better. “For example, researchers of the Moscow Zoo have demonstrated for the first time what effect a totally different interior may produce,” said Alexei Podturkin. “If there are too many changes, an animal will start to not feel well. So nobody doubts that a static interiors are unhealthy for animals, but even changes can have an adverse effect.”

Keepers watch their animals day by day and try to sense the moment when everything becomes too stable, too routine.  Then it is time for a change. Conversely, if an animal’s behavior changes, it is best to avoid any alterations in the enclosure to avoid any further stress for the animals.

We cannot write out a prescription and say: “Do This”

Animals need constant supervision. Researchers also have to monitor how their behavior programmes affect the animals. “These are living creatures,” said Irina Voshchanova. “There is never a guaranteed result. It can be forecast with a certain degree of probability but we always have to remember that we might have overlooked something and that an animal can react differently. It is always an experiment.”


Sometimes we buy food dispensers for the animals at regular pet shops. Toys for dogs are also quite popular. Some items for reinvigorating enclosures have to be purchased overseas. But most often, zoo workers have to make use of everyday items in an unusual and clever way.

Unbreakable things lose their value

Animals quickly lose interest in sturdy items, whereas plastic barrels and bright traffic cones that can be clawed or chewed are very popular with mammals. “When we were only looking for them, I’d walk along under construction roads to check out the traffic cones,” Irina Voshchanova says with laughter. “Then we asked the cone manufacturer how thick the plastic was and talked about whether it would be good for chewing. People were confused as to why anyone would chew on a traffic cone anyway.”

Volunteers and young zoologists from the zoo club share some of the work at the zoo. For example, they make peanut feeders for squirrels and birds. A papier-mâché ball is easy to make but time-consuming, so the zoo will ask volunteers for help. “They are made of safe materials under the supervision of an experienced instructor,” Irina Voshchanova said. “Last summer, children made peanut feeders for birds and monkeys at the zoo club. Then the staff filled them with food and gave them to the animals in front of the children.

How it all started

People have been keeping animals in zoos for hundreds of years but nobody worried about how the animals felt in captivity until the 1920s-30s. First, caretakers changed their attitude towards the animals bred for food, and began to realise that animals have needs too. It was not about sympathy, said Irina Voshchanova, “people don’t want to see suffering, but they began to understand that the life of the animals they used for meat wasn’t great.”

Gradually, experience about how animals are kept in zoos became more well known. For example, at first, the lions at the London Zoo didn’t live more than two years. As a result, activists in Europe and the US formed animal protection movements, and some people stopped going to zoos in protest against the perceived suffering.

Zoos began to be replaced by different kinds of facilities in Europe and then in the US. One example from the time was Carl Hagenbeck’s project at the Hamburg Zoo. He suggested that animals be exposed to conditions similar to those in the wild. They were kept close to each other in open enclosures but separate from visitors by a moat. It was a breakthrough approach, although Hagenbeck must have been more concerned about visitor interest than the animals’ quality of life. But the zoo staff noticed changes in the animals’ behaviour.

People’s ideas about an animal’s basic needs began to take shape at this time. Needs were created from opposites: freedom from pain, thirst and hunger, stress and worry, freedom to behave naturally. But this was not enough, so researchers began to study animals in the wild, and they used what they learned to improve an animal’s life in an enclosure.

Work ennobles animals too

In the 1930s-1940s, the world embraced the idea that work “ennobled man” and benefited people’s well-being. Curiously, this idea spread to zoos as well. In the 1950s, researchers came to realise that animals could get bored because they did not have to struggle in the search for food. Zoo animals, it was thought, should be forced to solve tasks to get food. The idea worked.

The first attempts to implement this concept did not pay off because they did not take into account an animal’s natural behavior and resembled circus tricks. One of the first projects was prize machines in which apes had to insert a token to get food. This idea was heavily criticized given the lack of vending machines in the wild.

The idea of environmental enrichment became fashionable around 1978. The objective was not to train the animal, but to create an environment where it could behave the same way as in the wild. The idea was that a correctly organized environment would form natural and interesting behaviour.

Researchers join the effort

Zoo experts and researchers came together to analyse their experience in this area and to develop action plans for the first time in 1993. Since then, they have had regular meetings, communicated online, posted videos with new developments, discussed and improved each other’s projects.

The concept of environmental enrichment has also changed. For instance, 30-40 years ago, a rope in a monkey enclosure was an element of enrichment, but now it is a minimal requirement. New approaches include the positive experience concept. “It’s important to not only enrich the animal’s life with some events, but also with difficulties they can handle. It improves their attitude towards life,” said Irina Voshchanova.

Neurobiological and physiological researchhave shown that environment enrichment improves memory and brain mass, and increase resilience to stress. If the animal is born into an enriched environment, it will show diverse natural behavior.

Experiences from Russian and foreign zoos were compiled by Alexei Podturkin and posted on an online database, the first such database in Russia. It was launched on the Moscow Zoo website last June. The catalogue includes over 200 projects with videos, photos, scientific commentaries, and references to sources and instructions. The database is constantly updated.

The catalogue allows searching for class, category, group, animal species, and subcategories with examples of enriched environments. Most of the projects were developed by foreign researchers, such as a feeder that slides along a hanging rope, a wooden ball with cracks with food, a flax piñata and other feeding puzzles. The Russian developments include food hung from a rope, a raft for turtles, a ball on a rope for cheetahs and other items. After perusing the catalogue, viewers might consider enriching the life of their elderly pet rabbit.