The zoologist Jordi Casamitjana looks at all the types of cages humans have been keeping non-human animals in, and how they are all bad news

I live in a small flat in London.

It’s small but perfectly adequate. It has everything I need, and I like it very much. One of my favourite parts of it is that I have access to a backyard where I grow my veggies in a veganic way. Another thing I like about it is that it is on the ground floor in a relatively quiet street close to the city centre. However, the best thing about it is that I can freely use it as I please. I can leave anytime I want. I can use my keys to open the front door and I can go to the park every day where I can walk for miles (my daily exercise) and forage some berries, seeds, and leaves to add to my dinner. If I want to, I can leave London at any time and visit other places, so my tiny flat is not a prison; it is not an enclosure where I am kept captive. It’s most definitely not a cage.

However, others less fortunate than I have been kept in cages, and do not have the freedom to go anywhere they want as I have. Other sentient beings have been kept captive in cages of different types for their entire lives. This has been happening for the last 10,000 years since humans began domesticating some animals and keeping them captive. Possibly, it all may have started with a rope. Then some form of enclosure with wooden sticks working as fences. At one point, metal bars and wire mesh may have been added, so people began calling the enclosure a cage. 

Different cultures may have used different types of cages to keep animals in for different reasons, but the basic purpose is essentially the same: to restrict their movement, to keep them captive, to prevent them from leaving, and to do it against their will, while at the same time, be able to observe them from the outside. Sometimes this was done to help those kept captive, but in the vast majority of cases, it was to exploit and abuse them.

Cages are often physical manifestations of a subtle form of violence inflicted against those kept in them. Cages have been key instruments of carnist societies, and as we all have grown up in such societies, we take them for granted. Vegans like myself do not like them, even if we may still be occasionally using them in animal sanctuaries, animal shelters, or wildlife rehabilitation centres.  It may be worth dedicating some time to this subject and finding out the reality of animal cages.

Minuscule Cages


A cage is often defined as a box or enclosure having some openwork for confining or carrying animals, or a barred cell for confining prisoners. For this article, I will broaden the definition to any enclosure design to keep a sentient being captive, because I have found that, over the years, the name cage has become unpopular, and many of those who keep others in cages have replaced it with all sort of euphemisms — such as enclosure, habitat, room, display, unit, system, etc. As the verb “to cage” means to confine or keep in, I think the noun “cage” should be preserved as any structure used by those who cage others to keep them confined.

By returning to the roots of the concept, we can find many types of cages people have used throughout history. I will describe some in order of size, from minuscule to big. 

The smallest cages of all must be the crates domestic pigs are kept in factory farms. These crates not only confine the animals but even prevent them from turning around because they are so minuscule that they are barely bigger than the size of the prisoners. There are two types, gestation crates and farrowing crates. 

Gestation crates (or sow stalls) are metal enclosures in which a farmed sow used for breeding may be kept during pregnancy. They normally measure 6.6 ft x 2.0 ft (2 m x 60 cm), which is just a little longer than the length of an average sow.  Pig farrowing crates are metal cages that mother pigs are placed inside to give birth to their piglets, and to nurse them afterwards. They are also made of metal bars which entirely restrict the movement of mother pigs, as they only can stand, lie down, and take one or two steps forward or backwards. Each cage is also around two metres (6.6 ft) long and less than one metre wide. The main purpose of the farrowing cage is to lower the risk of piglets being crushed by the mother, as pigs have been made so heavy by artificial selection and overfeeding that the normal instincts that would prevent a mother from avoiding such accidents can no longer operate properly (wild pigs do not have this problem). Therefore, these minuscule cages are a human-made problem made to solve another human-made problem. 

Gestation crates and farrowing crates are both extremely cruel forms of confinement which are very similar to each other both in size and purpose (immobilising the pig preventing her from turning or rolling over), but one side of the farrowing crates is grated, allowing the piglets to access the mother pig to nurse. A 2022 study in 17 different countries, some of them where gestation crates are common, some of them where the crates are restricted, and others where gestation crates are completely banned, found that rates of sow mortality were highest in countries using gestation crates.

Another minuscule cage can be found in the bear bile farming industry. Commercial bear bile farming began in China in the 1980s. It was also practised in Vietnam, South Korea, Laos, and Myanmar. By the early 1990s, there were over 400 bear farms in China alone, containing tens of thousands of suffering Asiatic black bears. Like in the case of pigs in the West, the cages the bears are kept in are so small that they cannot turn around or stand on all fours (so they can even be considered smaller as the pigs can at least stand).

Another example of these cages is the type of enclosure where some calves are kept in the veal industry. Calves kept alive for veal may be confined in minuscule cages, called narrow veal crates, that severely restrict their movement and do not allow them to turn around. These crates are designed to limit the calf’s ability to walk and exercise, keeping their muscles tender for the production of veal meat. Banned within the EU, narrow veal crates are still used in the US and many other countries. 

Miniscule cages can also be found in the exotic pet trade industry, often the containers in which the animals are transported. Reptiles and amphibians exhibited in pet trade fairs are often kept in minuscule plastic containers that do not allow them to turn around. 

Finally, the other types of minuscule cages are those used to transport animals (often to slaughterhouses) in such a way they cannot turn around. In some cases, the cage may be bigger but many animals are kept in them, so they cannot move and turn. Cows and pigs are often transported in these conditions. Dogs used for the food trade in countries such as China and Korea are often transported inside bags so they cannot turn around either. 

Tiny Cages


If we increase the size of the cages enough so the animals can turn around, but cannot move in any direction more than thrice the size of their bodies, I will call these “tiny cages”. Several animals are kept in these types of cages.

One such animal is the Betta fish, also known as the Siamese fighting fish (Betta Splendens). They can be found in pet shops kept in tiny barren water containers no bigger than 3 times the length of their body (I have seen them in UK pet shops kept in even smaller ones). Being flexible, they can turn around and face any direction, but this is pretty much it. Despite frequently being displayed and sold in tiny containers in the pet trade, Bettas do best in larger environments (so the idea that they like the small containers because they are solitary air-breathing anabantoids who live in puddles is a myth). The aquarium industry even euphemistically calls the tiny cages it provides “nano” aquariums. The Anabantoid Association guidelines state that the smallest tank suitable for Siamese fighters should have 5 litres of volume, but you will find them displayed in pet shops in much smaller containers than that. 

Bettas are very territorial fishes who fight with other males if kept in the same tank. Because of that, in Cambodia and other far-eastern Asian countries, such as Thailand and Vietnam, people use these fishes to organise fights and bet on the winner. In a typical fight, two males are placed in one jar, prompting a mutual attack. The victor is declared when one fish retreats to the jar’s perimeter chased by the other. In Cambodia, the activity is only illegal when the owners of the fishes bet on the outcome. Before and after the fight, they are kept in tiny tanks. 

Many people may not have heard of Betta fishes, but everyone knows about the next animal unfortunately kept in tiny cages: laying hens. The size of battery cages where most laying hens are kept in many Western countries varies depending on regulations, but they are generally very small, with a usable space per hen to a standard sheet of paper (around 90 square inches). In the US, under the UEP Certified standards, a battery cage system must allow 67 – 86 in sq of usable space per bird

Although several countries have banned the original battery cages for hens, they still allow “enriched” cages that are slightly bigger, but still tiny. The EU, for instance, prohibited classical battery cages in 2012 with the Council of the European Union Directive 1999/74/EC, replacing them with “enriched” or “furnished” cages, offering slightly more space and some nesting materials (for all intents and purposes they are still battery cages but by making them bigger and changing their name, politicians can fool their citizens by claiming they have banned them). Under this directive, enriched cages must be at least 45 centimetres (18 inches) high and must provide each hen with at least 750 square centimetres (116 square inches) of space; 600 square centimetres (93 sq in) of this must be “usable area” – the other 150 square centimetres (23 sq in) is for a nest-box.

The UK also enforces similar regulations. The enriched cages now have to provide 600 cm squared useable space per bird, still less than the size of an A4 piece of paper each. 

Other animals often kept in tiny cages are rabbits. The farming of rabbits typically involves confining them in small, overcrowded cages that provide minimal space for movement, denying rabbits the ability to express their natural behaviours, such as hopping, digging, and exploring. In the EU, the majority of rabbits reared for meat are housed in tiny wire cages within large sheds containing 500 to 1,000 breeding females (known as does) and 10 to 20,000 rabbits. These cages are often stacked on top of each other, which can lead to health problems. The lack of adequate exercise and mental stimulation leads to physical and psychological suffering.

The next animals kept in tiny cages are those exploited by the fur industry in fur farms. Foxes, minks, sables, chinchillas, ferrets, and raccoon dogs are kept in tiny wire cages with limited enrichment, which leads to stress and abnormal behaviours. A typical fur farm has open-sided sheds which contain several rows of tiny wire-mesh cages, with floors also made of wire so that faeces can fall to the ground. Cages are stacked one on top of the other, and the animals can see each other which causes them stress. Mink cages are about two-and-a-half feet long, a foot wide, and a foot high, while fox cages are about a foot wider and six inches higher.

Other animals who are often kept in tiny cages are exotic birds. I have witnessed large macaws in the UK kept in small cages so small, only able to take a few steps to either side of the bar where they are perched, unable to extend their wings. In 2003 I conducted an undercover investigation into a random sample of Scottish pet shops. Among several findings, I found that 4% of birds were kept in cages with a floor area smaller than the minimum floor area recommended. I also found that 22% of the birds were kept in enclosures with perches that did not provide enough space to allow all birds to fully stretch their wings without touching each other or the cage walls.

Tiny cages can also be found in the form of small tanks where large aquatic animals are kept, especially in restaurants where they keep lobsters or small public aquaria. In 2024 I conducted an undercover investigation into a random sample of UK public aquaria and I found that in more than half of them (58%) I could find tanks that would be easily identified as ‘bad’ by most people due to their small size, dirtiness, barrenness or poor maintenance. 

Those calves from the veal industry who are not kept in narrow veal crates may still be kept in tiny cages slightly bigger, but which still limit their movement to prevent them from toughening their muscles. 

Also, the animals used in the circus industry tend to be kept in tiny cages between performances. Such cages are very stereotypical as they often have metal bars, as most wild animal cages used to have, but they may also be on wheels so the animal can be transported to the next circus venue. 

Small Cages


The next category in cage size is what I call “small cages”, which are bigger than three times the body size of the animals kept in them, but smaller than 10 times their size. I consider them small because most animals require more space than that to live a decent life and have enough exercise. With the very few exceptions of very sedentary animals or parasites, animals have a minimum home range which is the minimum space they need to have a normal life. The term “home range” describes the area where, under normal circumstances, wild animals spend most of their lives. Each species or subspecies would have a variety of home ranges depending on the exact population analysed and the geography where they are found. From such variation, the smallest home range found is what we call the “minimum home range”. I would also consider a cage to be a “small cage” if it is more than ten times smaller than the minimum home range of the subspecies of the animal kept in it (and it is not a tiny or minuscule cage as described above).

Small cages are what we normally find in zoos and similar zoological collections (such as aquaria). In the past, such cages used to be more “typical” cages in the sense they were openly called cages and they used to have vertical metal bars or wire mesh. These days, they may be bigger, instead of metal bars they may have glass or moats, and they may be called “exhibits” or “habitats”, but they are just fancy cages. 

I did a study that quantified the size of zoo enclosures in the UK in relation to home ranges. In 2003, the then-called Captive Animals’ Protection Society (now called Freedom for Animals) published a scientific paper I wrote titled “Enclosure size in captive wild mammals: A comparison between UK zoological collections and the wild.” In the study, I compared the average enclosure size of a random sample of mammals kept during the years 2000-2001 in a random sample of UK zoos and the minimum home range of these mammals in the wild. I used allometric laws to estimate the home range area, while I measured the enclosure size area with direct observations from videotaped visits to the zoos. Using some formulas proven to give a good enough approximation of the minimum home range, I calculated minimum home ranges and average enclosure sizes of a randomly selected sample of 50 mammal species kept in 51 of the 103 UK zoos randomly selected. I concluded that mammals kept in UK zoological collections during the period 2000-2001 were confined in enclosures that, on average, had an area 100 times smaller than their minimum home range. This means that the vast majority of cages in zoos in the UK, one of the countries that boast to have the best zoos with the most strict licensing regulations, were small cages in 2001, and I am sure they are still small cages now as the sizes of the zoos have not increased significantly (certainly not to a factor of 10 times), while the number of animals kept in them has not decreased significantly after 20 years. 

Another setting with small animal cages is the pheasant farming industry that breeds pheasants to be shot. In the UK, where this is common, the minimum standards that exist regarding the keeping of animals for farming do not apply to “animals intended for use in competitions, shows, cultural or sporting events or activities”, which means that birds farmed for shooting are not afforded even the most basic animal welfare protection. For instance, since January 2012, traditional barren cages for egg-laying hens have been illegal in the EU and UK, but yet, no minimum legal space or enrichment requirements have been implemented for caged pheasants and partridges.

Some overcrowded “cage-free” chicken farms may keep hundreds or thousands of chickens in a shed which effectively limits the movements of each individual to the point one could say they have the same available space to move as if they were kept in a small cage. UK regulations require free-range farmed birds to have at least 4 m sq of outside space, and the indoor barn where the birds perch and lay eggs can have up to nine birds per square metre.

Small cages can also be typical for exotic animals kept as pets, including fishes in aquaria (and the dreaded bowl for goldfishes) and reptiles in terraria. Most hamsters, degus, lizards, snakes, parakeets, budgerigars, canaries, fancy mice, and pet rats are normally kept in these types of cages, as well as most animals used in the vivisection industry.  

Small cages can also be found as temporary accommodation in wildlife rehabilitation centres where wild animals are recovering from a problem before being returned to the wild, and also in animal shelters where dogs or cats are waiting to be adopted by humans. 

Large Cages 


If an enclosure with animals measures between half the minimum home range and the maximum home range of the species or subspecies of the animals kept in it, then I consider it to be a large cage. There are few cages like this. You may think that safari parks provide this type of cage, but most don’t. 

Another conclusion I came to during my study of enclosure sizes in UK zoological collections (which included safari parks) was that the heavier the mammals kept, the bigger the difference between the size of their enclosure and the size of their minimum home range. Between 2000 and 2001, mammals with a body mass bigger than 100 Kg (megafauna, which is what you normally see in safari parks) were confined to enclosures that had an average area 1,000 times smaller than their minimum home range. Safari parks may seem big to you, but they are still small cages for the large animals kept there, because the bigger the animals, the more space they require to have a normal life. Indeed, I remember seeing lions in UK safari parks pacing by the fence of their enclosure, as with other lions I have seen doing the same in tiny cages in inner city zoos. For captive lions, the fence is the source of their frustration, regardless of how big their cage is.

Perhaps one of the few places where we can see large cages may be particularly big low-security human prisons in some countries, but I think these types of cages may be rare for humans too. However, on average, humans imprisoned in developed countries may have bigger cages than non-human animals imprisoned in the same country.  As far as the UK is concerned, when I did the study mentioned, I also calculated what would be the equivalent enclosure size for a human, considering the estimated minimal human home range. The results of my study suggest that if a human mostly living in a small village of about 1 Kilometre square was confined to a space with the same spatial restrictions that wild mammals kept in captivity have in UK zoological collections in 2001, this human would be living in a space approximately of the size of a telephone box, clearly much smaller than the average prison cell.

There may be big ranches that keep cows, bulls, or sheep on fields to graze, but remain fenced in. This may indeed be what I call large cages. Also, some farm animal sanctuaries may fall into this category too.  The same could be said for wildlife parks that are fenced. However, once we reach the maximum home range size for the animals kept, I would no longer consider this captivity, as the animals may never reach the fence, and therefore may never realise that they live in a fenced area, and live their lives as if they were in the wild (this may be the situation of large natural reserves). 

The Anti-Cage Movement


There have been campaigns against cages for many years. When focused on wild animals kept in zoos and aquaria, these campaigns have been run by the anti-captivity movement. Organisations such as Freedom for Animals, the Born Free Foundation, and Zoo Check Canada are good examples of groups belonging to this movement. In the case of farmed animals, organisations against factory farming are leading the campaigns against cages. Animal Welfare groups such as The Humane League, Compassion in World Farming, and Four Paws are part of this anti-cage movement. 

The general public is also adverse to the concept of cages. In March 2024, the Citizens’ Committee of the End the Cage Age European Citizens’ Initiative (ECI) launched legal action on behalf of the 1.4 million people who signed the End the Cage Age ECI against the European Commission for missing its deadline to propose a cage ban in the EU. 

Their collective efforts have led to results in some places. For instance, gestation crates for pigs have been banned in several countries (such as Sweden in 1994, the UK in 1999, and New Zealand in 2015 ) but there is no federal ban on gestation crates in the US. Several states have banned them, including California from January 2024 with the famous Proposition 12. According to a 2018 survey by the National Pork Producers Council, 80% of US pig meat producers use gestation crates as standard practice. In the EU, although not banned, gestation crates must not be used after the fourth week of pregnancy following a 2013 EU Directive. Australia should have phased them out by 2017, but in 2022, it had not yet been done. The problem is that, as we have seen, some countries that have banned gestation crates still allow the use of farrowing crates, which confine mother pigs for shorter periods after giving birth (essentially, the minuscule pig cages have not been banned as claimed, but their use reformed). 

Bear bile farming has been illegal in Vietnam since 1992, but a loophole allows some existing farms to keep bears. On 17th October 2023, the animal welfare organisation Animals Asia rescued Apollo, the last bile bear in Vietnam’s Hai Duong Province, moving her to one of its sanctuaries. With this rescue, out of the 58 provinces in the country, only 17 are left with bile farms. Bear bile farming and bile extraction from Asiatic black bears will be banned in South Korea from 1st January 2026, as the South Korean Ministry of Environment and the Bear Farmers Association signed an agreement to phase out this horrible industry. Around 1,400 bears were kept in the Korean bile bear industry in the mid-2000s, but after the sterilisation programme, the captive bear population declined by 75%. Also, Laos has enacted laws to ban taking more bears from the wild to farm them.

Many European countries have now banned fur farming (or only have banned it for particular species). On 22nd September 2022, Latvia became the 15th European Union country to ban fur farming, and many such bans have happened since the COVID pandemic started, as there is evidence that minks can contract the disease too.

Narrow veal crates were banned across the EU in January 2007 (although bigger cages are allowed). Switzerland banned traditional battery cages for hens in 1992, being the first country to impose such a ban, and Germany followed suit in 2007, five years earlier than required by the EU Directive, which banned them in 2012 throughout the EU territory. The Australian Capital Territory prohibited traditional battery cages in early 2014. In April 2024, the Scottish government announced a new consultation on outlawing the use of any cages to house hens involved in egg production (a survey in 2020 found that 88% of people in the UK believed that using cages in farming was cruel). On 7th December 2012, the New Zealand government implemented a ban on the construction of new battery cages and initiated a ten-year phase-out of all battery cages in the country by 2022 (However, like the UK, the ban still allows producers to use enriched cages, referred to there as “colony cages”). The US lacks a federal ban on battery cages, but the passage of California Proposition 2 in 2008 aimed, in part, at reducing the problems associated with them by setting the standard for space relative to free movement and wingspan, rather than cage size. Proposition 12 went further a few years later, but it has not yet been properly implemented (instead, investigators exposing lack of implementation have been prosecuted). 

Some of this may seem progress, but remember that many of the battery cage bans did not ban the cages themselves, but just one type of cage, as they allowed “enriched” cages that, for the politicians, were much better, but for the animals, may not have created much of a difference (under my classification, both traditional and enriched cages are still “tiny cages”). Additionally, the countries that are considering also banning enriched cages in laying hens (they will be banned in Germany in 2025, in Czechia by 2027, in Slovakia by 2030, and perhaps in Scotland in 2030) will still be keeping hens in overcrowded enclosed sheds (also a cage) which may give the illusion of more freedom but the actual space the hens will be able to use before bumping on another hen may be equivalent to that of a small cage (cage-free does not mean cruelty-free).

Cages Are Bad News


For a vegan like me, animal welfare campaigns that aim to replace one type of cage for another (gestation cages with farrowing cages in pigs, or battery cages with enriched cages in hens) are not good enough, as they forget one important thing: all cages are bad news. When we look at all the different types of cages we humans have created, it does not take long to realise that all of them are “bad news”. Even those used for the benefit of the animals (shelters, rehab centres, vet clinics, etc) are bad in the sense that they are the best solution to an already bad situation (for instance, dogs and cats do not deserve to be kept in shelters, and don’t like to be there). 

Some captive animals, like some exotic birds kept as pets, seem to like their cage as it may be left open to allow them to fly a bit around the house, and they come back to it, but this is just because they see it as a safer familiar place for them than the bigger cage of the house — which would have all doors and windows shut when the birds are roaming, reminding us that it is just a bigger cage the birds would escape from, if given the opportunity. Some animals are so overwhelmed by the frightening world we have created around them, that they may see a cage as a temporary refuge from us. Even large cages in naturalised settings are bad as, at one point (as they are smaller than the animal’s home range), the animals will reach their limits, and become frustrated for not being able to go beyond them. 

Forced captivity is always bad because no animal wants to be captive, so at the very least it will cause distress. However, captivity is also a source of more serious animal welfare problems, because no matter which captive situations we are looking into, they all have what I call “the three hindrances of captivity.”  These are three deficiencies that can be found in any captive situation of an animal (and are even worse in the case of wild animals). These are 1) a reduction of the space the animals’ bodies evolved to live in, 2) a reduction of the quality and quantity of stimuli the animals’ senses evolved to receive, and 3) a reduction of the choices the animals’ brains evolved to make. The longer the animal experiences these hindrances, the more welfare problems will develop (including suffering from zoochosis, a type of mental illness). 

In this article, I have been talking only about cage size. We saw that most cages where non-human animals are kept are either minuscule, tiny, or small, likely to cause enormous, huge, and big problems for the animals, respectively. This is just one of the three hindrances. The other two are no less important, and they can be found in all cage scenarios too (even those with the highest enrichment and the best possible care). There is only one solution to all these captivity problems: the abolition of captivity in any form. This is precisely one of the goals of the vegan world that vegans like me are building, one step at a time. 

If animals are in a cage, something bad has happened. Either to the animals themselves, their parents, their human companions, or even to their ancestors (as for domestic species), but if they ended up in a cage, something bad had already happened. 

The reality of cages is that there is nothing good about them, even when used with the best intentions. 

A cage-free world would be a better world.

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Jordi Casamitjana
“Originally from Catalonia, but resident in the UK for several decades, Jordi is a vegan zoologist and author, who has been involved in different aspects of animal protection for many years. In addition to scientific research, he has worked mostly as an undercover investigator, animal welfare consultant, and animal protection campaigner. He has been an ethical vegan since 2002, and in 2020 he secured the legal protection of all ethical vegans in Great Britain from discrimination in a landmark employment tribunal case that was discussed all over the world. He is also the author of the book, ‘Ethical Vegan: a personal and political journey to change the world’.