Our domestic cats are descended from the wildcat (Felis silvestris) and are popular as pets around the world. The 2022 Cats Protection Report estimates that there are around 11 million owned cats around the UK, with a quarter (26%) of households owning a cat. 

However, not all people are cat lovers. There is a growing movement, particularly hotly debated in the U.S., that believes pet cats should be kept indoors. This is to reduce their apparent negative effect on wildlife populations. But is this the right thing to do? 

The arguments against free-roaming cats

The main argument made against allowing cats to roam is usually about their impact on wildlife populations. 

Let’s have a look at why cats can make themselves unpopular outside the home. 


Some widely used statistics from The Mammal Society estimate that over the spring and summer seasons, UK cats predate on up to 100 million creatures, 27 million of which are birds. The most common species caught are the house sparrow, blue tit, blackbird and starling. 

This seems like startling numbers, and may well horrify bird-lovers, but these figures should be interpreted in context. There is currently no evidence that the hunting prowess of domestic cats has had any negative impact on the actual bird populations. Millions of birds die every year, with common causes including starvation and disease, as well as by predators. Cats will often catch the weaker or sick birds, which would likely die anyway. They also predate on hatchlings, which is more emotionally distressing, but realistically, most baby birds do not survive to adult breeding age in the wild. The effect on bird population is therefore not thought to be impactful. 

Populations of bird species that are common in gardens are actually generally increasing. Blue tits, for example, have steadily increased their numbers. However, some species, like the sparrow and starling, have declining populations. And reducing cat predation may help lessen the pressure on these garden birds. Bird species which are most declining in the UK, such as skylarks and corn buntings, are thought to be mostly affected by habitat loss, rather than declining due to over-predation. 

The impact of cat predation is usually concentrated to around 100m of their homes. Within those areas, they have a higher impact on wildlife than wild predators. It can therefore be concluded that the risk to birds and small mammals will be greatest in areas with a high density of domestic cats. 

Indirect effects

Cats may affect wildlife populations even if they do not hunt, by their mere presence. Fear in small mammals and birds can reduce feeding and reproductive behaviours, and impact body condition and vulnerability to predators. A 2013 study found that merely placing a taxidermied cat near to a blackbird nest reduced feeding of their young, and increased nest predation by other birds. 

Feline populations can also provide competition within wildlife populations. If a pet cat eats a mouse, that same mouse cannot then be food for a larger predator such as a buzzard. This therefore may affect population growth of wild predators. 

Cats can transmit disease to wild animals, such as toxoplasmosis or feline leukaemia. They can also modify the populations of other cat species through hybridisation, such as the Scottish Wildcat. 

Other drawbacks to outdoor cats

There are some arguments made to restrict the freedom of cats based on their own safety. Cats who have access outdoors are more at risk of road traffic accidents, predation, injuries, disease, parasites and toxins. There are also those who argue that cats are domestic pets, and should therefore be kept under human control – we do not allow other pets such as dogs, reptiles or rodents to roam free over the environment and potentially other people’s properties. 

On the flip side: the pros of letting cats roam free

No argument would be complete without its opposing view, so here are some thoughts on the positive side of outdoor cats.

Expressing natural behaviours

Felines are generally territorial, and are highly motivated to patrol a peripheral territory away from their core ‘home’. This area is likely to be where they find food, toilet and interact with other cats. The ability to perform innate behaviours is linked to positive welfare, and if this is restrained, cats may suffer from stress and frustration. 


Cats are generally seen as being more aloof and independent than that other popular household pet: the dog. Cat owners are less likely to play, train and exercise their pets as compared to dog owners. However, cats still need both mental and physical stimulation, and therefore their welfare may suffer if restrained indoors with no enrichment opportunities. 


Obesity is a rising problem in the domestic feline world, with potentially between a third and a half of pet cats being overweight in the UK. Outdoor access provides essential exercise for our feline friends, as opposed to the extremely sedentary lifestyle of an indoor cat. 

So, what’s the answer?

As with all ethical questions, there is no clear answer. Cats are obligate carnivores, and adept hunters, and their growing numbers in the UK may threaten natural wildlife. However, cats also have the right to exhibit their natural behaviours and not have their welfare restricted. 

Is there a middle ground?

Compromise, compromise, compromise! There may well be some concessions that can be made to reduce the impact of our cats, without restricting their happiness.

If you’re concerned about the harm your cat may be doing, but also worry about the negative impact for your cat if you choose to keep them inside, there are some suggestions to help you navigate this difficult balance.

  • Make your garden more bird-friendly if you have cats by following these tips from the RSPB
  • Consider the use of a bell, or limit your cat’s outside time, to reduce the amount and success of hunting behaviour
  • Feed your cat a high protein diet and engage in lots of active play to reduce hunting behaviours. 
  • Consider a half-way house of an enclosed outdoor area in your garden, where your cat can roam and explore without predating on birds and small mammals.

If you are very concerned about wildlife populations and don’t want a cat who can cause havoc outside, consider these points.

  • It can be difficult to suddenly restrict a cat indoors who has been used to roaming outside. If you want an indoor cat, consider adopting an older cat who has always been a housecat, or a kitten who can be kept indoors from a young age. Certain breeds may be more suitable for indoor life. 
  • If you are keeping a cat indoors, ensure that their diet is appropriate, and that they are provided with ample opportunity to exercise, and perform hunting behaviours through play and enrichment. 

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