Understand pet cats and wildlife

With a population of about 9 million, cats are by far the most abundant predators in Britain. Yet they are also among the least studied and we know little about their impact on local wildlife.

Understand pet cats and wildlife article spread
With a population of about 9 million, cats are by far the most abundant predators in Britain. Yet they are also one of the least studied – while we understand their social behaviour, we still know remarkably little about their impact on local wildlife.
Here's how to interpret the behaviour of the most loved and loathed British predator.
  • Most cats are owned domestic pets, but there are an estimated 800,000 truly feral cats, owned by no one and living in colonies. An additional unknown number of stray cats move between owners.
  • In suburban Bristol, mean density is 348 cats per km2, with some areas having more than 500 cats per km2. Densities can be even higher in city centres.
  • Trends in cat ownership are rising dramatically. Over the past 12 years, domestic cat numbers have increased from 6.7 to 9.2 million, and this tendency seems set to continue.
  • Cats are popular pets, mainly because they’re low-maintenance – they can be left to roam and only return home to be fed.
  • Cats hunt even when they’re well fed – the drive to hunt is independent of hunger. Farmers exploit this, aware that if farm cats aren’t fed, they will go off looking for food. But when they are well nourished, they remain around the farmyard and have a much bigger impact on the local rats and mice.
  • Cats’ skill as pest controllers has long been exploited – the champion British ‘mouser’ was a male tabby in a Lancashire factory, which killed more than 22,000 mice in 23 years. The champion ‘ratter’ was a female tabby at the old White City stadium in London, which caught 12,480 rats in just six years.
Hunting behaviour
  • Cats are ‘sit-and-wait’ (ambush) hunters – they hide in cover for long periods waiting to pounce, listening out or watching for prey.
  • Like other predators, cats have binocular vision. Sometimes you’ll see them sway their heads from side to side – this helps them to judge the distance they have to pounce.
  • Cats hear much higher-pitched sounds than dogs, an adaptation for hunting small rodents (though not birds, a minor part of their natural prey). This enables them to pinpoint rustles and squeaks made by mice.
  • While stalking prey, cats twitch their tails, possibly a sign of tension or excitement. This can scare birds off, but when hunting rodents from dense cover such movements are invisible.
  • Domestic cats sometimes play with their prey before killing it. This is much rarer in wild cats, and is almost certainly a result of being well fed.
  • In the wild, cats start by bringing dead prey back to their kittens and eat in front of them. Later, they bring back live prey so the youngsters can practise hunting. Pet cats transfer this behaviour to their owners. Maybe they view humans as useless hunters who need a lesson or two!
  • A cat’s killing bite is a juddering jaw movement, which severs its victim’s spinal column. Domestic cats may make these jaw movements when indoors watching garden birds.
The ultimate invasive species
  • Domestic cats have been introduced all around the world and have become feral on most of the Earth’s islands.
  • About 64 per cent of all cat introductions have had a negative impact on local fauna – including extinctions of native species. This is two to three times higher than other introduced predators. Many conservationists consider cats to be the ‘Genghis Khans’ of the biological world.
  • There are up to 20 million feral cats in Australia, and these have led to the decline of many small marsupials. Bandicoots, bettongs and numbats are at particular risk. Australia has responded by creating fenced sanctuaries where all feral species are eradicated.
  • Their most profound impacts are on islands. Cats were introduced to Ascension Island in 1815, when 20 million seabirds nested on the island. By 2000, when a cat eradication programme started, there were no seabirds nesting on the main island.
What wildlife do domestic cats catch?
  • Generally, there is a balance between predators and prey. But because cats get most of their food from their owners, their numbers are not limited by prey availability. This is known as ‘hyperpredation’.
  • Cats younger than two years old catch more wildlife, and predation rates decline with age.
  • In Britain, mammals form 69 per cent of cat prey, birds 24 per cent, amphibians 4 per cent, fish and invertebrates 2 per cent and reptiles 1 per cent.
  • The commonest species caught in suburban gardens (53 per cent of all kills) is the wood mouse.
  • The density of cats compared to birds is extremely high. In Bristol, before the breeding season, there are fewer than four birds per cat. After the breeding season, there are fewer than eight birds per cat.
  • The bird species most frequently caught – blackbird, dunnock, house sparrow and robin – forage on the ground. In a Bedfordshire village, cats were responsible for up to half of all sparrow mortality. In Bristol, the biggest impact is on robins.
  • However, birds caught by cats are generally in poor condition. It’s unclear whether they would have survived anyway.
  • The high density of cats may alter the foraging behaviour of garden birds, and profoundly affect adult and juvenile survival and numbers of young produced. This may be a bigger problem than the number of birds cats actually kill.
  • Cats hunt bats by sitting outside their roosts or along flightpaths and ‘bopping’ them with their paws.
How to prevent cats catching wildlife
  • Several methods have been trialled to prevent cats from killing wildlife, but more work is required to develop completely effective techniques.
  • One study found that, over a four-week period, cats fitted with bells brought in 2.9 prey items; those with no bell brought in 5.5 prey items.
  • Cats with collar-mounted ultrasonic devices returned 38 per cent fewer mammals and 51 per cent fewer birds.
  • The RSPB trialled an ultrasonic device designed to stop cats from entering gardens. It reduced the amount of time they spent in gardens by about 30 per cent.
  • A trial in Australia of cats wearing bibs that prevent them from pouncing on prey found that this stopped 81 per cent from catching birds, 45 per cent from catching mammals and 33 per cent from catching reptiles and frogs.
  • Keeping cats inside is the best way to prevent predation, especially if they are not let out until later in the morning (after birds’ peak feeding time) and brought in before evening.
  • The biggest challenge is to change the attitudes of cat owners.


If you enjoyed this, watch out for our article on a major new study of cats in the magazine this winter! 

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