How much does letting domestic cats go outside affect wildlife conservation?

There are many cat owners, some of whom are my online friends, who strongly support keeping cats inside all the time. This article is not a criticism of them because I understand the motivation to keep cats inside. It is meant to be a fairly cold, scientific discussion about cats and conservation as at early 2019. I have a fairly neutral stance on this issue.

Concrete evidence

There is no concrete evidence (I emphasis the word ‘concrete’) that outside domestic cats affect wildlife populations year-on-year at a national level. There is a copious amount of speculated statistics on cat predation but it has to be admitted that the evidence is inconclusive that outside cats have a permanent negative impact on wildlife populations nationally (baring the known extinctions on small oceanic islands).

Therefore, in terms of wildlife conservation it is logical for cat owners who want to let their cats go outside to keep doing it. Clearly there are other reasons such as in the US coyotes preying on cats but this page concerns conservation reasons for keeping cats inside, full-time. This is the reason hammered home by ornithologists.

Also for the past ten years there has been a growing campaign against wandering domestic and feral cats. These online campaigns may have hardened the hearts of many cat owners to reject calls to keep their cats inside.

Australia is a testing ground

All of the studies on cat predation are based on ‘estimates’ and guesstimates. You only have to read the studies to constantly see words such as ‘perhaps’ and ‘estimated’ and the conditional tense being used. They often conclude by suggesting further research i.e. they are inconclusive studies. The conclusions do not present hard evidence at a national level. It is only such evidence which will convince cat owners to alter their ways.

For instance the experts in Australia don’t even know the number of feral cats in their country so how can the authorities begin to calculate the impact they have on wildlife? Their estimates of feral cat population size varies wildly.

Also in Australia, where restrictions have been placed on outdoor access for domestic cats, there appears to have been no great improvements in population sizes of animals upon which cats prey.

Cats benefit conservation?

Then there are counter arguments. Cats prey on rats and rats eat bird’s eggs, young birds and mammals. Consequently, in certain areas cats may have a positive impact on wildlife populations.

We constantly read of high number of birds killed by cats in the USA. The numbers are said to be in the billions and yet we don’t see this mass slaughter translated to observed evidence.

Habitat loss

In the UK, the RSPB say that habitat loss is the biggest bird killer and that blue tits are common prey for cats yet over the last 25 years this bird species has grown in populations size. I don’t want to harp on but there is no doubt that humans have a far greater negative impact on wildlife conservation than cats so lets prioritise that.

Until there is concrete evidence that cats have a lasting negative impact on wildlife population sizes, cat owners will be justifiably sceptical and carry on as they are.