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.

Domestic cat predation
Photo by Nastia Rodionova
Two useful tags. Click either to see the articles:- Toxic to cats | Dangers to cats

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.

15 thoughts on “How much does letting domestic cats go outside affect wildlife conservation?”

  1. Every time this issue comes up I grit my teeth. Predation is the way of nature, and the ongoing level has far more to do with evolution than the effects of outdoor cats, whether feral, stray or domestic. If you could tally and compare the percentages of predation in the wild, everywhere in the world, the level attributed to feline habitat would be so minimal as to barely be noticeable. Predation would continue on all levels even if no cats were left on earth. And some of the worst predators are of the human kind, I might add. 😠🙄😢💜💜🐾

    • Not a single new argument in support of your denial. No surprise there.

      Felis catus has nothing to do with ‘nature’. It never existed in any naturally-occurring ecosystem anywhere in the world until people selectively-bred and released it. F. catus’ invariable impact has been to destabilize ecosystems wherever they’ve been introduced via hyper-predation and spread of novel diseases.

      A relatively stable ecosystem consists of animals and plants which have co-evolved for tens of thousands–or millions–of years by struggling to eat and not-be-eaten until they attain mutually-sustainable numbers whereby prey species don’t exhaust their food supplies and then starve, and predator species don’t eradicate all their prey and then starve.

      Cats have no place in such a system. They’re reflex-killers. They are, along with dogs, pigs and commensal rodents, the worst invasive terrestrial vertebrates. As for humans being the worst predators, deliberate proliferation of F. catus is, next to habitat destruction, the primary way we’ve earned that title.

      The unnatural nature of your disease-ridden, invasive reflex-killers has caused extinction of 55 birds, 10 rodents, 5 marsupials, 5 lizards and one lagomorph (rabbit-relative). Recent studies indicate eight more species, mostly in Australia, have been wiped out by cats. But you don’t care. Those species aren’t “cute”.

      • Totally disagree with your point of view and your “facts.” The world has changed, yes, but predation in the wild will always remain. The contribution of modern day cats is barely a miniscule part of the whole. I do not need an arsenal. I am not here to argue. This is the end of my conversation. 😑🤔

      • Quote: “I accept your surrender.” I did not know this was a battle of wits. 🤣 Michael, that was no big deal. I know that you do not like us to interact with trolls. I just had to leave a statement because this is a feline informational website. I am not here to do hours of research and look up statistics to refute or satisfy one person’s skewed viewpoint. If I wanted to argue, I would join a debate club. 😼

        • Frances, I don’t read these troll comments or hardly do, so I don’t know what he said or what you are referring to on this occasion. I guess he wants to win an argument. It does not interest me. He’s been banned. I got to it late because I have been busy doing other things.

          I really appreciate your comments though 🙂

  2. Sorry, your so-called ‘study’ is merely anecdote. Nothing scientific about it. Did you do a comparison count, and determine ‘species-richness’ both before and after you introduced cats into a novel system? Did you have a cat-free system with which to compare? Did you analyze stomach contents from your free-roaming cats? Did you even monitor the cats or in any what quantify their kills?

    Correction: I was too kind with the ‘anecdote’ description. I should have used the term ‘lying through one’s teeth’. That’s the cat-advocate’s strategy of first resort.

    In any event, here’s a link to a study in which my friend Sonya Hernandez participated. They used collar-mounted cameras to monitor 50 free-roaming, WELL-FED ‘pet’ cats. We’re talking hard data and first-hand evidence here, not anecdote or “guesstimates”:

    One of their findings was that the cats only brought home 25%-50% of the animals they tortured and slaughtered. The rest where simply left where they were killed.

    Cats are reflex-killers. Their killing and feeding reflexes are governed by different regions of their little brains. This is a ‘paedomorphic’ neurological character-state resulting from human-engendered selection. Cats are hyper-destructive because we bred them that way.

    So I’ve provided a scientific study which demonstrates unconfined cat impact on native wildlife. Got plenty more where that came from.

    But how about you? Can you show quantitative date from your alleged “scientific study” which supports your conclusion? Go ‘head. I’ll wait, but I won’t hold my breath

    • The article is a general overview of the state of play as I see it. I am not referring to a single study. That should be clear.

      The trouble with you is that your ‘science’ is colored by your extreme anger. You hate cats and cannot be objective about cat predation. At least I do my level best to be objective. I have read studies and they are always inconclusive on hard facts.

      And you really struggle to avoid being rude and insulting because you also hate people who like domestic and feral cats.

      • Difference is I can and do back up my arguement with facts you can’t refute. Anyone can when you collide with such facts. Either you flee in shamed silence, or you claim “you don’t have time” to address them.

      • My commment was in reply to Albert Shepis’ ridiculous claim of having “scientifically analyzed” his cats outdoors, not to your article. That didn’t merit a reply.

  3. Yes, habitat loss is often mentioned but not to the extent that cats are blamed for losses caused by that. Neither occurs in a vacuum.

    Being a scientifically minded, fact-based person myself (and neutral on the subject), I did my own study of my cats’ predation many years ago, and their supposed damage has been so minimal it’s not worth mentioning. I was curious and I don’t like to see killings either, so if I became convinced that my cats were causing undue harm, I would have done anything I could to minimize or stop it, even keeping them in permanently. I have been good at supervising and playing with them which helps, I’m sure. I also have neighbors who don’t like cats and who would gladly show me proof of the cats’ predation damage (which I’ve asked for), but they never have. Cat haters assume cats do such damage, and if they do observe one time they assume it happens all the time, which it doesn’t. That’s the mistake the professionals seem to make too. Also, I haven’t seen any study that wasn’t biased or paid for by ornithologists, which is more reason not to trust them.

    Lastly I rarely see, if ever, the positive effect cats have of weeding out those birds who are less effective in being preyed upon, ultimately allowing the effective birds to breed better offspring, creating stronger species overall. This being a well established fact of evolution it can’t be denied. It’s often seen that in isolated conditions, any animal species that doesn’t have natural predators creates generations that become more and more vulnerable.

    So, by my personal observation and those Michael mentioned, it suggests that none of the studies are valid, or not valid yet in my opinion anyway.

    P.S. That I’m a cat owner does not limit my caring for all animals including birds. I’ve cared for horses, have (at risk to my own safety) rescued injured birds from the middle of highways, etc. Brought animal neglect cases to authorities. I like all animals and also have a pet fish and a backyard squirrel.


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