Assessing Domestic Cat Predation on Wildlife

It is impossible to accurately assess the extent of domestic cat predation on wildlife. The latest high profile attempt in a study in the UK supports that statement. The latest UK cat predation study is weak, in my opinion. Yet the findings of the study are reported on major newspaper websites as providing definitive answers and the general tone of the reporting is that the domestic cat kills a lot of wildlife, particularly birds. This is misleading and a misrepresentation of the findings of the study. The reason for this is:

  • the study is written up in a very opaque, near impregnable style designed to be read by other scientists. I feel it is a bad decision to write in this style as people from all backgrounds should be able to read the report. On the upside the authors have kindly allowed access by anyone. Often access to reports like this have to be bought for $30+.
  • newspapers like to sensationalize and scientific studies are rarely sensational.
Cat Stalking Prey

Cat Stalking Prey

Problems With Assessing Domestic Cat Predation Accurately

All general cat predation studies make presumptions and extrapolate conclusions. What I mean is this. You study a sample of cats in a certain area doing certain things and then based on other studies or on your own presumptions you decide that all cats across the country do the same thing. That method has an element of “hit and hope” about it. It is pot luck as to whether the conclusions are accurate or not. The conclusions might be accurate but you don’t know. If you can’t be sure of the conclusions, they are not very useful.

The current study is a very good case in point. The study is called:

Spatio-Temporal Variation in Predation by Urban Domestic Cats (Felis catus) and the Acceptability of Possible Management Actions in the UK – by Rebecca L. Thomas and colleagues.

It is, basically, about domestic cat predation and how cat owners manage it or don’t want to bother to manage it. I have dissected out some major statements from the study. I am allowed to quote them.

Key Weakness

A key weakness in the study on assessing how much wildlife cats kill is that the authors asked cat owners in Reading, UK, to complete a questionnaire in which they disclosed how much wildlife their cats brought home over the year. The scientist then used other studies to decide that cats actually killed 3.3 times that number of animals (the actual figure they came up with is 18.3 animals per cat per year) . The trouble with this is that we don’t know how good the previous studies are; but we told that they include estimates that vary a lot. In short it seems like guesswork to me. The scientists:

elected to use a return rate of 30% (i.e. a conversion factor of 3.3), as this would generate minimum estimates of predation rates…”

Note the word “elected”. It was a decision they made under what appears to have been difficult conditions (vague reports). As a result the conclusions of this study are written in a style that indicates great uncertainty about the accuracy of the results.

“In summary, our data suggest that the numbers of birds killed by pet cats in some localities within urban areas may be sufficiently large that they could be negatively affecting prey populations. In comparison, most urban residents did not consider cat predation to be a significant problem.” – note that the use of language is conditional and cautious. It is inconclusive.

“Overall, cat predation did appear to be of sufficient magnitude to affect some prey populations, although further investigation of some key aspects of cat predation is warranted.” – an admission that the findings are inconclusive.

The study also makes some interesting statements, if you can find them. For example regarding the density of bird populations in certain parts of the UK the study seems to conclude that bird populations have increased in the area where the study took place (Reading).

“…..avian density within the UK has been shown to increase generally within the range 620–3201 houses km−2, which was the range present in the current study….”

My Conclusion

Take these scientific studies on cat predation with a pinch of salt. Even though they are carried out by scientists they don’t know what cats are doing across the country. The overall conclusion that I deduce from the studies that I have seen is that the domestic cat mainly hunts mice and other rodents and not birds and has no substantial impact on bird populations.

Other Findings From the UK Study

This is a bulleted list of some other findings:

  • 65% of cat prey are mammals of which the wood mouse made up 40%. Birds were 30% of animals preyed on.
  • About a quarter of households in the study area kept a cat or cats. They had on average 1.54 cats each.
  • Very few of the cat owners in the survey – about 1 in 10 (10%) had views on cats killing wildlife…“Few cat-owners (7%) and non-owners (12%) listed consequences for wildlife as a nuisance value in response to open-ended questions in face-to-face surveys..”
  • The most popular way to manage and prevent cat preying “was fitting pets with a collar-mounted anti-predation device.”

I’ll leave it there, otherwise this page will start to get as heavy as the original report. You can read that if you have a spare hour on this page.

Associated Page (there are lots if you search): The bird is more important than the cat.

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Assessing Domestic Cat Predation on Wildlife — 1 Comment

  1. Well at least they didn’t go making blanket statements about how right they are or anything. That is the one thing I like about England the most – opinions are usually much more informed and therefore not what you would expect on average. When I lived in Canada people just said what they thought they should say – including the total anti/activists too – in their own way. So I suppose we have to hope that whoever read this is clever enough to understand it for what it is and being England I have a little faith. Can I ask what newspaper you saw this in? Mirror, Mail or Independent, times sort of thing. If it really was unfiltered to plain english I cant imagine it was in a tabloid but you never know. That certainly is a long dry read 🙂

    Anyhow. I believe it would be at least better to make measurements to the average amount of birds depending on amount of trees versus houses. I mean I wonder if you can even come up with a meaningful estimate just working with one small town(?) – maybe then it’s possible. There are things like currents of air and weather that effect the dispersion of birds I would imagine so extrapolating is useless – as we discussed in the last article about this, and in my opinion extrapolation biased. However this article does kind of admit what I have just said in a round about way. They have not learned much of anything since they already knew that cats ‘might’ effect the bird population significantly. Infact it always might, lol, just like I might know how to fly a plain. We pretty much know I ‘can’ fly a plain but the question of whether I do or not will always mean I might. Sorry, I’m making fun. If you catch me sitting in a plane though it doesn’t necessarily mean I’m driving it. For that matter if my cat comes home with a bird it doesn’t necessarily mean he killed it, lol, but its the equivalent to if I was sitting in the drivers seat of the plane, and the plane had just landed. Anyway, I guess all I am saying is that if you include the words ‘might’ or ‘may’ in a sentence you can really have alot of fun making alot of stuff up too without actually proving or disproving it.

    Anyhow – at least they admit it. I think other reports would be dramatic and sound like its proof. “Decimation of Bird Population througout the country” above a photo iof a cat holding a bird. That kind of thing. or “By 2015 the bird population will be one thrid smaller – irresponsible cat owners might be to blame”.
    What they should have is a photo of a bird that died being hit by a wind turbine along with “A new and dangerous predator is threatening bird species into a quicker demise” – well at least that one IS true, no ‘mights’ or ‘maybes’.

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