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Hunting Evidence for Killer Cat Claims

by on 2013/10/02

Academics can get quite tiresome on the topic of primary sources. My students must get bored of me telling them to use, and accurately reference, primary scientific literature. But there are important reasons for doing this. As Ben Goldacre has said, linking to primary sources “shows your working, and it allows people to check whether what you wrote was true”. But journalists don’t always do this, which can make it very difficult to evaluate the evidence for supposedly scientific claims reported in the media.

I came across an example of this recently, with a science news story that was of interest to me both professionally and personally. The Daily Mail published an article (9 September 2013) with the alarming headline: “How we turned ‘tame’ cats into killing machines: Scientist claims neutering pets means felines only evolve in the wild where hunting skills are key to survival”. As a psychologist with a particular interest in animal behaviour and evolution this was intriguing, and as a lifelong cat-owner, I was even more compelled to find out more.

What did the media say?

The Daily Mail article reported that John Bradshaw, a scientist from the University of Bristol, had claimed that cat owners who neuter (sterilise) their pets are inadvertently causing the species to become less domesticated, because feral cats are reproducing more prolifically than their indoor counterparts. However, by way of source material, the Daily Mail provided only a link to an article published on US website Medical Daily the previous day (8 September). This was not primary source material; it was just another media report, the gist of which was very similar to the Mail article. If I wanted to find the evidence upon which this claim had been based, I was going to have to dig deeper. But the Medical Daily article linked only to an article on the NBC News website, although at least this finally offered a clue as to why this was being reported as a “news” story: Bradshaw’s book Cat Sense was due for US release that week, apparently the source of the claim.

What about the primary research?

The UK edition of Cat Sense turned out to have been released almost a month earlier (15 August), perhaps unsurprising given the author is a UK academic. So my hunt for the source of the news had taken me across the pond to media websites and the US edition of a book, only to end up consulting the UK edition, the release of which had not made headlines at the time. So for the Daily Mail to report this as a science news story was already somewhat misleading.

But what about the claim itself? Are well-meaning owners really causing the species to become less tame by removing their docile housecats from the gene pool? Well, Cat Sense is still not primary scientific literature so in itself it does not represent evidence. It is however a good example of secondary scientific literature, with full references provided for primary sources where appropriate. So a little careful reading allowed me to establish that the evidence, such as it was, came from a survey reported in a 1999 journal article indicating high rates of neutering amongst Southampton cat owners, along with an unpublished follow-up study looking at the behaviour of some kittens born within this population (a study which Bradshaw freely acknowledges was, “too small to draw any firm conclusions”). The claims about the effects of widespread neutering are therefore speculative, rather than evidence-based.

This should not be taken as an indictment of the book as a whole however. It is fact-packed and thoroughly fascinating, and the reflections on neutering are restricted to just part of one of eleven chapters. Much greater attention is devoted to the critical role of learning and early life experience in determining cats’ behaviour and temperament (information which is liable to be of more immediate practical use to cat owners). Bradshaw also points out that many unwanted cats are euthanized every year and that “neutering is the only humane way of ensuring that there are as few unwanted cats as possible”. He suggests that directing neutering programmes at feral cat populations may be advisable (in this respect advocating more neutering, not less). It’s quite a departure from the headline in the Daily Mail.

How was the story handled in other media outlets?

Other newspapers had in fact responded much more sensibly to the release of Cat Sense, covering it in their book review sections rather than as a science news story. For example, Tom Cox (Observer, 24 Aug) represented Bradshaw’s book very well, offering well-chosen highlights that gave a balanced view of the content (without mentioning neutering at all).


So my hunt turned out to be a wild goose chase, because in the end there was no primary source to unearth. The take-home message is that you cannot always rely on someone else’s account of a scientific finding, and you should be particularly sceptical of articles that do not link to or reference original research papers. And if you ever do find yourself in doubt about a science news story, please do get in touch with us! We love a hunt, even if all we find is a red herring.

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