Contextualizing the predation of reptiles by cats in Australia

A recent study on how many reptiles are killed by cats in Australia concluded that 649 million reptiles are killed annually by both domestic cats and feral cats on the continent. The news media headlines translate this to cats killing almost 2 million lizards a day in Australia and even causing the extinction of some reptile species.

However, the study makes it clear that is difficult to interpret the statistics which ultimately are estimates any case. There are no firm figures for the population size of feral cats in Australia and neither are the population sizes of most Australian reptile species known.

Therefore, the scientist cannot come to conclusion as to how cat predation on reptiles in Australia affects the conservation status of these reptiles. What I mean is that does cat predation result in any particular species of reptile becoming endangered on the continent? The answer is we don’t know. Perhaps the population sizes of these species of reptile are stable. And perhaps human commercial activities have a far greater downward impact on population sizes.

It needs to be stressed too that, as mentioned, the study “provides a well-rounded estimate of the number of reptiles killed by cats”. The bottom line is that these are estimates and even though the scientists collated data from more than 80 Australian studies resulting in 10,000 samples they are still estimates. I suspect that each of the studies concerned a limited area or limited number of cats. Consequently, there has to be an extrapolation of results to what they think happens across the entire continent of Australia which is arguably a dubious way of coming to an estimate.

I’m not trying to belittle or reduce the impact of the study. It is just nice to get to the truth. The problem is that news media get hold of these figures and rework them to create some sort of startling headline which invariably leads to calls to kill as many feral cats as possible by any means.

They concluded that of the 649 million reptiles killed, 53 million were killed by pet cats and the remainder by feral cats. There is constant pressure by these sorts of scientific studies on local authorities in Australia to create legislation which confines pet cats to their owner’s property.

Update few days later: cat haters blinded by their emotions are trolling me for what? I am simply quoting the study! Here are the exact words used by the study in the summary (the abstract). Apparently the words used in the body of the study are more certain but the summary is clear. By ‘contextualising’ I mean this predation needs to be seen the context of the wider picture: what is the precise impact in terms of population sizes of these reptile species? Perhaps their numbers are stable? We don’t know.

“Conclusions: Cat predation exerts a considerable ongoing toll on Australian reptiles. However, it remains challenging to interpret the impact of this predation in terms of population viability or conservation concern for Australian reptiles, because population size is unknown for most Australian reptile species, mortality rates due to cats will vary across reptile species and because there is likely to be marked variation among reptile species in their capability to sustain any particular predation rate.” – i.e. they don’t know the impact in terms of conservation and pop. viability. This is what I am saying.

“Implications: This study provides a well grounded estimate of the numbers of reptiles killed by cats, but intensive studies of individual reptile species are required to contextualise the conservation consequences of such predation.” – i.e. more studies are required.

Read the study and think before attacking me. I not defending the feral cat. I am defending common sense, science and decency. I am against news media hype. One paper, The Independent, has a headline in which it states that Australian reptiles are being made extinct by cats. The study clearly does not state that.

Source: The study.