Complex interplay between Australia’s feral cats, invasive rabbits and native mammals

There is a confusing (to me) and complex interplay between the feral cats on the Australian continent, the rabbits upon which they prey, and the conservation of precious native mammals. European rabbits were introduced to Australia in the 18th century. European cats were also introduced to the continent at a similar time (as were rats!). These species are a massive invasive species problem to Australian conservationist. I’m told that the rabbit is the primary prey of feral cats in Australia.

Feral cat of Australia
Feral cat of Australia. Image: sunphlo, Flickr
Two useful tags. Click either to see the articles: Toxic to cats | Dangers to cats

The objective of one study was to find out how feral cats would react when the rabbit population was dramatically reduced. Would the feral cats switch prey animals to native mammals that the conservationists wanted to protect or would there be benefits from a conservational point of view?

The scientists reduced the rabbit population in a 37 km² enclosure by 80%. They used an adjacent enclosure as a control i.e. it was left as it normally is. They found that the feral cat population declined by 40%, I guess through starvation. The surviving cats switch to different prey animals including reptiles, birds and invertebrates.

The scientists say that “there was no change in either the proportion of scats [poop] that contained the remains of small mammals”. In other words, they concluded that the feral cats did not switch to small mammals but other species. This was encouraging for the conservationists because there are less feral cats and native mammals appeared to have a better chance of survival.

As an added benefit they said, because the feral cats were very hungry, they were more likely to be attracted to food lures or baits. I presume that they mean poison bait to kill them. I don’t think they mean that it would be easier to trap and sterilise the feral cats because they just don’t do that in Australia because it’s too humane and too slow ?.

I’m confused because in an article by Jason Goldman on the Earth Touch News Network, the title is: “When the rabbit’s away, the cat will devour all the native animals”. The strong implication is that if you reduce the primary prey of the feral cat, the rabbit, which Australians want to eradicate anyway, they turn their attentions to precious native species.

And I think that is the correct conclusion because a cat is not going to leave small mammals alone unless they are harder to prey upon which is not the case. I think the conclusion of the first study that I mention is incorrect. This is the complexity of the matter. If you dramatically reduce rabbit populations some feral cats die but the ones that survive eat more native species and therefore there appears to be little or no net gain in terms of conservation.

And if you just poison feral cat with a toxin which is particularly popular with the Australian authorities, Sodium monofluoroacetate (1080), you are likely to indiscriminately kill other animals which are not targeted and which are owned by Australian citizens such as domestic cats and dogs.

If you use biological measures by which I mean rabbit-borne diseases to kill off an entire population, that might present a problem to the conservation of, for example, the highly endangered Iberian lynx on the southern tip of Iberian Peninsula where they are reliant upon a scarcity of rabbits to survive. Biological warfare against rabbits in Australia is of concern to conservationist in other places.

Australian conservationists have been struggling for many years with how to control and reduce the numbers of feral cats. The difficulty is illustrated in this article. The matter has become very complicated and intractable.

Reason why TNR is ‘illegal’ in Australia except for ACT (Australian Capital Territory)

How many feral cats are there in Australia?

Catastrophic loss of wildlife hits Australia. Cause? Humans.

Useful tag. Click to see the articles: Cat behavior

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