The domestic cat as an invasive species? Balderdash - Photo by Eran Finkle (Flickr)
I challenge the assessment that the domestic cat is an invasive species. The respected IUCN (International Union for Conservation of Nature) says it is. They work in association with the Species Survival Commission to assess and advise on the Invasive Species Specialist Group (issg.org). In short a large number of specialists (7,500 volunteer experts) have decided that the domestic and feral cat is an invasive species - one of the worst.
They define "invasive species" as “animals, plants or other organisms introduced by man into places out of their natural range of distribution, where they become established and disperse, generating a negative impact on the local ecosystem and species.”
This article is a critique of the assessment. They make a number of errors on their page listing the cat as an invasive species, which indicates that so called experts are often not expert at all. I guess we know that.
First on the issg.org website they bundle together domestic and feral cats. I think that is a bad idea as many millions of domestic cats in the USA live indoors permanently and these cats cannot fall within the above definition as they cannot have a negative impact or indeed any impact on the local ecosystem.
Secondly they say that "Felis catus was domesticated in the eastern Mediterranean c. 3000 years ago". Felis cats was not domesticated. Felis silvestris catus is the scientific name of the domestic cat. The wild cat Felis silvestris was domesticated. And current information points to the fact that it happened first 9,500 years ago.
Thirdly, ISSG says "Felis catus is a small animal in the wild (up to 5kg, but more commonly 1.5 -3.0kg) but may be considerably heavier when domesticated." I presume by this that they mean that the feral cat is smaller than the domestic cat. They say therefore that the feral cat commonly weighs 3.3 to 6.6 pounds or in-between those figures at less than 5 pounds. This is incorrect in my view. Feral cats have similar weights to domestic cats unless the domestic cat is obese.
ISSG admit that they do not have hard data on the impact of domestic or feral cats in respect of their impact on native species. They say "However, unambiguous evidence of cats causing a decline in a prey species is difficult to find as other factors, such as other predator species, may also be involved in the decline (Dickman 1996)." In other words the feral cat might not have a negative impact on local species. In fact it is conceivable that the cat may have a beneficial impact by reducing other so called invasive species that are clearly detrimental to the environment such as rats. This precludes the cat from being an invasive species.
Also it is by pure chance that the wild cat was domesticated in the Mediterranean. Indeed there may be undiscovered evidence to suggest that the wildcat was domesticated in other areas. That would make it native to those areas and not introduced "by man".
The act of domestication of the wildcat is not an act that falls within the phrase "introduced by man".
I also question the whole concept of invasive species. We devised the concept. And we do the introducing. If we willingly introduce animals to areas where they have not evolved naturally we have no right to blame the species and then to try and destroy the species. The ISSG should be suggesting ways to stop the introductions.
In respect of the cat, it has provided so much in the way of benefit to countless millions of people. To brand the domestic cat an invasive species that needs to be eradicated is ridiculous.
I therefore challenge the assessment that the domestic cat is an invasive species. In general, there is no hard evidence to suggest that it meets the definition.