Showing posts with label extinctions due to cat predation. Show all posts
Showing posts with label extinctions due to cat predation. Show all posts

Tuesday 10 August 2021

Human destruction of animals versus cat destruction of animals

This is going to be short because I don't have a lot of reference material on it but I would like to remind people that when humans criticise the feral and to a lesser extent the domestic cat for the destruction of native animal species, they are forgetting that humans destroy far more through their activities.

Humans destroy animals through habitat destruction and on a much lesser scale through the destruction of prey animals which support native species. There are three ways that humans destroy habitat. For the sake of clarity, I'm referring to the habitat in which wild animals live and without which they cannot live. The three ways are (1) exploitation of resources and (2) pollution and (3) the introduction of exotic species. Habitat destruction by humans is considered to be the most important cause of species extinctions in many studies.

Habitat destruction includes deforestation primarily. Many wild cat species live in forests and depend upon the forests. Across the globe there is massive deforestation. The island of Borneo was pretty much covered in forests but thousands of square miles have been erased over the last 50 years. The Borneo Bay cat lives in this forest. An elusive cat which is highly endangered now because of deforestation. That is just one example.

Bornean Bay Cat. Photograph copyright Jim Sanderson, Ph.D – Please respect copyright.
Bornean Bay Cat. Photograph copyright Jim Sanderson, Ph.D – Please respect copyright.

Other ways that humans have destroyed habitat is through water quality deterioration, drainage of wetlands, mining, agricultural use of prairies, and fertilisers, pesticides and herbicides all change the environment of a variety of bird habitat which led to declines in populations. I don't have hard data but these environmental changes negatively impact birds far more than feral cat predation.

And the experts say that it is "crucial to view cat predation within the context of habitat destruction, since cats have not been shown to be the primary cause of the loss of native species on mainland continents (Mead 1982; Mitchell and Beck 1992). MR Slater says that "unfortunately, evidence regarding extinction is often anecdotal, circumstantial or historical."

I am quoting from MR Slater's section in the book The Welfare of Cats. This section deals with the extinction of native species. It is highly relevant today because global warming is putting pressure on nature and the animals that live within it. Global warming is due to human activity but humans in reaction to that knowledge are reluctant to curb activities which create global warming and instead they criticise the feral cat in Australia for decimating wildlife species.  Humankind is myopic in respect of endangering wild species. Humankind wants to deflect attention away from their anti-conservation behavior.

And MR Slater states something which I like to read, and I'll say it again; habitat destruction by humans is the most important cause of species extinctions. It was and it is and it will be the major cause of the extinction of species because the world relies on economic growth. In relying on growth, you have to rely on increased population size and inevitably economic growth leads to the destruction of habitat.

Until politicians and economists totally adjust their ideal model for society which as stated is economic growth there will be more wild animal extinctions.

Friday 23 July 2021

Extinction of mammals on islands by introduced domestic and feral cats

When the predation of wildlife by feral and domestic cats is raised as a topic the devastating impact of cats on islands is invariably a major issue. Wildlife species on islands are particularly vulnerable because they are isolated from many of the diseases, predators and parasites that plague mammals on the mainland.

Stewart Island
Stewart Island - Photo: Getty Images / tsvibrav

Dr. Bradshaw states that island species account for 83% of all documented extinctions of mammals. However, scientists can only implicate feral cats in the destruction of wildlife on these islands in about 15% of such extinctions. And further, within that 15% of such extinctions to which the blame is only the feral cat, other introduced predators should take their share of the responsibility according to Bradshaw in his book Cat Sense.

He says that mongooses, cane toads and especially rats are equally if not more devastating than feral cats on wildlife predation. Black rats a.k.a. ship rats, it is claimed, can do more damage than any other introduced predator. It is ironic, therefore, that it may be beneficial or there are at least some benefits to not slaughtering feral cats because cats are reasonably effective hunters of black rats according to Dr. Bradshaw.

If you attempt to exterminate feral cats (as is currently the objective of Australian legislatures) you might find that the outcome is far worse than imagined in terms of the population of black rats. He cites the example of Stewart Island off the coast of New Zealand. On that island feral cats have existed for more than 200 years with an endangered flightless parrot called the kakapo (owl parrot Strigops habroptilus). The cats mainly fed on the introduced species of the brown and black rat. Those species of rat have been held responsible for the extinction of several other species of birds in the same area.

Removing the cats in these places might lead to an increase in the rat population which in turn might lead to the extinction of the kakapo.

That's just an example because sometimes eradicating cats from an island can lead to a dramatic recovery in the population of certain vertebrate species. Bradshaw cites examples such as iguanas on Long Cay in the West Indies. Also, deer mice on Coronado Island in the Gulf of California.

Although, there is no doubt that the sheer number of feral cats in most places must have a significant impact on wildlife. The difficulty, as I see it, is quantifying that impact and the way that ornithologists and their organisations latch onto biased or estimated predation rates in rather poor studies to further their agenda which is to in effect kill large numbers of cats.

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