Draft:Human–cat conflict

= Cat - human conflict = Domestic cats (hereafter just cats) are the most numerous and widespread mammalian predator, so may be expected to prey on large numbers of wild animals. (Domestic dogs are are also numerous and widespread but have less opportunity to hunt.) People raise three main concerns about cats as predators: predation, fear or disturbance to prey, and zoonosis. Predation is the most common contention, partly because it is the most visible, especially predation of birds as birds are relatively easy to count and are indicators of flourishing ecosystems.

Origin and geographic range
The original domestic cats were wildcats (Felis silvestris lybica) living in Mesopotamia about 10,000 years ago at the dawn of civilization after the ice age. The prevailing view is that the more tractable wildcats preyed on rodents frequenting grain stores of early farmers. They may then have became part of village life by people socializing young ones as pets. Some researchers write that cats are a domesticated species and consequently have no natural range and are an alien species worldwide. But originating in Mesopotamia this region is the cat’s natural geographic range, and more broadly north Africa, Europe and west Asia, which is the geographic range of its parent species, the wildcat.

Predation
Early 20th century naturalists began to take an interest in cat predation and the American ornithologist E H Forbush (1858 - 1929) revealed his thoughts about it in the title of his book published in 1916: The Domestic Cat: Bird Killer, Mouser and Destroyer of Wild Life. He wrote that a cat may catch about 50 birds per year, but not all cats do this because there would not be enough birds to go round. However, he guessed the number of birds cats kill annually to be 2 million in Massachusetts, 3.5 million in New York state, and up to 5 million in New England.

More recently, researchers in a number of countries have tried to estimate figures for cat predation on birds and arrived at large totals. In particular, a small group of US researchers published one of the most cited research papers on cat predation. They reviewed scientific literature to quantify the annual number of prey cats take in the US. No one had previously tried using such a large amount of information and analyzing it statistically. In round terms, they calculated that across contiguous US free-ranging cats annually kill up to 4 billion birds, up to 22 billion mammals, and hundreds of millions of reptiles and amphibians,  far exceeding the estimates of previous researchers. In a follow up paper they calculated that bird mortality from cats in the US is much greater than all other man-made threats combined, such as the tens to hundreds of millions of birds dying annually in collisions with buildings, motor vehicles, power lines and wind turbines, and one of the leading threats to wildlife in the US.

In a follow-up book about cats, one of the authors writes:

Cats are clearly having an impact and in that sense contributing to the sixth mass extinction. Are they the primary driver? No. But we cannot afford to focus solely on the main driver. We must tackle all the component parts and certainly the ones we have the power to control.

However, although cats may kill millions of prey each year, the claim that cats kill by the billion and are destroying wildlife - and the popular media that reported it largely without question - provoked much dispute and criticism about the estimates of cat predation.

1 Method Flaws
The method used by Loss et al. to calculate predation figures uses flawed statistical arguments such that even a major revision would not merit publication of their results [Matthews 2013]. The authors make unsafe generalisations across large regions based on data from small areas  and the effect of predation may not be the same across all habitat types.

The authors state when discussing bird collisions with building in other published research that there is considerable uncertainty about mortality and population abundance of bird species. Yet when discussing predation by cats on birds, even though the same uncertainties apply, they say the results are clear.

2 Numbers
The US Fish and Wildlife Service estimate at least 10 billion birds breed in North America and may be double that after the breeding season, cautioning that these figures are only an educated guess. If this figure is roughly correct and the figure of cats killing up to four billion birds a year is roughly correct, then cats will be killing up to about one in five birds (20 percent) in the breeding season and up to about two in five birds (40 percent) after the breeding season, figures that are too vast to accept, even without all the other mortality factors acting on birds, like window collisions.

3 Mortality hypothesis
Whether or not cats significantly affect prey populations might depend in part on whether cats are killing the breeding population (so called additive mortality) or whether they are taking the surplus population (so called compensatory mortality). The breeding population of a species makes many more individuals than its habitat can support with necessities like food and shelter. This results in a large excess of animals that die each year, mostly before they reach breeding age.

However, researchers who provide numbers of prey taken by cats do not and cannot say whether cats are taking the breeding population (that is additive) or the surplus population (that is compensatory) of birds and other animals. There is not sufficient data and no certain estimates for the size of bird populations in the United States.

As an example, say an isolated island sustains a maximum of 100 birds. In one year these birds breed 100 more birds. So now there are 200 birds on the island. Inevitably 100 birds will die - by starvation, exposure, disease and predation - and this happens year after year. The same applies to much larger geographic regions because no region has unlimited resources.

The Royal Society for the Protection of Birds says about birds in Britain: “It is possible that most of the birds killed by the cats would have died anyway from other causes before the next breeding season.” And furthermore, bird species that have the most serious population declines in Britain rarely encounter cats and these declines are usually caused by loss of habitat, particularly in farming areas.