Cat predation on wildlife

A feral cat with an American Robin. Plate from Forbush (1916).

A 2013 study by Scott R. Loss and others of the Smithsonian Conservation Biology Institute and the U.S. Fish and Wildlife Service found that free-ranging domestic cats are likely the top human-caused threat to birds and small mammals in the United States, killing an estimated 1.3 to 3.7 billion birds and 6.3 to 22.3 billion mammals annually.[5][6] These figures were much higher than previous estimates for the U.S.[5]^: 2 Unspecified species of birds native to the U.S. and mammals including mice, shrews, voles, squirrels and rabbits were considered most likely to be preyed upon by cats.[5]^: 4 Perhaps the first U.S. study that pointed to predation by cats on wildlife, as a concern was ornithologist Edward Howe Forbush's 1916 report for the Massachusetts State Board of Agriculture, The Domestic Cat: Bird Killer, Mouser and Destroyer of Wildlife: Means of Utilizing and Controlling It.[7]

Island settings pose particular challenges for wildlife. A 2001 study identified cats alone as responsible for the plight of some island bird species, such as the Townsend's shearwater, socorro dove, and the Marquesan ground dove.[8]^: 400 The same study identified the greatest cause of endangerment of birds as habitat loss and degradation, with at least 52% of endangered birds affected,[8]^: 399 while introduced species on islands, such as domestic cats, rats and mustelids,[8]^: 403 affected only 6% of endangered birds.[8]^: 399 Other studies caution that removing domestic cats from islands can have unintended consequences, as increasing rat populations can put native bird[9] and mammal species[10][11] at risk.

Mouse partially eaten by a house cat

Cats are sometimes intentionally released into urban environments on the popular assumption that they will control the rat population; but there is little scientific basis for this. The reality is that cats find rats to be large and formidable prey, and so they preferentially hunt defenseless wildlife such as lizards and songbirds instead. Scientists and conservationists oppose the use of cats as a form of rodent control because they are so inefficient at destroying pest species that the harm they do to native species in the process outweighs any benefit.[45][46][47]

Despite this, cat rescue groups sometimes release unadoptable feral cats into rat-infested neighborhoods under the pretext of giving the cats "jobs" as rat control, as is being done in Chicago and Brooklyn; the cats will largely ignore the rats and instead will beg for food from people or eat garbage and whatever small wildlife they can catch. Jamie Childs, a public health researcher who has studied urban feral cats, told The Atlantic that he sees cats and rats peaceably eating from the same pile of garbage at the same time.[48][49]

Ecology of fear or "fear effect": is a negative impact on prey that leads to a decrease in their population due to predators' presence or scent. The study "Urban bird declines and the fear of cats" refers to how native species are reproducing less to avoid predators, even if predator mortality is low. This study indicates how small predator mortality is, which is less than 1%, but it has a considerable impact on the birds' fecundity and reduces the abundance of birds to 95%.[50] The fear effect is one indirect way cats affect native species besides diseases. The presence of cats altered the prey foraging, movement, and stress response and significantly impacted survival and reproduction.[51]

Wildlife that are attacked by cats fare poorly, even when provided with veterinary treatment by licensed wildlife rehabilitators (over 70% of mammals and over 80% of birds died in spite of treatment in one study).[52]^{: p. 171} Even those that had no visible injuries from the cat attack often died (55.8% of birds, 33.9% of mammals).[52]^{: p. 169} Typical wildlife injuries caused by cats include cuts, degloving (the stripping off of skin), and small puncture wounds caused by prey being gripped by the cat's teeth that are easily hidden by fur or feathers.[52]^{: p. 171} Systemic infection, usually caused by Pasteurella multocida, a highly pathogenic bacterial species that's found naturally in cat mouths, can kill small animals in as little as 15 hours.[52]^{: p. 171} Few other causes of injury that are commonly seen by wildlife care facilities lead to death as rapidly[52]^{: p. 171} or as frequently as interaction with a cat.[52]^{: p. 170}

According to a study published by People and Nature in 2018, predation by pet cats is an environmental issue that cannot be resolved until cat owners accept that the problem exists and individually take responsibility for addressing it.[53] Surveys of cat owners find they often view the depredation of wildlife as a normal thing that cats do, and rarely feel an individual obligation to prevent it.[53] They may experience some level of cognitive dissonance toward the subject, because when surveyed they're more likely than the general public to believe that cat predation isn't harmful to wildlife, despite the likelihood they have witnessed acts of predation firsthand, and in many cases have been receiving "gifts" of animal carcasses from their cats.[54] Those that express concern also often express a belief that, despite owning the animal, they have no control over what it does, or believe that they can't manage its behavior without compromising the cat's welfare in some way.[53] A few cat owners even take pride in the animals their cats return home, believing it represents the cat's authenticity or skill.[53]

Ancient Egyptian cat statuette intended to contain a mummified cat 332–30 B.C.

The relationship between cats and humans began as a commensal relationship due to their predation on rodents, dating back to 7500 B.C. in connection to the inception of commensal rodents near Neolithic sedentary communities. There is some debate regarding exactly how early domestication began, but there is enough evidence (DNA and Art) to conclude that humans started domesticating cats in Ancient Egypt. Ancient Egyptians found cats to be beneficial for pest reduction. Human influence on cat evolution can be seen morphologically after the domestication of the cat and the increase of global trade routes, as cats were recruited for rodent control.[55][56]

Unlike other wild predators, cats are given different forms of aid from humans such as food, shelter, and medical treatment. Aid given by humans present cats with a survival advantage which would not be seen otherwise in the wild, leading to high populations[57] As opportunistic hunters, cats are extremely adaptive to their environments, even if they are a house cat living in a home.

A secondary effect of cat predation on wildlife is the ability to transmit a range of diseases to animals. Cats can spread diseases to animals they interact with and to marine animals. This includes transmission of diseases to humans. In recent years tick populations have increased in size and geographic distribution due to climate change, habitat fragmentation, and host availability. In North America, cats are common tick hosts. Diseases capable of being transmitted through ticks include Theileria Orientalis, and R. rickettsii, hemorrhagic fever.[58] Some of the diseases that can be transmitted from cats to humans include Toxoplasmosis, Hookworms (Uncinaria stenocephala, Ancyclostoma tubaeforme, A. brazilense and A. ceylanicum), Cat-scratch disease (bartonellosis), Rickettsia disease (Rickettesia typhi), Tularemia (Francisella tularensis), and Plague (Yersinia pestis).[59]

Toxoplasmosis

Toxoplasma Lifecycle

Toxoplasmosis is caused by the single-celled parasite Toxoplasma gondii, which usually occurs in warm-blooded animals. Still, cats usually are the carriers,[60] which is very dangerous for many birds in Hawaii. Species toxoplasmosis has been found to be fatal are: the Hawaiian crow, the nene, the red-footed booby, and the Hawaiian monk seal, many of which are endangered . Toxoplasmosis found in marine life is attributed to freshwater runoff from cities.[61] Toxoplasmosis can be transmitted from cats to marine organisms, in some instances it is fatal to Hawaiian marine animals.[33] Toxoplasmosis transmitted from cats have been reported in mammalian, avian, marine, marsupial, sheep, and goat species.[59]

Sterilized cat with a tipped ear

Various methods of population control are used to reduce the number of feral cats in areas where they are too abundant, thereby reducing the adverse effects that they often have on wildlife in those areas. Some of the methods most used, particularly in urban areas, are “Trap-Neuter-Return” (TNR) and “Trap-Euthanize” programs, as well as neutering kittens and allowing them to be adopted. Scientific research has not found TNR to be an effective means of controlling the feral cat population.[62] Literature reviews have found that when studies documented TNR colonies that declined in population, those declines were being driven primarily by substantial percentages of colony cats being permanently removed by a combination of rehoming and euthanasia on an ongoing basis, as well as by an unusually high rate of death and disappearance.[62][63] TNR colonies often increase in population because cats breed quickly and the trapping and sterilization rates are frequently too low to stop this population growth, because food is usually being provided to the cats, and because public awareness of a TNR colony tends to encourage people in the surrounding community to dump their own unwanted pet cats there.[62] The growing popularity of TNR, even near areas of particular ecological sensitivity, has been attributed in part to a lack of public interest regarding the environmental harm caused by feral cats, and the unwillingness of both scientific communities and TNR advocates to engage.[64]

Because hunting behavior in cats is driven by instinct and not by hunger, feeding cats (as in TNR colonies) does nothing to stop them from hunting, even if the cats are overfed. Feeding cats can allow a state of hyperpredation to come about, where human intervention causes an unnaturally high predator population density to continue indefinitely, even if the local prey populations collapse.[65]

Housecats are common in western societies which has an effect on how society views the moral implication of feral cat population management. A study was done in rural and urban England, to determine the perspective of cat owners on managing cat predation of local wildlife. The majority of cat owners agreed that cats should not remain inside to prevent them from hunting. Many cat owners were more concerned about an individual cat's safety then their predation on other animals.[3]

Cat-exclusion zones (CEZ) have been proposed in conservation areas where certain species are vulnerable to predation by cats. These zones are intended for Rural–urban fringe areas serving as a buffer zone to mitigate cat predation from urban cats in rural areas. Cat-exclusion zones were presented in response to the lack of success from existing forms of population management. [66] There is probable controversy associated with this policy as it can be perceived as restricting one's freedom,[67] due to the relationship between humans and cats.

• Surplus killing, biology

• Marra, Peter P.; Santella, Chris (2016). Cat Wars: The Devastating Consequences of a Cuddly Killer. Princeton University Press. ISBN 9780691167411.
• Spotte, Stephen (2014). Free-ranging Cats: Behavior, Ecology, Management. Wiley. ISBN 9781118884010.
• Thomsen, Søren Bay Kruse (11 November 2022). "The Flightless Wren and the Lighthouse Cat". TheExtinctions.com.