Conference Paper

KittyCams: A new look at suburban free-roaming cat predation

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Background/Question/Methods: Domestic cats (Felis catus) are extremely efficient and abundant non-native predators. The predation rate of the domestic cat remains a topic of considerable social and scientific debate and warrants attention using improved methodology. Previous predation studies relied on homeowner reports of wildlife take from prey returns to the household. We monitored the activities of 60 owned, free-roaming cats in suburban Athens, Georgia over a one year period (Nov. 2010- Oct. 2011) using KittyCam video cameras. KittyCams are animal-borne National Geographic “CritterCams” that allow recording of an animal-eye view without disrupting behavior. Cats were recruited through a survey about perceptions of domestic cats and free health screens and annual vaccinations were offered as an incentive for participation. Enrolled cats wore a video camera for 7-10 total days and all outdoor activity was recorded for analysis. Specific research goals related to predation included: 1) quantifying the frequency of cat interactions with native wildlife 2) identifying common prey species of suburban cats 3) examining predictors of outdoor behavior. Results/Conclusions: We collected an average of 37 hours of footage from each project cat. Preliminary results indicate that a minority of roaming cats (44%) hunt wildlife and that reptiles, mammals and invertebrates constitute the majority of suburban prey. Hunting cats captured an average of 2 items during seven days of roaming. Carolina Anoles (Anolis carolinensis) were the most common prey species and these new results suggest that additional research is needed regarding cat impact on suburban reptile populations. Eighty-five percent of wildlife captures were witnessed during the warm season (March-November in the southern US). Twenty-three percent of cat prey items were returned to households; 49% of items were left at the site of capture and 26% consumed. These results suggest that previous studies on pet cat depredation vastly underestimated capture rate. Cats roaming in rural areas were more likely to be hunters while cat age, sex, and time spent outside did not significantly influence hunting behavior. The KittyCams project aims to contribute reliable statistics and irrefutable images to the growing debate over free-roaming cats in the environment. Scientific manuscripts and educational materials for the general public are currently in preparation.

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1. A questionnaire survey of the numbers of animals brought home by domestic cats Felis catus was conducted between 1 April and 31 August 1997. A total of 14 370 prey items were brought home by 986 cats living in 618 households. Mammals made up 69% of the items, birds 24%, amphibians 4%, reptiles 1%, fish < 1%, invertebrates 1% and unidentified items 1%. A minimum of 44 species of wild bird, 20 species of wild mammal, four species of reptile and three species of amphibian were recorded. 2. Of a sample of 696 individual cats, 634 (91%) brought home at least one item and the back-transformed mean number of items brought home was 11.3 (95% CI 10.4–12.2). The back-transformed means and number of cats retrieving at least one item from each prey group were: 8.1 (7.4–8.9) mammals for 547 (79%) cats, 4.1 (3.8–4.5) birds for 506 (73%) cats, 2.6 (2.2–3.0) herpetofauna for 145 (21%) cats and 2.2 (1.8–2.7) other items for 98 (14%) cats. 3. The number of birds and herpetofauna brought home per cat was significantly lower in households that provided food for birds. The number of bird species brought home was greater in households providing bird food. The number of birds and herpetofauna brought home per cat was negatively related to the age and condition of the cat. The number of mammals brought home per cat was significantly lower when cats were equipped with bells and when they were kept indoors at night. The number of herpetofauna brought home was significantly greater when cats were kept in at night. 4. Based on the proportion of cats bringing home at least one prey item and the back-transformed means, a British population of approximately 9 million cats was estimated to have brought home in the order of 92 (85–100) million prey items in the period of this survey, including 57 (52–63) million mammals, 27 (25–29) million birds and 5 (4–6) million reptiles and amphibians. 5. An experimental approach should be taken to investigate the factors found by this descriptive survey to influence the numbers of prey brought home by cats. In particular, investigation of potential management practices that could reduce the numbers of wild animals killed and brought home by cats will be useful for wildlife conservation, particularly in suburban areas.
The purpose of this report is to explore the role of a buffer in the problems of predation. The particular system used was that of cat-rat because the numbers of predators and of prey can be counted and manipulated and a buffer can be easily provided. While of course this system lacks the complexities of a completely wild predator-prey relationship, it is believed that much can be learned by simplifying the problem and approaching it experimentally. The theory of a predator-prey system has been elaborated mathematically by many writers for a generation and is now a part of general ecological knowledge. In brief, the system involves several species, some of which eat the others. As the prey increase the predators follow and in some cases consume enough prey to cause a decline of prey. Then the predators decline till they no longer can hold the prey in check and the prey again increase. The critical point in reference to buffers is the extent of decline of prey. It is possible for the prey to become so scarce that the predators may starve or leave. Then of course the prey can increase very rapidly until other predators arrive. But if a buffer is present the predators can turn to it when the prey become scarce and thus the predators remain and are ready when the prey begins to increase. The buffer thus may keep the predators on hand to check the increase of prey and thereby the predators may hold down the prey population. Among predator-prey systems involving two vertebrates there exist few cases in which the predator really limits the prey population, although such cases are common among invertebrates, especially insects. Apparently the adjustment of changes in populations is not suitable, among vertebrates, to permit predators to maintain a number …
Studies of predation by house cats in Australia have not attempted to compare the composition of prey taken by cats with the relative availability of prey. Information on the composition of vertebrate prey caught by house cats in Canberra was collected by recording prey deposited at cat owners’ residences over 12 months. A total of 1961 prey representing 67 species were collected or reported. In all, 64% of prey were introduced mammals, especially mice and rats, with birds comprising 27% (14% native, 10% introduced, 3% unidentified), reptiles 7%, amphibians 1% and native mammals 1%. Predatory behaviour by house cats appeared largely opportunistic with respect to spatial (habitat) and temporal (daily and seasonal) prey availability and accessibility, although there is mounting evidence from this and other studies that small mammals are the preferred prey. While this means that introduced mice and rats are common prey of house cats in urban and suburban environments, it also suggests that in relatively undisturbed environments adjoining new residential developments, predation by house cats may have a substantial impact on locally abundant, patchily distributed populations of native fauna, particularly mammals. Imposing night-time curfews on cats is likely to lessen predation of mammals but will probably not greatly reduce predation of birds or reptiles.
Mammalian carnivores are particularly vulnerable to extinction in fragmented landscapes, and their disappearance may lead to increased numbers of smaller carnivores that are principle predators of birds and other small vertebrates. Such `mesopredator release' has been implicated in the decline and extinction of prey species. Because experimental manipulation of carnivores is logistically, financially and ethically problematic,, however, few studies have evaluated how trophic cascades generated by the decline of dominant predators combine with other fragmentation effects to influence species diversity in terrestrial systems. Although the mesopredator release hypothesis has received only limited critical evaluation and remains controversial, it has become the basis for conservation programmes justifying the protection of carnivores. Here we describe a study that exploits spatial and temporal variation in the distribution and abundance of an apex predator, the coyote, in a landscape fragmented by development. It appears that the decline and disappearance of the coyote, in conjunction with the effects of habitat fragmentation, affect the distribution and abundance of smaller carnivores and the persistence of their avian prey.
ABSTRACT As companion animals, domestic cats Felis catus can attain very high densities, and have the potential to exert detrimental effects on prey species. Yet, there is a paucity of information on the impact of cat predation in urban areas, where most cats are likely to be present. We quantified the minimum number of animals killed annually by cats in a 4.2-km2 area of Bristol, UK, by asking owners to record prey animals returned home by their pets. The potential impact of cat predation on prey species was estimated by comparing the number of animals killed with published estimates of prey density and annual productivity. Predator density was 229 cats/km2. Five mammal, 10 bird and one amphibian prey species were recorded. Mean predation rate was 21 prey/cat/annum. The most commonly recorded prey species was the wood mouse Apodemus sylvaticus. Predation on birds was greatest in spring and summer, and probably reflected the killing of juvenile individuals. For three prey species (house sparrow Passer domesticus, dunnock Prunella modularis, robin Erithacus rubecula), estimated predation rates were high relative to annual productivity, such that predation by cats may have created a dispersal sink for juveniles from more productive neighbouring areas. The impact of cats on these species therefore warrants further investigation.
Fluctuations of bird abundances have been attributed to such factors as supplemental feeding, landscape change, and habitat fragmentation. Notably absent from consideration, however, is the role of private landowners and their actions, such as owning free-ranging domestic cats (Felis catus; cats allowed free access to the outdoors). To understand the impacts of cat predation on birds, we surveyed all 1694 private landowners living on three breeding bird survey (BBS) routes (∼120 km) that represent a continuum of rural-to-urban landscapes in Southeastern Michigan, where the majority (>90%) of land is privately owned. Our data indicate that among the 58.5% of landowners that responded, one quarter of them owned outdoor cats. On average a cat depredated between 0.7 and 1.4 birds per week. A total of 23+ species (12.5% of breeding species) were on the list of being killed, including two species of conservation concern (Eastern Bluebirds and Ruby-throated Hummingbirds). Across the three landscapes there were ∼800 to ∼3100 cats, which kill between ∼16,000 and ∼47,000 birds during the breeding season, resulting in a minimum of ∼1 bird killed/km/day. While the number and density (no./ha) of free-ranging cats per landowner differed across the rural to urban landscapes, depredation rates were similar. Landowner participation in bird feeding showed no relationship with the number of free-ranging cats owned. Similarly, selected demographic characteristics of landowners were not significantly related to the number of free-ranging cats owned. Our results, even taken conservatively, indicate that cat predation most likely plays an important role in fluctuations of bird populations and should receive more attention in wildlife conservation and landscape studies.