Polarized opinions approach on Feral Cat Management

Lorden, R. (2016). Polarized Opinions and Shared Goals: Feral Cat Management in an Academic Community in Kentucky. In Companion Animals in Everyday Life (pp. 183-200). Palgrave Macmillan US.

Although there is general agreement among government agencies, conservation groups and animal welfare organizations that cat populations need to be managed, the management of cats is frequently a topic of debate between biologists/environmental groups and animal welfare/animal rights advocacy groups. The two groups’ beliefs are polarized in regard to impacts on wildlife, management strategies and efficacy of trap-and-neuter (TNR) programs. Concerns of conservation biologists relate to cats as predators, but welfare proponents feel that humans must take responsibility for free-ranging house pets and their feral offspring. It is not surprising that discussions of feral cat management become volatile. Much of the debate hinges upon whether management solutions should use lethal or non-lethal control strategies. Conservation biologists largely support cat euthanasia, while animal welfare activists support non-lethal treatments such as TNR for free-ranging cats. The issues of this larger conservancy/welfare debate framed the discourse of the cat problem and guided solution strategies at Eastern Kentucky University, where a population of cats has existed on the campus for many years. A tentative agreement has been forged between an administration that subscribed to a trap and remove policy, and a network of TNR volunteers. Both sides have focused on the common goal of a reduction in the number of campus cats. In addition, both sides have realized that each setting has its own particular constraints and that solutions must be tailored to those situations. Instead of resorting to invective, data are being collected. When well-meaning people meet and focus on solutions to a shared goal, positive outcomes become possible.

Feral dog impact on a urban fragment of Atlantic forest in Brazil

Galetti, M. & I. Sazima. 2006 . Impacto de cães ferais em um fragmento urbano de Floresta Atlântica no sudeste do Brasil.  Natureza & Conservação 4 (1): 58-63

Os cães ferais domésticos são um dos principais predadores da vida selvagem nativa em áreas
protegidas em todo o mundo. Entretanto, o número de presas caçadas por cães ferais não é registrado
de maneira precisa. Foram encontradas, em um fragmento urbano de 250 hectares de Floresta
Atlântica na Região Sudeste do Brasil, 46 carcaças de no mínimo 12 espécies de vertebrados, caçadas
pelos cães ao longo de 44 meses. Os cães ferais não demonstraram qualquer seleção aparente em
relação às diferentes espécies de presa, matando desde veados a pequenos sapos. Os mamíferos
foram a presa mais freqüentemente encontrada (75%). Nossos dados indicam que os cães ferais têm
um grande impacto sobre a vida selvagem da Floresta Atlântica, especialmente em áreas onde os
animais silvestres precisam mover-se entre os fragmentos florestais. Os programas de erradicação,
embora controversos, são a única maneira de reduzir a predação da vida selvagem por cães ferais.

Feral dogs are one of the main predators of native wildlife inside protected areas all around the world. Nevertheless, the number of preys hunted by feral dogs has not been precisely recorded. In a 250 hectares Atlantic forest fragment in Southeast Brazil, 46 carcasses have been found from at least 12 vertebrate species, hunted by feral dogs along 44 months. Feral dogs didn't have any apparent selection related to their different preys, killing from deer to small toads. Mammals were the most frequently found preys (75%). Our data show that feral dogs have a great impact on wildlife in the Atlantic forest, especially in areas where wild animals have to move between forest fragments. Eradication programs, even if controversial, are the only way to reduce predation of wildlife by feral dogs.

Cat predation on wildlife in Haute Savoie, France

Vuagnat-Kolter, M. Prédation du chat domestique, Felis catus (linnaeus, 1758) sur la faune sauvage, dans une commune péri-urbaine de Haute-Savoie (74). Le Bièvre, 22.

Le chat domestique, Felis catus (Linnaeus, 1758) est une espèce invasive, un redoutable prédateur et un animal de compagnie qui ne dépend pas de la disponibilité des proies pour survivre. Ces trois aspects associés à l’importante densité de chats font de sa prédation sur la faune sauvage, un facteur important dans le fonctionnement des écosystèmes, qui peut entraîner localement le déclin d’espèces
indigènes. La présente étude a eu lieu en Haute-Savoie dans la commune de Feigères. Toutes les proies  ramenées au domicile par 44 chats domestiques ont été identifiées sur une durée de 3 mois. Un total de 163 proies ont été tuées (86 micromammifères, 69 oiseaux, 8 reptiles) pour une moyenne de 3,7 proies par chat. Neuf espèces d’oiseaux ont été identifiées, parmi lesquelles le moineau domestique (58 %) est le plus représentée devant le merle noir (13  %). Le moineau domestique est placé en première position car il est commensal de l’homme et vit dans toutes sortes de zones modifiées par celui-ci, notamment les jardins. L’extrapolation des résultats à l’échelle de la commune montre que 2068 proies dont 878 oiseaux ont été potentiellement tuées sur trois mois entre mi-avril et mi-juillet. Le suivi télémétrique réalisé sur une durée de cinq semaines sur cinq chats, a permis de démontrer que les chats sont inactifs la majeur partie du temps (77 %) et que leurs périodes d’activité privilégiées sont l’aube et le crépuscule, lorsque les températures sont les plus basses de la journée. Le domaine vital des chats est relativement petit, ils n’effectuent pas de grandes distances et occupent principalement leur foyer ainsi que le jardin attenant à celui-ci.

The domestic cat Felix catus (Linn. 1758) is an invasive species, a formidable predator and a pet which is not dependent on the availability of prey for its survival. These three elements, plus the high density of cats, make its preying on wildlife a major factor in the functioning of ecosystems. This can lead to a decline in indigenous species locally. The present study took place in the Haute-Savoie department (France), in the commune of Feigères. All the prey brought home by 44 domestic cats were identified over a period of 3 months. There were 163 prey items in all (86 small mammals, 69 birds and 8 reptiles) for an average of 3.7 prey items per cat. 9 species of bird were identified, among which the House Sparow was the most numerous (58  %) followed by Blackbird (13  %). The House Sparrow came first because it is closely associated with man and lives in all sorts of places modified by him, notably gardens. Extrapolating the results to the scale of the commune produces 2068 prey items including 878 birds which were potentially killed over the three-month period from mid-April to mid-July. Radiotracking carried out on 5 cats over 5 weeks showed that cats are inactive most
(77  %) of the time. Their preferred periods of activity are dawn and dusk when the day temperatures are at their lowest. The cats’ territories are relatively small, not covering large distances, and mainly
occupy their homes and the adjacent gardens.

Camera trapping of college's feral cats

Bainum, III,M., K.E. Sieving, R. McCleery, & D Wald.2015. Demonstrating camera trap techniques and their application for identifying feral cats across a college campus. University of Florida-Journal of Undergraduate Research, 16 (3)

Urban and suburban wildlife can be difficult to study through traditional wildlife techniques using direct, in situ human involvement. The use of remote sensing technology like trip cameras (or camera traps) can allow researchers to obtain high quality photographs of target species to be used to confirm the presence of species and even indentify individuals of a local population. A study at the University of Florida campus employed eight camera traps at four sampling locations to attempt to identify individuals of the feral cat (Felis catus) population as well as survey local mesopredator diversity. High-resolution photographs were used to select distinguishing characteristics of each cat in order to assign it an identification code and determine if individuals were moving among the sampling sites. Ten individuals were identified out of 118 total photographs with confirmed feral cat appearances. Only one individual appeared at more than one sampling site. The trip cameras captured photo evidence of four other species, all of which appeared at sites alongside cats suggesting some degree of resource competition may exist between these opportunistic predators. 

Cat predation assessed through kitty-cams

Morling, F. (2014). Cape Town's cats: reassessing predation through kitty-cam. Mini Thesis.

Domestic cats (Felis catus) are abundant generalist predators that exploit a wide range of prey within and adjacent to the urban matrix. Cats are known to have contributed to the extinction and endangerment (mostly on islands) of a number of indigenous species, including birds, small mammals, reptiles and amphibians. Most research on this important topic has been carried out in the developed world, predominantly in Australia, New Zealand, the U.K., the U.S. and Canada with only four studies carried out in Africa. Of these, two studies in Cape Town suggest that domestic cats have a big impact on wildlife but these studies may have underestimated predation because they failed to account for the proportion of prey not returned to participants’ homes. In this study I used kitty-cams in an attempt to provide a prey correction factor for urban cats in Cape Town, South Africa. I investigated hunting of wildlife by free-ranging domestic cats in Newlands, a suburb of Cape Town, South Africa over 5 weeks in 2013. I monitored 13 cats (6 deep-urban and 7 urban-edge) by questionnaire survey, asking cat owners to record all prey items returned by their cats. A total of 43 prey items were returned, 42% of which were small mammals, 30% invertebrates, 12% reptiles, 9% amphibians and 7% birds. Combining these data with two similar survey studies carried out in Cape Town I estimated that a total of 118 cats caught an average of 0.04 prey items per cat per day. Ten of the 13 cats were also monitored for 3 weeks using kitty-cam video cameras. Participating cats wore a video camera and all activity was analysed for prey captures and behavioural activity patterns.

Conservation solutions regarding owned outdoor cats

Gramza, A. (2014). Applying social science to inform conservation solutions regarding owned outdoor cats in urbanizing landscapes (Doctoral dissertation, COLORADO STATE UNIVERSITY).


Free-ranging domestic cats (Felis catus) incur and impose risks on ecosystems and represent a complex issue of critical importance to wildlife conservation and domestic cat and human health. There is an inherent social dimension to the issue of owned free-ranging cats, as humans are their caregivers and can contribute to the cause as well as the solution to this issue. To address this social component, we examined public risk perceptions, attitudes, and beliefs towards owned free-ranging cats along a gradient of urbanization via a survey of residents in two study areas in Colorado. Residents did not view all types of risks uniformly; they viewed the risks of cat predation on wildlife and carnivore predation on cats as more likely than the risks of disease transmission to and from wildlife. Additionally, risk perceptions were related to such factors as attitudes and general beliefs about cats, prior experiences with cats and their interactions with wildlife, and cat owner behavior. These findings provide support for the notion that changes in risk perceptions can result in behavior change, and they offer insight for development of communication campaigns aimed at promoting risk aversive behaviors and cat management strategies that are both acceptable to the public and have direct conservation implications. Our study can also be used as a model for further research focused on integrating social and biological information to promote conservation of wildlife and habitats.

Toxoplasmosis in White tailed deers

Ballash, G. A., Dubey, J. P., Kwok, O. C. H., Shoben, A. B., Robison, T. L., Kraft, T. J., & Dennis, P. M. 2014. Seroprevalence of Toxoplasma gondii in White-Tailed Deer (Odocoileus virginianus) and Free-Roaming Cats (Felis catus) Across a Suburban to Urban Gradient in Northeastern Ohio. EcoHealth, 1-9.

Felids serve as the definitive host of Toxoplasma gondii contaminating environments with oocysts. White-tailed deer (WTD; Odocoileus virginianus) are used as sentinel species for contaminated environments as well as a potential source for human foodborne infection with T. gondii. Here we determine the seroprevalence of T. gondii in a WTD and felid population, and examine those risk factors that increase exposure to the parasite. Serum samples from 444 WTD and 200 free-roaming cats (Felis catus) from urban and suburban reservations were tested for T. gondii antibodies using the modified agglutination test (MAT, cut-off 1:25). Antibodies to T. gondii were found in 261 (58.8%) of 444 WTD, with 164 (66.1%) of 248 from urban and 97 (49.5%) of 196 from suburban regions. Significant risk factors for seroprevalence included increasing age (P < 0.0001), reservation type (P < 0.0001), and household densities within reservation (P < 0.0001). Antibodies to T. gondii were found in 103 (51.5%) of 200 cats, with seroprevalences of 79 (51%) of 155 and 24 (53.3%) of 45 from areas surrounding urban and suburban reservations, respectively. Seroprevalence did not differ by age, gender, or reservation among the cats’ sample. Results indicate WTD are exposed by horizontal transmission, and this occurs more frequently in urban environments. The difference between urban and suburban cat densities is the most likely the reason for an increased seroprevalence in urban WTD. These data have public health implications for individuals living near or visiting urban areas where outdoor cats are abundant as well as those individuals who may consume WTD venison.

Space use and intraguild interactions among three opportunistic predators

Krauze-Gryz, D., Gryz, J. B., Goszczyński, J., Chylarecki, P., & Zmihorski, M. (2012). The good, the bad, and the ugly: space use and intraguild interactions among three opportunistic predators—cat (Felis catus), dog (Canis lupus familiaris), and red fox (Vulpes vulpes)—under human pressure. Canadian Journal of Zoology, 90(12), 1402-1413.

Examples of interspecific interactions have been described for mammalian predators, but less is known regarding disturbances of native predator guilds by domestic predators. We investigated intraguild interactions among three opportunistic predators (dog (Canis lupus familiaris L., 1758), cat (Felis catus L., 1758), and red fox (Vulpes vulpes (L., 1758)) co-occurring in the extensive farmlands of central Poland. Their space use was monitored using tracking stations distributed in field and forest plots along a distance gradient from buildings and analyzed using the occupancy-modeling framework. For all three species occupancy decreased with increased distance from buildings, although for the fox the pattern was relatively weak. The occurrence of cats at the stations was higher in the forest than in the field; for fox and dog, there was a strong variation between study plots. For all three predators, the probability of detection was higher during the night than during the day and varied between the seasons; however, the exact patterns were species-specific. The presence of one predator was also linked to the presence of the other two species—generally, a given species was detected more frequently in the absence of the other two species. We recorded spatiotemporal niche segregation among the three species. We conclude that interspecific antagonistic interactions and differences in foraging ecology are the main drivers shaping co-occurrence of the three species in the agriculture landscape.

Artificial nest predation in forest tracts and its relationshib with the decline of birds

Wilcove, D.S. 1985. Nest predation in forest tracts and the decline of migratory songbirds. Ecology 66: 1211- 1214

Nest predation has been suggested as an important cause of the decline of breeding populations of migratory songbirds in small woodlots in eastern North America. I tested this hypothesis by placing artificial nests with fresh quail eggs in forest of different sizes in Maryland and Tennessee. Predation rates were higher in small woodlots than in large tracts. Predation was especially intense in woodlots near suburban neighborhoods compared to woodlots in isolated rural areas. Experimental open—cups nests were move vulnerable to predators when placed on the ground vs. 1—2m above ground. In either position these open—cup nests were move vulnerable to predators than experimental cavity nests. Since most species of migratory songbirds construct open—cup nests, and several species place them near the ground, migratory songbirds should by strongly affected by higher predation rates in small forest tracts

Urban and periurban mammal communities and its importance to conservation

Chupp, A. D., Roder, A. M., Battaglia, L. L., & Pagels, J. F. (2013). A case study of urban and peri-urban mammal communities: Implications for the management of National Park Service areas. Northeastern Naturalist, 20(4), 631-654.

The primary objective of this study was to compare urban and peri-urban mammal assemblages and relate variation in these communities to local differences in vegetation. We surveyed 15 locations in both urban and peri-urban habitats (n = 30). Boundaries of our survey areas coincided with those of National Park Service (NPS) areas in central Virginia. Over a 14-month period, we used five trap-types to document species in three guilds. A total of 9 and 15 species were documented at urban and peri-urban locations, respectively. Top predators Canis latrans (Coyote) and Felis rufus (Bobcat) were undetected at urban sites, while mesopredators were consistently more abundant. The absence of four small prey species and reduced abundances of the most common native generalist, Peromyscus leucopus (White-footed Mouse), were also associated with urban locations. Multivariate analyses of relative abundance data indicated significantly dissimilar mammal communities in urban and peri-urban locations. Shrub cover was highest in peri-urban locations, while grass cover was highest in urban sites—a pattern that was only marginally significant due to greater variability among these sites. The exotic grass Microstegium vimineum (Japanese Stiltgrass) was present at several urban sites and contributed to the complex relationship between percent grass cover and the small-mammal assemblages that we surveyed. Our results suggest that disturbances that reduce the recruitment of shrubs and other native plants and promote the spread of invasive grasses may have severe consequences for small-mammal communities. In addition, culturally preserved areas within both survey sites (i.e., battlefields planted with fescue grasses) were inhospitable to most small-mammal species and wildlife in general. In many NPS areas, there is great opportunity for development of adaptive management strategies that integrate ongoing NPS efforts to control invasive plant species with the enhancement of wildlife habitat in both culturally and naturally preserved areas. There is an urgent need for the conservation of native habitat in NPS areas and non-park sites threatened by urbanization. The primary focus of these efforts should include the control of exotic species and mesopredators, facilitation of native shrub recruitment, and, in many of these areas, the ecological restoration of historic sites. NPS lands in urbanized areas offer unique conditions for wildlife management and abundant opportunities for conserving native communities.

Pet cats reduce effective protected area

Lilith, M., Calver, M.C. and Garkaklis, M.J. (2008) Roaming habits of pet cats on the suburban fringe in Perth, Western Australia: What size buffer zone is needed to protect wildlife in reserves? In: Lunney, D., Munn, A. and Meikle, W., (eds.) Too close for comfort : contentious issues in human-wildlife encounters. Royal Zoological Society of New South Wales, Mosman, NSW, pp. 65-72.

We radiotracked 18 pet cats Felis catus from rural and urban areas within the City of Armadale, Western Australia, both at night and during the day between August 2003 and February 2005 to estimate the size of buffer zone required to reduce incursions by pet cats into native bushland. Home ranges of rural cats ranged from 0.07ha to 2.86ha, while those of urban cats were 0.01 ha to 0.64ha. Male and female cats had similar home ranges and there was no evidence of seasonal differences in home ranges.The longest linear distance moved by any cat was 300m, so allowing a 20% margin for estimation error a buffer zone of 360m is needed to reduce incursions by pet cats into native bushland in this municipality.

Pet cats' impact on biodiversity in Australian suburbia

Lilith, M. (2007) Do pet cats (Felis catus) have an impact on species richness and abundance of native mammals in low-density Western Australian suburbia? PhD thesis, Murdoch University.

Cat ownership in Australia is declining compared to an increasing trend of cat ownership in the United Kingdom, United States and Europe. The decline in Australia may be linked to concerns over perceived impacts of cat predation and an associated dislike of cats. However, while there are numerous studies on feral cats and their impacts on declining native fauna, the impact of pet cats on suburban wildlife or fauna in remnant bushland is relatively unknown although there is a wide perception of risk. The primary aim of this thesis was to apply the precautionary principle to the question of the putative impact of pet cats on the abundance and diversity of small mammals in urban bushland adjacent to low-density suburbia in the City of Armadale, a municipality on the south-east fringe of Perth, Western Australia. At the time of writing, Western Australia is yet to introduce state legislation governing cat control although many local councils within the state have either implemented or are in the process of implementing cat regulations.

The precautionary principle was deemed an ideal approach to this question, because it provides a rationale for deciding on possible actions where both the potential risk to environmental values and the uncertainty about possible impacts are high. In such cases the precautionary principle requires two broad lines of action: firstly, detailed consultation with stakeholders to determine their perceptions of risk and the actions they are prepared to take to reduce it and, secondly, research to reduce uncertainty.

With regard to stakeholder consultation, local residents were surveyed in regard to their attitudes and current cat husbandry practices. A substantial proportion of respondents within this municipality believed cat regulations were necessary (75% of owners and 95% of non-owners). At least 70% of both owners and non-owners agreed with the propositions that cats not owned by licensed breeders should be desexed, local councils should restrict the maximum number of cats that can be owned on one property and that pet cats entering nature reserves are harmful to wildlife. Most (c.85%) cat owners agreed that they would license their cats if that became compulsory. Although fewer owners (c.60%) were prepared to keep their cats on their property at all times to protect wildlife, over 80% were willing to confine their cats at night if it was required. Owners seemed to be substantially motivated by the value of these measures in reducing injury to cats and facilitating the return of lost animals rather than concern over wildlife protection.

Attempts to reduce uncertainty involved (i) assessing roaming patterns of pet cats to determine the sizes of appropriate buffer zones around nature reserves, and (ii) determining species diversity, species richness and abundance of small mammals in remnant bushland adjacent to sub-divisions with varying regulations governing cat husbandry. Radio tracking results to assess cat roaming patterns showed substantial variation in home range size between cats in high density suburbia (ranged between 0.01 ha - 0.64 ha) and those in low density suburbia (ranged from 0.07 ha - 2.86ha). Larger home range sizes of cats in the rural areas (up to 2.9 ha) suggest buffer zones of up to 500 metres around nature reserves are needed to exclude almost all roaming cats. The abundance and species richness of small mammals were investigated in four areas of remnant bushland. Two were adjacent to subdivisions where cat ownership was unrestricted, one next to a subdivision where cat ownership was prohibited and the remaining one next to a subdivision where compulsory night curfew and bells on pet cats were enforced. No definitive evidence of predatory impact by pet cats on the small mammals was found. Mammal species diversity was not significantly different between sites and species richness and absolute abundance were not higher in sites where cats were restricted. Vegetation comparisons showed significant differences in the structure and species composition of the vegetation between most sites and the mammal species richness and abundance appeared linked to ground cover density in the various sites. This factor, not cat restrictions, appeared to be the primary determinant of species richness, species diversity and absolute numbers of small mammals in these sites.

This study in the City of Armadale has shown that the implementation of proposed cat legislation must have a 'whole of ecosystem' approach, i.e. protecting identified remnant bushland containing biodiversity from threatening processes such as plant disease and inappropriate fire, especially arson, as well as possible predations from pet cats. Habitat restoration and protection may be more important conservation activities than regulation of cats. Regulation of cats can be done at differing levels of intensity and cost, bearing in mind that this community is receptive to regulation of some aspects of cat ownership. Community education on the values of cat confinement in regards to cat welfare might increase chances of compliance.

Antipredator strategies of house finches in towns

Valcarcel, A., & Fernández-Juricic, E. (2009). Antipredator strategies of house finches: are urban habitats safe spots from predators even when humans are around?. Behavioral Ecology and Sociobiology, 63(5), 673-685.

Urbanization decreases species diversity, but it increases the abundance of certain species with high tolerance to human activities. The safe-habitat hypothesis explains this pattern through a decrease in the abundance of native predators, which reduces predation risk in urban habitats. However, this hypothesis does not consider the potential negative effects of human-associated disturbance (e.g., pedestrians, dogs, cats). Our goal was to assess the degree of perceived predation risk in house finches (Carpodacus mexicanus) through field studies and semi-natural experiments in areas with different levels of urbanization using multiple indicators of risk (flock size, flight initiation distance, vigilance, and foraging behavior). Field studies showed that house finches in more urbanized habitats had a greater tendency to flock with an increase in population density and flushed at larger distances than in less urbanized habitats. In the semi-natural experiment, we found that individuals spent a greater proportion of time in the refuge patch and increased the instantaneous pecking rate in the more urbanized habitat with pedestrians probably to compensate for the lower amount of foraging time. Vigilance parameters were influenced in different ways depending on habitat type and distance to flock mates. Our results suggest that house finches may perceive highly urbanized habitats as more dangerous, despite the lower number of native predators. This could be due to the presence of human activities, which could increase risk or modify the ability to detect predators. House finches seem to adapt to the urban environment through different behavioral strategies that minimize risk.

Cat predation on rural and urban landscapes

Lepczyk, C.A., Mertig, A.G. & Liu, J. (2003) Landowners and cat predation across rural-to-urban landscapes. Biological Conservation 115: 191–201

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.

Diet of feral cats and dogs in suburban Brazil

Campos, C. B., Esteves, C. F., Ferraz, K. M. P. M. B., Crawshaw, P. G., & Verdade, L. M. (2007). Diet of free‐ranging cats and dogs in a suburban and rural environment, south‐eastern Brazil. Journal of Zoology, 273(1), 14-20.

In spite of the worldwide occurrence of domestic cats and dogs, and their close relationship with humans, the number of published papers on free-ranging cats Felis catus and dogs Canis familiaris, is small. The diet of both species was estimated in a suburban and rural environment in July 2002 and January 2003. Visual observations and scat collection of both species were accomplished along a 10 km transect line in the Campus ‘Luiz de Queiroz’, University of São Paulo, Piracicaba, south-eastern Brazil. The diet of both species was determined by analysis of sterilized, washed, dried and sorted scats. Estimated abundances of free-ranging cats and dogs in the sampled area were 81 (±4.32) and 42 (±2.96), respectively. Cats and dogs were more abundant in the suburban than in the rural environment (t=3.78, P<0.001, N=55; t=8.38, P<0.001, N=55, respectively) and cats were more abundant than dogs in the suburban environment (t=6.76, P<0.001, N=55), even though there was no significant difference between the abundance of both species in the rural environment (t=0.82, P=0.46, N=55). Invertebrates were the most commonly consumed item by both species, followed by mammals (cats: 63.24 and 20.51%; dogs: 57.05 and 25.15%, respectively). Niche breadth was 0.4892 for cats and 0.4463 for dogs. Niche overlap was almost complete (0.97108). The consumption of mammals was estimated to be between 16.76 and 25.42 kg individual−1year−1 for dogs and between 2.01 and 2.9 kg individual−1year−1 for cats. These data might be useful to establish a management program to minimize the predation pressure of free-ranging cats and dogs on wildlife.

Two classics in ecology: Mesopredator release

Soulé, M. E., Bolger, D. T., Alberts, A. C., Wrights, J., Sorice, M., & Hill, S. (1988). Reconstructed dynamics of rapid extinctions of chaparral‐requiring birds in urban habitat islands. Conservation Biology, 2(1), 75-92.

The distribution of native, chaparral-requiring bird species was determined for 37 isolated fragments of canyon habitat ranging in size from 0.4 to 104 hectares in coastal, urban San Diego County, California. The area of chaparral habitat and canyon age (time since isolation of the habitat fragment) explains most of the variation in the number of chaparral-requiring bird species. In addition, the distribution of native predators may influence species number. There is statistical evidence that coyotes control the populations of smaller predators such as foxes and domestic cats. The absence of coyotes may lead to higher levels of predation by a process of mesopredator release. The distance of canyons from other patches of chaparral habitat does not add significantly to the explained variance in chaparral-requiring species number–probably because of the virtual inability of most chaparral-requiring species to disperse through developed areas and nonscrub habitats. These results and other lines of evidence suggest that chaparral-requiring birds in isolated canyons have very high rates of extinction, in part because of their low vagility. The best predictors of vulnerability of the individual species are their abundances (densities) in undisturbed habitat and their body sizes; together these two variables account for 95 percent of the variation in canyon occupancy. A hypothesis is proposed to account for the similarity between the steep slopes of species-area curves for chaparral-requiring birds and the slopes for some forest birds on small islands or in habitat fragments. The provision of corridors appears to be the most effective design and planning feature for preventing the elimination of chaparral-requiring species in a fragmented landscape.

En el condado urbano de San Diego, California 37 fragmentos de hábitat de cañón que varían de tamaño de 0.4 a 104 hectáreas fueron examinados para determinar la distribución de especies de aves nativas que requieren de chaparral. El tamaño del área de hábitat de chaparral y la edad del cañón (tiempo transcurrido desde que ocurrió el aislamiento del fragmento de hábitat explican la mayor parte de la variación en el número de especies de aves que requieren de este hábitat Así mismo, la distribución de depredadores nativos puede influenciar el número de especies. Existen evidencias estadísticas de que los coyotes controlan las poblaciones de depredadores menores tales como los zorros y los gatos domésticos. La ausencia de coyotes puede conducir a niveles de depredación mas altos mediante un proceso de liberación de mesodepredadores. El aislamiento de cañones con respecto a otros pedazos de hábitat de chaparral no incrementa significativamente la varianza en el número de especies que requieren chaparral – probablemente debido a la virtual inhabilitad de la mayoría de las especies que requieren chaparral para dispersarse en áreas desarrolladas y en hábitats no—arbustivos. Estos resultados y otras evidencias sugieren que las aves que requieren chaparral en los cañones aislados tienen muy altas tasas de extinción, en parte debido a su baja dispersabilidad. Los mejores pronosticadores de la vulnerabilidad de una especie en particular son su abundancia (densidad) en habitats no perturbados y el tamaño de sus cuerpos; juntas, estas dos variables explican el 95% de la variación de su residencia en el cañón. Una hipótesis es propuesta para explicar la similaridad entre las fuertes pendientes de la curves de especies-área para las aves que requieren chaparral y las pendientes para algunas aves de bosque en pequeñas islas o en hábitats fragmentados. La provisión de corredores parece ser el diseño y el rasgo de la planificación más efectivo para prevenir la eliminación de especies que requieren chaparral en un paisaje fragmentado.

Crooks, K. R., & Soulé, M. E. (1999). Mesopredator release and avifaunal extinctions in a fragmented system. Nature, 400(6744), 563-566.

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.

Up to 31% of recoveries of banded birds killed by cats

Mead, C. J. (1982). Ringed birds killed by cats. Mammal Review, 12(4), 183-186.

Mead examined the fate of banded birds in Britain and discovered that for six species more than 25 percent of the recoveries were of birds caught by cats. He ascribed 31% of recoveries of ringed robins and dunnocks to cat predation, but believed that there was no evidence that cats affected the overall populations of these species. Catchability is very different in different species, depending on gregarious habits, terrestrial feeding, avoidance of potential hiding places, etc. but some cats are even able to catch aerial species.
He emphasised that birds in rural and suburban parts of Britain have co-existed with cats for hundreds of generations and may now be under less pressure from cats than they were in the past from assorted 'natural' predators.

Predation by house cat in Canberra

Barratt, D. G. (1997). Predation by house cats, Felis catus (L.), in Canberra, Australia. I. Prey composition and preference. Wildlife Research, 24(3), 263-277.

This paper attempts to apply theory from more than 100 years of scientific experience and experimentation in predator-prey ecology and introduced species ecology to predict the likely effects of predation by domestic cats (Felis catus) on prey populations and community structure. Those aspects of the predatory behaviour of domestic cats which are of most importance in predicting their impact on prey populations: I) the degree of prey selectivity or 'dietary preference'; 2) the exhibition of switching behaviour; 3) changes in predatory activity in response to changes in prey density; and 4) the extent to which high and constant densities of the predator are ameliorated by reduced prey consumption rates as a result of dietary supplement.

In suburban environments, the influence of predation by domestic cats on prey abundance and community structure probably increases, relative to the influence of habitat change, with increasing suburb age, particularly in the absence of physical disturbances such as fire. However, it may never be as important as habitat availability and indeed may never be significant at all. Removal of the predator may allow some animal species to increase in abundance but others may decline. The details of these changes are very difficult to predict. Similarly, following predator removal, total species diversity is as likely to decline due to increased inter-specific competition, as it is to increase due to the invasion of species previously excluded by predation.

In remnant habitat, the impact of predation by domestic cats is probably less likely to be important in determining the relative abundance of the more common species than in suburban environments, but more likely to contribute to local extinctions of rare species. As in suburban environments, predation on introduced species in remnant habitat may reduce predation on native species. However, the ability of domestic cats to control introduced species which prey on, or compete with, native species will be difficult to demonstrate. In light of this uncertainty, any attempt to prevent domestic cats hunting in remnant habitat patches should be integrated with a program to eliminate or control populations of other introduced species, such as black rats and rabbits, which are preyed upon by domestic cats and are known to prey on or compete with native species

Barratt, D. G. (1998). Predation by house cats, Felis catus (L.), in Canberra, Australia. II. Factors affecting the amount of prey caught and estimates of the impact on wildlife. Wildlife Research, 25(5), 475-487.

Information on the amount of vertebrate prey caught by house cats in Canberra was collected by recording prey deposited at cat owners’ residences over 12 months. The amount of prey taken was not significantly influenced by cat gender, age when neutered, or cat breed. Nor did belling or the number of meals provided per day have a significant influence on the amount of prey caught. The age of the cat and the proportion of nights spent outside explained approximately 11% of the variation in the amount of prey caught by individual cats. In all, 43% of variation in predation on introduced species (predominantly rodents) was explained by distance from potential prey source areas (i.e. rural/grassland habitat) and cat density. The mean number of prey reported per cat over 12 months (10.2) was significantly lower than mean predation per cat per year based on estimates made by cat owners before the prey survey began (23.3). Counts of the amount of prey caught by house cats were highly positively skewed. In all, 70% of cats were observed to catch less than 10 prey over 12 months, but for 6% of cats, more than 50 prey were recorded. Estimates of predation by house cats, particularly extrapolated estimates, should be treated with caution. The total number of prey caught by house cats in Canberra estimated using the sample median was approximately half the estimate based on the sample mean. Predation estimates alone do not prove that prey populations are detrimentally affected, especially in highly disturbed and modified environments such as suburbs. Impacts on native fauna are likely to be most significant in undisturbed habitat adjacent to new residential developments.



Read a short review about belling effectiveness

Inside/outside cats' impact on a suburban nature reserve

Roland K, DeWan A (2004) Ecological impacts of inside/outside cats around a suburban nature preserve. Animal Conservation 7: 1–11.

While subsidised populations of feral cats are known to impact their prey populations, little is known about the ecological impact of inside/outside hunting cats (IOHC). We studied IOHC around a suburban nature preserve. Mail surveys indicated an average of 0.275 IOHC/house, leading to a regional density estimate of 0.32 IOHC/ha. A geographical model of cat density was created based on local house density and distance from forest/neighbourhood edge. IOHC hunted mostly small mammals, averaging 1.67 prey brought home/cat/month and a kill rate of 13%. Predation rates based on kills brought home was lower than the estimate from observing hunting cats (5.54 kills/cat/month). IOHC spent most outside time in their or their immediate neighbours’ garden/yard, or in the nearby forest edge; 80% of observed hunts occurred in a garden/yard or in the first 10 m of forest. Radio-tracked IOHC averaged 0.24 ha in home range size (95% minimum convex polygon (MCP)) and rarely entered forest. Confirming this, scent stations detected cats more often near the edge and more cats were detected in smaller forest fragments. There was no relationship between the number of cats detected in an area and the local small mammal abundance or rodent seed predation rates. Cold weather and healthy cat predator populations are speculated to minimise the ecological impact of IOHC on this area.

Cat predation quantified with cams

Loyd, K. A. T., Hernandez, S. M., Carroll, J. P., Abernathy, K. J., & Marshall, G. J. (2013). Quantifying free-roaming domestic cat predation using animal-borne video cameras. Biological Conservation, 160, 183-189.

Domestic cats (Felis catus) are efficient and abundant non-native predators. Predation by domestic cats remains a topic of considerable social and scientific debate and warrants attention using improved methods. Predation is likely a function of cat behavior, opportunity to hunt, and local habitat. Previous predation studies relied on homeowner reports of wildlife captures from prey returns to the household and other indirect means. We investigated hunting of wildlife by owned, free-roaming cats in a suburban area of the southeastern USA. Specific research goals included: (1) quantifying the frequency of cat interactions with native wildlife, (2) identifying common prey species of suburban cats, and (3) examining predictors of outdoor behavior. We monitored 55 cats during a 1-year period (November 2010–October 2011) using KittyCam video cameras. Participating cats wore a video camera for 7–10 total days and all outdoor activity was recorded for analysis. We collected an average of 38 h of footage from each project cat. Forty-four percent of free-roaming cats hunted wildlife, of which reptiles, mammals, and invertebrates constituted the majority of prey. Successful hunting cats captured an average of 2.4 prey items during 7 days of roaming, with Carolina anoles (Anolis carolinensis) being the most common prey species. Most wildlife captures (85%) occurred during the warm season (March–November in the southern USA). Twenty-three percent of cat prey items were returned to households; 49% of items were left at the site of capture, and 28% were consumed. Our results suggest that previous studies of pet cat predation on wildlife using owner surveys significantly underestimated capture rates of hunting cats.

Highlights:
► We examined predatory behaviors of 55 owned, free-roaming domestic cats.

► We used animal-borne video cameras in suburban Athens, Georgia, USA. 

► Thirty percent of our sample captured wildlife. 

► Native reptiles, mammals, and invertebrates constituted the majority of prey. 

► Twenty-three percent of prey were returned to households.