Feeding cats deplates native fauna

Hawkins, C.C., W.E. Grant & M.T. Longnecker. 1999. Effect of subsidized house cats on California birds and rodents. Transactions of the Western Section of The Wildlife Society, 35: 29-33

Cat advocates are establishing feeding stations in public parks, often claiming that well-fed cats pose little threat to wildlife. This claim was tested east of San Francisco, California, in a cat area and a no-cat area. In 1995, more harvest mice were trapped in the no-cat area. In 1996, more harvest mice (Reithrodontomys megalotis) and deer mice (Peromyscus sp.) were trapped in the no-cat area, and more house mice were trapped in the cat area. The numbers of trapped California meadow voles (Microtus californicus) were not different between the areas in either year. More native rodents were trapped in the no-cat area. Birds present during the breeding season were seen more often in the no-cat area. California quail (Callipepla californicus) and California thrashers (Toxostoma redivivum) were present in the no-cat area and absent in the cat area. Cats at artificially high densities, sustained by supplementary feeding, reduced the abundance or native rodent and bird populations, changed the rodent species composition, and may have facilitated the expansion of the house mouse into new areas. Thus we recommend that the feeding of cats in parks should be strictly prohibited. 

Modelling biological control of cat populations

Courchamp, F. & G. Sugihara. 1999. Modelling biological control of alien predator populations to protect native island prey species from extinction. Ecological Applications, 9: 112-123.

Introduced feral cat (Felis catus) populations are an important threat to many island vertebrate populations and to bird species in particular. Elimination of feral cat populations is desirable in most of these ecosystems. Release of a parasite species in these mostly immune-naive populations is thought to be an efficient eradication measure. Such an approach is theoretically investigated here, using a mathematical model that describes the effects of introducing a virus into the cat population on population dynamics of both the cat and its prey. We studied the effects of two types of introduced feline viruses: Feline Immunodeficiency Virus and Feline Leukemia Virus, both of which are good candidates for eradicating a cat population. Results show that eradication is possible with Feline Leukemia Virus, if natural immunity is sufficiently low. Feline Immunodeficiency Virus cannot fully eradicate cat populations, but can be an effective agent for long-term control of cat populations on islands where total cat eradication is not possible (e.g., there is a high likelihood of continued introduction of cats) or not desirable (e.g., when rats are present). Culling, which by itself would require a very prolonged and logistically demanding effort to eliminate cat populations, may be more efficient when applied simultaneously with virus introduction.

Feeding ecology and population dynamics of the feral cat in Australia

Molsher, R., Newsome, A., & Dickman, C. (1999). Feeding ecology and population dynamics of the feral cat (Felis catus) in relation to the availability of prey in central-eastern New South Wales. Wildlife Research, 26(5), 593-607.

The diet of feral cats (Felis catus) was studied at Lake Burrendong, central-eastern New South Wales, from July 1994 to June 1997. Mammals were the major prey in 499 scats that were analysed. Rabbits (Oryctolagus cuniculus) were the staple prey, while carrion was an important secondary food. Invertebrates, other mammalian prey, vegetation, birds and reptiles were generally minor components of the diet. Few significant seasonal differences in diet were found; however, invertebrates contributed less and possums more to the diet in winter and summer respectively. A significant dietary response was found to changes in rabbit abundance, but not for the other prey types. Cats continued to prey heavily on rabbits even after a 90% decline in rabbit abundance occurred, which coincided with the advent of Rabbit Calicivirus Disease (RCD). House mice (Mus domesticus) increased in importance in the diet ten months post-RCD. Although the abundance of cats was correlated with the abundance of some prey species, other factors may have influenced the observed patterns; these are discussed.

Myths and facts about “managed” cat colonies

Winter, L. (undated). Myths and facts about “managed” cat colonies. ABC

1. Cat colonies don't just die out in one or two years: Although promoters of Trap/Neuter/Release (TNR) often claim that the colonies die out through attrition in just a few years, there is very little evidence to support this claim. Even the Adams Morgan cat colony of only 30 original cats in the District of Columbia, which was "managed" by the founders of Alley Cat Allies, took 10 years to die out. It is often difficult to trap all of the cats, the cat food that is left out attracts more cats, and cat colonies often become dumping grounds for unwanted pets (Donald, R.L. 1992. Should Feral Cats Be Euthanized? Shelter Sense: 3-7). Volunteers can become overwhelmed and may not have all of the financial resources or the manpower needed to trap and alter every cat in a colony (Passamsi, w.c., D.W. Macdonald. 1990. The Fate of Controlled Feral Cat Colonies. Universities Federation for Animal Welfare, Hertfordshire, England. 48).
Please note the following: "It's just so overwhelming. I'm in over my head. I can't even afford to eat or buy clothes or do anything. I wake up in the morning hoping I can make it through the day." (Puzzanghera, J. 1995. So Many Cats, So Little Time, San Jose Mercury News, July 19, 1995.)

2. TNR is not meant to eliminate colonies of cats: The purpose of TNR is NOT to eliminate cat colonies, but to perpetuate them because cat feeders believe that if a neutered colony is removed, an intact colony will move in and take it's place.
Please see the following: "You will never get rid of the cats in that area, and it is not advisable to do that. Because if you're doing a neutering to eradicate the cats by neutering, and remove them completely from the area, you are just being the same as somebody who wishes to go and trap them out and kin them. All you're doing is delaying the day Of death." (From a presentation by Roger Tabor, Alley Cat Allies Seminar, "Focus on Ferals," July 8, 1994, Washington, DC.)
More cats may move into an area ONLY if the food source remains. If cats are trapped out and the food source is removed, a cat colony will not reform in that location. This is exactly what occurred at Riverside National Park where over 25 cats were being fed daily. Over the strong objections of the cat feeders and Alley Cat Allies, and in the face of a negative media campaign, the National Park Service removed the cats, the feeding was stopped, and no additional cats have congregated in the area. The Cats were not euthanized, but taken to a local Shelter (Sealy, D. 1996. Removal of a Colony of Free-Ranging Cats From an Area Administered by the National Park Service: A Case History, in: Proceedings of the 1995 International Wildlife Rehabilitation Council Conference, Virginia Beach, VA. Pp 75-77).

3. Cat colonies attract other predators: The cat food left out attracts raccoon, skunk, opossum, fox, coyote, and rats, all predators of birds and carriers of diseases that can be transmitted to other cats, wildlife, or humans, such as rabies. No one is neutering and giving rabies vaccinations to these animals to control their populations and the spread of disease. I have personally witnessed a huge rat hole right under a cat feeding station, and studies have shown that cats do not do a very good job of Controlling rat populations (Childs, J. E. 1991. And the Cat Shall Lie Down With the Rat, Natural History: 16 - 19).
I also have slides of raccoons at cat feeding stations, and e-mail messages from cat feeders discussing the problem of raccoon and opposum at their stations.

4. The cats are not always tested or vaccinated for fatal feline diseases: Some groups, such as the Feral Cat Coalition (http://www.feralcat.com/tpolicy.html), do not follow the American Veterinary Medical Association's guidelines which state that cats in a "managed" cat colony should be tested and vaccinated for infectious diseases and adopted or euthanized if positive. Thus, diseased cats in "managed" cat colonies could come in contact with and infect free-roaming pet cats. Cats with fatal feline diseases will suffer and die a miserable death, calling into question the very humaneness of this practice.

5. Domestic cats are not strictly territorial: Cat feeders will often say that altered cats defend their territory, and do not let other cats join the colony. There is scant scientific evidence to support this claim either. It is well-known that the home ranges of domestic cats overlap. In fact, Dr. Carol Haspel, who conducted a number of studies of cat colonies in Brooklyn, NY, says that cats occupying a certain area "absolutely do not" keep others out, "particularly if there is a feeder." (Donald, R.L. 1992. Should Feral Cats Be Euthanized? Shelter Sense: 3-7).

6. Well-fed, altered cats still kill birds and can impact wildlife populations: It has been extensively documented that domestic cats can severely impact seabird populations on islands (Moors, P.J. and I.A.E. Atkinson. 1984. Predation on seabirds by introduced animals, and factors affecting its severity. ICBP Technical Publication 2:667-690), and well-fed Cats still kill wildlife (Adamec, R.E. 1976. The interaction of hunger and preying in the domestic cat (Felis catus): an adaptive hierarchy? Behavioral Biology 18: 263-272.)
Cats and other predators can also have an impact on songbird populations in fragmented and isolated habitat (Wilcove, D.S. 1985. Nest predation in forest tracts and the decline of migratory songbirds. Ecology 66: 1211- 1214.)

Please see the following quote regarding a scientific study conducted in two California parks-one with over 20 cats that were fed daily, and one without cats:
Cats at artificially high densities, sustained by supplemental feeding, reduced the abundance of native rodent and bird populations, changed the rodent species composition, and may have facilitated the expansion of the house mouse into new areas. Thus we recommend that the feeding of cats in parks Should be Strictly prohibited. (Hawkins, C.C., W.E. Grant, М.Т. Longnecker. 1999. Effect of Subsidized House Cats on California Birds and Rodents. 1999 Transactions of the Western Section of The Wildlife Society 35: 29-33.)

Secondary poisoning of feral cats in NZ

Three papers analyse different effect of secondary poisoning on feral cats.

Alterio, N. (1996). Secondary poisoning of stoats (Mustela erminea), feral ferrets (Mustela furo), and feral house cats (Felis catus) by the anticoagulant poison, brodifacoum. New Zealand Journal of Zoology, 23(4), 331-338.

A poisoning operation using Talon 20P™, active ingredient brodifacoum, targeting rabbits (Oryctolagus cuniculus) in coastal grasslands on the Otago Peninsula, New Zealand, also killed stoats (Mustela erminea), ferrets (Mustela furo), cats (Felis catus), and mice (Mus musculus) and probably possums (Trichosurus vulpecula), hedgehogs (Erinaceus europaeus), rats (Rattus rattus), hares (Lepus europaeus occidentalis), and chaffinches (Fringilla coelebs). A new immigrant ferret also died 41 days after poisoning. If repeated in other habitats such as tussock grasslands and forests this method could greatly assist in restoration of mainland ecosystems and mitigation of bovine tuberculosis (Mycobacterium bovis) by controlling a variety of pests/ Tb carriers in one operation. The removal of small mammalian predators following poisoning operations could decrease immediate predation pressure on native wildlife. However, the efficacy of this multi‐species pest control method and unwanted side‐effects must be researched before its routine use. This research also demonstrates the potential threat of second‐generation anticoagulantpoisons such as brodifacoum to small mammalian carnivores with high conservation value in their native countries.

Heyward, R. P., & Norbury, G. L. (1999). Secondary poisoning of ferrets and cats after 1080 rabbit poisoning. Wildlife Research, 26(1), 75-80.

The incidence of secondary poisoning was determined by using radio-telemetry to assess the survival of 68 ferrets and 21 cats on two treatment sites and one control site in the dry tussock grasslands of New Zealand. The treatment sites were aerially poisoned with 1080-coated carrot baits (0.02% wt/wt) to control rabbits. The control site was not poisoned. Ferrets and cats were monitored at two-weekly intervals for at least 1 month before, and 2 months after the poison operations. Muscle samples from ferrets and cats that died within 50 days of poisoning on the treatment sites were assayed for 1080. In all, 7–11% (n = 28) of ferrets on one site and 8–15% (n = 26) of ferrets at the other site apparently died of secondary 1080 poisoning. Natural mortality rates of ferrets were 46–81% per annum. While we have evidence that secondary poisoning of cats does occur, we monitored insufficient numbers of cats to reliably estimate mortality rates.

Declines in predator numbers are commonly observed after rabbit poisoning. This study indicates that secondary poisoning contributes to these declines.

Gillies, C. A., & Pierce, R. J. (1999). Secondary poisoning of mammalian predators during possum and rodent control operations at Trounson Kauri Park, Northland, New Zealand. New Zealand Journal of Ecology, 23(2), 183-192.

A poison baiting operation at Trounson Kauri Park in Northland, New Zealand using first 1080 and then brodifacoum targeted possums (Trichosurus vulpecula) and rodents (Rattus rattus, Rattus norvegicus and Mus musculus). Predatory mammals were monitored by radio telemetry during the operation. All six feral cats (Felis catus), the single stoat (Mustela erminea) and the single ferret (Mustela furo) being monitored at the beginning of the operation died of secondary poisoning following the 1080 operation. A further two cats and four stoats were monitored through the ongoing poisoning campaign using brodifacoum in a continuous baiting regime. None of these radio tagged carnivores died of secondary poisoning. However, tissue analysis of additional carnivores trapped at Trounson found that cats, weasels (Mustela nivalis) and, to a lesser extent, stoats did contain brodifacoum residues. The duration that the radio-tagged predators were alive in and around Trounson Kauri Park suggests that the secondary poisoning effect was much reduced under the continuous baiting strategy compared to the initial 1080 poison operation.

Domestic dogs in Wildlife habitats

Sime, C. A. 1999. Domestic Dogs in Wildlife Habitats. Pages 8.1-8.17 in G. Joslin and H. Youmans, coordinators. Effects of recreation on Rocky Mountain wildlife: A Review for Montana. Committee on Effects of Recreation on Wildlife, Montana Chapter of The Wildlife Society. 307pp.

It is difficult to segregate human demographic trends from trends in rural development and outdoor recreational participation in settings like the West where they appear to be interrelated. One extension of human recreation in wildlife habitats is the effect of disturbance, harassment, displacement, or direct mortality of wildlife attributable to domestic dogs that accompany recreationists. At some level, domestic dogs still maintain instincts to hunt and/or chase. Given the appropriate stimulus, those instincts can be triggered in many different settings. Even if the chase instinct is not triggered, dog presence in and of itself has been shown to disrupt many wildlife species. Authors of many wildlife disturbance studies concluded that dogs with people, dogs on-leash, or loose dogs provoked the most pronounced disturbance reactions from their study animals. During winter, concerns are primarily related to human activity on ungulate winter ranges. Dogs extend the zone of human influence when off-leash. Many ungulate species demonstrated more pronounced reactions to unanticipated disturbances, as a dog off-leash would be until within very close range. In addition, dogs can force movement by ungulates (avoidance or evasion during pursuit), which is in direct conflict with overwinter survival strategies which promote energy conservation. During summer, concerns are primarily related to the birth and rearing of young for all wildlife species. Dogs are noted predators for various wildlife species in all seasons. Domestic dogs can potentially introduce diseases (distemper, parvovirus, and rabies) and transport parasites into wildlife habitats. While dog impacts to wildlife likely occur at the individual scale, the results may still have important implications for wildlife populations. For most wildlife species, if a “red flag” is raised by pedestrian-based recreational disturbance, there could also be problems associated with the presence of domestic dogs. Managers may consider the following when evaluating recreational impacts of dogs in wildlife habitats: species biology, reproductive potential, abundance, density, distribution, degree of habitat specificity or reliance on certain habitat components, and predisposition and sensitivity to disturbance by other agents. This information is intended to increase awareness among natural resource professionals and the public about the potential implications of uncontrolled domestic dogs in wildlife habitats and to encourage responsible outdoor recreation ethics.

Feral cat vs. dingo perception: a gender-cultural bias or a real ecological difference?

Smith, N. (1999). The howl and the pussy: feral cats and wild dogs in the Australian imagination. The Australian journal of anthropology, 10(3): 288-305.

This paper looks at recent attention given to feral cats in Australia, particularly focusing on their symbolic status in eco-nationalist discourses. Australian eco-nationalism is a specific blend of environmentalist and patriotic sentiments which, in an exaggerated way, positions the feral cat as a rapacious European invader predating on native wild life. This vilification of the cat can be related to much earlier forms of (mainly European) symbolism associating the creature with femininity and evil, which I illustrate by looking at the manner in which the feral cat is opposed to the masculinised Australian wild dog—the dingo. I argue that the recent surfacing of this totemic opposition between ‘the howl and the pussycat’ is related to an eco-nationalist sense of place which simultaneously recognises and denies that the human colonisation of Australia was (and is) a form of feral invasion.

Hytten, K. F. (2009). Dingo dualisms: Exploring the ambiguous identity of Australian dingoes. Australian Zoologist, 35(1), 18-27.

How wildlife is defined, and which wildlife is accorded protection, emerges from competing constructions of nature and culture. Few species of Australian wildlife have as ambiguous an identity as dingoes. This paper identifies three dualisms that characterise discourses relating to Australian dingoes Canis lupus dingo. They are at once classified as both a pest and protected species, perceived to be feral and native, and most recently categorised as either pure or hybrid. It is argued that these dualisms are underpinned by different versions of the nature-culture dichotomy. Portrayals and perceptions of dingoes around Australia are explored to reveal how different aspects of the dualisms identified are drawn upon within different contexts. Illustrations of the contradictory constructions of dingoes highlight the need to critically deconstruct discourses relating to wildlife, particularly when they inform actions. As such, this paper demonstrates the important contribution a discourse-sensitive approach can make to understanding human perceptions of wildlife.



Letnic, M., Ritchie, E. G., & Dickman, C. R. (2012). Top predators as biodiversity regulators: the dingo Canis lupus dingo as a case study. Biological reviews, 87(2), 390-413.

Top-order predators often have positive effects on biological diversity owing to their key functional roles in regulating trophic cascades and other ecological processes. Their loss has been identified as a major factor contributing to the decline of biodiversity in both aquatic and terrestrial systems. Consequently, restoring and maintaining the ecological function of top predators is a critical global imperative. Here we review studies of the ecological effects of the dingo Canis lupus dingo, Australia's largest land predator, using this as a case study to explore the influence of a top predator on biodiversity at a continental scale. The dingo was introduced to Australia by people at least 3500 years ago and has an ambiguous status owing to its brief history on the continent, its adverse impacts on livestock production and its role as an ecosystem architect. A large body of research now indicates that dingoes regulate ecological cascades, particularly in arid Australia, and that the removal of dingoes results in an increase in the abundances and impacts of herbivores and invasive mesopredators, most notably the red fox Vulpes vulpes. The loss of dingoes has been linked to widespread losses of small and medium-sized native mammals, the depletion of plant biomass due to the effects of irrupting herbivore populations and increased predation rates by red foxes. We outline a suite of conceptual models to describe the effects of dingoes on vertebrate populations across different Australian environments. Finally, we discuss key issues that require consideration or warrant research before the ecological effects of dingoes can be incorporated formally into biodiversity conservation programs.

Controlling cats through the control of rabbits

Courchamp, F., Langlais, M., & Sugihara, G. (1999). Control of rabbits to protect island birds from cat predation. Biological Conservation, 89(2), 219-225.

Both introduced predators (e.g. domestic cats) and introduced small grazers (e.g. rabbits) are harmful to many island vertebrate species. The effects of cats on indigenous species are direct (predation), whereas the most obvious effects of rabbits are often indirect and in the longer term. Thus, in situations where both cats and rabbits are present, priority is frequently given to control of cats. However, the presence of rabbits can allow an increased predator population which can lead to extinction of the indigenous and less well adapted prey species, and increase the difficulty of predator control. Through a mathematical model, we show that control of introduced prey facilitates the control of the introduced predator population. Moreover, predator control may fail to protect the indigenous prey if control of the introduced prey is not undertaken simultaneously. Therefore, control of both introduced species is the best strategy.

Impact of cats and foxes on the small vertebrate fauna in Western Australia

Short, J., Calver, M. C., & Risbey, D. A. (1999). The impact of cats and foxes on the small vertebrate fauna of Heirisson Prong, Western Australia. I. Exploring potential impact using diet analysis. Wildlife Research, 26(5), 621-630.

The diets of cats (Felis catus) and foxes (Vulpes vulpes) killed during predator control at a semi-arid site in Western Australia were studied to see which prey species may be affected by predation from these introduced predators. The number of items, biomass and frequency of occurrence of each food type in the gut contents from 109 fetal cats, 62 semi-feral cats and 47 foxes were used to calculate an Index of Relative Importance for each food category for each predator. Mammals were the most important prey group for all three predators, with rabbit being the most highly ranked prey species. The diets of feral and semi-feral cats were similar in dietary diversity but differed in the frequency of occurrence of some food categories. Native rodents, birds and reptiles occurred more frequently and were ranked higher in the diet of feral cats, and food scraps occurred more frequently in the diet of semi-feral cats. The diet of foxes was less diverse than that of either group of cats. Invertebrates and sheep carrion were more important prey categories for foxes than for cats. In the summer-autumn period, foxes ate more sheep carrion and invertebrates than they did in winter-spring. The diet of feral cats was more diverse in summer-autumn, including a greater range of invertebrates and more rodents, birds and reptiles than in the winter-spring period. We predict that cats are more likely to have an impact on small vertebrates at this site and that the control of cats could lead to recoveries in the populations of native rodents, birds and reptiles. By contrast, the control of foxes alone may lead to a rise in cat numbers and a consequent detrimental impact on small vertebrate populations.


Risbey, D. A., Calver, M. C., Short, J., Bradley, J. S., & Wright, I. W. (2000). The impact of cats and foxes on the small vertebrate fauna of Heirisson Prong, Western Australia. II. A field experiment. Wildlife Research, 27(3), 223-235.

The hypothesis that predation by feral cats and introduced foxes reduces population sizes of small, native vertebrates was supported by results of a predator-removal experiment at Heirisson Prong, a semi-arid site in Western Australia. The methods of control used against cats and foxes to protect native mammals reintroduced to Heirisson Prong produced three broad ‘predator zones’: a low-cat and low-fox zone, where foxes were eradicated and spotlight counts of cats declined after intensive cat control; a high-cat and low-fox zone where spotlight counts of cats increased three-fold after foxes were controlled; and a zone where numbers of cats and foxes were not manipulated. Small mammals and reptiles were monitored for one year before and three years after predator control began. Captures of small mammals increased in the low-cat and low-fox zone, but where only foxes were controlled captures of small mammals declined by 80%. In the absence of cat and fox control, captures of small mammals were variable over the sampling period, lower than where both cats and foxes were controlled, yet higher than where only foxes were controlled. The capture success of reptiles did not appear to be related to changes in predator counts. This study presents the first experimental evidence from mainland Australia that feral cats can have a negative impact on populations of small mammals.

Bells and electronic sonic device reducing predation by cats in UK

Nelson, S. H., Evans, A. D., & Bradbury, R. B. (2005). The efficacy of collar-mounted devices in reducing the rate of predation of wildlife by domestic cats. Applied Animal Behaviour Science, 94(3), 273-285.

Volunteer cat owners from across the UK were recruited to take part in two trials designed to test the efficacy of collar-mounted warning devices in reducing cat predation rates of native wildlife. Cats equipped with a bell returned 34% fewer mammals and 41% fewer birds than those with a plain collar. Those equipped with an electronic sonic device returned 38% fewer mammals and 51% fewer birds compared with cats wearing a plain collar. There was no significant difference in prey return rates by cats wearing collars equipped with one bell, two bells or the sonic device. Warning devices mounted on quick-release collars are recommended as an effective way of reducing wildlife kill rates by domestic cats. Future research and development aimed at further improving the efficacy of sonic devices is recommended.

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You can see early reports of CatAlert device here

Clark, N. A. & N.H.K. Burton (1998). A pilot field trial into the effectiveness of the CatAlert™ collar at reducing predation by domestic cats. British Trust for Ornithology.

Clark, N. A. (1999). Progress report on the effectiveness of the Mark II CatAlert™ collar at reducing predation by domestic cats. British Trust for Ornithology.

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Read a short review about belling effectiveness

Potential use of secondary poison to control feral cat on islands

Dowding, J. E., Murphy, E. C., & Veitch, C. R. (1999). Brodifacoum residues in target and non-target species following an aerial poisoning operation on Motuihe Island, Hauraki Gulf, New Zealand. New Zealand Journal of Ecology, 23(2), 207-214.

Aerial poisoning using Talon^® 7-20 baits (active ingredient 20 ppm brodifacoum) was carried out on Motuihe Island, Hauraki Gulf, during the winter of 1997. The operation aimed to eradicate Norway rats (Rattus norvegicus) and house mice (Mus musculus) and to reduce rabbit (Oryctolagus cuniculus) numbers significantly. We studied the diet of feral house cats (Felis catus) before the operation, then monitored the impact of the operation on them to determine whether secondary brodifacoum poisoning caused a reduction in their numbers. Large numbers of rabbits remained after poisoning; this and other observations suggested that insufficient bait had been applied to achieve the aims of the programme. Cat mortality, based on radio-collared animals, was 3/14 (21%). Cats on Motuihe Island appeared to eat rabbit muscle tissue in preference to internal organs; brodifacoum concentrations are lower in muscle than in liver and we suggest that rabbits may be a poorer vector than rodents for secondary poisoning of cats. We also confirmed the risk of an aerial brodifacoum application to a range of non-target bird species. Mortality of pukeko (Porphyrio p. melanotus) and paradise shelducks (Tadorna variegata) was 49% and 60% , respectively. No mortality of New Zealand dotterels (Charadrius obscurus) or variable oystercatchers (Haematopus unicolor) was detected. Twenty-nine individuals of 10 bird species (five indigenous and five introduced) were found dead after the operation and livers of all of them contained residues of brodifacoum; toxin levels averaged 0.84 µg g^-1 (range 0.12-2.31 µg g^-1).

PVA supports cats' control to manage endangered mammal

Forys, E. A., & Humphrey, S. R. (1999). Use of population viability analysis to evaluate management options for the endangered Lower Keys marsh rabbit. The Journal of wildlife management, 251-260.

We conducted a population viability analysis (PVA) for the federally endangered Lower Keys marsh rabbit (Sylvilagus palustris hefneri). We estimated parameters via livetrapping, radiotelemetry, and fecal-pellet counting during a 2.5-year study. Historically, this subspecies ranged throughout the Lower Keys of Florida, but today the marsh rabbit is limited to 41 subpopulations occurring in 3 distinct metapopulations. To evaluate this subspecies' risk of extinction, we used VORTEX, a simulation modeling program, that combined deterministic and stochastic birth and death events, differing migration rates based on spatially explicit patch structure, and extinction and recolonization. Our simulation calculated the chance that each metapopulation would go extinct under current conditions and several management scenarios. Under current conditions, the model predicted there is a 100% chance that all metapopulations will go extinct. The metapopulation with many small patches went extinct faster than the metapopulations with fewer, larger patches. The most effective strategy to decrease the risk of extinction of all 3 metapopulations was to increase the survival rate in several age and sex classes by eliminating predation by domestic cats.

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.

Cat and catkeepers in Rome

Natoli, E., Ferrari, M., Bolletti, E., & Pontier, D. (1999). Relationships between cat lovers and feral cats in Rome. Anthrozoos: A Multidisciplinary Journal of The Interactions of People & Animals, 12(1), 16-23.


The aim of this study was to assess the relationships between cat lovers and feral cats in Rome. One hundred and fifty-eight cats from 3 populations were observed for 1108 hours of data collection: some demographic characteristics of the colonies were investigated, together with the behavior of cat lovers (those who fed and cared for the cats). The quantity of food eaten and uneaten by the cats was recorded, and the cost to support each colony calculated. The quantity of food provided ranged from 20.47 to 264 kg/month. The mean quantity of food eaten/day by each cat in the study areas never surpassed 130.4 g. In total, the quantity of food wasted ranged from 522 g to 34.05 kg/month. The results of this study can help public administrations decide on how to allocate funds for the management of feral cats. Indeed, they provide statistics on the individual food intake/cat/day, as well as information on the type of collaboration one should expect from cat lovers. In addition, this study outlines advantages and limits of the "Roman model" where the Public Veterinary Services (PVS) and associations of cat lovers cooperate to manage feral cats.

Feeding ecology and population dynamics of feral cats in New South Wales

Molsher, R., Newsome, A., & Dickman, C. (1999). Feeding ecology and population dynamics of the feral cat (Felis catus) in relation to the availability of prey in central-eastern New South Wales. Wildlife Research, 26(5), 593-607.

The diet of feral cats (Felis catus) was studied at Lake Burrendong, central-eastern New South Wales, from July 1994 to June 1997. Mammals were the major prey in 499 scats that were analysed. Rabbits (Oryctolagus cuniculus) were the staple prey, while carrion was an important secondary food. Invertebrates, other mammalian prey, vegetation, birds and reptiles were generally minor components of the diet. Few significant seasonal differences in diet were found; however, invertebrates contributed less and possums more to the diet in winter and summer respectively. A significant dietary response was found to changes in rabbit abundance, but not for the other prey types. Cats continued to prey heavily on rabbits even after a 90% decline in rabbit abundance occurred, which coincided with the advent of Rabbit Calicivirus Disease (RCD). House mice (Mus domesticus) increased in importance in the diet ten months post-RCD. Although the abundance of cats was correlated with the abundance of some prey species, other factors may have influenced the observed patterns; these are discussed.

Role of ferals in the population dynamics of cats

Bradshaw JWS, Horsfield GF, Allen JA, Robinson IH (1999) Feral cats: their role in the population dynamics of the Felis catus. Applied Animal Behaviour Science 65: 273–283.

The so-called domestic cat occupies a unique position within the truly domestic animals since it freely interbreeds with feral populations, and there is considerable gene flow in both directions. This is possible because the likelihood of an individual cat forming a relationship with people is strongly affected by its experiences during the socialisation period (3–8 weeks of age), although this does not preclude differences between owned and feral populations in the relative frequencies of alleles which affect social behaviour towards humans. We suggest a hitherto unconsidered reason why a separate domesticated population of cats (apart from pedigree breeds) has not yet emerged: the unusual and stringent nutrient requirements of the cat may historically have militated against successful breeding on a completely human-provided diet, and led to the retention of the ability to achieve a nutritionally complete diet by scavenging and/or hunting. More recently, the widespread availability of nutritionally complete manufactured foods and veterinary care in western countries appears to be leading towards a rapid change in the population dynamics and population genetics of both owned and feral cats.

Hybridization between wolves and dogs

Vila, C., & Wayne, R. K. (1999). Hybridization between wolves and dogs.Conservation Biology, 13(1), 195-198.

Concern has been expressed that European populations of gray wolves (Canis lupus) have extensively hybridized with domestic dogs (C. familiaris). We reviewed and analyzed surveys of mitochondrial and biparentally inherited genetic markers in dogs and wild populations of wolf-like canids. Although dog-wolf hybrids have been observed in the wild, significant introgression of dog markers into wild wolf populations has not yet occurred. Our investigation suggests that hybridization may not be an important conservation concern even in small, endangered wolf populations near human settlements. The behavioral and physiological differences between domestic dogs and gray wolves may be sufficiently great such that mating is unlikely and hybrid offspring rarely survive to reproduce in the wild.


En algunas ocasiones se ha sugerido que las poblaciones europeas de lobos (Canis lupus) pueden estar profundamente hibridadas con perros domésticos (C. familiaris). Revisamos y analizamos estudios que utilizan marcadores genéticos mitocondriales y de herencia biparental en perros y poblaciones silvestres de cánidos del grupo del lobo. Aunque existen observaciones de híbridos entre perros y lobos en condiciones naturales, nunca se ha observado una significativa introducción de marcadores genéticos de perros en las poblaciones de lobos. Nuestra revisión sugiere que la hibridación puede no ser un problema importante ni tan sólo para la conservación de poblaciones de lobos pequeñas y amenazadas, cerca de asentamientos humanos. Las diferencias fisiológicas y de comportamiento entre perros y lobos pueden ser suficientemente grandes como para que su apareamiento sea improbable y los híbridos tengan escasas posibilidades de sobrevivir y reproducirse en libertad.

See more about wild canid hybridisation with dogs

Cats: perceptions and misconceptions

Perry, G. (1999). Cats–perceptions and misconceptions: two recent studies about cats and how people see them. In Proceedings of the 8th National Conference on Urban Animal Management in Australia, Gold Coast, Queensland.

 Current figures suggest that cat ownership in Australia is declining, yet cats, properly managed, make ideal pets for those living in high density housing and/or whose lifestyles require that their pets spend long periods alone. State governments and local authorities are increasingly requiring that owners control their cats and that animal management staff enforce these regulations.

These studies suggest that the majority of cat owners are responsible. Once they have adopted a cat, usually a ‘moggie’, they have their cat neutered, but sometimes not until it has had a litter. While many of their cats hunt, as many do not and few hunt often, so this problem is probably overemphasised by non-owners. Contrary to popular belief, they more often hunt lizards than birds.

With the emphasis on the identification of owned cats, it is important to note the reasons given for identifying or not. Any education program to raise awareness of the importance of identification of cats should emphasise the problems which could occur for an unidentified cat and the value of microchipping as an identification tool. All companion animals cause community problems — dogs bark, parrots screech — but both provide companionship whose value outweighs the problems they cause. Cats are particularly misunderstood and often cat owners feel guilt for the sins of their much loved couch potato’s feral counterpart. It is important that the benefits of responsible cat ownership be acknowledged and that strategies are put in place to educate owners on the value of early desexing, confinement and correct identification.

Cats "protecting" birds

Courchamp F, Langlais M, Sugihara G. 1999. Cats protecting birds: Modelling the mesopredator release effect. Journal of Animal Ecology, 68: 282–292

1- Introduced predators account for a large part of the extinction of endemic insular species, which constitutes a major component of the loss of biodiversity among vertebrates. Eradication of alien predators from these ecosystems is often considered the best solution.
2- In some ecosystems, however, it can generate a greater threat for endemic prey, through what is called the "mesopredator release". This process predicts that, once superpredators are suppressed, a burst of mesopredators may follow that leads their shared prey to extinction.
3- This process is studied through a mathematical model describing a three species system (prey-mesopredator-superpredator). Analysis of the model, with and without control of meso- and superpredators, shows that this process does indeed exist and can drive shared prey to rapid extinction.
4- This work emphasises that, although counter-intuitive, eradication of introduced superpredators, such as feral domestic cats, is not always the best solution to protect endemic prey when introduced mesopredators, such as rats, are also present.

Virus to control island populations of cats

Courchamp F & Sugihara G (1999) Modeling the biological control of an alien predator to protect island species from extinction. Ecological Applications, 9 (1): 112-123.

Introduced feral cat (Felis catus) populations are an important threat to many island vertebrate populations and to bird species in particular. Elimination of feral cat populations is desirable in most of these ecosystems. Release of a parasite species in these mostly immune-naive populations is thought to be an efficient eradication measure. Such an approach is theoretically investigated here, using a mathematical model that describes the effects of introducing a virus into the cat population on population dynamics of both the cat and its prey. We studied the effects of two types of introduced feline viruses: Feline Immunodeficiency Virus and Feline Leukemia Virus, both of which are good candidates for eradicating a cat population. Results show that eradication is possible with Feline Leukemia Virus, if natural immunity is sufficiently low. Feline Immunodeficiency Virus cannot fully eradicate cat populations, but can be an effective agent for long-term control of cat populations on islands where total cat eradication is not possible (e.g., there is a high likelihood of continued introduction of cats) or not desirable (e.g., when rats are present). Culling, which by itself would require a very prolonged and logistically demanding effort to eliminate cat populations, may be more efficient when applied simultaneously with
virus introduction.