Control of feral cats for nature conservation (parts I to IV)

Risbey, D. A., Calver, M., & Short, J. (1997). Control of feral cats for nature conservation. I. Field tests of four baiting methods. Wildlife Research, 24(3), 319-326.

Four methods of baiting were evaluated on a radio-collared population of feral cats on Heirisson Prong, Shark Bay, Western Australia. Dried-meat baits, baiting rabbits to kill cats through secondary poisoning, a fishmeal-based bait and a bait coated in the flavour enhancer Digest were tested. All proved to be ineffective for controlling feral cats. Future research should explore baits more ‘natural’ in appearance and the effect of visual lures, and possibly bait over a larger area to increase the number of cats exposed to baits.

Short, J., Turner, B., Risbey, D. A., & Carnamah, R. (1997). Control of feral cats for nature conservation. II. Population reduction by poisoning. Wildlife Research, 24(6), 703-714.

A feral cat population was substantially reduced by poisoning at a semi-arid site in Western Australia. The control programme was designed to protect two species of endangered native mammals that had recently been reintroduced to the site. Feral cats were poisoned with carcasses of laboratory mice, each impregnated with 4.5 mg of sodium monofluoroacetate (1080). Baits were placed at 100-m intervals along the track system each night for four consecutive nights. Kill rates were assessed by monitoring survival of radio- collared cats and by spotlight counts of cats before and after baiting. All radio-collared cats were killed and there was a 74% reduction in spotlight counts of cats after baiting. Bait removal varied with the abundance of rabbits, the primary prey item for cats in this area. Effectiveness of control operations against feral cats is maximised by baiting at times of low prey abundance. Monitoring the changing abundance of the primary prey species provides important information for timing control operations against feral cats.

Short, J., Turner, B., & Risbey, D. (2003). Control of feral cats for nature conservation. III. Trapping. Wildlife Research, 29(5), 475-487.

We present comparative success of various trapping methods trialed during control of feral cats at a site for the reintroduction of threatened mammals at Shark Bay, Western Australia. Our results come from 31 703 trap-nights that caught 263 cats (an average of 0.83 per 100 trap-nights). Cats differed markedly in their vulnerability to trapping depending on whether they primarily scavenged at rubbish tips or around human settlement or whether they hunted for their food in the bush. Cage traps were an effective means of controlling the former, with 9.4 cats captured per 100 trap-nights. Scavenging cats included a higher proportion of sub-adults and kittens and lower proportion of adult males than hunting cats. Variation between years in capture success for hunting cats was largely explained by the abundance of rabbits relative to that of cats and whether the rabbit population was increasing or decreasing. These factors accounted for a nine-fold difference in trap success. The number of cats caught in any particular trapping session could be explained by location (rubbish tip or town versus bush), trapping effort (typically greater effort yielded higher captures), abundance of cats at the site (captures were highest when cats were abundant), and season (captures were highest in the first half of the year when the young of the year were becoming independent). Concealed foot-hold traps, in a range of possible sets, provided effective methods for capturing cats that hunt, except where capture of non-target species was a critical limiting factor. Cage traps caught cats at a comparable rate to foot-hold traps for standard sets, but caught a significantly different cohort. Concealed foot-hold traps caught a higher percentage of adult cats, particularly males, than did cage traps. Mouse carcases and rabbit pieces were significantly more effective as lures when rabbits (the major food of cats at the site) were at low densities, whereas the success of commercial scent lures was unrelated to food availability. Significantly more cats than expected were caught using food as an attractant at times of food shortage (late summer, autumn and early winter) for both scavenging and hunting cats. In contrast, scent lures caught significantly more cats than expected in spring and summer when cats were defending access to mates and/or territory. Hence, no single trap type, trap set, or lure provided unequivocally superior performance over others. Control is likely to be best achieved by a variety of trapping methods and lure types used in combination, supplementing well timed poisoning efforts. Trap success is likely to be maximised by trapping at times when the dominant prey of cats are scarce relative to the number of cats and are decreasing in abundance.

Short, J., & Turner, B. (2005). Control of feral cats for nature conservation. IV. Population dynamics and morphological attributes of feral cats at Shark Bay, Western Australia. Wildlife Research, 32(6), 489-501.

The dynamics of feral cats (Felis catus) were assessed at Shark Bay at two adjoining sites subject to differing intensities of predator control. The Heirisson Prong conservation reserve (12 km²) was fenced to exclude predators and was subject to intensive control actions, while a portion of the adjoining Carrarang pastoral lease (60 km²) was subject to a lesser level of control. Foxes (Vulpes vulpes) were largely absent at both sites owing to effective control. Densities of cats were highly variable over time, showing strong annual fluctuations over 14 years of records Three independent estimates of peak density were made, varying between 1.5 and 2.8 km^-2. Rate of increase was assessed as 0.98 on the pastoral lease and 0.99 on the conservation reserve (to give an approximate doubling of the population every 8.5 months). A logistic model, with K = 1.5 km^-2 and r of 0.98, gave a maximum sustained yield of 0.37 cats km^-2 year^-1 and a harvest rate of >0.6 cats km^-2 year^-1 for their elimination in 5 years or less (for K = 2.8 km^-2  these values increase to 0.69 and >1.05 km^-2 year^-1 respectively). Harvest outcomes at both sites were consistent with these models. However, the effort required to maintain a given offtake rate increased 6-fold at low cat densities and offtake by trapping as a function of cat density took the form of a Type 3 functional response. The functional response for cat trapping (the offtake with constant effort per unit time) overlaid against the curve of cat productivity suggested a stable equilibrium point at low cat densities (0.07–0.13 cats km^-2). Hence, trapping effort needed to be greatly intensified at low cat densities and/or augmented by other methods of control to eradicate cats from the closed system of the reserve. The strongly male-biased sex ratio of captures at the barrier fence suggested high levels of reinvasion from beyond the harvested area of the pastoral lease and this made effective control in this open system difficult.

Infection strategies of retroviruses to control feral cats

Fromont, E., Courchamp, F., Pontier, D., & Artois, M. (1997). Infection strategies of retroviruses and social grouping of domestic cats. Canadian journal of zoology, 75(12), 1994-2002.

It is thought that parasites may exert selective pressure on the social structure of host populations. We compared the impact of feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV), two retroviruses commonly found in domestic cats (Felis catus). Because of low transmissibility and virulence, both infections have a worldwide distribution and low prevalence. Transmission modes differ: FIV is transmitted only through biting, while FeLV transmission occurs by biting, licking, grooming, and sharing food and from mother to fetus. FeLV is also more pathogenic than FIV. We compared FIV and FeLV prevalence and risk factors within five populations of cats. FIV infection occurred almost exclusively among adult male cats fighting to acquire and maintain dominant status. Classes at risk for FeLV infection included sexually intact cats allowed to roam freely. The impact of FeLV on host population growth was greater than that of FIV but varied among populations. Our results show that FIV is favoured by individual aggressiveness and a hierarchical social system, while FeLV is more prevalent among socially active cats. FeLV may constitute a source of selective pressure against numerous amicable contacts, particularly in urban cat populations, where aggression among individuals is reduced.

Biology and ecology of feral, free-roaming, and stray cats in California

Ogan, C. V., & Jurek, R. M. (1997). Biology and ecology of feral, free-roaming, and stray cats. In Mesocarnivores of northern California: biology, management, and survey techniques, workshop manual (pp. 87-92).

No abstract available. Click for full-text

Interactions among dogs, people and wildlife

Bekoff, M., & Meaney, C. A. (1997). Interactions among dogs, people, and the environment in Boulder, Colorado: A case study. Anthrozoos: A Multidisciplinary. Journal of The Interactions of People & Animals, 10(1), 23-31.

From September 1995 to April 1996 we studied interactions among dogs, people, and the environment in Boulder, Colorado. Data on behavioral disturbances by off-leash dogs who were accompanied by a person were collected with respect to dog-dog and dog-human interactions, dog-wildlife encounters, dogs trampling vegetation, and dogs entering and disturbing bodies of water. A questionnaire also was administered. Behavioral data showed that off-leash dogs generally did not travel far off trail, that when they did it was for short periods of time, and that they rarely were observed to chase other dogs, disturb people, chase wildlife, destroy vegetation, or enter bodies of water. Results from analyses of the questionnaire (skewed toward non-dog owners) showed that dog owners and non-dog owners agreed that people were more disruptive to the environment than dogs and that unruly people were more problematic than unruly dogs. We conclude that the well-being and interests of dogs should not summarily and dismissively be compromised when dogs and people attempt to share limited space that can be used by all parties for recreational purposes. Indeed, a higher percentage of people reported that the quality of dogs' experience of the outdoors would be compromised more than their own enjoyment if dogs could not walk off-leash in areas where this is currently permitted. The methods used and the results from this case study can serve as a model for other locations in which dogs and people compete for limited spatial resources.

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

Farm cat ecology in Australia

Barratt, D. G. (1997). Home range size, habitat utilisation and movement patterns of suburban and farm cats Felis catus. Ecography, 20(3), 271-280.

The movements of 10 house cats (4 desexed females, 5 desexed males and 1 intact male) living on the edge of a suburb adjoining grassland and forest/woodland habitat, and a neighbouring colony of seven farm cats, were examined using radio-telemetry over nine months. Nocturnal home range areas of the suburban cats varied between 0,02 and 27,93 ha (mean 7,89 ha), and were larger than diurnal home range areas (range 0,02 to 17 19 ha – mean 2 73 ha) Nocturnal home range areas of cats from the farm cat colony varied between 1,38 and 4,46 ha (mean 2,54 ha), and were also larger than diurnal home range areas (range 0,77 to 3,70 ha – mean 1,70 ha) Home ranges of cats in the farm cat colony overlapped extensively, as did those of cats living at the same suburban residence There was no overlap of home ranges of female cats from different residences, and little overlap between males and females from different residences Four of the suburban house cats moved between 390 m and 900 m into habitat adjoining the suburb Polygons describing the home ranges of these animals were strongly spatially biased away from the suburban environment, though the cats spent the majority of their time within the bounds of the suburb Movements further than 100–200 m beyond the suburb edge were always made at night There is evidence that home range sizes and spatial movement patterns of house cats are largely determined by a) the density and spatial distribution of cats utilising separate food resources, b) the personality and social dominance of individual cats, c) the location of favoured hunting and resting/sunning sites, and, d) barriers such as busy roads

Cats & Wildlife. A Conservation Dilemma

Coleman, J.S. Stanley A. Temple & Scott R. Craven. 1997. Cats & Wildlife. A conservation dilemma. Texas Parks and Wildlife. PWD LF W7000-658 (11/00)

Domestic cats first arrived in North America with European colonists several hundred years ago. Since that time, cats have multiplied and thrived as cherished pets, unwanted strays, and semi-wild predators. Although often overlooked as a problem, free- ranging cats affect other animals, often far from the homes and farms they share with people. Because we brought the domestic cat to North America, we have a responsibility to both the cats and to the wild animals they may affect. Here are some interesting and perhaps surprising facts concerning the contemporary dilemma posed by free-ranging domestic cats in the United States.

Feral cats' diet in Australia

Another pair of articles and a review on cats' diet in Australia.

Paltridge, R., D. Gibson & G. Edwards. 1997. Diet of the Feral Cat (Felis catus) in Central Australia. Wildlife Research 24(1) 67 - 76

Feral cats (Felis catus) occur throughout central Australia. In this study, we analysed the stomach contents of 390 feral cats collected between 1990 and 1994 from the southern half of the Northern Territory. Cats fed on a wide variety of invertebrates, reptiles, birds and mammals, including animals up to their own body mass in size. Mammals were the most important prey but reptiles were regularly eaten in summer and birds were important in winter. Invertebrates were present in the diet in all seasons. Carrion appeared in stomach samples during dry winters only and this has implications for future control of feral cats.

Martin, G.R., L.E. Twigg & DJ Robinson. 1996. Comparison of the Diet of Feral Cats From Rural and Pastoral Western Australia. Wildlife Research 23(4): 475 - 484

The stomach contents of 93 cats from rural and pastoral Western Australia were compared using the number and biomass of food items, and by calculating an Index of Relative Importance for each food category. Species of small native mammals (e.g. dasyurids, rodents) and geckos were significantly (P < 0.03) more prevalent in the diet of pastoral cats, and rural cats consumed greater (P < 0.03) quantities of introduced rodents and rabbits. Several other groups of native animals (e.g. snakes, skinks, agamids) were also more prevalent in the stomachs of pastoral cats (P < 0.10). Birds and orthopterans were important food items to cats from both habitats. There was reasonable dietary overlap (mean = 0.71) between the cats from both habitats, but the dietary breadth of the pastoral cats (mean = 0.44) was two-fold greater than that of the rural cats (mean = 0.21). These findings are compared with previous studies, and are discussed with respect to possible implications for future management strategies for feral cats.

Major prey of prey of feral cats in Australia (from Dickman, C. R. 1996)

Data collected from 22 studies of feral cats in mainland Australia suggest that mammals comprise the major prey of feral cats in most localities. Introduced rabbits (Oryctolagus cuniculus) and house mice (Mus domesticus) predominate in semi-arid to arid habitats, whereas marsupials (especially the common ringtail possom (Pseudocheirus peregrinus) are predominant in temperate forest, urban and suburban habitats (Dickman 1996). Brushtail possoms (Trichosurus vulpecula), sugar gliders (Petaurus breviceps), greater gliders (Petauroides volans) and smaller prey such as brown antechinus (Antechinus stuartii), brush rat (Rattus fuscipes) and swamp rat (Rattus lutreolus) are consistently part of the diet of feral cats in the temperate forests of Australia. In wet-dry tropical habitats where rabbits do not occur native Rattus spp. become more important, including the pale field rat (Rattus tunneyi), dusky rat (R. colletti) and the long-haired rat (Rattus villosissimus).
Smaller rodents such as the spinifex hopping mouse (Notomys alexis) and the sandy inland mouse (Pseudomys hermannburgensis) may also be preyed upon. Birds are represented most highly in
temperate forest, urban and suburban habitats. Small species such as wrens (Malurus spp.), robins (Petroica spp.) and thornbills (Acanthiza spp.) have all been recorded, as have larger species such as galahs (Cacatua roseicapilla), magpies (Gymnorhina tibicen) species of parrots (Psephotus spp.). Species such as geckos and flap-footed lizards and diurnal species of skinks, dragons, goannas and snakes have often been recorded in the feral cat's diet (Dickman 1996).
Reviews of the diet of feral cats in mainland areas in other parts of the world reveal great similarities with the situation in Australia (Corbett, 1979, Fitzgerald and Karl 1979, Liberg 1984, Fitzgerald 1988, Kitchener 1991, in Dickman 1996). In all studies, mammals have consistently comprised the major part of the diet throughout the year, with other vertebrates, especially birds, comprising only a minor component. Rabbits
and murid rodents, especially Rattus species, appear to be favoured prey, and together comprise the bulk of the diet of feral cats in some localities over long periods.

Kiwi casualties by dogs ...

Pierce, R.J. & Sporle, W., 1997. Causes of kiwi mortality in Northland. Conservation Advisory Science Notes No. 169. Department of Conservation, Wellington.

194 kiwi deaths reported in Northland between 1990 and June 1995 were caused primarily by dogs, indicating that the "Waitangi dog incident" of 1987 was not an isolated instance. Over the five and a half year period, dogs accounted for 135 (70%) of all reported kiwi deaths and 78% of all deaths for which the precise cause was established. The second greatest cause of death was vehicles (12; 6% of deaths). Although the data were biased against more cryptic predators, e.g. cats and mustelids, the figures nevertheless represent an alarming impact by dogs. Several categories of dog figured prominently, particularly stray/feral dogs and pet dogs, but farm dogs and hunters' dogs also killed many birds.

FIV and FeLV dynamics

Courchamp, F., C. Suppo, E. Fromont, & C. Bouloux. 1997. Dynamics of two feline retroviruses (FIV and FeLV) within one population of cats. Proceedings of the Royal Society, Biological Sciences, 264(1383): 785–794.
We present a deterministic model of the dynamics of two microparasites simultaneously infecting a single host population. Both microparasites are feline retroviruses, namely Feline Immunodeficiency Virus (FIV) and Feline Leukaemia Virus (FeLV). The host is the domestic cat Felis catus. The model has been tested with data generated by a long-term study of several natural cat populations. Stability analysis and simulations show that, once introduced in a population, FIV spreads and is maintained, while FeLV can either disappear or persist. Moreover, introduction of both viruses into the population induces an equilibrium state for individuals of each different pathological class. The viruses never induce the extinction of the population. Furthermore, whatever the outcome for the host population (persistence of FIV only, or of both viruses), the global population size at the equilibrium state is only slightly lower than it would have been in the absence of the infections (i.e. at the carrying capacity), indicating a low impact of the viruses on the population. Finally, the impact of the diseases examined simultaneously is higher than the sum of the impact of the two diseases examined separately. This seems to be due to a higher mortality rate when both viruses infect a single individual.

FeLV dynamics

Fromont, E., D. Pontier, M. Langlais, F. Courchamp, & M. Artois. 1997. Modelling the feline leukemia virus (FeLV) in natural populations of cats (Felis catus). Theoretical Population Biology 52: 60–70.

A compartmental model was built in order to study the circulation and impact of Feline Leukemia Virus (FeLV) in populations of domestic cats. The model was tested with data from a long-term study of several feline populations. The study of stability shows that FeLV is maintained in the population with a stable equilibrium and a slight reduction of population size. Estimation of the transmission rate allows us to make a comparison with the values previously estimated in the literature. We compare the impact of mass vaccination or removal programmes in controlling FeLV infection, and conclude that vaccination is more efficient