Potential biological control of cats in Australia

Moodie, E. (1995). The potential for biological control of feral cats in Australia. New South Wales National Parks and Wildlife Service.


There is a need to clarify the impacts of feral cats on wildlife populations and thus set clear objectives for their control.

No method of biological control is available for immediate use. Fertility control using a contraceptive vaccine is the option with the most promise. This approach and two other broad strategies (a mortality approach usint lethal disease and environmental manipulation) are discussed in detail.

Although Feline Parvovirus has been used in attempts to control feral cats elsewhere, animal welfare concerns and probable immunity are likely to prevent its use in mainland Australia. No other feline diseases would cause rapid death in a relatively humane manner to a large enough proportion of a cat population to be useful for biological control.

The diseases and ecology (including population dynamics, reproduction and behaviour) of cats, and community attitudes to their control are discussed in depth. Relatively little information was available on feral cats. Most is derived from studies of domestic cats. Research currently underway is described. More information is needed on the ecology and epidemiology of diseases in feral cat populations in order to develop predictive models for specific biological control agents. Serological surveys for viral diseases in feral populations are given nights priority.

A fertility control approach using an immunocontraceptive vaccine probably has a reasonable chance of success in relation to public acceptability if the technical hurdles can be overcome. These include ensuring that the vaccine is cat specific, that it induces sterility without affecting social behaviour and that it's effects last long enough to be worthwhile. No effective chemical sterilants are available.

Results of research programs on immunocontraception of rabbits and foxes should indicate whether it is a feasible option for vertebrate pest control. Non-transmissible agents are more likely to be publicly acceptable because of concerns over the safety or other species and pet cats.

Attributes of successful pest control programs (for cats and other vertebrate pest species) are discussed. Refinement and combined use of conventional control methods will be essential for future cat control whether of not biological control is used.

Spatial organisation of urban feral cats in Jerusalem

Mirmovitch, V. (1995). Spatial organisation of urban feral cats (Felis catus) in Jerusalem. Wildlife Research, 22(3), 299-310.

Feral cats were studied for 10 months in a residential area in Jerusalem and their spatial distribution compared during two 1-month periods, the first in the autumn prior to the mating season and the second during the mating season (winter). Cat locations were recorded by direct observations, and home-range sizes were calculated with the minimum convex polygon method. No significant change in home-range size of adult males or females was found between the 2 periods. Young males expanded their home ranges considerably during their first mating season. Home ranges of males were significantly larger than those of females in both periods (0.56 and 0.30 ha, respectively, in autumn; 0.75 and 0.27 ha in winter). The home ranges of both sexes overlapped considerably with individuals of the same sex. Overlap among home ranges of females indicated a group pattern. High overlap (80%) was found among females that fed from the same set of garbage bins with similar frequency. Lower overlap (20%) was found between individual females that shared only a subset of their food resources and used it with different frequency. It is suggested that the distribution of food patches (garbage bins), the amount of food available and the rate of food renewal determined the cats' spatial organisation.

Impact of two feline retroviruses on natural populations of domestic cat

Courchamp, F., D. Pontier, E. Fromont & M. Artois. 1995. Impact of two feline retroviruses on natural populations of domestic cat. Mammalia. 59 (4): 589-598.

We compared the pattern of spread and the impact of two retroviruses, feline immunodeficiency
virus (FIV), and feline leukemia (FeLV) within natural populations of domestic. A four years epidemiological study shows that FIV is present in three studied rural cat populations, whereas FeLV is absent in one out of the three, with no evolution in time for either virus. Factros influencing FIV transmission are directly linked to agressive behaviour , while factors influencing FeLV transmission are rather characteristic of amicable interactions. Results of a deterministic model show that both infections are maintained in the population at a stable equilibrium between susceptible and infected animals, slightly reduce the number of individuals at equilibrium, and have long transmission rates. Results of a long term dynamical study indicate that the probability of dying from tese viruses is low in natural conditions, and that, despite their presence, the size and structure of the population remains stable.
In conclusion, despite FIV and FeLV have different spread patterns (FIV infects and kills at-risk individuals, while FeLV infects more indiscriminately), the impact of both retroviruses on cat populations seems to be low. 

Modelling FIV

Courchamp,F., D. Pontier & M. Artois. 1995. Modelling the Feline Immunodeficiency Virus within populations of domestic cats (Felis catus). Journal of Biological Systems, 3 (3): 769-777.

We attempt to model the circulation of the Feline Immunodeficiency Virus (FIV), a retrovirus analogous to the HIV, within populations of domestic cats. Domestic cats exhibit different patterns of population dynamics, social behaviour and reproductive strategies. In fact, cats can be either solitary or living in large social groups, with many intermediate states.

The aim of the presented model is to provide a conceptualization of the mechanisms of FIV spreading rather than to be a predictive tool. As one of our goals is to integrate easily new informations when available, and to remain simple and close to the biological reality, parameters, such as sex, age classes and dispersion, have been incorporated successively. This model can also be adapted to different types of cat populations by simple changes, as it could be to other host populations. A study of the stability of the model has been done. Based on available data, values of two parameters has been estimated: the carrying capacity and the transmission rate. Results are in good accordance with biological data.

Ecology of a feral cat population in rural Northern Italy

Genovesi, P., Besa, M., & Toso, S. (1995). Ecology of a feral cat Felis catus population in an agricultural area of northern Italy. Wildlife Biology, 1: 233-237.

The ecology of a feral cat population in an intensively cultivated region of northern Italy was studied. The study area is a land accretion territory, reclaimed in the early 1970s, characterised by the absence of any food source of human origin (e.g. garbage dumps, farms, houses) and surrounded by a continuous irrigation channel that is likely to limit immigration/emigration of cats. The cat population was censused for two successive years using the sighting-resighting method; spacing patterns were studied by means of radio-telemetry; hunting behaviour was assessed by observation. Feral cats avoided any direct contact with humans, and reproduced in the wild. The density of the population remained stable throughout the study period. Turnover appeared very high, and was remarkably higher than that of cats regularly fed by humans. Very low densities, large home range sizes, solitary habits, territorial patterns similar to those of the wildcat, seasonal parturition, and prevalence of hunting activity were found. We speculate that these patterns are related to the peculiar conditions of resource availability and dispersion in the study area. Our results indicate that feral cats, even in agricultural areas and in the absence of any food provided by humans, have solitary habits and low densities, thus confirming a key role of resource availability and dispersion on the ecology of carnivores.

Comparative social ecology of feral dogs and wolves

Boitani, L., & Ciucci, P. (1995). Comparative social ecology of feral dogs and wolves. Ethology Ecology & Evolution, 7(1), 49-72.

In this paper we compare some socio-ecological traits of feral dogs and wolves in order to assess the social ecology of feral dogs in terms of its adaptive value in the natural environment, and to evaluate to what extent the domestication process altered the wolf's socio-ecological patterns. Referring to feral dogs as those dogs living in a wild state with no food and shelter intentionally provided by humans, and showing a continuous and strong avoidance of direct human contacts, we review the currently available information on feral dog ecology, and particular reference is made to a 3-year term project on feral dog ecology in Abruzzo, Italy. Through comparison of relevant behavioural and ecological features of both wolves and feral dogs, we hypothesize that some aspects of the feral dogs' ecology, having escaped natural selection pressures, represent primarily expression of “evolutionary inertia” or an epiphenomena of artificial selection. Fitness-related measures of sociality, demography, reproduction, space-use, activity patterns, and feeding ecology in feral dogs tend to support our original hypothesis: feral dogs are not reproductively self-sustaining, suffer from high rates of juvenile mortality, depend indirectly upon humans for food, co-optable individuals, and space, and their demography appears dominated by unpredictable mechanisms. However, further research is needed, especially concerning different ecological conditions and multi-generational time-scales, as well as the role that dominant breed-types and cross-breeding history within feral dog groups might play in the expression of the analyzed socio-ecological features.

Breeding of Procellariidae before and after eradication of feral cats at Marion Island

Cooper, J. Marais, A.V.N., Bloomer, J.P. & Bester, M.N. 1995. A success story: breeding of burrowing petrels (Procellariidae) before and after eradication of feral cats Felis catus at sub-Antarctic Marion Island. Marine Ornithology 23: 33-37.

Greatwinged Petrels Pterodroma macroptera and Blue Petrels, Halobaena caerulea bred more successfully alter the eradication in 1991 of feral domestic cats Felis catus at subantarctic Marion Island. The larger Whitechinned Petrel Procellaria aequinoctialis did not show such improvement, although percentage burrow occupancy in the late breeding season increased significantly between 1982/83 and 1988/89 for that species, suggesting decreased cat predation during this period of cat control. Breeding success and burrow density of selected species of burrowing petrels should be monitored to ascertain the rate of recovery of their populations now that Marion Island is cat-free. 

FIV dynamics

Courchamp F, D. Pontier, M. Langlais & M. Artois. 1995. Population dynamics of feline immunodeficiency virus within cat populations. Journal Theoretical Biolology, 175(4): 553–560.

A deterministic model was constructed for studying the circulation of Feline Immunodeficiency Virus (FIV), a feline retrovirus homologous to Human Immunodeficiency Virus (HIV) within populations of domestic cats. The model has been tested with data generated by a long!term study of several natural cat populations. Simulations and a study of stability show that once introduced\ the retrovirus is maintained within the population, with a stable equilibrium stage reached by both numbers of susceptible and infected individuals. An estimation of parameters indicates that the transmission rate is low and depends of the structure of the population. In addition, FIV has a low impact on the population in that the total number of cats at equilibrium when this virus is present is almost always equal to the habitat carrying capacity in the absence of the virus. Those results, in agreement with other observations, suggest that FIV originally arose in the distant past.