Prospects for domestic and feral cat management on an inhabited tropical island

Dias, R. A., Abrahão, C. R., Micheletti, T., Mangini, P. R., de Oliveira Gasparotto, V. P., de Jesus Pena, H. F., ... & Silva, J. C. R. 2017. Prospects for domestic and feral cat management on an inhabited tropical island. Biological Invasions, 1-15.

Cat management campaigns have been implemented on several islands worldwide. However, few successful campaigns have occurred on permanently inhabited islands. Cats are known for causing severe impacts on the native insular fauna, posing an important threat to biodiversity. Moreover, this species is also responsible for zoonosis maintenance and transmission. A thorough understanding of cat population structure (e.g., supervised vs. unsupervised) is strongly suggested as a management action on inhabited islands, as it might promote more efficient and effective management of this species. Fernando de Noronha is an archipelago in the tropical Atlantic Ocean. The total cat population on the main island was estimated at 1287 animals, most of them supervised and subsidized around inhabited areas. Free-roaming cats currently threaten the endemic terrestrial fauna of Fernando de Noronha, and the cat density found by the present work is among the highest ever recorded on an island. Using population dynamic simulations, the long-term effects of reproduction control and removal of cats from the archipelago were assessed. Removal of cats was also suggested as a necessary management strategy to achieve negative population growth. In addition, it was more cost-effective than reproduction control. However, applying both removal and sterilization strategies to this population resulted in a higher population decrease than removal alone. For these reasons, a combination of reproductive control and cat eradication should be implemented in Fernando de Noronha.

Simulating free-roaming cat population management options in open demographic environments

Miller, P. S., Boone, J. D., Briggs, J. R., Lawler, D. F., Levy, J. K., Nutter, F. B., Margaret Slater, M. & Zawistowski, S. (2014). Simulating Free-Roaming Cat Population Management Options in Open Demographic Environments. PloS one, 9(11), e113553.

Large populations of free-roaming cats (FRCs) generate ongoing concerns for welfare of both individual animals and populations, for human public health, for viability of native wildlife populations, and for local ecological damage. Managing FRC populations is a complex task, without universal agreement on best practices. Previous analyses that use simulation modeling tools to evaluate alternative management methods have focused on relative efficacy of removal (or trap-return, TR), typically involving euthanasia, and sterilization (or trap-neuter-return, TNR) in demographically isolated populations. We used a stochastic demographic simulation approach to evaluate removal, permanent sterilization, and two postulated methods of temporary contraception for FRC population management. Our models include demographic connectivity to neighboring untreated cat populations through natural dispersal in a metapopulation context across urban and rural landscapes, and also feature abandonment of owned animals. Within population type, a given implementation rate of the TR strategy results in the most rapid rate of population decline and (when populations are isolated) the highest probability of population elimination, followed in order of decreasing efficacy by equivalent rates of implementation of TNR and temporary contraception. Even low levels of demographic connectivity significantly reduce the effectiveness of any management intervention, and continued abandonment is similarly problematic. This is the first demographic simulation analysis to consider the use of temporary contraception and account for the realities of FRC dispersal and owned cat abandonment.

Low density feral cats cause local extirpation of small mammals in Australia

Frank, A.S.K, C.N. Johnson, J. M. Potts, A. Fisher, M. J. Lawes, J.C. Z. Woinarski, K. Tuft, I. J. Radford, I.J. Gordon, M.-A. Collis & S. Legge. 2014. Experimental evidence that feral cats cause local extirpation of small mammals in Australia's tropical savannas. Journal of Applied Ecology. doi: 10.1111/1365-2664.12323

Small mammal species are declining across northern Australia. Predation by feral cats Felis sylvestris catus is one hypothesised cause. Most evidence of cat impacts on native prey comes from islands, where cat densities are often high, but cats typically occur at low densities on mainland Australia.

We conducted a field experiment to measure the effect of predation by low-density cat populations on the demography of a native small mammal. We established two 12.5-ha enclosures in tropical savanna in the Northern Territory. Each enclosure was divided in half, with cats allowed access to one half but not the other. We introduced about 20 individuals of a native rodent, Rattus villosissimus, into each of the four compartments (two enclosures x two predator-access treatments). We monitored rat demography by mark-recapture analysis and radio-tracking, and predator incursions by camera surveillance and track and scat searches.

Rat populations persisted over the duration of the study (18 months) in the predator-proof treatment, where we detected no predator incursions, but declined to extinction in both predator-accessible compartments. In one case, cat incursions were frequently detected and the rat population was rapidly extirpated (< 3 months); in the other, cat incursions were infrequent, and the population declined more gradually (c. 16 month) due to low recruitment. We detected no incursions by dingoes Canis dingo, the other mammalian predator in the area.

Synthesis and applications. This is the first study to provide direct evidence that cats are capable of extirpating small mammals in a continental setting, in spite of their low population densities. This finding supports the hypothesis that predation by feral cats is contributing to declines of small mammals in northern Australia. The conservation management of native small mammals in northern Australia may require intensive control of cat populations, including large cat-free enclosures.

Cost‐effectiveness analisys of fencing vs. pest trapping

Norbury, G., Hutcheon, A., Reardon, J., & Daigneault, A. (2014). Pest fencing or pest trapping: A bio‐economic analysis of cost‐effectiveness. Austral Ecology.

Scofield et al. discredited the utility of pest-exclusion fences for restoring biodiversity partly on the grounds of unquantified costs and benefits. We estimated the discounted costs of mammal exclusion fences, semi-permeable (‘leaky’) fences and trapping, over 50 years and adjusted costs by their observed effectiveness at reducing mammalian predator abundance. We modelled data from two large predator management programmes operated by the New Zealand Department of Conservation. Using typical baseline costs and predator control efficacies (scale 0 to 1), the model predicted that an exclusion fence (efficacy 1.0) is the cheapest and most cost-effective option for areas below about 1 ha, a leaky fence (efficacy 0.9) is most cost-effective for 1–219 ha, and trapping (efficacy 0.6, based on 0.2 traps per hectare and a 1500-m buffer to reduce predator reinvasion) for areas above 219 ha. This ranking was insensitive to adjustments in efficacy, but reducing efficacy of leaky fences to 0.8 or increasing trapping efficacy to 0.7 reduced the cost-effective range of leaky fences by about 90 ha. Reducing trap maintenance costs from $300 to $100 per trap per year (e.g. using long-life lures), or reducing trap buffer widths to 500 m, significantly elevated trapping as the most cost-effective method for areas greater than 11–15 ha. These results were largely consistent with an ecological measure of effectiveness based on observed rates of recovery of two indigenous skink species inside exclusion fences or with trapping. The results support criticisms that exclusion fences are generally not cost-effective, but highlight the value of considering cheaper leaky designs for small- to medium-sized areas. Because this study is based largely on reductions in predator abundance, it has general application to broader biodiversity protection interests, but not to indigenous species that are highly sensitive to predation and only ever adequately protected on the mainland by exclusion fences.

Modelling feral cat population under TNR

Lee, L. E., Robl, N., Bugman, A. M., Nguyen, A. T., Lammers, B., Fisher, T. L., Weimer, H., Lenhart, S. & New Jr, J. C. (2014). Modeling Feral Cat Population Dynamics in Knox County, TN. University of Tennessee Honor Thesis Projects.

Feral cats (Felis catus) are recognized as a problem internationally due to their negative impact on wildlife and potential to spread infectious disease to people and other animals. Trap-neuterreturn (TNR) programs are employed in many areas to control feral cat populations as a humane method, and this approach is used on a limited basis in Knox County, Tennessee. Despite the frequent use of TNR as a strategy, its effectiveness remains controversial. The objective of this mathematical model is to predict the impact of selected strategies on the population of feral cats. The model with three age classes predicts the population over a period of 5 years in one month time steps. TNR rates are varied to investigate the effects of targeting spay/neuter programs seasonally, and such targeting predicts a measurable decline in feral cat population growth over a five year period. Targeting TNR intervention at adult females during the time prior to mating season in highly populated feral colonies may further decrease the population. These results suggest a more efficacious strategy than non-targeted TNR programs.

A multivariate model of stakeholder preference for lethal cat management

Wald, D. M., & Jacobson, S. K. (2014). A Multivariate Model of Stakeholder Preference for Lethal Cat Management. PloS one, 9(4), e93118.

Identifying stakeholder beliefs and attitudes is critical for resolving management conflicts. Debate over outdoor cat management is often described as a conflict between two groups, environmental advocates and animal welfare advocates, but little is known about the variables predicting differences among these critical stakeholder groups. We administered a mail survey to randomly selected stakeholders representing both of these groups (n = 1,596) in Florida, where contention over the management of outdoor cats has been widespread. We used a structural equation model to evaluate stakeholder intention to support non-lethal management. The cognitive hierarchy model predicted that values influenced beliefs, which predicted general and specific attitudes, which in turn, influenced behavioral intentions. We posited that specific attitudes would mediate the effect of general attitudes, beliefs, and values on management support. Model fit statistics suggested that the final model fit the data well (CFI = 0.94, RMSEA = 0.062). The final model explained 74% of the variance in management support, and positive attitudes toward lethal management (humaneness) had the largest direct effect on management support. Specific attitudes toward lethal management and general attitudes toward outdoor cats mediated the relationship between positive (p<0.05) and negative cat-related impact beliefs (p<0.05) and support for management. These results supported the specificity hypothesis and the use of the cognitive hierarchy to assess stakeholder intention to support non-lethal cat management. Our findings suggest that stakeholders can simultaneously perceive both positive and negative beliefs about outdoor cats, which influence attitudes toward and support for non-lethal management.

Predicting effects of cat predation on their avian preys

Maclean, M. M., Carslake, D. J., Evans, M. R., Townley, S., & Hodgson, D. J. (2008). The usefulness of sensitivity analysis for predicting the effects of cat predation on the population dynamics of their avian prey. Ibis, 150(s1), 100-113.


Sensitivity analyses of population projection matrix (PPM) models are often used to identify life-history perturbations that will most influence a population's future dynamics. Sensitivities are linear extrapolations of the relationship between a population's growth rate and perturbations to its demographic parameters. Their effectiveness depends on the validity of the assumption of linearity. Here we assess whether sensitivity analysis is an appropriate tool to investigate the effect of predation by cats on the population growth rates of their avian prey. We assess whether predation by cats leads to non-linear effects on population growth and compare population growth rates predicted by sensitivity analysis with those predicted by a non-linear simulation. For a two-stage, age-classified House Sparrow Passer domesticus PPM slight non-linearity arose when PPM elements were perturbed, but perturbation to the vital rates underlying the matrix elements had a linear impact on population growth rate. We found a similar effect with a slightly larger three-stage, age-classified PPM for a Winter Wren Troglodytes troglodytes population perturbed by cat predation. For some avian species, predation by cats may cause linear or only slightly nonlinear impacts on population growth rates. For these species, sensitivity analysis appears to be a useful conservation tool. However, further work on multiple perturbations to avian prey species with more complicated life histories and higher-dimension PPM models is required.

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.

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. 

Nesting site availability vs. cat predation on seabirds

Pontier, D., Fouchet, D., Bried, J., & Bahi-Jaber, N. (2008). Limited nest site availability helps seabirds to survive cat predation on islands. Ecological modelling, 214(2), 316-324.

Introduced cats Felis catus have a high detrimental impact on native seabirds on islands, especially when alien preys, like rabbits Oryctolagus cuniculus, co-occur. Seabirds are highly vulnerable because of their long reproductive cycles, slow turn-over of generations and the absence of efficient behaviour against terrestrial predators, especially in some burrow-nesting species. Through a deterministic modelling approach, we explored a neglected mechanism that may explain the resistance of some seabird species to cat predation. It was indeed observed that seabirds may compete for nest sites. As a consequence, part of the breeders foregoes breeding when nest sites are a limiting resource. Our model linked the dynamics of cats with that of seabird species. We showed that the annual impact of cats on seabirds was lower when seabirds faced competition for burrows than when the latter were not a limiting resource. This was due to the fact that limited nest site availability prevents an optimal growth of the cat population. Cats in turn cannot manage to exterminate all the prospecting birds during the same breeding season. The limitation of the number of nest sites generates a mechanism leading the bird population to conserve a large pool of sexually mature individuals while only slightly reducing the production of juveniles in the colony. This pool of floaters may play an important role in natural populations by buffering the decrease in colony size during years with harsh environmental conditions on land. In combination with buffer mechanisms, the limitation of the number of nest sites may greatly improve the chances of survival of bird populations facing predation.

Reply to McCarthy et al. (2013) on methods to control feral cats

Lepczyk, C. A., Conant, S., Duffy, D., Unit, P. C. S., Honolulu, H., Bird, D. M., & Calver, M. (2013). Feral cat management. Zoonoses Public Health, 60, 189-195.

Reply to McCarthy et al. (2013) 

Non surgical vs. surgical sterilization in feral cat populations

Budke, C. M., & Slater, M. R. (2009). Utilization of matrix population models to assess a 3-year single treatment nonsurgical contraception program versus surgical sterilization in feral cat populations. Journal of Applied Animal Welfare Science, 12(4), 277-292.

This study constructed matrix population models to explore feral cat population growth for a hypothetical population (a) in the absence of intervention; (b) with a traditional surgical sterilization-based trap, neuter, and return program; and (c) with a single treatment 3-year nonsurgical contraception program. Model outcomes indicated that cessation of population growth would require surgical sterilization for greater than 51% of adult and 51% of juvenile (<1 year) intact female cats annually, assuming an approximate 3-year mean life span. After the population stabilizes, this would equate to sterilizing approximately 14% of the total female population per year or having approximately 71% of the total female and 81% of the adult female population sterilized at all times. In the absence of juvenile sterilization, 91% of adult intact females would need to be sterilized annually to halt population growth. In comparison, with a 3-year nonsurgical contraception program, an annual contraception rate of 60% of female juvenile and adult intact cats would be required to halt population growth, assuming that treatedcats were retrapped at the same rate after 3 years.

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.

TNR vs. TVHR to control feral cats

McCarthy, R. J., Levine, S. H., & Reed, J. M. (2013). Estimation of effectiveness of three methods of feral cat population control by use of a simulation model. Journal of the American Veterinary Medical Association,243(4), 502-511.

Objective—To predict effectiveness of 3 interventional methods of population control for feral cat colonies.

Design—Population model.

Sample—Estimates of vital data for feral cats.

Procedures—Data were gathered from the literature regarding the demography and mating behavior of feral cats. An individual-based stochastic simulation model was developed to evaluate the effectiveness of trap-neuter-release (TNR), lethal control, and trap-vasectomy-hysterectomy-release (TVHR) in decreasing the size of feral cat populations.

Results—TVHR outperformed both TNR and lethal control at all annual capture probabilities between 10% and 90%. Unless > 57% of cats were captured and neutered annually by TNR or removed by lethal control, there was minimal effect on population size. In contrast, with an annual capture rate of ≥ 35%, TVHR caused population size to decrease. An annual capture rate of 57% eliminated the modeled population in 4,000 days by use of TVHR, whereas > 82% was required for both TNR and lethal control. When the effect of fraction of adult cats neutered on kitten and young juvenile survival rate was included in the analysis, TNR performed progressively worse and could be counterproductive, such that population size increased, compared with no intervention at all.

Conclusions and Clinical Relevance—TVHR should be preferred over TNR for management of feral cats if decrease in population size is the goal. This model allowed for many factors related to the trapping program and cats to be varied and should be useful for determining the financial and person-effort commitments required to have a desired effect on a given feral cat population.



See reply here

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.

Decision analysis network used to evaluate feral cat management

Loyd, K. T., & J. L. DeVore. 2010. An evaluation of feral cat management options using a decision analysis network. Ecology and Society 15(4): 10.

The feral domestic cat (Felis catus) is a predatory invasive species with documented negative effects on native wildlife. The issue of appropriate and acceptable feral cat management is a matter of contentious debate in cities and states across the United States due to concerns for wildlife conservation, cat welfare, and public health. Common management strategies include: Trap-Neuter-Release, Trap-Neuter-Release with removal of kittens for adoption and Trap-Euthanize. Very little empirical evidence exists relevant to the efficacy of alternative options and a model-based approach is needed to predict population response and extend calculations to impact on wildlife. We have created a structured decision support model representing multiple stakeholder groups to facilitate the coordinated management of feral cats. We used a probabilistic graphical model (a Bayesian Belief Network) to evaluate and rank alternative management decisions according to efficacy, societal preferences, and cost. Our model predicts that Trap-Neuter-Release strategies would be optimal management decisions for small local populations of less than fifty cats while Trap-Euthanize would be the optimal management decision for populations greater than 50 cats. Removal is predicted to reduce feral cat populations quickly and prevent cats from taking a large number of wildlife prey.

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

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.

TNR for feral cat: demography, ecology and potential pathogens

Nutter, F. B. (2006). Evaluation of a Trap-Neuter-Return Management Program for Feral Cat Colonies: Population Dynamics, Home Ranges, and Potentially Zoonotic Diseases. PhD
Management of feral cats is controversial, and alternatives to lethal control methods are gaining popularity. To evaluate the effectiveness of sterilization programs, nine feral cat colonies were divided into groups of three, managed either by spaying females and castrating males, spaying females and vasectomizing males, or leaving all cats intact. Colonies were followed intensively for four years, and intermittently for three additional years. Most cats were trapped in fewer than ten trap nights each. Breeding females produced a mean of 1.4 litters/year and 3 kittens/litter. Kitten mortality was 75% by 6 months of age. Feral and pet domestic cats had similar baseline health status and prevalences of FIV, FeLV, Cryptosporidium, Giardia, and Toxocara cati, but feral cats had higher prevalences of Bartonalla henselae and Toxoplasma gondii. Castrated male and spayed female cats survived longer than intact male and female cats. Survival times of vasectomized males were equivalent to those of intact males. Control colonies decreased in size and remained stable in composition, while intact colonies increased in size and had high turnover. One neutered colony went extinct and several others had fewer than five cats at the end of the project. Home ranges of both intact and neutered cats were small, usually less than 1 ha. Vasectomized males had larger home ranges than either intact or castrated males, probably because they were searching for intact females. Community-level stakeholder meetings were successful in building consensus among groups, and a basic decision tree for feral cat management was developed. Computer simulation modeling using VORTEX software suggested that harvesting breeding colonies every one or two years at 50% to 100% can keep colonies small, but will not lead to long-term reductions in cat numbers. Models of neutered colonies suggested that 75% to 80% sterilization is necessary to cause population decrease and eventual extinction. The mean estimated time to extinction of 12.8 years fits well with ongoing observations of steady decline in sterilized colonies.