Lethal control of stray dogs could increase frequency of conflicts in India

Yoak, A. J., Reece, J. F., Gehrt, S. D., & Hamilton, I. M. (2016). Optimizing free-roaming dog control programs using agent-based models. Ecological Modelling, 341, 53-61.

Urban free-roaming dog populations in the developing world are managed by a patchwork of local veterinary practitioners, government programs, and non-governmental organizations with varied effectiveness. While lethal removal is still commonly practiced, vaccination and fertility control methods are increasingly being adopted. Identifying which method(s) provides the most cost effective management is needed to inform dog population managers who seek to limit conflicts like dog bites, the spread of disease, and predation on wildlife. Here we describe an agent-based model that simulates the population of free-roaming dogs in Jaipur, a northwestern Indian city. We then apply various lethal and fertility control methodologies to identify which most effectively lowered the dog population size. This spatially explicit model includes temporal and demographic details of street dog populations modeled after data from the study city. We tested each pairing of control type (lethal or fertility) with search method (how to target efforts) to see their efficacy at altering the city’s dog population size, age structure, sterilization coverage, as well as the number of dogs handled. Models were run for 15 years to assess the long term effects of intervention. We found that the fertility control method that targets areas of the city with the highest percentage of intact bitches outperforms all other fertility control and lethal removal programs at reducing the population size while sterilizing a significantly higher proportion of the population. All lethal program methods skewed population demographics towards significantly younger dogs, thus likely increasing the frequency of conflict with humans. This work demonstrates the benefits of modeling differing management policies in free-roaming dogs.

Modelling the population control of the domestic cat from an island

Lessa, I. C. M., & Bergallo, H. G. (2012). Modelling the population control of the domestic cat: an example from an island in Brazil. Brazilian Journal of Biology, 72(3), 445-452.

The domestic cat is an invasive species that often causes great impacts where introduced due to its high predatory and reproductive potential, especially on islands. In this study, carried out on Ilha Grande (RJ, Brazil), we aimed to: i) estimate the population density of domestic cats, ii) calculate the number of animals preyed upon annually by domestic cats, and iii) evaluate the efficiency of methods to control the cat population. We used the Vortex program to project the population growth of domestic cats in fifty years, and simulated different scenarios of population control (without control, castration, spay and harvest). Population density of owned cats was 662 cats/km². The annual predation rate was 1.97 prey animals/cat which is an average of 1497.96 prey/year. The population would only be reduced if 70% of females were spayed or removed annually. Measures to control the domestic cat population must be undertaken urgently, since uncontrolled growth of this predator has the potential to seriously impact the biodiversity of Ilha Grande.

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O gato doméstico é uma espécie invasora que frequentemente causa grandes impactos onde é introduzido, em razão do seu alto potencial predatório e reprodutivo, especialmente em ilhas. Com este estudo realizado na Ilha Grande-RJ, Brasil, tivemos como objetivos: i) estimar a densidade populacional de gatos domésticos; ii) calcular o número de animais predados anualmente por gatos domésticos, e iii) estimar a eficiência de métodos para o controle da população de gatos. Nós utilizamos o programa Vortex para projetar o crescimento da população de gatos em 50 anos e simulamos diferentes cenários de controle populacional: sem controle, castração, esterilização de fêmeas e remoção de indivíduos. A densidade populacional de gatos que possuem donos foi de 662 gatos/km². A taxa anual de predação foi de 1,97 animais predados/gato, ou seja, uma média de 1497,96 presas/ano. A população de gatos pode ser reduzida apenas se no mínimo 70% das fêmeas forem esterilizadas ou removidas anualmente. Medidas para o controle populacional de gatos domésticos devem ser tomadas com urgência, uma vez que o crescimento descontrolado da população desse predador tem o potencial de causar graves impactos à biodiversidade da Ilha Grande.

Defining priorities for dog population management through mathematical modeling

Baquero, O. S., Akamine, L. A., Amaku, M., & Ferreira, F. (2015). Defining priorities for dog population management through mathematical modeling. Preventive veterinary medicine.

We simulated dog population dynamics for a thirty-years period using a logistic growth model. Through sensitivity analyses, we determined the influence of the parameters used in the model. Carrying capacity was the most influential parameter in all simulations. In the owned-dog population, the influence of immigration, abandonment and births was 19%, 16% and 6% of the influence of the carrying capacity, respectively. In the sterilized owned-dog population, the influence of abandonment, female and male sterilization was 37%, 30% and 27% of the influence of the carrying capacity. In the stray population, the influence of abandonment, carrying capacity of the owned-dog population and adoption was 10%, 9% and 6% of the influence of the carrying capacity. In the sterilized stray population, the influence of births, female sterilization and male sterilization was 45%, 15% and 13% of the influence of the carrying capacity. Other parameters had lower influence values. Modification of the carrying capacity requires different interventions for the owned- and stray-dog populations. Dog trade control is a way to reduce immigration. The evaluation of sterilization effects must focus on the variations in the infertile population fraction. Adoption may improve the effects of the reduction in carrying capacity on the stray-dog population.

Modelling eradication of feral cats

Beeton, N. J., McMahon, C. R., Williamson, G. J., Potts, J., Bloomer, J., Bester, M. N., ... & Johnson, C. N. (2015). Using the Spatial Population Abundance Dynamics Engine for conservation management. Methods in Ecology and Evolution.

1. An explicit spatial understanding of population dynamics is often critical for effective management of wild populations. Sophisticated approaches are available to simulate these dynamics, but are largely either spatially homogeneous or agent based, and thus best suited to small spatial or temporal scales. These approaches also often ignore financial decisions crucial to choosing management approaches on the basis of cost-effectiveness.
2. We created a user-friendly and flexible modelling framework for simulating these population issues at large spatial scales – the Spatial Population Abundance Dynamics Engine (SPADE). SPADE is based on the Spatio-Temporal Animal Reduction (STAR) model (McMahon et al. 2010) and uses a reaction–diffusion approach to model population trajectories and a cost-benefit analysis technique to calculate optimal management strategies over long periods and across broad spatial scales. It expands on STAR by incorporating species interactions and multiple concurrent management strategies, and by allowing full user control of functional forms and parameters.
3. We used SPADE to simulate the eradication of feral domestic cats Felis catus on sub-Antarctic Marion Island (Bester et al., South African Journal of Wildlife Research, 32, 2002, 65) and compared modelled outputs to observed data. The parameters of the best-fitting model reflected the conditions of the management programme, and the model successfully simulated the observed movement of the cat population to the southern and eastern portion of the island under hunting pressure. We further demonstrated that none of the management strategies would likely have been successful within a reasonable time frame if performed in isolation.
4. Spatial Population Abundance Dynamics Engine is applicable to a wide range of population management problems and allows easy generation, modification and analysis of management scenarios. It is a useful tool for the planning, evaluation and optimisation of the management of wild populations and can be used without specialised training.

Feral cats population would decrease in range in NSW under climate change

Caley, P., Tennant, P., & Hood, G. (2011). Modelling the distribution of vertebrate pests in New South Wales under climate change. Invasive Animals Cooperative Research Centre.

Feral cats were considered to occur in all but 0.4% of cells during the 2004 survey, with densities considered highest in the south-west plains (no data was collected for the ACT). All climate models forecast a substantial decrease in the area of moderate and high cat density, with a commensurate increase in low cat density

Modelling future distribution of feral cats in NZ under Climate change

Aguilar, G.D., M.J. Farnwortha & L. Winder. 2015. Mapping the stray domestic cat (Felis catus) population in New Zealand: Species distribution modelling with a climate change scenario and implications for protected areas. Applied Geography, 63: 146–154

Species distribution models of stray cats were developed using two types of occurrence data: (i) a combined dataset of stray cats and cat colonies in Auckland and projected to the wider New Zealand area; and (ii) population density as an analogue for country-wide stray cat occurrence. These occurrence data, together with sets of environmental variables were used as input to the Maxent modelling tool to produce maps of suitability for the species. Environmental variables used in the models consist of current bioclimatic conditions, and a future climate scenario (RCP8.5 for year 2070 CCSM model). Commonly occurring bias in the modelling process due to latitude, the area for selecting background points in model evaluation, inherent spatial autocorrelation of occurrence points, and correlated bioclimatic variables were explicitly addressed. Results show that the North Island consistently provide more suitable areas for stray cats with increased suitability in a high emission climate change condition. Key protected areas at risk from the increased suitability to stray cats are also presented.