Live-capture of feral cats using different methods

McGregor, H. W., Hampton, J. O., Lisle, D., & Legge, S. (2016). Live-capture of feral cats using tracking dogs and darting, with comparisons to leg-hold trapping. Wildlife Research, 43(4), 313-322.

Context: Predation by feral cats is a key threatening process to many species of native Australian wildlife. Unfortunately, cats are difficult to capture using standard trapping techniques, limiting the potential to conduct research on their ecology and impacts.

Aims: We present an alternative capture method: remote chemical immobilisation after tracking with trained dogs. We also compare capture rates to a concurrent soft-jaw leg-hold trapping program.

Methods: We used dogs to capture cats detected by spotlighting at night, and also recaptured cats fitted with telemetry collars during the day. Cats were either bailed on the ground or treed and then hand-netted, or chemically immobilised using darts shot from a CO2-powered dart rifle, loaded with tiletamine–zolazepam at ~6 mg kg–1. Factors affecting the success rate of capturing cats using dogs were assessed. Efficiency in terms of cats captured per person-hours of fieldwork were compared using trained dogs versus leg-hold trapping.

Key results: We attempted 160 cat captures using the tracking dogs with 114 of those being successful. There were no mortalities or debilitating physical injuries associated with chemical immobilisation; however, sedated cats had prolonged recoveries (>4 h). Capture success with the tracking dogs increased as the dogs gained experience. Capture success rates per person-hour of fieldwork were four times greater using spotlighting with tracking dogs than using leg-hold traps. The success rate of recaptures using dogs was 97%.

Conclusions: The use of trained tracking dogs proved an effective method for capturing feral cats. The method had a much higher success rate than live-trapping with leg-hold traps, took less effort (in terms of person-hours) and caused less physical injuries than did leg-hold traps. However, substantial setup costs and time are required, which are discussed.

Implications: Using these methods could improve efficiency and outcomes when catching feral cats, and enable more data per individual cat to be collected than otherwise.

Distribution and correlates of feral cat trapping permits in Los Angeles

Kingsley, G. (2015). Distribution and correlates of feral cat trapping permits in Los Angeles, California (doctoral dissertation, University of Southern California)

Uncontrolled populations of feral cats in urban settings have become of concern to public officials, wildlife scientists, animal rights advocates and the public in general due to the risks they pose to public health, urban wildlife, and esthetics. Solutions to the problem of unmanaged cat populations in cities have been limited in scope by the lack of actual data on feral cats and the urban geographic ranges they occupy. Full extent censuses and environmental analyses have not been collected or performed due to the resources allocations and costs involved. A method for collecting this data without the use of field crews and research summaries exists in the form of unused paper records. Past studies on the problem have used data mining of available records to model cat territories and densities (Aguilar and Farnworth 2012). This approach mitigates the cost while providing information regarding the distributions of these animals. This thesis investigates the spatial properties of feral cat populations in a large metropolitan area (Los Angeles, California) using a previously non-spatialized dataset as a proxy for concentrations of feral cats. The following case study explores two matters: 1) development of a workflow to create a spatial model of feral cat extents from geographic data brought into an analyzable format and 2) analysis of the model data to determine what, if any, variables are correlated with these distributions. The data used for the model were obtained from the City in the form of paper records and successfully imported into a Geographic Information System. Densities of applications were determined from the cleaned and geocoded records and concentrations of both raw density and patterns of clustering were mapped. Modeling of correlations found positive associations with population density and a weak negative correlation with median income. The analysis was assessed and future work on this type of data was considered.

Long-term protection of seabird breeding colonies on Tasman Island through eradication of cats

Robinson, S., Gadd, L., Johnston, M., & Pauza, M. (2015). Long-term protection of important seabird breeding colonies on Tasman Island through eradication of cats. New Zealand Journal of Ecology, 39(2), 0-0.

A restoration programme was initiated in 2008 in response to high levels of seabird predation by feral cats (Felis catus) at Australia’s largest fairy prion (Pachyptila turtur) colony on Tasman Island, Tasmania. The primary knockdown involved aerial baiting with para-aminopropiophenone (PAPP) in meat baits. The efficacy of baiting was lower than expected resulting in trapping and hunting commencing earlier than planned. Cats were successfully eradicated over two weeks. Key to the success of the programme was the identification of a narrow window of low prey availability for cats. Post-eradication monitoring of the two most common seabird species, fairy prions and short-tailed shearwaters (Ardenna tenuirostris), showed positive signs towards population recovery. Prion activity increased three-fold and shearwater breeding success increased.

Progress in eradicating cats on Christmas Is

Algar, D., Hamilton, N., & Pink, C. (2014). Progress in eradicating cats (Felis catus) on Christmas Island to conserve biodiversity. Raffles Bulletin of Zoology. Supplement No. 30: 45–53

The impact of cats (Felis catus) on the biodiversity of Christmas Island is of significant concern to land management agencies and the broader community. In 2010, a management plan for cats, and also black rats (Rattus rattus), was commissioned that would mitigate the environmental and social impacts of these alien invasives across the island. A strategy was recommended that provided a staged approach to their management and control leading to eradication of one or both target species. For cats, Stage 1 initially involved gaining approval of revisions to the current local cat management laws that prohibited importation of new cats; this was then followed by a veterinary programme to de-sex, micro-chip and register all domestic cats. Stage 2 required removal of all non-domestic (i.e., stray/feral) cats within the residential, commercial and light industrial zones. Without implementation of Stage 2, a significant source of cats, particularly natal recruits, would be available to disperse into or reinvade territories vacated across the island. Stage 2 was required before an island-wide control programme (Stage 3) could be implemented. 

Stage 1 of the programme has been completed with 135 domestic cats currently registered. Stage 2 has led to the majority of stray/feral cats being destroyed within the residential, commercial and light industrial area. Two hundred and seventy-eight stray/feral cats were removed from this area since May 2011, primarily through cage-trapping. Two baiting programmes have been conducted around the periphery of the residential area with between 36–49 cats being removed in 2011 and a further 103–142 stray/feral cats poisoned during a more extensive programme in 2012. The combined trapping and baiting programmes have resulted in between 417–469 stray/feral cats being removed since the commencement of the plan. Continued funding is essential for a successful conclusion to the cat

eradication programme on the island.

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.