Quantifying the success of feral cat eradication, San Nicolas Island, California

It is usually uncertain when to declare success and stop control in pest eradication operations that rely on successive reductions of the population. We used the data collected during a project to eradicate feral cats from San Nicolas Island, California to estimate both the number of cats remaining towards the end of the project, and the amount and type of surveillance effort required to declare successful eradication after the last known cat was removed. Fifty seven cats were removed between June 2009 and April 2010 and our model estimated that there was a 95% chance that a further 1 to 4 cats remained, with 1 cat being the most likely number. After this time a further two cats were detected and removed and the model predicted this outcome with a probability of 0.25. If managers wished to confirm eradication success at this point, we estimated that 55 km of effort searching for recent evidence of cats over the whole island without detecting any would provide 99% certainty that no cats remained (stopping rule 1). Alternatively, the optimal amount of search effort for evidence that minimized the joint cost of searching and the cost of wrongly declaring eradication was 75 km (stopping rule 2). The equivalent amount of camera-nights (26 cameras were available) required to declare successful eradication were 416 (stopping rule 1) and 1196 camera nights (stopping rule 2). During the confirmation phase, 270 km of sign search effort and 3294 camera-nights surveillance were used from late June 2010, when the last cat was removed, through August 2010, without detecting signs of survivors. Managers can be very confident that eradication has been successful

Reducing the impacts of leg hold trapping on critically endangered foxes by modified traps and conditioned trap aversion on San Nicolas Island, California, USA

Padded leg-hold live traps were used as the primary removal technique in the successful eradication of feral cats Felis silvestris catus from San Nicolas Island, California, USA. Risk of injury to endemic San Nicolas Island foxes Urocyon littoralis dickeyi, a similarly sized and more abundant non-target species, was mitigated by using a smaller trap size, modifying the trap and trap set to reduce injuries, and utilising a trap monitoring system to reduce time animals spent in traps. Impacts to foxes during the eradication campaign were further reduced by having a mobile veterinary hospital on island to treat injured foxes. Compared to other reported fox trapping efforts, serious injuries were reduced 2-7 times. Trapping efforts exceeded animal welfare standards, with 95% of fox captures resulting in minor or no injuries. Older foxes were more likely to receive serious injury. Fox captures were also reduced through aversive conditioning, with initial capture events providing a negative stimulus to prevent recaptures. Fox capture rates decreased up to six times during seven months of trapping, increasing trap availability for cats, and improving the efficacy of the cat eradication program. No aspect of the first capture event was significantly linked to the chance of recapture

Plans to eradicate invasive mammals on an island inhabited by humans and domestic animals (Corvo, Azores, Portugal)

Oppel, S., Beaven, B.M., Bolton, M., Bodey, T.W., Geraldes, P., Oliveira, N., Hervias, S., Henriques, A., Silva, C

The importance of integrating science and management: lessons from terrestial vegetation change on Macquarie and Heard Islands.

Scientific observations have demonstrated massive changes in tall tussock and megaherb cover on Macquarie Island, substantial colonisation of bare ground by native vegetation on Heard Island, expansion of the range of Poa annua on Heard Island, and local changes in vegetation associated with changes in the locations of animal aggregations. Suggested recent declines in Sphagnum and Azorella on Macquarie Island may have occurred but are yet to be proven. Climate change seems certain to have been responsible for vegetation expansion on Heard Island, but its role on Macquarie Island is less clear. The role of variation in rabbit populations on Macquarie Island in causing changes in the areas of vegetation dominated by tall tussocks and megaherbs is scientifically well-established. However, the relative contribution of variation in cat populations, variation in the effectiveness of the Myxoma virus and climate change on variation in rabbit populations has been the subject of unresolvable differences in scientific opinion. While science has been generally productive in determining needs for vegetation management and its appropriate course when needed, the bureaucratic separation of managers and scientists within Tasmania, and an emphasis on peer review and strategic research within the Australian Antarctic Division, have contributed to some fracturing of management-related science in the twenty-first century, and have resulted in scientific publication and publicity that has criticised, rather than supported, appropriate conservation management. Long-term involvement of individual scientists in both research and management planning seems to have been a key driver of good nature conservation. A renewed focus on the integration of science and management is recommended

Understanding invasive predation: detections of feral cats (Felis catus) on Kangaroo Island’s Western River Refuge

Feral cats (Felis catus) are a priority-level threat for small to medium-sized native vertebrates across Australia and especially so in insular environments like that of Kangaroo Island, South Australia. The island is home to several endangered and geographically restricted species, including the Kangaroo Island Dunnart (Sminthopsis aitkeni), an endangered marsupial endemic to Kangaroo Island. When bushfires spread across the island and burned x percent of native vegetation in late 2019 to early 2020, these populations were critically impacted and post-fire feral cat predation on the island risked their extinctions, motivating the creation of a refuge with predator exclusion fencing around remaining unburnt vegetation to protect surviving dunnarts and other threatened species. The Western River Refuge was created for this purpose and protecting the area has included trapping feral cats in a variety of ways. As continued trapping is necessary, it is important to analyze capture and camera trap data to understand trapping efficiency and success rates, and how these might be improved. This study reviewed six months of capture data and camera trap photographs from the WRR property in order to identify individual feral cats and any patterns in detections prior to either capture or disappearance from cameras, as well as in comparison to AI-targeted Felixer first detections. Camera trap photographs were filtered through the AI system eVorta for high confidence (\u3e0.99) cat photographs. Twelve cats were captured during the study period and 110 instances of cat detections were recorded on camera traps and Felixer target photos. 53.64% of detections were matched to individual cats. All detections were an average of 1.67 days (±0.27 SE) apart. Cats averaged 51.9 days (±16.66 SE) between first camera detection and capture. 58.33% of captured cats were recorded as targets by Felixers while 41.67% were either not detected or not identified as targets. Felixer activation will increase speed of removing cats from the area, but various trapping methods are still necessary to catch all cats that enter the area. Higher levels of detections in the WPA indicate the successes of trapping and align with capture hotspots, but all conclusions are limited by small sample sizes and require further data collection

Preventing Extinctions: Seabird Conservation Through Island Restoration

Seabirds, which play a critical role in maintaining ocean health, are among the most threatened animals on Earth. Some of the islands they depend on to breed and feed are home to invasive species that prey on seabird eggs, hatchlings and destroy habitat and nests.The Packard Foundation supports organizations to restore island habitat, primarily in the Pacific Ocean, where it is feasible to remove introduced, invasive species. Learn more about this cost effective approach to prevent seabird extinctions, preserve biodiversity and restore island ecosystems through the downloadable infographic resource