Rapid recolonisation of feral cats following intensive culling in a semi-isolated context

Abstract

Invasive feral cats threaten biodiversity at a global scale. Mitigating feral cat impacts and reducing their populations has therefore become a global conservation priority, especially on islands housing high endemic biodiversity. The New Caledonian archipelago is a biodiversity hotspot showing outstanding terrestrial species richness and endemism. Feral cats prey upon at least 44 of its native vertebrate species, 20 of which are IUCN Red-listed threatened species. To test the feasibility and efficiency of culling, intensive culling was conducted in a peninsula of New Caledonia (25.6 km²) identified as a priority site for feral cat management. Live-trapping over 38 days on a 10.6 km² area extirpated 36 adult cats, an estimated 44% of the population. However, three months after culling, all indicators derived from camera-trapping (e.g., abundance, minimum number of individuals and densities) suggest a return to pre-culling levels. Compensatory immigration appears to explain this unexpectedly rapid population recovery in a semi-isolated context. Since culling success does not guarantee a long-term effect, complementary methods like fencing and innovative automated traps need to be used, in accordance with predation thresholds identified through modelling, to preserve island biodiversity. Testing general assumptions on cat management, this article contributes important insights into a challenging conservation issue for islands and biodiversity hotspots worldwide.

Evaluating methods for controlling feral cats that minimise non‐target impacts at Taunton National Park (Scientific)

“…Baiting well beyond the Park boundary would most likely help to reduce the immigration of cats and the time it takes for cats to move back onto the Park following control operations (Comer et al 2020;Palmas et al 2020). Without a suitable landscape scale cat control method, Taunton will most likely continue to act as a 'sink' (Palmas et al 2020). While baiting offers the only real landscape scale solution to managing cats, our study indicates that baiting must be augmented with trapping and spotlight shooting to be effective.…”

“…Trapping and shooting are quite labour intensive, and we were only able to trap/shoot half of the Park at any one timelet alone extend the controls to the entire Park and/or neighbouring areas. Baiting well beyond the Park boundary would most likely help to reduce the immigration of cats and the time it takes for cats to move back onto the Park following control operations (Comer et al 2020;Palmas et al 2020). Without a suitable landscape scale cat control method, Taunton will most likely continue to act as a 'sink' (Palmas et al 2020).…”

Hares in the long grass: increased aircraft related mortality of the Irish hare (Lepus timidus hibernicus) over a 30-year period at Ireland’s largest civil airport

“…Whilst the translocation of individuals of conservation concern (e.g., Irish hare) to suitable, low-density areas could help to control airside population size whilst aiding national conservation efforts, removal programs on their own may not always be an effective long-term solution due to rapid recolinisation by a species (e.g. Palmas et al 2020). Therefore, the presence and activity patterns of animals at airfields can be determined through the use of modern, remote monitoring equipment (e.g., camera traps and GPS collars) allowing for the collection of high-quality data in sensitive, airport environments (e.g.…”

Predicting targets and costs for feral‐cat reduction on large islands using stochastic population models

“…All three islands have permanent human residents (French Island: 110; Bruny Island: 800; Christmas Island: 1840) and are considered large (>1,000 ha; Nogales et al, 2004). Our model is also applicable to mainland density control and eradications but it is only recommended for eradication in exclusion zones because cats can rapidly recolonize areas that have undergone density reduction (Moseby & Hill, 2011; Palmas et al, 2020). Our model also has applications for other species, including European red foxes (Edwards, Pople, Saalfeld, & Caley, 2004) in Australia (particularly mainland exclusion zones), brush‐tailed possums ( Trichosurus vulpecula ) and stoats ( Mustela erminea ) in New Zealand (Brown, Elliott, Innes, & Kemp, 2015), and mainland application for species such as racoons ( Procyon lotor ) in central Europe (Beltrán‐Beck, García, & Gortázar, 2012).…”