Feral cats threaten the outstanding endemic fauna of the New Caledonia biodiversity hotspot

Abstract

A B S T R A C TFeral cats (Felis catus) are one of the most successful and harmful invasive predator species, leading to dramatic loss of biodiversity across the globe. Our study assessed feral cat predation in a major biodiversity hotspot: the New Caledonian archipelago. We focused on the consequences of this predation for the outstanding endemic fauna found throughout the rich range of New Caledonian natural habitats. We analyzed > 5300 cat scats sampled from 14 selected sites representing the 4 main natural habitats, with 4 to 6 sampling sessions per year over > 4 years per habitat. Our study reveals previously unreported patterns of cat predation on both alien and endemic species. Throughout the archipelago, cats prey strongly upon squamates, flying foxes and petrels. Feral cat prey included at least 44 native vertebrate species, 20 of which are IUCN Red-listed threatened species. This study adds some 44.4% to the number of IUCN threatened species vulnerable to and preyed upon by feral cats on the world's islands. New Caledonia, while it represents only 0.12% of the total area of islands worldwide (Australia included), hosts 30.8% of IUCN threatened species known to be predated by feral cats. This study recommends prioritizing management and conservation strategies by focusing actions on maquis mosaic and humid forest habitats, where feral cats pose the greatest threat. To limit the impact of feral cats, we recommend conducting targeted management actions on sites key to threatened species conservation, and preventing arrival or promoting eradication on islets.

Precipitation and prey abundance influence food habits of an invasive carnivore

“…We documented significant seasonal and annual variability in prey consumption, which was correlated with precipitation patterns and corresponding abundance of rodents. Similar to findings on other islands, cats on SCI used rodents as a primary prey source when available (Fitzgerald & Karl, ; Fitzgerald, Karl & Veitch, ; Molsher, Newsome & Dickman, ; Bonnaud et al ., ) and used reptiles as a secondary prey source (Konecny, ; Palmas et al ., ). Following dry years, lizard consumption increased and rodent consumption decreased, suggesting that more frequent or severe droughts could alter cat predation patterns and increase predation on the recently de‐listed island night lizard.…”

“…We paired stomach contents with indices describing rodent abundance and precipitation data to assess cat diet variability and explore what may drive these patterns. To our knowledge, this study includes the longest time series of cat diet data analyzed to date and one of the largest sample sizes (Palmas et al ., ), offering novel insights into cat predation patterns, their impacts on island ecosystems, and elucidating the factors affecting predation patterns.…”

A conservation paradox: endangered and iconic flightless kagu (Rhynochetos jubatus) apparently escape feral cat predation

“…Cats were introduced to New Caledonia around 1860 by European settlers and are now present in a wide range of habitats, even in the most remote areas (Beauvais et al 2006;Palmas et al 2017). Throughout the New Caledonian archipelago, feral cats prey upon at least 44 native vertebrate species ranging from small insects to medium-sized birds and mammals (Palmas et al 2017).…”

“…Cats were introduced to New Caledonia around 1860 by European settlers and are now present in a wide range of habitats, even in the most remote areas (Beauvais et al 2006;Palmas et al 2017). Throughout the New Caledonian archipelago, feral cats prey upon at least 44 native vertebrate species ranging from small insects to medium-sized birds and mammals (Palmas et al 2017). Surprisingly, no remains of a flightless New Caledonian endemic bird, the kagu (Rhynochetus jubatus), were found among all the 5356 cat scats collected from the 14 study sites of a previous larger study (Palmas et al 2017).…”

“…Throughout the New Caledonian archipelago, feral cats prey upon at least 44 native vertebrate species ranging from small insects to medium-sized birds and mammals (Palmas et al 2017). Surprisingly, no remains of a flightless New Caledonian endemic bird, the kagu (Rhynochetus jubatus), were found among all the 5356 cat scats collected from the 14 study sites of a previous larger study (Palmas et al 2017). This intriguing result motivated us to focus on cat scat sampling and analysing in the two major bastions for this bird species.…”