Feral Cats and Biodiversity Conservation (original) (raw)
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A global review of the impacts of invasive cats on island endangered vertebrates
Global Change Biology, 2011
Cats are generalist predators that have been widely introduced to the world's~179 000 islands. Once introduced to islands, cats prey on a variety of native species many of which lack evolved defenses against mammalian predators and can suffer severe population declines and even extinction. As islands house a disproportionate share of terrestrial biodiversity, the impacts of invasive cats on islands may have significant biodiversity impacts. Much of this threatened biodiversity can be protected by eradicating cats from islands. Information on the relative impacts of cats on different native species in different types of island ecosystems can increase the efficiency of this conservation tool. We reviewed feral cat impacts on native island vertebrates. Impacts of feral cats on vertebrates have been reported from at least 120 different islands on at least 175 vertebrates (25 reptiles, 123 birds, and 27 mammals), many of which are listed by the International Union for the Conservation of Nature. A meta-analysis suggests that cat impacts were greatest on endemic species, particularly mammals and greater when non-native prey species were also introduced. Feral cats on islands are responsible for at least 14% global bird, mammal, and reptile extinctions and are the principal threat to almost 8% of critically endangered birds, mammals, and reptiles.
Underlying impacts of invasive cats on islands: not only a question of predation
Biodiversity and Conservation, 2014
The domestic cat has been introduced on most islands worldwide, where it has established feral populations and is currently known to be one of the worst invasive mammalian predators. Predation is the strongest deleterious effect of cats on wildlife, inducing a direct negative impact on population size and dynamics, breeding success and changes in species assemblages. Direct predation is not the only damaging impact on native wildlife, since cats can be responsible for other poorly-documented underlying ecological impacts, like competition, hybridization, disease transmission, ecological process alteration, and behavioral change. Here, we pinpoint relevant examples of these ecological impacts, by searching for accurate data from published literature. We used electronic databases covering most of the world islands where the effects of cats were documented. Knowledge of these impacts can be of great importance to preserve insular ecosystem functions and persistence of endangered native species. We emphasize that direct predation processes should not be the only factor considered in the management of invasive cats on islands.
A Review of Feral Cat Eradication on Islands
Conservation Biology, 2004
Feral cats are directly responsible for a large percentage of global extinctions, particularly on islands. We reviewed feral cat eradication programs with the intent of providing information for future island conservation actions. Most insular cat introductions date from the nineteenth and twentieth centuries, whereas successful eradication programs have been carried out in the last 30 years, most in the last decade. Globally, feral cats have been removed from at least 48 islands: 16 in Baja California (Mexico), 10 in New Zealand, 5 in Australia, 4 in the Pacific Ocean, 4 in Seychelles, 3 in the sub-Antarctic, 3 in Macaronesia (Atlantic Ocean), 2 in Mauritius, and 1 in the Caribbean. The majority of these islands (75%; n = 36) are small (≤5 km 2 ). The largest successful eradication campaign took place on Marion Island (290 km 2 ), but cats have been successfully removed from only 10 islands (21%) of ≥10 km 2 . On Cousine Island (Seychelles) cat density reached 243 cats/km 2 , but on most islands densities did not exceed 79.2 cats/km 2 (n = 22; 81%). The most common methods in successful eradication programs were trapping and hunting (often with dogs; 91% from a total of 43 islands). Frequently, these methods were used together. Other methods included poisoning (1080; monofluoracetate in fish baits; n = 13; 31%), secondary poisoning from poisoned rats (n = 4; 10%), and introduction of viral disease ( feline panleucopaenia; n = 2; 5%). Impacts from cat predation and, more recently, the benefits of cat eradications have been increasingly documented. These impacts and benefits, combined with the continued success of eradication campaigns on larger islands, show the value and role of feral cat eradications in biodiversity conservation. However, new and more efficient techniques used in combination with current techniques will likely be needed for success on larger islands.
Feral cats threaten the outstanding endemic fauna of the New Caledonia biodiversity hotspot
Biological Conservation
Feral 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.
Journal of Zoology
Populations of feral (not owned by humans) and domestic cats Felis catus coexist in most inhabited islands, and they have similar impacts on native species. Feral cats are generally believed to vary their diet according to prey availability; however, no previous studies of diet have tested this hypothesis on insular ecosystems with a limited range of available prey. Because domestic cats kill prey independently of hunger, the spatial extent of their impact on wildlife will be influenced by home-range size. In this study, we combined dietary information with cat movements to assess the impacts of feral and domestic cats on island biodiversity. We quantified the diet of cats from scat samples collected across one year and tested whether diet varies by season. The abundance of main prey categories was also estimated to document seasonal variation in prey availability for cats. Finally, we tracked domestic cats by global positioning system units in all four seasons to examine whether home-range patterns varied seasonally. The diet of cats constituted three prey groups (rodents, birds and invertebrates), and the seasonal variation in consumption of each taxon matched the seasonal variation in prey availability, thus supporting the generalist behaviour of cats on oceanic islands. Roaming behaviour varied among individuals and across seasons, but could not be explained by availability of prey. Unconfined cats had larger home-ranges than confined cats, but most domestic cats strayed <1 km from home. Thus, confinement of domestic cats might reduce the spatial extent of cat impact on native prey populations on oceanic islands.
The global contribution of invasive vertebrate eradication as a key island restoration tool
Scientific Reports, 2022
Islands are global hotspots for biodiversity and extinction, representing ~ 5% of Earth's land area alongside 40% of globally threatened vertebrates and 61% of global extinctions since the 1500s. Invasive species are the primary driver of native biodiversity loss on islands, though eradication of invasive species from islands has been effective at halting or reversing these trends. A global compendium of this conservation tool is essential for scaling best-practices and enabling innovations to maximize biodiversity outcomes. Here, we synthesize over 100 years of invasive vertebrate eradications from islands, comprising 1550 eradication attempts on 998 islands, with an 88% success rate. We show a significant growth in eradication activity since the 1980s, primarily driven by rodent eradications. The annual number of eradications on islands peaked in the mid-2000s, but the annual area treated continues to rise dramatically. This trend reflects increases in removal efficacy and project complexity, generating increased conservation gains. Our synthesis demonstrates the collective contribution of national interventions towards global biodiversity outcomes. Further investment in invasive vertebrate eradications from islands will expand biodiversity conservation while strengthening biodiversity resilience to climate change and creating co-benefits for human societies.
Eradication of feral cats from large islands: an assessment of the effort required for success
Feral cats (Felis catus) are predators and competitors of native species on many islands and are therefore the target of control efforts. Cat eradication has been achieved on 83 islands worldwide. Six of these successes have been from large islands (over 2000 ha) and have reported sufficient data to examine how the eradication was achieved through combinations of aerial and ground-based poison baiting, fumigation in rabbit burrows used by cats, cage and leghold trapping, day and night shooting, and hunting with dogs. No common sequence of tactics was deployed although leghold traps were used in the latter phases of most projects. It took a mean reported effort of 543 ± 341 person-days per 1000 ha of island over 5.2 ± 1.6 years to completely remove cats and validate success from the six islands. These precedents may assist in planning future proposals to eradicate cats from other large islands.
PLOS ONE
The data underlying the results presented in the study are publicly available from tib.islandconservation.org. These include data on islands, threatened species and invasive species, and are searchable within a map and tabular format. Requests for information regarding data can be sent to science@islandconservation.org. As cited in our manuscript, these data have also been described in the recent publication Spatz et al. (2017), including tables of all islands and threatened species,
Invasive mammal eradication on islands results in substantial conservation gains
Proceedings of the National Academy of Sciences, 2016
More than US$21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact. Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of which is highly threatened with extinction. Indeed, island species make up nearly two-thirds of recent extinctions. Islands therefore are critical targets of conservation. We used an extensive literature and database review paired with expert interviews to estimate the global benefits of an increasingly used conservation action to stem biodiversity loss: eradication of invasive mammals on islands. We found 236 native terrestrial insular faunal species (596 populations) that benefitted through positive demographic and/or distributional responses from 251 eradications of invasive mammals on 181 islands. Seven native species (eight populations...
Proceedings of the Vertebrate Pest Conference
Mexican islands' biodiversity is very rich and diverse; several reptile, bird, and mammal endemic species live on them. However, ecological and evolutionary processes have been negatively affected by invasive species. To date, more than 20 island endemics, including mammals, birds and reptiles, have gone extinct on Mexican islands. As a very opportunistic predator that adapts easily to different environments, the feral cat is one of the most lethal invasive species. Restoration of island ecosystems can be achieved effectively by the eradication of this noxious species. In Mexico, 18 islands (<400 km 2) have been cleared of feral cats using traditional techniques, i.e. trapping and hunting. These techniques are still being implemented on smaller islands or on islands where populations are small. Nevertheless, on big islands with complex terrain and topography, varied habitats and climates, and with non-target species, there are challenges to overcome. This includes Socorro (130 km 2), Cerralvo (135 km 2), and Guadalupe (240 km 2) Islands. To achieve successful cat eradications on these islands, dispersion of toxic baits will be necessary. Currently, bait trials are being developed by Grupo de Ecología y Conservación de Islas, A.C., and supported by Australian and New Zealand institutions, as part of island-specific eradication plans. To date, these studies comprise feral cat and native species ecology for Cerralvo and Socorro Islands. All data gathered is valuable for eradication planning.