Eradication of Invasive Mammals on Islands Inhabited by Humans and Domestic Animals

Abstract

Non-native invasive mammal species have caused major ecological change on many islands. To conserve native species diversity, invasive mammals have been eradicated from several islands not inhabited by humans. We reviewed the challenges associated with campaigns to eradicate invasive mammals from islands inhabited by humans and domestic animals. On these islands, detailed analyses of the social, cultural, and economic costs and benefits of eradication are required to increase the probability of local communities supporting the eradication campaign. The ecological benefits of eradication (e.g., improvement of endemic species' probability of survival) are difficult to trade-off against social and economic costs due to the lack of a common currency. Local communities may oppose an eradication campaign because of perceived health hazards, inconvenience, financial burdens, religious beliefs, or other cultural reasons. Besides these social challenges, the presence of humans and domestic animals also complicates eradication and biosecurity procedures (measures taken to reduce the probability of unwanted organisms colonizing an island to near zero). For example, houses, garbage-disposal areas, and livestock-feeding areas can provide refuges for certain mammals and therefore can decrease the probability of a successful eradication. Transport of humans and goods to an island increases the probability of inadvertent reintroduction of invasive mammals, and the establishment of permanent quarantine measures is required to minimize the probability of unwanted recolonization after eradication. We recommend a close collaboration between island communities, managers, and social scientists from the inception of an eradication campaign to increase the probability of achieving and maintaining an island permanently free of invasive mammals.

Estimating Burdens of Neglected Tropical Zoonotic Diseases on Islands with Introduced Mammals

“…), cats (Felis catus), and dogs (Canis familiaris) are the most common introduced mammals. 5,6 These introduced mammals co-occur with over 470 million people on at least 560 islands that also harbor Critically Endangered and Endangered vertebrates as defined by the International Union for Conservation of Nature (IUCN). 7,8 Peri-domestic rodents and domestic, stray, and feral cats and dogs are reservoirs for many neglected zoonotic diseases, including angiostrongyliasis, some strains of leptospirosis and rabies, as well as toxoplasmosis, toxocariasis, and echinococcosis (Supplemental Table 1).…”

“…For many islands, complete eradication of introduced rodents, and feral cats and dogs is possible, with island size and human population size being key limiting factors on where that can occur. 6,20,21 Where this is not currently feasible, controlling rodents, and feral dogs and cats on islands utilizes techniques to reduce populations of these introduced mammals to a desired state, ideally an outcome state for a native species. 22,23 Islands represent a potential opportunity for reducing zoonotic disease burden because control or eradication of introduced mammal populations could result in disease alleviation or disease elimination, particularly if reintroductions of reservoirs can be prevented.…”

“…The costs include the economic cost of control or eradication, economic and cultural benefits of the introduced mammal, and nontarget ecological impacts of removal. 6,20 The benefits potentially include reduction of zoonotic disease in human populations, enhanced economic growth due to alleviation of economic costs of zoonotic disease on human livelihoods and local economies, 24 reduced costs of disease control, and recovery of impacted native diversity. 25 A first step in quantifying the potential benefits of management of introduced mammals is an assessment of the burden of zoonotic diseases on island communities.…”

Understanding Invasive Species in the Galapagos Islands

“…They prey on seabirds (eggs, chicks, and adults) and are opportunistic feeders and very adaptable to new environments. They can be blamed for seabird extirpation and population decline (Jones et al 2008;Oppel et al 2011). In the case of the Galapagos, many of these unintentional introductions were brought on by early explorers, pirates, and whalers between the fifteenth and eighteenth centuries.…”

“…Glen et al (2013), based on a global analysis of 1224 successful eradications of invasive plants and animals, determined that 808 of them were on islands, where small size and isolation can be a positive characteristic. On oceanic islands, there have been successful campaigns to eradicate vertebrates (Keitt et al 2011;Oppel et al 2011). Most of these campaigns have taken place on non-inhabited islands (Schoener et al 2005;Oppel et al 2011).…”