Underlying impacts of invasive cats on islands: Not only a question of predation

Biodiversity and Conservation (Impact Factor: 2.37). 02/2014; 23(2). DOI: 10.1007/s10531-013-0603-4


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.

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Available from: Felix Manuel Medina, Dec 26, 2013
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    • "On Corvo there is no health control of the herbivore populations, but these diseases can be transmitted to cows and therefore impact negatively on local farming. Feral cats wander in the local dump, which is situated close to Vila do Corvo; therefore they can potentially transmit parasites and diseases to stray and domestic cats, and to humans (see Medina et al., 2014). The health risk generated by IAS would suppose an indirect economic cost for health care services and in plague prevention. "
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    ABSTRACT: The Portuguese government has awarded islands with more protection statutes than continental ecosystems, so it seems to recognise the exceptional biodiversity of the insular regions. However, the effectiveness of these protection statutes is questionable since, in most cases, no measures are taken to guarantee the protection against invasive alien species (IAS). This study reviews the current legislative framework addressing IAS at national, regional and local levels. Information on ecological and socio-economic impacts of IAS was used to analyse whether regional laws covering island ecosystems are ensuring the protection of their biodiversity. We detected some weakness in the Portuguese legislation: IAS are not the main focus, inconsistent terminology, vectors not targeted, a few diversity of ecosystems covered, no coordination of actions and no enforcement of management plans. In addition, the uniqueness of biodiversity on Macaronesian islands is not protected by the regional legislation. Although some non-indigenous species introduced on islands are currently threatening the integrity of their fragile ecosystems and the socio-economic spheres, they are not considered as IAS. A stronger strategic framework to address the overall impacts of IAS is required mainly in these Macaronesian islands whose one of the most imposing threat is the presence of these introduced species.
    Environmental Science & Policy 10/2015; 52. DOI:10.1016/j.envsci.2015.05.002 · 3.02 Impact Factor
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    • "Feral cats are acknowledged as one of the world's worst 100 invasive species (Lowe et al. 2000) and are thought to have been an important contributing factor to at least 14% of bird, reptile and mammal extinctions globally (Medina et al. 2011) and at least 16 mammal extinctions in Australia (Johnson 2006). Predation by feral cats can jeopardise conservation programs aiming to reintroduce native fauna into areas of their former range (Moseby et al. 2011; Potts et al. 2012), and cats can have non-lethal impacts on susceptible populations through competition, disease transmission, induced predator-avoidance behaviour and hybridisation (Daniels et al. 2001; Medina et al. 2014). Reducing the impacts of feral cats "
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    ABSTRACT: Feral cats (Felis catus) have a wide global distribution and cause significant damage to native fauna. Reducing their impacts requires an understanding of how they use habitat and which parts of the landscape should be the focus of management. We reviewed 27 experimental and observational studies conducted around the world over the last 35 years that aimed to examine habitat use by feral and unowned cats. Our aims were to: (1) summarise the current body of literature on habitat use by feral cats, in the context of existing ecological theory (i.e. habitat selection, foraging theory); (2) develop testable hypotheses to help fill important knowledge gaps in the current body of knowledge on this topic; and (3) build a conceptual framework that will guide the activities of researchers and managers in reducing feral cat impacts. We found that feral cats exploit a diverse range of habitats including arid deserts, shrublands and grasslands, fragmented agricultural landscapes, urban areas, glacial valleys, equatorial to sub-Antarctic islands and a range of forest and woodland types. Factors invoked to explain cat habitat use included prey availability, predation/competition, shelter availability and human resource subsidies, but the strength of evidence used to support these assertions was low, with most studies being observational or correlative. We therefore provide a list of key directions that will assist conservation managers and researchers in better understanding and ameliorating the impact of feral cats at a scale appropriate for useful management and research. Future studies will benefit from employing an experimental approach and collecting data on the relative abundance and activity of prey and other predators. This might include landscape-scale experiments where the densities of predators, prey or competitors are manipulated and then the response in cat habitat use is measured. Effective management of feral cat populations could target high-use areas, such as linear features and structurally complex habitat. Since our review shows often-divergent outcomes in the use of the same habitat components and vegetation types worldwide, local knowledge and active monitoring of management actions is essential when deciding on control programs.
    Wildlife Research 01/2015; · 1.49 Impact Factor
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    • "both direct and indirect effects from top predators ( Peckarsky et al . 2008 ) . For example , feral cats may limit rabbit and rodent activity not only by predation , but also by constraining behaviour ( Medina et al . 2013 ) . Because a lower number of top predators in an area may reduce the perceived risk to prey species ( Brown , Laundr e & Gurung 1999 ; Bonnington , Gaston & Evans 2013 ) , the reduction in cat activity following our cat control may have resulted in increased activity and roaming behaviour of rabbits and rodents , thus resulting in high"
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    ABSTRACT: Invasive non-native species are one of the greatest drivers of the loss of biodiversity worldwide. Consequently, removing or controlling invasive predators should generally benefit vulnerable native species. However, especially on islands, where most mammalian predators are introduced, these predators may also prey on other invasive mammals. Removing only apex predators may lead to increases of meso-predators that may in turn increase predation pressure on native wildlife.We examined the benefits of a feral cat Felis catus control programme on nest survival of a critically endangered ground-nesting bird, the St Helena Plover Charadrius sanctaehelenae in two habitat types, harbouring ~30% of the global population of this species. We monitored nest success and the activity of introduced mammals (cats, rabbits Oryctolagus cuniculus, rats Rattus rattus and R. norvegicus, and mice Mus musculus) over two years, before and after controlling feral cats.Live trapping removed 56 feral cats from our study areas. In the semi-desert, rabbit and mouse activity increased, but rat activity remained low after feral cat control. In pastures, rat and mouse activity increased after feral cat control, while rabbit activity remained constant.Nest survival of plovers increased more than threefold in the semi-desert, but increased only marginally in pastures. This difference may be due to an increase in rat activity and potentially rat predation following cat control in pastures, whereas no increase in rat activity was observed in the semi-desert.Synthesis and applications. Our study shows habitat-specific consequences of feral cat control on ground-nesting bird productivity after one year, probably mediated by differences in the availability of alternative prey. The results highlight the importance of experimental trials and a thorough understanding of the interactions between multiple invasive species before predator-control operations are implemented over larger scales. On islands with multiple invasive species, there may not be a simple generic approach to predator management (other than removing all invasive species simultaneously).This article is protected by copyright. All rights reserved.
    Journal of Applied Ecology 05/2014; 51(5). DOI:10.1111/1365-2664.12292 · 4.56 Impact Factor
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