Modeling the biological control of an alien predator to protect island species from extinction

Introduced feral cat (Felis catus) populations are an important threat to m any island vertebrate populations and to bird species in particular. Elimin ation of feral cat populations is desirable in most of these ecosystems. Re lease of a parasite species in these mostly immune-naive populations is tho ught to be an efficient eradication measure. Such an approach is theoretica lly investigated here, using a mathematical model that describes the effect s of introducing a virus into the cat population on population dynamics of both the cat and its prey. We studied the effects of two types of introduce d feline viruses: Feline Immunodeficiency Virus and Feline Leukemia Virus, both of which are good candidates for eradicating a cat population. Results show that eradication is possible with Feline Leukemia Virus, if natural i mmunity is sufficiently low. Feline Immunodeficiency Virus cannot fully era dicate cat populations, but can be an effective agent for long-term control of cat populations on islands where total cat eradication is not possible (e.g., there is a high likelihood of continued introduction of cats) or not desirable (e.g., when rats are present). Culling, which by itself would re quire a very prolonged and logistically demanding effort to eliminate cat p opulations, may be more efficient when applied simultaneously with virus in troduction.