Density and population size of mammals introduced on a land-bridge island in southeastern Brazil
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The introduction of alien species is one of the main threats to the conservation of native species, especially in island ecosystems. Here, we report on the population growth of 15 species of mammals introduced in 1983 on the island of Anchieta, an 828 ha land-bridge island in southeastern Brazil. We estimated the density of mammals through 296 km of line transect census. Five species introduced became extinct (coypu, brocket deer, six-banded armadillo, nine-banded armadillo, maned three-toed sloth); six became over-abundant (marmoset, coati, agouti, seven-banded armadillo, and capybara); one has a stable population (capuchin monkey). Anchieta Island has the highest density of mammals in the entire Atlantic forest (486.77 ind/km2), especially nest predators (232.83 ind/km2) and herbivores (253.58 ind/km2). Agoutis (Dasyprocta spp.) and marmosets (Callithrix penicillata) were, by far, the species with the highest population growth. The high density of mammals in this island may have strong consequences for plant recruitment and bird diversity.
KeywordsDistance sampling Exotic species Herbivores Line transect Nest predation
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We would like to thank FAPESP (Project Biota 2001/14463-5), the International Foundation for Science (IFS), conservação Internacional (Brasil) and Idea Wild for the financial support. We are also grateful to the Instituto Florestal for the permission to work on Anchieta Island. R. Bueno, M. Soares and R. M. Marques for invaluable help in the field work. MG is a CNPq research fellow and RSB received a research grant from PIBIC-CNPq.
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