Colonization of the Krakatau islands by vertebrates

Abstract

80 species of non-marine, non-migrant vertebrates, excluding also shore birds, have been recorded from the Krakatau archipelago since the explosive eruption of 1883.73 of these are believed to have established breeding populations and successfully colonized the islands (47 resident land birds species, 13 bats, 11 reptiles and 2 rats). A large proportion of these colonizers consists of species with wide distributions, broad ecological tolerances and/or association with urban or rural situations. 11 of the 73 colonizing species (8 resident land birds, 2 reptiles and a bat) have become extinct on the islands. No amphibian species has yet been recorded and successful non-volant mammal colonists consist only of rats. Species turnover is considered to be largely associated with successional change of habitat. Progressive loss of coastal habitat through marine erosion and of open inland habitats through forest formation and canopy closure has been important and volcanic activity is indicated in the case of one or two extinctions. Active flight has been the predominant dispersal method (63 of the recored species, 79%, are birds or bats). Of the 17 recorded non-volant vertebrates, 6 species are assessed as having dispersed by swimming, 4 by means of natural rafts and 7 most likely through human agency (on boats). Human-assisted dispersal is seen to be of increasing importance with the increasing number of tourist visits and this may prove to be significant in determining the nature and rate of future colonization by vertebrates. © 1992 Kluwer Academic Publishers.