The terrestrial vertebrate fauna of the krakatau islands, sunda strait, 1883-1986

Abstract

The results of terrestrial vertebrate collecting on the Krakatau Islands, Sunda Strait, during La Trobe University-L.I.P.I. expeditions in 1984, 1985 and 1986 are reported and previous records from the islands are consolidated and reviewed. Since the 1883 eruption of Krakatau, 15 species of terrestrial vertebrates (13 reptiles and 2 mammals) have been recorded from the Krakatau Group. Two of the species records ( Crocodylus porosus and Cosymbotus platyursare only incidental but the remaining thirteen species have at some stage established breeding populations on one or more islands. In the first 50 years up to 1933, ten species (eight reptiles and two mammals) reached the islands, eight of which ( Hemidactylus frenatus, Lepidodactylus lugubris, Emoia atrocostata, Mabuya multifasciata,Varanus salvator, Python reticulatus, Rattus rattus and Rattus tiomanicus ) had established breeding populations. Results of collections made over the period 1982-1986 showed that two of the species (L. lugubris and E. atrocostata) with breeding populations in 1933 had become extinct, whereas five new species ( Gekko gecko, Gekko monarchus, Hemiphyllodactylus typus, Chrysopelea paradisi and Ramphotyphlops braminus ) have reached the islands and established breeding populations. Therefore at the end of 100 years, eleven species of terrestrial vertebrates have extant breeding populations on one or more islands in the Krakatau group; two species have become extinct; and two species have incidental records. Significant ecological changes in the development of the present day terrestrial fauna are discussed. These include canopy closure of the forests and continual marine erosion of the coasts that together have eliminated most of the open habitats on Rakata, Sertung and Panjang; heavy ash falls from volcanic eruptions on Anak Krakatau that have periodically disrupted successional stages and habitats on Sertung, Panjang and Anak Krakatau. The dispersal of terrestrial vertebrates in the Sunda Strait is discussed in the light of the heavy boat traffic and the predominant southwest ocean currents. It is concluded that dispersal by human agency on boats is highly significant, seven of the 15 recorded species (46%) being most likely to have reached the islands in this way; and the prevailing southwest flow of water in Sunda Strait makes Sebesi and Sumatra the probable source areas for the eight species most likely to have dispersed on ocean currents by swimming or rafting. Anak Krakatau, the volcanic island that became permanent in Aug. 1930, has three species of terrestrial vertebrates ( H. frenatus, V. salvator . and C. paradisi ) all of which have established breeding populations on Rakata, Sertung and Panjang. The early arrival of H. frenatus and V. salvator and their present abundance on all four islands distinguishes them as the most successful terrestrial vertebrate colonizers of the Krakatau group.

Ecological aspects of plant colonisation of the Krakatau Islands

“…However, given these data and the close proximity and geographic location of the islands, we believe it highly probable that Sebesi was a significant contributor of propagules to Krakatau, and there is nothing in the data that contra-indicates this. Furthermore, Dammerman (1948) was convinced of the importance of Sebesi and other islands off Sumatra in recolonisation of Krakatau by animals (see also Rawlinson et al 1990). As a test-ground for plant geographic theory, the island has effectively been written-off by the removal of virtually all forest below--700 m, a process thought to have been completed during the 1970s, although underway much earlier (Docters van Leeuwen 1923b; I.W.B.…”

Photographic evidence of rate of development of plant cover on the emergent island Anak Krakatau from 1971 to 1991 and implications for the effect of volcanism

“…The The monitor, Varanus salvator, is occasionally found in deep ash-filled inter-block caverns on the older flows, and tracks of the paradise tree-snake, Chrysopelea paradisi, have been seen high on the outer ash cone (Rawlinson et al 1990). The high inner cone has been occupied in recent years by the oriental hobby, Falco severus, and subsequently by a pair of peregrine falcons, Falco peregrinus.…”

“…The fauna of the vegetated area comprises one rat species, 3 bats, 28 resident land birds, 2 shore birds and 9 migrants (5 of them shore birds), 3 reptiles and hundreds of invertebrate species Rawlinson et al 1990;Tidemann et al 1990;Zann et al 1990). Whittaker et al (1992, this volume) have argued that the 1972/3 eruptions so damaged (or completely destroyed) the vegetation that it is likely that the present succession originated from that time rather than from the 1952/3 eruptions, which are generally accepted as having been extirpating.…”

The origin of platyrrhines: An evaluation of the Antarctic scenario and the floating island model

“…The rafting hypothesis was first suggested by Alfred Russell Wallace in the mid-19th century (Simons, 1976;Jokiel, 1990), and has been addressed to explain the origin of many organisms, notably the South American acridian insects (Amedegnato, 1993), West Indian Coleoptera (Nichols, 1988), Lake Malawi fishes (Oliver and McKaye, 1982), many shallow-water animals (Jokiel, 1990), some amphibians and reptiles (Estes and Baez, 1985;Buffetaut and Rage, 1993) including Crocodilia (Densmore and White, 1991), Crotalus rattlesnakes of Baja California (Stewart, 1990), land reptiles of Western Samoa (Gill, 1993), South American indigenous gekkos (Kluge, 1969), some land vertebrates of the Krakatau Islands (Rawlinson et al, 1990), land mammals of the Mediterranean islands (Schü le, 1993), South American caviomorph rodents (Lavocat, 1969(Lavocat, , 1980Wood, 1980;George, 1993), a group of Australian rodents (Simpson, 1953), and possibly a group of South American sloths (Storch, 1993).…”