Mammals, reptiles and crabs on the Krakatau Islands: Their roles in the ecosystem

In 1982 I studied the changes which had taken place in the fauna of the Krakatau Islands over the last fifty years, and elucidated the roles of terrestrial consumers and reducers in the developing ecosystems of these islands. Only two species of rat were found ( Rattus rattus and R. tiomanicus ) as observed by Dammerman (1948) in 1933, but R. tiomanicus had newly established its population on Sertung. No rats were found on Anak Krakatau. Although many skinks ( Mabuya multifasciata ) were observed on R. Besar, this species was not found on the other islands. The rat and skink are considered strong competitors to the sand crab ( Ocypode kuhli ), because while the crab was restricted to the sandy beach on the three islands where rat and skink live it had expanded inland on Anak Krakatau where there are no rats and skinks. The two banded monitor ( Varanus sarvator ) was found on every island and it mainly fed on crabs ( Gecarcoidea natalis and Metasesarma aubryi ). Thus it is suggested that the crab plays an important role in the process of faunal succession on the Krakatau Islands.