Agent-based Modelling to Simulate the Past Dispersal of Fauna into and out of Sulawesi

Muhammad Anshari Matin*, Mika Rizki Puspaningrum, Astin Nurdiana, and Iwan Pramesti Anwar

The island of Sulawesi harbours a higher proportion of indigenous fauna and flora compared to other islands in Indonesia. Similar pattern has occurred in the past, as fossil taxa found on Sulawesi and surrounding islands are often unique, and absent from other islands of the archipelago. The most notable fossil excavation site in Sulawesi is located in the Sengkang Basin, South Sulawesi Province. The fossil mammals found in the basin show very limited similarity to those found in Java and Flores, but instead show affinities with taxa identified further north, particularly in Sangihe and the Phillippines. Recent discovery of Proboscidea and Suidae fossils in North Minahasa further support the possibility of past faunal dispersal from or to the northern regions. For throughout the history of its formation, even during the Last Glacial Maximum, Sulawesi was never connected to any neighbouring land mass due to the surrounding deep waters. Given the occurrence of similar mammalian fossils found on the surrounding islands, this study investigates the probability of successful faunal migration across water barriers using the agent-based model SEAcross. The model simulates dispersal based on animal physiological properties, such as energy expenditure and swimming speed, as well as the characteristics of water barriers, including width, seasonal current speed and direction. The primary output of the simulation is the crossing success rate, representing the probability of animals successfully reaching the opposite shore during two different seasons.