Predation by invasive Platydemus manokwari flatworms: a laboratory study

Abstract Platydemus manokwari de Beauchamp, 1963 is an invasive flatworm found on islands in the tropics, especially in the Pacific Ocean. It has been implicated in the decline of several snail populations, including the extinction of some Partula species. Its predatory behaviour was investigated to quantify predation rates and elucidate climatic influences. This laboratory study of the invasive flatworm confirms earlier reports that P. manokwari is a generalist predator of snails. It prefers small prey and avoids species defended by copious mucus, chemical defences or a tough integument. Prey are found by following damp mucus trails up to 15 h old. Flatworm activity is limited by temperature and humidity, with peak feeding at 24–30°C and 85–95% humidity. This determines the geographical spread of the species and probably also the effectiveness of arboreal predation. Aboveground air circulation leads to drying, reducing the ability of the flatworms to locate trails and remain active high off the ground. Local climatic factors may dictate how significantly P. manokwari affects snail populations.