The sp. inhabits swift mountain streams at montane elevations of southern Papua New Guinea. In this study the duration for which adult 3 3 and 9 9 remained at a given site in rainforest streams was determined, and the dispersal distance and direction of marked individuals leaving the site of initial observation was assessed. Territorial defence was non-exclusive and S 3 held territories for up to 45 days. On average, 3 3 remained 9 days, 9 9 11 days at a given site. Both sexes stayed significantly longer at sites with suitable oviposition substrates than at a site without. Mating occurred only twice during the study period, and the scarcity of mating events might explain long territory holding times. On a daily basis d 3 moved larger distances than 9 9, suggesting that 9 9 remain at a site for a longer period before moving a long distance. Both sexes showed similar lifetime dispersal distances (1000-1300m), and dispersal was predominantly directed upstream. It is concluded that this unidirectional dispersal of adults may compensate for downstream drift of larvae in rapid flowing streams.