SEASONAL MIGRATION OF PREDATORS AND PREY - A STUDY OF PYTHONS AND RATS IN TROPICAL AUSTRALIA

Although seasonal migrations of large predatory mammals that follow mi grating prey are well documented, no equivalent phenomenon has been de scribed previously in terrestrial reptiles. We surveyed and radio-trac ked water pythons (Liasis fuscus) in Fogg Dam and its adjacent floodpl ain in the wet-dry tropics of northern Australia to document patterns of movement, with particular emphasis on the ways in which the snakes exploit their major prey species, the dusky rat (Rattus colletti). The distribution and abundance of these rodents vary seasonally. During t he dry season the rats live in soil crevices in the floodplain, but we t-season flooding forces them to higher ground, primarily to natural l evee banks. Python and rat abundances on the floodplain adjacent to Fo gg Dam were significantly correlated through time: both reached a maxi mum during the dry season, and fell dramatically during the wet season . Activity of pythons was centered around Fogg Dam during the dry seas on, but all of the radio-tracked snakes moved away from this area duri ng the wet season. Most pythons migrated to the vicinity of levee bank s on the floodplain up to 12 km away from their dry-season range. By m igrating seasonally, water pythons can efficiently utilize a migratory prey species that would otherwise be unavailable for much of the year .