Seasonal migration of predators and prey - a study of pythons and rats in tropical Australia

Although seasonal migrations of large predatory mammals that follow migrating prey are well documented, no equivalent phenomenon has been described previously in terrestrial reptiles. We surveyed and radio-tracked water pythons (Liasis fuscus) in Fogg Dam and its adjacent floodplain 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 the dry season the rats live in soil crevices in the floodplain, but wet-season flooding forces them to higher ground, primarily to natural levee banks. Python and rat abundances on the floodplain adjacent to Fogg Dam were significantly correlated through time: both reached a maximum during the dry season, and fell dramatically during the wet season. Activity of pythons was centered around Fogg Dam during the dry season, but all of the radio-tracked snakes moved away from this area during the wet season. Most pythons migrated to the vicinity of levee banks on the floodplain up to 12 km away from their dry-season range. By migrating seasonally, water pythons can efficiently utilize a migratory prey species that would otherwise be unavailable for much of the year.