Space invaders? A search for patterns underlying the coexistence of alien black rats and Galápagos rice rats

摘要: The introduction and spread of the black rat Rattus rattus is believed to have caused worst decline any vertebrate taxon in Galapagos. However, “extinct” Santiago rice Nesoryzomys swarthi has recently been rediscovered sympatry with R. providing first exception this general pattern displacement. We carried out an exploratory investigation novel system aim identifying patterns that may facilitate apparent coexistence two species. extensive survey Island map current distribution endemic explore broad scale distribution–habitat associations. then used live-trapping, radio-tracking, spool-and-line tracking quantify abundance–habitat correlations test for evidence interspecific spatial segregation, alteration N. activity (spatial temporal), microhabitat partitioning. found disappeared from part its historical range appears be restricted a 14 km stretch north-central coast, characterised by high density cactus Opuntia galapageia. In contrast, generalist was at all sites. no home size, temporal did not vary local rattus. pre-dawn post-dusk levels increased perhaps reflecting increase foraging effort necessary compensate costs exploitation or interference competition. distribution, selection, relations suggest O. galapageia coexistence. Further research should include comparison inter-seasonal resource preference species coupled replicated field experiments confirm competition elucidate mechanism competitive