Habitat Selection by Female Rattus lutreolus Drives Asymmetric Competition and Coexistence with Pseudomys higginsi

Abstract

Two native Australian rodents, the velvet-furred swamp rat ( Rattus lutreolus velutinus ) and the long-tailed mouse ( Pseudomys higginsi ), are sympatric in wet sclerophyll forests on Mount Wellington, Tasmania, Australia. Their relatively large macrohabitat overlap implies that these species partition one or more resources to coexist. We used census data to examine the role of microhabitat structure in resource partitioning. At trap stations where only one species or the other was trapped, significant differences in microhabitat structure existed. R. lutreolus was trapped in areas of densest vegetation ≤1 min height. Male and female R. lutreolus exhibited macrohabitat separation during the non-breeding season (winter). At that time, adult and subadult female rats occupied areas of thickest ground cover; males occupied surrounding, more open areas of forest at lower densities. After the onset of breeding, male rats visited areas occupied by female rats. P. higginsi was never trapped in areas where most female R. lutreolus were captured but was most often trapped in the same macrohabitat as male R. lutreolus . After the onset of breeding, relative rate of capture of P. higginsi increased in these areas as male R. lutreolus shifted their trap-revealed ranges to incorporate areas where females were resident. We propose that the seasonal intersexual habitat separation exhibited by R. lutreolus , and particularly the habitat use by females, may be an essential component in structuring the rodent community in wet sclerophyll forests.