| Summary: | Ph.D. University of Hawaii at Manoa 2010. Includes bibliographical references. Introduced rats (Rattus rattus, R. norvegicus, and R. exulans) and/or mice (Mus musculus) occur on more than 80% of the world's island groups, where they pose great threats to native species. Understanding the interactions between these introduced rodents and the environments which they have invaded can assist in land management and conservation efforts on islands. In three mesic forests in the Waianae Mountains, Oahu, Hawaii, rat and mouse abundances were estimated using mark-and-recapture, microhabitat use and den sites were determined using spool-and-line tracking, and rat home-ranges were estimated using radio-tracking. The diets of three of the rodents (R. norvegicus was absent from the three sites) were assessed using stomach content and stable isotope analyses. Additionally, field and captive-feeding trials were used to assess fruit and seed removal and consumption, and seed predation and dispersal, by R. rattus. Rattus rattus dominates these forests in abundance (7.1 indiv./ha) relative to the two smaller rodents, R. exulans (0.3 indiv./ha) and M. musculus (3.7 indiv./ha). Home-range estimates for R. rattus (N = 19) averaged 3.8 ha, and the single radio-tracked R. exulans had a home-range of 1.8 ha. Except for one individual M. musculus, all den sites of R. exulans and M. musculus were belowground, whereas dens of R. rattus were both above-and belowground. Most (> 88%) rodent activity occurred in areas where vegetation closely (10-30 cm above individuals) covered the rodent; 70% of the monitored movements of both M. musculus and R. exulans were on the ground surface, whereas R. rattus was mainly arboreal (32% ground, 64% arboreal) and was typically observed at ca. 3 m height when aboveground. Consistent with the evidence for (micro-) habitat partitioning among these three rodents, the diets of the three rodents may also provide evidence of niche partitioning. Rattus exulans had an intermediate diet (stomachs containing ...
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