The silver rice rat (Oryzomys argentatus), a rare endemic rodent, and the black rat (Rattus rattus), an exotic species, have coexisted for <500 years in the Florida Keys. Determination of fine8 scale movements and behavior, by use of neck-attached fluorescent dust dispensers, revealed the degree of overlap in use of space, and some food resources, in free-ranging animals. Food selection tests were conducted in the laboratory. Significant differences in vegetation association, behavior, arboreality, and diet were found. From estimates of spatial niche overlap based on four indices I suggested the differences were biologically insignificant; the average value of four estimators on the habitat-choice resource axis was 89%, higher than reported for 47 of 48 pair-wise comparisons of native rodent species. I suggest that silver rice rat populations may be jeopardized by the presence of black rats whose invasion was reported to have caused oryzomine extinctions in the Galapagos and Antilles islands.

Eight individual rock iguanas (Iguana pinguis) from Anegada Island were relocated to Guana Island by Lazell, 1984–1987, in order to establish a second population reservoir for this endangered species. The species may have originally occupied the entire Puerto Rico Bank. The relocation has been successful and, in the area currently providing the best habitat, we estimate a density of 9 or 12 animals of various age classes per 19 ha. The optimal area contains a sheep exclosure with relatively dense understory vegetation and numerous exotic as well as native species of plants. Iguana activity is concentrated on east facing slopes and ridge‐tops that get morning sun. Outside the exclosure most edible ground cover and shrubs have been eaten by sheep, leaving toxic or noxious species, such as Croton or Lantana, in the understory where I. pinguis adults generally forage. Removal of sheep may be critical to continued population growth of these reptiles. Views on relocation or repatriation of other endangered Antillean Iguana species are advanced, with some ideas on minimum viable population sizes and a possible explanation for the extirpation of I. pinguis from much of its former range.

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