Population Ecology of Rattus Rattus Across a Desert-Montane Forest Gradient in the Galapagos Islands

摘要: Populations of introduced black rats (Rattus rattles) were studied by removal trapping in five nonagricultural habitats the Galapagos Islands: montane forest, scrub, tropical deciduous woodland, thorn and savannah. Density ranged from 0.4 to 18.9/ha, both density biomass significantly correlated with an index vegetation biomass. The estimated quantity per individual unit decreased increasing rat density. These results suggest that populations food-limited. A 2-mo drought lowered condition (mass/length) forest scrub rats. Analysis size reproductive classification resident immigrant showed significant heterogeneity among subgroups based on sex period capture. Rats two lowest appeared have more specific microhabitat requirements than denser populations. Breeding was confined hot early cool seasons (January through July) all habitats. Mean minimum body lengths positively time since arrival arid zone rains, while coefficients variation these quantities negatively correlated. Sex ratio varied seasonally; percentage males increased during nonbreeding season. Intraisland pelage differentiation observed. Compared other rodents, Rattus rattles been very successful range occupied maintained.