Population Ecology of Oryzomys longicaudatus philippii (Rodentia: Cricetidae) in Southern Chile

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Abstract
(1) Population fluctuations and demography were followed in a 4-year live-trapping study of a population of the rice rate Oryzomys longicaudatus philippii in a southern Chilean temperature rain forest. (2) Years of alternating high and low abundance were observed, with intra-annula seasonal fluctuations in the numbers of individuals. Higher numbers were found in autumn-winter periods due to recruitment, and lower numbers in spring-summer periods. (3) A low survival rate is characteristic for this species with complete disappearance of individuals from the study area during summer months. (4) High recruitment, low resident survival, and large home ranges may be related to high vagility in this species. (5) Sex ratios were skewed towards males in all years studied with the exception of winter-spring periods in years of high abundance. (6) Age structure, determined for mobile cohorts using relative age of individuals born in the same period, showed the presence of five cohorts with different survival rates in the population. (7) There was a single, limited reproductive period each year. Prior to years of higher numbers, a longer reproductive period occurred; conversely, shorter periods preceded years of low numbers.