ANNUAL AGE STRUCTURE AND REPRODUCTIVE PATTERNS IN MARMOSA-INCANA (LUND, 1841) (DIDELPHIDAE, MARSUPIALIA)

Investigated were the annual age structure and reproductive indicators in museum specimens of the mouse opossum Marmosa incana. Monthly dist ributions of relative age classes, indexed by tooth eruption and wear, suggest an almost total cohort turnover in an annual cycle (males: on e year; females: one year and half). Analysis of tegumentary indicator s of reproductive activity, gauged by examination of internal reproduc tive tracts, demonstrated that all the sexually matured individuals be long to the two oldest age classes. These populational features combin ed with a three-month seasonal breeding period, detected in the greate r part of the geographic range of M. incana, apparently result in an u nusual life history strategy for this species, characterized by only o ne ''big-bang'' reproductive event in a lifetime.