We designed an individual-based model to explore the effects of unusual life-history parameters and changing ecological conditions on the population dynamics and persistence of the monogamous Hypogeomys antimena, a Malagasy rodent with a recently dramatic decline in its geographical range. Model parameters were derived from extensive field studies carried out since 1992. The simulations predict that Hypogeomys is quite sensitive to small fluctuations in reproductive rate, offspring and adult mortality. Minimum habitat requirements of a viable population that is able to cope for the next 100 years with fluctuating ecological conditions were reached in forest areas of about 3000 ha. However, this habitat size will not represent a stable population. Under current conditions, the population size will continuously decline almost independently of the modelled forest block size. A stable population demography can only be reached by slightly improving the life-history conditions. The survival prospect of the largest at least partly protected forest fragment currently inhabited by H. antimena are discussed.