Population dynamics and reproduction of Cricetid rodents in a deciduous forest of the Urucum Mountains, western Pantanal, Brazil

Abstract

The population dynamics and reproduction of Cricetid rodents of the Urucum Mountains were analyzed in a region poorly known in terms of life history characteristics of mammals. Animals were obtained from a museum’s mammal collection, but were originally captured using pitfalls. Data collection was performed for five days every month in three areas, from December 2000 to September 2002. The most frequent species found were the rodents Akodon toba, Calomys callosus, Euryoryzomys nitidus, and Oecomys bicolor. These species were usually more abundant in the rainy season and in the beginning of the dry season. However, there were differences between young and adults for A. toba and E. nitidus, with both species showing a peak of young in the rainy season, followed by a posterior peak of adults in the early dry season. Thus, there was a correlation between the population variations of A. toba and C. callosus, and between E. nitidus and O. bicolor. The seasonal availability of resources should be influencing the reproduction rate as well as the occurrence of young in the populations, since the climatic seasons are well defined in the region. Calomys callosus showed the largest litter size and presence of sexual dimorphism in size and mass. The species showed mostly similar responses to climatic seasonality, but differed in attributes related to their specific life histories.

Key words: reproductive effort, abundance, sexual dimorphism, sex ratio, small mammals, litter size, seasonality response, male reproductive condition.