ECOLOGICAL STRATEGIES OF A DESERT MOUSE OPOSSUM, THYLAMYS PALLIDIOR, IN the MONTE DESERT, ARGENTINA

M. SOLEDAD ALBANESE, M. ANA DACAR AND RICARDO A. OJEDA

Mendoza, Argentina

Congreso; Xth International Mammalogical Congress; 2009

International Federation of Mammalogists

The desert mouse opossum is a small marsupial inhabiting the aridlands from South America with the broadest distribution in the genera. Knowledge about its ecology is scarce being this the first study of a marsupial in the Monte. The objective of our research was to characterize three aspects of its ecology (population structure, habitat use and diet) in a seasonal and heterogeneous environment. During 2005-2007 we sampled four seasons and three habitat types (Prosopis woodland, Larrea shrubland and sand dunes) in the MaB Ñacuñan Reserve, Mendoza. On each habitat we set up 6 grids (36 Sherman ground traps+10 tree traps) the first year and 4 grids the second year. Individuals were measured, marked and released at the capture site. The habitat use was analyzed at three spatial scales (habitat, grid, and patch). We captured 118 mouse-opossums (capture effort: 27600 trap-nights). Our results show that the abundance is mainly influenced by rainfall (p<0.001), and the reproduction was strongly seasonal, with evidence of semelparity. At the highest spatial scale there was no difference in the use of 3 habitats at any season. The scale of selection that explained most of the habitat utilization by the desert mouse opposum was the grid (1ha; p<0.001; deviance explained 42%). During dry season, it selected areas with low complexity and high grass cover, whereas in wet season less than 20% of the variation is explained by the models (p<0.001). The diet is composed by arthropods (71.5%), and unlike Australian desert small marsupials, T.pallidior feeds on leaves (22.44%), fruits (3.13%) and seeds (2.3%). This composition does not vary between seasons, sex or age classes. Except for its diet, this species showed strong seasonality in many aspects of their natural history. These strategies allow the desert mouse opossum to cope with rigorous conditions that characterize arid environments (Supported by PICT-AGENCIA 11768-25778-PIP CONICET-5944).