SPATIAL-BEHAVIOR IN THE BRAZILIAN SHORT-TAILED OPOSSUM (MONODELPHIS-DOMESTICA) - COMPARISON WITH THE NORWAY RAT (RATTUS-NORVEGICUS) IN THE MORRIS WATER MAZE AND RADIAL-ARM MAZE

The spatial behavior displayed in a swimming pool and radial arm maze by the Brazilian gray, shea-tailed opossum (Monodelphis domestica) was compared with that of the laboratory rat (Rattus norvegicus). The per formance of the opossums was clearly different from that of the rats i n both tasks. The opossums failed to learn to find a hidden platform i n the swimming pool (place task), but they did learn to swim to a visi ble platform. The opossums did learn working and reference memory comp onents of the radial arm maze but showed different search strategies i n this situation. The results are discussed with reference to possible species differences in motor behavior, ecology, brain structure and e volution.