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, short-tailed opossum (Monodelphis domestica) was compared with that of the laboratory rat (Rattus norvegicus). The performance of the opossums was clearly different from that of the rats in both tasks. The opossums failed to learn to find a hidden platform in the swimming pool (place task), but they did learn to swim to a visible platform. The opossums did learn working and reference memory components of the radial arm maze but showed different search strategies in this situation. The results are discussed with reference to possible species differences in motor behavior, ecology, brain structure and evolution.