The yellow-sided opossum (Monodelphis dimidiata) is an opossum species from South America. It is found in Argentina, Brazil and Uruguay. They have grey or black fur on their dorsal side with yellowish fur on the lateral side that continues down to the feet. They are the most mysterious of all the Monodelphis that is found specifically in the Pampean region or Pampa of Argentina. It is suspected to be a once-in-a-lifetime breeder as seen in a three-year observational study of one population in the marshy grasslands of the Pampean region. It is important to note the importance of maintaining their native grasslands in order for them to keep a stable population.
Marsupials are not typically predatory, other than the ‘‘didelphids’’ and ‘‘dasyurids’’, and this one species of Monodelphis. There is sexual dimorphism between the males and females in that the males are typically 100-150 g and the females are 30-70 g. Both males and females hunt. For dealing with various kinds of prey they crush the heads of arthropods and biting the neck of smaller mice. As seen in captivity, they will get a grab the neck of mice in a way that it can not move and then proceed to attack the head until it is dead. M. dimidiata is thought to be analogous to the various sabertooth predators seen in fossil records. Like extinct sabertooths, it has one of the largest canines of any marsupial relative to body size. It may serve as a living model to test hypotheses about hunting strategies of the extinct predators.