The yellow-sided opossum (''Monodelphis dimidiata'') is an

opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered North ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

from

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

. It is found in

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

and

Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...

. 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 The Pampas (from the qu, pampa, meaning "plain") are fertile South American low grasslands that cover more than and include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos, and Córdoba; all of Uruguay; and Brazil ...

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. Maintaining their native grasslands is important for them to keep a stable population. They show

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

in overall size: adult males are typically 100-150 g whereas adult females are 30-70 g.

Behavior

This species displays a rich repertoire of stereotyped behaviors. Postures, locomotion, and grooming seem to be similar to those described for other didelphids. They can carry nest materials using their short but still prehensile tails. Both males and females hunt insects and small vertebrates and show specialized behavior for dealing with particular preys. Attacks and initial consumption are initially directed typically towards the head of the prey, especially for large insects. However, hairy caterpillars are not immediately grabbed; instead, several rounds of scratching over the stinging hairs are performed before the prey is eaten. Small mice are chased and attacked until a firm bite at the neck is attained. They then hold the neck bite until the mice dies. ''M. dimidiata'' is thought to be a miniature analog to the marsupial sabertooths ''

Thylacosmilus ''Thylacosmilus'' is an extinct genus of Saber-toothed predator, saber-toothed metatherian mammals that inhabited South America from the Miocene, Late Miocene to Pliocene Epoch (geology), epochs. Though ''Thylacosmilus'' looks similar to the "Mac ...

''. Like extinct sabertooth predators, it has one of the largest canines of any marsupial relative to body size and was proposed as a living model to test hypotheses about hunting strategies of the extinct predators.Blanco, R. E., Jones, W. W., & Milne, N. N. (2013). Is the extant southern short-tailed opossum a pigmy sabretooth predator?. Journal of Zoology, 291(2), 100-110. Yellow-sided opossums also show a variety of behaviors used in social contexts, including male-to-male agonistic rituals, and a variety of vocalizations whose social or adaptive significance deserves further investigation.

References

Opossums Marsupials of South America Mammals of Brazil Mammals of Argentina Mammals of Uruguay Mammals described in 1847 {{marsupial-stub