Common Fat-tailed Mouse Opossum vs Polynesian rat

Thylamys pusillus compared with Rattus exulans

Taxonomic Classification

Rank	Common Fat-tailed Mouse Opossum	Polynesian rat
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum same	Chordata (Chordates)	Chordata (Chordates)
Class same	Mammalia (Mammals)	Mammalia (Mammals)
Order	Didelphimorphia (Didelphimorphia)	Rodentia (Rodents)
Family	Didelphidae	Muridae (Mice & Rats)
Genus	Thylamys	Rattus
Species	Thylamys pusillus	Rattus exulans

Evolutionary Relationship

Common Fat-tailed Mouse Opossum and Polynesian rat share a common ancestor at the Class level: Mammalia. (Mammals)

Conservation Status

Common Fat-tailed Mouse Opossum

LC — Least Concern

Polynesian rat

LC — Least Concern

Physical Characteristics

Attribute	Common Fat-tailed Mouse Opossum	Polynesian rat
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Common Fat-tailed Mouse Opossum

Habitat

Typically found in diverse terrestrial and aquatic ecosystems.

Polynesian rat

Habitat

Found across multiple habitat types including tropical and subtropical moist broadleaf forests, tropical and subtropical dry broadleaf forests, and tropical and subtropical coniferous forests, among 4 distinct biome types spanning the Australasia and Indomalayan realms. Populations are also found in montane and highland environments at higher elevations.

Range

Widely distributed across Asia (6 countries), Europe (United Kingdom), North America (United States), Oceania and the Pacific (11 countries), and South America (Chile).

Common Fat-tailed Mouse Opossum

The Common Fat-tailed Mouse Opossum (<em>Thylamys pusillus</em>) is a small marsupial belonging to the genus Thylamys within the family Didelphidae. Like other members of its genus, this species typically stores fat in its tail, which becomes swollen during periods of food abundance and is metabolised during leaner times, a physiological adaptation that provides energy reserves. <em>Thylamys pusillus</em> is generally found in diverse terrestrial and aquatic ecosystems, often in dry woodlands, scrublands, and grassland habitats of South America. The species is assessed as Least Concern on the IUCN Red List, indicating it is not currently considered at risk of extinction. Detailed geographic range data are not available in the current record, but members of this genus are typically distributed across parts of Argentina, Bolivia, Paraguay, and Uruguay. Biological traits including average lifespan, body dimensions, and specific dietary composition remain poorly documented in the scientific literature, though Thylamys species are generally considered omnivorous, often consuming insects, small vertebrates, and plant material.