About Thylamys elegans (Waterhouse, 1839)
The elegant fat-tailed mouse opossum (Thylamys elegans) is a medium-sized opossum. Key features of this species include white limbs, a gray to light brown coat, lighter-colored flanks and underbelly, and a thick, hairy tail that measures 12.7 to 14.6 centimetres (5.0 to 5.7 in) long. A distinct facial marking is a black ring around each eye, and these rings extend slightly toward the nose. Coat color varies across different geographic regions. The tail can thicken as fat accumulates inside it, and at its base (where it connects to the body) the tail can reach 1 centimetre (0.39 in) in diameter. The head-and-body length of this opossum ranges from 11 to 13.7 centimetres (4.3 to 5.4 in); hindfeet measure 1.7 centimetres (0.67 in) on average, and ears measure 2.3 centimetres (0.91 in).
This species can enter torpor, a short-term physiological state that greatly reduces the opossum's need for food and energy, unlike the longer-term state of hibernation. When water is scarce, this opossum produces highly concentrated urine to conserve water.
The elegant fat-tailed mouse opossum is found west of the Andes in central Chile, where it inhabits a range of habitats from cloud forests to chaparrals, at altitudes up to 2,500 metres (8,200 ft) above sea level. The IUCN Red List classifies this species as least concern, due to its wide distribution and assumed large total population. However, population declines have been recorded in parts of its range as a result of deforestation and agricultural expansion.
Ecologically, the elegant fat-tailed mouse opossum is crepuscular, meaning it is most active around twilight. It makes its nests in tree hollows, under rocks, and under roots; nests are either built by the opossum itself or reused from abandoned bird or rodent nests. It is both arboreal (tree-dwelling) and terrestrial (land-dwelling). Its diet consists mainly of arthropods and larvae, and it also eats fruits, small vertebrates, and carrion. Regardless of its thickness, the prehensile tail allows this opossum to climb efficiently and grasp branches, an ability that is less developed in other small Chilean mammal species. Nests are usually occupied by only one individual. In southern Chile, the opossum's home range covers 1,383 square metres (14,890 sq ft) in July, and shrinks to 781 square metres (8,410 sq ft) in December. Known predators of this opossum include the culpeo fox, burrowing owl, and great horned owl.
Both male and female elegant fat-tailed mouse opossums reach sexual maturity by their first year. The annual breeding season typically runs from September to March, and a female can produce one to two litters per season. A female can carry up to 17 embryos, but the number of surviving offspring depends on the number of functional nipples, which is usually between 11 and 13.
