Because this species is small and nocturnal, communication between individuals is likely primarily olfactory in nature. Palma (1997) reports that the olfactory and visual regions of the brain of Thylamys elegans, a closely related species, are especially well developed.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical
This species is listed as "Least Concern" by the IUCN.
IUCN Red List of Threatened Species: least concern
There are no known negative effects of Thylamys pallidior.
There are no known positive impacts of Thylamys pallidior on humans.
Thylamys pallidior acts as an important predator to many arthropod species and some small vertebrates. It is prey to several bird and medium-sized mammals, such as owls and foxes. Braun et al. (2010) list six ecto- and endoparasites associated with Thylamys pallidior.
Commensal/Parasitic Species:
Albanese et al. (2010) examined the feces of wild Thylamys pallidior individuals and found that its diet primarily consisted of arthropods. Other dietary components include leaves, fruit, and seeds. Other Thylamys species have been observed consuming small vertebrates (e.g. rodents, lizards), so it is possible that Thylamys pallidior also feeds on those prey items (Palma, 1997)
Animal Foods: insects
Plant Foods: leaves; seeds, grains, and nuts; fruit
Primary Diet: carnivore (Insectivore )
Thylamys pallidior is distributed from southern Peru to central Argentina, including Chile and western Bolivia.
Biogeographic Regions: neotropical (Native )
This species inhabits a number of different dryland habitats, including the high Andean steppe (Puna grassland), the Monte desert and dry Chaco of Argentina, and the Sechura Desert of Peru. For much of its range, it is found in high-elevation habitats of the Andes. At the southern extreme of its distribution, it can be found in lowland areas.
Range elevation: 0 to 3750 m.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral ; mountains
Braun et al. (2010) note an account of Thylamys pallidior from the early 20th century wherein a captured juvenile survived for 1.5 years in captivity, tripling in size over its life span.
Range lifespan
Status: captivity: 1.5 (high) years.
Like other members of its genus, Thylamys pallidior is notable for its incrassate (fattened) tail. The size of the tail varies by season in accordance with food availability. Although this species is a marsupial, females do not have a pouch. This species is tricolored, with darker dorsal fur, paler lateral fur, and a white ventral region. This species is broadly similar to other members of the Elegans Group (which includes T. elegans, T. pallidior, and T. tatei) as described by Giarla et al. (2010). Giarla et al. (2010) report head + body lengths that range from 73 to 104 mm (average 95 mm) and tail lengths that range from 97 to 118 mm long (average 109 mm). Braun et al. (2010) report body masses ranging from 13 to 39 g (average 19 g)
Range mass: 13 to 39 g.
Average mass: 19 g.
Range length: 170 to 222 mm.
Average length: 204 mm.
Other Physical Features: endothermic ; bilateral symmetry
Like other small mammals, Thylamys pallidior is likely well adapted to avoiding predators by being nocturnal and inconspicuous. This species has been noted as a prey item for two owl species.
Known Predators:
Anti-predator Adaptations: cryptic
Little is known about the mating system in Thylamys pallidior. Palma (1997) reports that two Thylamys elegans adults (a closely related species) have never been found in the same nest, suggesting that this species does not form monogamous breeding pairs.
Little is known about the general reproductive behavior of Thylamys pallidior. Anecdotal evidence from the early 20th century (reviewed in Braun et al., 2010) suggests that this species and other small opossums breed one to three times per year. Juvenile animals tend to be captured early in the calendar year, with only adult specimens being captured in the last few months of the year.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Little is known about the parental care of Thylamys pallidior. Like other Thylamys species, females lack a pouch, with exposed young clinging to the nipples.
Parental Investment: altricial ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)
The white-bellied fat-tailed mouse opossum (Thylamys pallidior) is a species of opossum in the family Didelphidae. It is found in Argentina, Bolivia, Chile and Peru.[1]
The white-bellied fat-tailed mouse opossum is a member of the genus Thylamys, and is placed in the family Didelphidae. It was first described by English zoologist Oldfield Thomas as Marmosa elegans pallidior in 1902.[2][3] The present binomial name was suggested in a 1989 paper.[4] No subspecies are recognized.[2]
The cladogram below, based on a 2016 study, shows the phylogenetic relationships of the white-bellied fat-tailed mouse opossum.[5]
Patagonian opossum (Lestodelphys halli)
ThylamysDwarf fat-tailed mouse opossum (T. velutinus)
Karimi's fat-tailed mouse opossum (T. karimii)
Buff-bellied fat-tailed mouse opossum (T. venustus)
Cinderella fat-tailed mouse opossum (T. cinderella)
Argentine fat-tailed mouse opossum (T. sponsorius)
Paraguayan fat-tailed mouse opossum (T. macrurus)
Tate's fat-tailed mouse opossum (T. tatei)
Elegant fat-tailed mouse opossum (T. elegans)
White-bellied fat-tailed mouse opossum (T. pallidior)
T. citellus
T. pulchellus
Common fat-tailed mouse opossum (T. pusillus)
The generic name is composed of the Greek words thylas ("pouch") and mys ("mouse"), and the specific name pallidior derives from the Latin pallidus ("pale"). Alternative names for the white-bellied fat-tailed opossum include pallid fat-tailed opossum, comadreja enana, comadrejita comun, llaca de la puna and marmosa palada.[6]
The white-bellied fat-tailed mouse opossum, one of the smallest in its genus, differs from most other mouse opossums in having a gray to brown coat and completely white underside. It has well-developed, blackish eye rings that extend toward the nose (similar to the buff-bellied, elegant and Tate's fat-tailed mouse opossums but unlike the common, dwarf, Karimi's and Paraguayan fat-tailed mouse opossums). The head-and-body length of the white-bellied fat-tailed mouse opossum is 7.3 to 10.5 centimetres (2.9 to 4.1 in); the tail, slightly longer, ranges from 9 to 11.5 centimetres (3.5 to 4.5 in). Adults weigh between 13 and 39 grams (0.46 and 1.38 oz).[3][6][7]
The coat is smooth with gray and brown hairs, and notably darker along the midline of the back than the flanks. A gray band, seen in other mouse opossums, is absent or inconspicuous. The face is significantly paler than the coat, hence its name.[3][7] The tail is prehensile, with only sparse hairs, albeit in a similar color to those on the body. The tail becomes noticeably thicker, especially at the base, during the autumn, when the animal lays down fat reserves in preparation for winter. The fur on the feet is white, and relatively dense about the ankles.[6]
The white-bellied fat-tailed mouse opossum is found in southern Peru and south-western Bolivia, in the northernmost regions of Chile, and along the eastern slopes of the Andes mountains in western and central Argentina. It inhabits arid and semi-arid environments from sea level to 4,500 metres (14,800 ft), ranging from the coastal deserts of Peru, through the Andes and the Monte Desert, and into the Patagonian steppe of Argentina. It generally inhabits rocky environments with little plant cover, but can be found in dry forest or thorn scrub.[6][8]
White-bellied fat-tailed mouse opossums are nocturnal animals with good climbing abilities, although they prefer to spend most of their time on the ground. They nest in natural cavities, either in trees or shrubs, or beneath rocks. Although they do not truly hibernate through the winter, they do enter torpor if temperatures fall below around 15 °C, and therefore may be inactive through much of the winter period.[6]
In the wild, they rarely drink, being able to subsist on the water in their food. They eat a wide range of insects and spiders, but prefer beetles, of which they may eat up to twenty a night. Although such small invertebrates compose the majority of their diet, they also eat a moderate amount of leaves and seeds, and will occasionally consume small vertebrates such as mice and lizards. Their main predators include the barn owl and the Magellanic horned owl.[6]
White-bellied fat-tailed mouse opossums are believed to be able to breed up to three times a year, although most probably only give birth once or twice. The young are born in litters of up to fifteen individuals, typically during the summer months. Unlike some other marsupials, the females do not have a pouch; the teats are variable in both number and arrangement, and may not all be functional at the same time.[9] Individuals have lived up to eighteen months in captivity.[6]
It is closely related to T. karimii.[7] However, phylogenetic analysis shows that the species' closest relatives are probably the elegant, common, and Tate's fat-tailed mouse opossums, all of which also inhabit arid environments. Although fossils are known only from the Holocene, estimates for the divergence of the species from its closest relatives range from 2.2 to 6 million years ago.[8]
The white-bellied fat-tailed mouse opossum (Thylamys pallidior) is a species of opossum in the family Didelphidae. It is found in Argentina, Bolivia, Chile and Peru.
