Karimi's fat-tailed mouse opossum  (Thylamys karimii)

Karimi’s fat-tailed mouse opossum is classified as Vulnerable (VU) on the IUCN Red List (1).

Karimi’s fat-tailed mouse opossum (Thylamys karimii) is a South American marsupial named for its short tail, which becomes seasonally thickened through the storage of fat (3).

Karimi’s fat-tailed mouse opossum occurs only in Brazil. It is widely distributed within the two major biomes in Brazil, the cerrado and the caatinga, in the northeast and central parts of the country (1) (3).

Karimi’s fat-tailed mouse opossum is known to inhabit dry, open vegetated regions at elevations between 300 and 1,100 metres above sea level (6). The two main regions where it is found are the dry caatinga forest and the dense savannah of the cerrado (1).

Compared to other opossum species, there is relatively little known about Karimi’s fat-tailed mouse opossum. It is known to be a fairly terrestrial animal, which tends to stay down at the lower levels of vegetation (6). As a result, it is not as adapted for climbing trees and lacks the prehensile tail of other opossum species. Instead, the tail of Karimi’s fat-tailed mouse opossum can become swollen as it acts as a store of fat (3).

Although the diet of this species is not known, it is likely to be similar to other mouse opossums, which feed on insects, fruit and small vertebrates (5).

Like other mouse opossums, it is possible that the Karimi’s fat-tailed mouse opossum breeds from September to March, during which time the female may have two litters (5). Mouse opossums, like all marsupials, have a short gestation period, and the young are poorly developed at birth and crawl immediately to the female’s teats (7). Although each litter can contain as many as 15 young (5), many will die as the female produces more young than she has mammae (7).

Most development takes place as the young feed on the female's milk (7). The length of time that the female Karimi’s fat-tailed mouse opossum feeds the young for is not known, but like other mouse opossums it is likely to be more than 68 days (7). Unlike most other marsupials, the Karimi’s fat-tailed mouse opossum lacks a pouch in which the young are protected as they feed (3).

Even though Karimi’s fat-tailed mouse opossum is widely distributed in Brazil, it occurs in low densities and is threatened by habitat loss (1).

The open habitats occupied by Karimi’s fat-tailed mouse opossum are being converted for large-scale farming, in particular for soybean plantations (1). 

There are currently no specific conservation measures in place for Karimi’s fat-tailed mouse opossum, but it reportedly occurs within a number of protected areas(1), which should offer this species some protection.

Karimi’s fat-tailed mouse opossum is also likely to benefit from the work of organisations such as WWF, which are working with farmers to identify how the negative environmental impacts of soybean production can be reduced (8).

Learn more about soybean production and conservation:

• WWF – Soybeans:
  http://wwf.panda.org/what_we_do/footprint/agriculture/soybeans

Find out about conservation in Brazil:

• The Nature Conservancy:
  http://www.nature.org/ourinitiatives/regions/southamerica/brazil
• Wildlife Conservation Society:
  http://www.wcs.org/where-we-work/latin-america/brazil.aspx