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).