Monodelphis kunsi
pygmy short-tailed opossum

Pygmy short-tailed opossums are a very poorly known species. Not many specimens of this mysterious mammal have been collected (about 15 individuals total); the are from Bolivia (seven) and the rest from Brazil and Argentina. However, the range of Monodelphis kunsi probably extends to Peru since the reported collection sites were in close proximity to the national borders of this country. The first type specimen of this opossum was collected in Bolivia at "La Granja" near the west margin of Itonamas River, 4 km north of Magdalena (13° 18' S, 64° 09'W) at approximately 200 m of elevation. In Argentina, the first specimen of Monodelphis kunsi was collected quite recently (2005) at 22° 18' 41.4'' S, 63° 58' 7.1''W, 700 m above sea level. (Anderson, 1982; Jayat and Miotti, 2005; Salazar et al., 1994; Vargas, Tarifa, and Cortez, 2003)

Not much is known about the preferred habitat of Monodelphis kunsi. Based on the topography of the sites from which the specimens were collected, it appears that M. kunsi occupy a wide range of terrestrial habitats. Locations from which the specimens were collected are characterized by a wide range of elevations, from 200 m to 1500 m. One specimen of the pygmy short-tailed opossum was collected in an area with thick brush, many rocks and fallen wood, and ground covered by occasional small forbs and ferns. The ground was steeply sloped (30°) and there was about 10 to 12 cm layer of mulch and litter. In contrast, another specimen was collected in a banana field about 30 m from a river. On this flat terrace with very moist soil and about 2 cm of leaf litter; the trees (7 to 8 m tall) and shrubs combined, provided 30 to 60 % cover. While these two areas represent somewhat moderately disturbed ecosystems, pygmy short-tailed opossums have also been collected in quite pristine habitats. (Anderson, 1982; Salazar et al., 1994)

Monodelphis kunsi is probably the smallest species in the genus Monodelphis. The mass of specimens lies between 7.5 and 30 grams and length between 103 and 147 millimiters. Monodelphis kunsi lacks a sagittal crest on the skull and enlarged canines. Unlike M. americana and M. brevicaudata, pygmy short-tailed opossums have no dorsal stripes or lateral reddening. M. kunsi have throat glands covered by thin fur. Over the body, the fur of these opossums is short, generally warm brown on the dorsal side and with whitish areas on the ventral side. The tail is bicolored, darker dorsally and buffy ventrally; covered by fine hair, except for the tip which may serve a tactile function. The skull is small (about 22 mm in length) with no postorbital processes and a relatively blunt rostrum. The head is covered with numerous mystacial, genal, supraorbital, and interramal vibrissae. The hind feet have noticeable webs between digits 3 and 4 and a less conspicuous web between digits 2 and 3. All members of the genus Monodelphis lack abdominal pouches. (Anderson, 1982)

The lifespan of Monodelphis kunsi is unknown.

Nothing is known about the behavior of Monodelphis kunsi. Like most other Didelphids these opossums are probably solitary except for the mating season. (Mandavia and Myers, 2004; Salazar et al., 1994)

Home Range

Based on the methods of Rabinowitz et al.(1986) and Arita et al.(1990) for determining rarity, it was established that Monodelphis kunsi has a wide distribution but low densities locally. (Salazar et al., 1994)

Nothing is known about the communication and perception of Monodelphis kunsi. It is possible that this species depends on its sense of touch (numerous vibrissae on the head and feet) and smell as it moves about its environment. Other didelphids rely primarily on their senses of touch, smell, hearing, and, to a lesser extent, sight. (Anderson, 1982; Mandavia and Myers, 2004; Vargas, Tarifa, and Cortez, 2003)

Based on morphological characteristics such as build, size and dentition; which are similar to the members of the family Soricidae, Monodelphis kunsi is probably invertivorous, or possibly omnivorous. The diet of M. kunsi is probably determined by the availability of food resources in a particular area. (Anderson, 1982; Vargas, Tarifa, and Cortez, 2003)

Nothing is known about the predators or anti-predatory behavior of Monodelphis kunsi. These opossums are probably preyed on by mammal carnivores, reptiles, or predatory birds. Their small size and cryptic coloration may help them to evade some predation. (Anderson, 1982; Mandavia and Myers, 2004)

Nothing is known about the role that M. kunsi plays in the ecosystem. These opossums could have an effect on the population sizes of the insects on which they feed. If there is a predator for which M. kunsi is the major food source, it is possible that these opossums could have an impact on population size of this particular predator. (Anderson, 1982; Mandavia and Myers, 2004; Vargas, Tarifa, and Cortez, 2003)

There are no known negative effects of Monodelphis kunsi on humans.

There are no known positive effects of Monodelphis kunsi on humans. (Anderson, 1982; Vargas, Tarifa, and Cortez, 2003)

According to the IUCN Red List of Threatened Species Monodelphis kunsi is an endangered species due to a decline in area of occupancy, extent of occurrence and/or quality of habitat. Vargas, Tarifa and Cortez (2003) reported that numbers of M. kunsi are declining due to human induced habitat degradation. They estimated that populations declined as much as 50% in the last decade. (Vargas, Tarifa, and Cortez, 2003)

The name Monodelphis is from the Greek word for "single womb" and the specific epithet kunsi honors Dr. Merle L. Kuns who obtained the type specimen. (Anderson, 1982)