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.
Biogeographic Regions: neotropical (Native )
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.
Range mass: 7.5 to 30 g.
Range length: 103 to 147 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
Catalog Number: USNM 461348
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Male; Adult
Preparation: Skin; Skull
Collector(s): E. Lotore
Year Collected: 1971
Locality: La Granja, W bank Rio Itonamas, 4 km N Magdalena, Itenez Province, El Beni, Bolivia, South America
Microhabitat: Cut-over brush
Elevation (m): 200
- Type: Pine, R. H. 1975 Dec 20. Mammalia. 39: 321.
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.
Range elevation: 200 to 1500 m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: rainforest
Other Habitat Features: agricultural
Habitat and Ecology
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.
Animal Foods: insects
Primary Diet: carnivore (Insectivore , Eats non-insect arthropods); omnivore
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.
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.
Anti-predator Adaptations: cryptic
Life History and Behavior
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.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
The lifespan of Monodelphis kunsi is unknown.
Nothing is known about the reproduction of M. kunsi. It is possible that these tiny opossums are promiscuous, similarly to many other members of the family Didelphidae. Generally, species in this group are solitary and interact with each other only for the purpose of mating.
Nothing is known about the reproductive behavior of Monodelphis kunsi. Since M. kunsi are in the infraclass Metatheria (marsupial mammals), they almost certainly have a short gestation period and young fairly undeveloped at birth, as these traits generally characterize this group of animals.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Nothing is known about the type of parental investment in Monodelphis kunsi. As in all mammals, lactating females nourish and protect the developing young.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)
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.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2008Least Concern(IUCN 2008)
- 2008Least Concern
Relevance to Humans and Ecosystems
There are no known negative effects of Monodelphis kunsi on humans.
There are no known positive effects of Monodelphis kunsi on humans.
Pygmy short-tailed opossum
The Pygmy Short-tailed Opossum, Monodelphis kunsi, is an opossum species from South America and is one of the three endangered marsupials of the world.  It is found in Argentina, Bolivia, Brazil and Paraguay. It is also found in the Rio Lipeo department of Tarija, which is between 200 m and 640 m in elevation.  They are most likely insectivorous and have a diet similar to the shrews of that region. The young are referred to as 'joeys'. The females are referred to as 'Jill' and the males 'jack'. M. kunsi is typically found in forested or wooded areas. They are generally encountered in shrub forests of 6-12 m in height in Paraguay.  Pale gray fur on the dorsal side that becomes progressively darker as it goes more towards the head which grows anywhere between 3 to 2 mm. The tail is hairless at the tip which is seen in many members of the Short-tailed opossum genus. This is thought to be used for tactile purposes. It was thought to have been endangered in 2001, but has since been moved to least concern by the International Union for Conservation of Nature.
- Gardner, A. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 15. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Solari, S., de la Sancha, N. & Vilela, J. (2011). "Monodelphis kunsi". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 18 January 2012. Database entry includes justification for why this species is of least concern
- Jones, M. Dickman, Predators with Pouches: The Biology of Carnivorous Marsupials, Marsupials of the World,Print. 2003.
- Anderson, Sydney. Monodelphis Kunsi. Digital image. Clark Science Center. Smith College, 1982.
- Noe de la Sancha, First Records of Monodelphis kunsi PINE (DIDELPHIMORPHIA, DIDELPHIDAE) from Paraguay, with an Elevation of its Distribution", Mastozoología Neotropica, 2007.
- Carvalho, B de A., Oliveira, L. F. B., Langguth, A. Freygang, C. C., Ferrax, R. S., Mattevi, M. Phylogenetic relationships and phylogeographic patterns in Monodelphis (Didelphimorphia: Didelphidae). Journal of Mammalogy. 92(1): 121-133. 2011
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