Marmosa robinsoniRobinson's mouse opossum

Geographic Range

Marmosa robinsoni occurs in Panama, Colombia, northern Venezuela, adjacent continental-shelf islands (Isla Margarita, Trinidad, Tobago), and Grenada. (Rossi, et al., 2010)


Most records of this species are from semideciduous and dry lowland forests, but it has also been collected in montane forest. It is sometimes reported to be more abundant at the edges of clearings and in secondary growth than in primary forest. (Alvizu and Aguilera, 1998; O'Connell, 1979; O'Connell, 1983; Rossi, et al., 2010)

  • Range elevation
    0 to 2600 m
    0.00 to 8530.18 ft

Physical Description

Like other species of mouse opossums, Marmosa robinsoni is a small pouchless marsupial with large membranous ears; prominent eyes; a mask of dark fur surrounding the eyes; and a long, slender, prehensile tail. The dorsal fur is usually some shade of yellowish or grayish brown, and the ventral fur is typically pale yellowish or buffy. Among other diagnostic traits, this species differs from other species of Marmosa by having a short rostral process of the premaxillae, well-developed palatine fenestrae, and relatively large auditory bullae. This species is sexually dimorphic (males are larger than females). (Alvizu and Aguilera, 1998; Lopez-Fuster, et al., 2000; Rossi, et al., 2010)

  • Sexual Dimorphism
  • male larger
  • Range mass
    26 to 110 g
    0.92 to 3.88 oz
  • Average mass
    44 (females) 71 (males) g
  • Range length
    83 to 218 mm
    3.27 to 8.58 in
  • Average length
    130 (females) 149 (males) mm


Nothing definite seems to be known about the mating system or reproductive seasonality of this species. Previous reports about these aspects of reproductive biology of Marmosa robinsoni were actually based on studies of other species (e.g., Marmosa isthmica). (Gutierrez, et al., 2010)

Marmosa robinsoni is a spontaneous ovulator that gives birth to very altricial young (about 0.1 g at birth) after a short (14 days) gestation. Eleven young (on average) were found attached to the nipples of females captured in trapping studies. The young remain attached to the mother's teats for 21 days and become fully independent after 60-70 days. Sexual maturity is reached after about 40 weeks but "full breeding behavior" is said to occur at about one year of age. Copulation occurs with the pair suspended by their tails from an overhead support. Although evidence from field studies of this species (e.g., O'Connell, 1979) is inconclusive, closely related species (such as M. xerophila) are known to be seasonal breeders, and M. robinsoni typically occurs in habitats with highly seasonal rainfall, so it is probably also a seasonal breeder. It is not known whether or not individuals of this species breed more than once in a lifetime, but some closely related species are known to be semelparous. (Barnes and Barthold, 1969; Barnes and Wolf, 1971; Godfrey, 1975; O'Connell, 1979; Rossi, et al., 2010)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • viviparous
  • Breeding interval
    The frequency of breeding in this species is unkown, but other species of Marmosa are thought to breed only once in their lifetime.
  • Breeding season
    The breeding seasonality of this species is unknown.
  • Average number of offspring
  • Range gestation period
    13 to 15 days
  • Range weaning age
    60 to 70 days
  • Range time to independence
    60 to 70 minutes
  • Average age at sexual or reproductive maturity (female)
    280 days
  • Average age at sexual or reproductive maturity (male)
    280 days

Females nurse the young for several weeks and presumably groom them and protect them from predators at the same time. (Barnes and Wolf, 1971)

  • Parental Investment
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female


Nothing definite seems to be known about the longevity of this species in the wild or in captivity, but other species of Marmosa are not thought to live much longer than one year in the wild. (Tate, 1933)


The behavior of this species (except as described above in the context of reproduction) has not been the focus of any published study, but trapping results suggest that it is nocturnal and arboreal or scansorial. (Alvizu and Aguilera, 1998; O'Connell, 1979)

Home Range

The only field study focussed on the home range of this species obtained estimates of about 2.5 hectares for each sex using the minimum convex polygon method. (Alvizu and Aguilera, 1998)

Communication and Perception

Mating is preceeded by hissing and chirping sounds that presumably communicate sexual or agressive intentions. Adult males possess a gular gland that presumably has some social scent-marking funtion. The eyes, ears, nasal turbinates (thin bones that support olfactory epithelium), and tactile hairs are well developed in this species (as in other opossums), so vision, hearing, and touch are probably important senses. (Barnes and Barthold, 1969; Rossi, et al., 2010)

Food Habits

There has been no study of the food habits of this species in the wild, but captives seem to do best when insects and fruit are provided daily. The dental morphology of Marmosa robinsoni, like that of other Marmosa species, is consistent with a mainly insectivorous diet. (Godfrey, 1975)

  • Animal Foods
  • insects
  • Plant Foods
  • fruit


Nothing seems to be known about the natural predators of this species, but they probably include snakes, owls, and wild felids. (Tate, 1933)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Marmosa robinsoni is probably a primary consumer (of fruit) and a secondary consumer (of insects). It is probably eaten by snakes, owls, and carnivorans; and it is certainly host to many species of invertebrate ecto- and endo-parasites. Probable ectoparasites include species of Arachnida (Acari: mites) and Insecta (Siphonaptera: fleas). Probable endoparasites include species of Acanthocephala (spiny-headed worms), Cestoda (tapeworms), Digenea (flukes), and Nematoda (roundworms).

Economic Importance for Humans: Positive

This species is not known to be of any positive economic importance for humans.

Economic Importance for Humans: Negative

There are no known adverse effects of Marmosa robinsoni on humans.

Conservation Status

Marmosa robinsoni is geographically widespread and thrives in many kinds of human-modified landscapes. (Rossi, et al., 2010)

Other Comments

There has been much taxonomic confusion about this species. For the first half of the 20th century, it was known as Marmosa mitis (a junior synonym). Then, after 1951 and until 2010, the name M. robinsoni was used to include several other taxa that are now recognized as distinct species, including M. isthmica and M. simonsi. Therefore, late 20th-century publications about "Marmosa robinsoni" (e.g., O'Connell, 1983) may report observations that do not apply to, or that cannot be confidently attributed to, this species. (Rossi, et al., 2010)

Phylogenetic analyses of cytochrome-b sequence data suggest that (1) the sister taxon of Marmosa robinsoni is M. xerophila; (2) that the sister taxon to M. robinsoni + M. xerophila is a clade containing M. isthmica, M. mexicana, and M. zeledoni; and (3) that the sister taxon to these two clades is M. simonsi. Other species of Marmosa are yet more distantly related. (Gutierrez, et al., 2010)


Robert Voss (author), American Museum of Natural History, Sharon Jansa (editor), American Museum of Natural History, Alexa Unruh (editor), Animal Diversity Web Staff.



living in the southern part of the New World. In other words, Central and South America.

World Map


uses sound to communicate


living in landscapes dominated by human agriculture.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females


An animal that eats mainly insects or spiders.


having the capacity to move from one place to another.


This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

scrub forest

scrub forests develop in areas that experience dry seasons.


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate


Living on the ground.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Alvizu, P., M. Aguilera. 1998. Uso del espacio de Marmosa robinsoni (Didelphidae: Marsupialia) en una zona xerofila de los Andes venezolanos. Ecotropicos, 11(2): 81-92.

Barnes, R., S. Barthold. 1969. Reproduction and breeding behavior in an experimental colony of Marmosa mitis Bangs (Didelphidae). Journal of reproduction and Fertility (supplement), 6: 477-482.

Barnes, R., H. Wolf. 1971. The husbandry of Marmosa mitis as a laboratory animal. International Zoo Yearbook, 11: 50-54.

Godfrey, G. 1975. A study of oestrus and fecundity in a laboratory colony of mouse opossums (Marmosa robinsoni). Journal of Zoology, 175: 541-555.

Gutierrez, E., S. Jansa, R. Voss. 2010. Molecular systematics of mouse opossums (Didelphidae: Marmosa): assessing species limits using mitochondrial DNA sequences, with comments on phylogenetic relationships and biogeography. American Museum Novitates, 3692: 1-22.

Lopez-Fuster, M., R. Perez-Hernandez, J. Ventura, M. Salazar. 2000. Effect of environment on skull-size variation in Marmosa robinsoni in Venezuela. Journal of Mammalogy, 81: 829-837.

O'Connell, M. 1979. Ecology of didelphid marsupials from northern Venezuela. Pp. 73-87 in J Eisenberg, ed. Vertebrate ecology in the northern Neotropics. Washington, DC: Smithsonian Institution Press.

O'Connell, M. 1983. Marmosa robinsoni. Mammalian Species, 203: 1-6.

Rossi, R., R. Voss, D. Lunde. 2010. A revision of the didelphid marsupial genus Marmosa. Part 1. The species in Tate's 'mexicana' and 'mitis' sections and other closely related forms. Bulletin of the American Museum of Natural History, 334: 1-81.

Tate, G. 1933. A systematic revision of the marsupial genus Marmosa. Bulletin of the American Museum of Natural History, 66: 1-250.