Robinson's mouse opossum (''Marmosa robinsoni'') is a species of

opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North A ...

in the family Didelphidae. It is found in

Belize Belize is a country on the north-eastern coast of Central America. It is bordered by Mexico to the north, the Caribbean Sea to the east, and Guatemala to the west and south. It also shares a maritime boundary with Honduras to the southeast. P ...

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

Ecuador Ecuador, officially the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, and the Pacific Ocean on the west. It also includes the Galápagos Province which contain ...

Grenada Grenada is an island country of the West Indies in the eastern Caribbean Sea. The southernmost of the Windward Islands, Grenada is directly south of Saint Vincent and the Grenadines and about north of Trinidad and Tobago, Trinidad and the So ...

Honduras Honduras, officially the Republic of Honduras, is a country in Central America. It is bordered to the west by Guatemala, to the southwest by El Salvador, to the southeast by Nicaragua, to the south by the Pacific Ocean at the Gulf of Fonseca, ...

Panama Panama, officially the Republic of Panama, is a country in Latin America at the southern end of Central America, bordering South America. It is bordered by Costa Rica to the west, Colombia to the southeast, the Caribbean Sea to the north, and ...

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

Trinidad and Tobago Trinidad and Tobago, officially the Republic of Trinidad and Tobago, is the southernmost island country in the Caribbean, comprising the main islands of Trinidad and Tobago, along with several List of islands of Trinidad and Tobago, smaller i ...

, and

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

. Robinson's mouse opossums move along tree branches and vines with the help of a

prehensile tail A prehensile tail is the tail of an animal that has Adaptation (biology), adapted to grasp or hold objects. Fully Prehensility, prehensile tails can be used to hold and manipulate objects, and in particular to aid arboreal creatures in finding and ...

and may leap between gaps as they search for fruit and insects. The species is named after Wirt Robinson, the collector of the specimen from which it was first described.

Description

''Marmosa robinsoni'' is typically cinnamon brown with a yellow underside. Its dorsal color varies from russet to gray. The top of the head is generally paler in color than the rest of the body. The black facial mask is always present but varies in size according to the region of that individual. It possesses a prehensile tail about 1.3 times its body length, which is covered in fine white hairs. Its feet are modified for grasping with pads and an opposable

hallux Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plantigrade''; ...

Habitat

The species was originally collected on Margarita Island, Venezuela. It occupies a variety of habitats from sea level to 2,600 m elevation, including lowland and montane moist forests, lowland dry forests,

mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach th ...

s, and

xeric shrublands Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric (Ancient Greek 'dry') shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this habitat ...

. A study conducted in a xeric shrubland of northwestern Venezuela found that females of ''Marmosa robinsoni'' increase in mass three time faster than males. The same study also found that individual of both sexes typically are active in areas of approximately 25 m², but pregnant females dramatically reduce such area to ca. 1–6 m². There are observations that ''M. robinsoni'' feeds on fruits of columnar cacti, although the species is also expected to prey on insects (as many didelphids do). In Venezuela, specimens inhabiting agricultural lands and disturbed forests are larger than those from

cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles, suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...

and

gallery forest A gallery forest is one formed as a corridor along rivers or wetlands, projecting into landscapes that are otherwise only sparsely treed such as savannas, grasslands, or deserts. The gallery forest maintains a more temperate microclimate above th ...

likely due to the higher productivity of the former habitats.

Behavior

''Marmosa robinsoni'' generally first appears as sunset and is active intermittently until sunrise. These activity periods usual begin with a grooming session with special attention given to the face and snout. Based on current observations it appears to be a solitary species in the wild. Captivity showed the formation of social hierarchies. This hierarchy is related to reproduction and involves the males asserting their dominance by marking their cages with an oily secretion. ''M. robinsoni'' is

insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores we ...

, with fruit also playing an important role in the diet. It will also feed on earthworms, birds, bats and mice.

Range

The known distribution of ''Marmosa robinsoni'' extends from Finca Santa Clara in the western Panamanian province of Chiriquì, eastward across the

isthmus An isthmus (; : isthmuses or isthmi) is a narrow piece of land connecting two larger areas across an expanse of water by which they are otherwise separated. A tombolo is an isthmus that consists of a spit or bar, and a strait is the sea count ...

to Colombia and northern Venezuela. Although most Venezuelan specimens are from north of the

Orinoco River The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers approximately 1 million km2, with 65% of it in Venezuela and 35% in Colombia. It is the List of rivers by discharge, f ...

, found one specimen from Ciudad Bolivar on the south (right) bank of the river in Bolivar state. The species is also known from several islands on the continental shelf of Central America (e.g., Isla del Rey, Isla Saboga) and South America (

Isla Margarita Margarita Island (, ) is the largest island in the Venezuelan state of Nueva Esparta, situated off the north west coast of the country, in the Caribbean Sea. The capital city of Nueva Esparta, La Asunción, is located on the island. History ...

, Trinidad, and Tobago), and from the Caribbean island of Grenada.

Reproduction

''Marmosa robinsoni'' reproduces according to a simple schedule. It gives birth to 6 to 14 young after a gestation period of just 14 days. The tiny young, measuring only up to 12 millimeters, attach themselves to the mother's

mammae A mammary gland is an exocrine gland that produces milk in humans and other mammals. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in primates (for example, humans ...

where they may remain for around 30 days. Unlike many marsupials, female mouse opossums do not possess a pouch to protect the young as they develop. The young are so undeveloped their eyes do not open until 39 to 40 days. It is likely that the young are completely weaned after around 65 days, and they may have an incredibly short life span of only one year. ''Marmosa'' species build nests for shelter, or use abandoned bird nests, holes in trees, or banana stalks. These nest sites are unlikely to be permanent; rather, the opossum will use whatever site is available as the sun begins to rise.

Conservation

There are no current threats to this species, except for the reduction of its habitat from deforestation or resource obtainment.

References

{{Taxonbar, from=Q194331 Opossums Marsupials of Central America Vertebrates of Belize Marsupials of Colombia Marsupials of Ecuador Fauna of Grenada Vertebrates of Honduras Vertebrates of Panama Marsupials of Peru Mammals of Trinidad and Tobago Marsupials of Venezuela Mammals of the Caribbean Mammals described in 1898 Taxonomy articles created by Polbot Taxa named by Outram Bangs