Brown four-eyed opossums (Metachirus nudicaudatus) have a fairly large Central and South American range. These animals can be found as far north as southern Mexico, south into northeastern Brazil and Argentina, east into Guyana, French Guiana and Suriname and west into Peru and Ecuador. (Brito, et al., 2012; Gardner and Dagosto, 2008; Nowak, 2005)
Brown four-eyed opossums can be found in a wide range of elevations, from sea level to over 2,100 m. Likewise, their habitats may range from super-humid restinga forests, cerrados and riparian forests. They may be found in brushy environments or secondary forests with sparse undergrowth. Regardless, they are usually found nesting in areas with a thick layer of forest litter. In one of their restinga habitats, the average annual temperature was 26 to 28°C, with an annual average rainfall of 1,250 to 1,600 mm. (Brito, et al., 2012; Freitas, et al., 1997; Gardner and Dagosto, 2008; Helder-Jose and Freymuller, 1995; Loretto, et al., 2005; Nowak, 2005; Santori, et al., 1995)
Brown four-eyed opossums are medium-sized marsupials and the largest didelphid without a pouch. Their head and body length is 190 to 310 mm and their tails range from 195 to 390 mm. Sexual dimorphism is present in this species; in general, females are about 20 to 30 mm shorter than males. Males average 490 grams, females average 350 grams and the average overall body weight for the species is 460 grams. Their short, dense, silky dorsal pelage may vary based on their range, from reddish to yellowish-brown. Their dorsal fur often darkens as it approaches their rump and lightens on their sides. Their fur may have thin pale streaks along their dorsum. Ventrally, their pelage is yellowish or buffy brown. Brown four-eyed opossums have thin skulls with a long rostrum. Their face is dusky and blackish. They have whitish spots above each eye and a pale rostrum and pale cheeks. Brown four-eyed opossums also have a thick reddish-brown stripe encircling each eye, from their nose up to their hairless brown ears. Their dental formula is similar to other didelphids: 5/4, 1/1, 3/3, 4/4, with 50 teeth total. Their sparsely furred tail is longer than their head and body length and appears brownish, with a white tip. These animals also have whitish feet. (Gardner and Dagosto, 2008; Helder-Jose and Freymuller, 1995; Nowak, 2005; Reid, 2009; Richard-Hansen, et al., 1999; Smith, 2008)
There is currently very little information available regarding the mating systems of brown four-eyed opossums specifically. However, members of family Didelphidae are generally considered polygynous. Males from studied species compete for reproductive females. Generally, didelphids show neither courtship displays nor pair bonds. (Fernandes, et al., 2010; O'Connell, 2006)
Brown four-eyed opossums likely breed throughout the wet season, from October to April. These polyestrous animals probably have 2 litters annually. Lactating females have been captured throughout much of the year in February, April, May, June, September and October. Females with young have been found in February, April, June and October through December. Likewise, lone juveniles have been captured January through June and November. As this wide range in dates shows, there is still a great deal to be understood about the reproductive season in brown four-eyed opossums. Their litter sizes range from 1 to 9 offspring, with an average of 5 young per litter. Females do not have a pouch, but instead have a single lateral skin fold on their abdomen with 5, 7 or 9 mammae. (Bergallo, 1994; Brito, et al., 2012; Diaz and Flores, 2008; Gardner and Dagosto, 2008; Nowak, 2005; Smith, 2008)
Very little is known of the parental investment of brown four-eyed opossums. Females are believed to reproduce in the wet season and there have been reports of offspring associated with females throughout much of the dry season. After remaining exclusively within their mother’s pouch for a period of time, juvenile brown four-eyed opossums likely ride on their mother’s back during nightly excursions. (Bergallo, 1994; Diaz and Flores, 2008; Smith, 2008)
Brown four-eyed opossums are solitary and terrestrial. Both males and females of this species create spherical nests of dry leaves and twigs in the forest litter and between tree roots. These animals are nocturnal; their peak activity occurs between 8 and 11 pm; after 2 am they do not show any activity. These animals may also increase their activity rate after a rainfall. Brown four-eyed opossums are cautious and anxious, they move quickly and run silently when disturbed, they are also less likely to be successfully trapped than other didelphids. (Brito, et al., 2012; Emmons, 1990; Gardner and Dagosto, 2008; Loretto, et al., 2005; Moraes Junior, 2004; Nowak, 2005; Reid, 2009)
These animals have large home ranges and move often, they use the same nesting site for no more than two months. Their mean home range sizes average 7,400 meters squared (+/- 5,400 m2), with no significant difference between genders. A tracked female covered an average distance of 549.9 meters (+/- 49.5 m) per night. On average, there are 8.3 individuals per kilometer squared. (Bergallo, 1994; Gentile and Cerqueira, 1995; Loretto, et al., 2005; Moraes Junior, 2004; Robinson and Redford, 1986)
Brown four-eyed opossums are generally quiet animals; however, when they perceive a threat they may click or gnash their teeth and hiss. A cornered female with pouch young has been observed pulsating her body against her leafy nest, which gave her the appearance of a much larger animal. Due to her pouch young, her ability to run quickly may have been impaired. These animals also have 2 paracloacal scent glands, which are larger in males. Generally, didelphids also have good eyesight and hearing, although these specific sensory functions have not been reported for brown four-eyed opossums. (Gardner and Dagosto, 2008; Helder-Jose and Freymuller, 1995; Loretto, et al., 2005; O'Connell, 2006)
Brown four-eyed opossums are primarily insectivorous; because these animals rarely leave the forest floor their diet is mostly restricted to items from the leaf litter. Their invertebrate diet includes cockroaches, ants, beetles, termites, millipedes, grasshoppers, flies, cicadas, earwigs, crayfish, snails and spiders. Their diet also includes some fruits and seeds and small vertebrates such as mammals, reptiles and amphibians as well as eggs. (Freitas, et al., 1997; Gardner and Dagosto, 2008; Loretto, et al., 2005; Nowak, 2005; Reid, 2009; Santori, et al., 1995)
The remains of brown four-eyed opossums have been found in the stomach contents of a variety of owl species including striped owls. Harpy eagles are also known to prey on four-eyed opossums. Likewise, their habitat is also occupied by a variety of felid species including ocelots, oncillas, margays, jaguars, cougars and jaguarundis, as well as the canid species culpeo foxes, short-eared dogs and bush dogs, all of which may prey on brown four-eyed opossums. (Gardner and Dagosto, 2008; Smith, 2008; Solari, et al., 2006)
Brown four-eyed opossums are known to carry a wide variety of parasites including botflies, fleas, ticks, nematodes, trematodes, cestodes and acanthocephalan worms. (Bossi Paolinetti and de Godoy Bergallo, 1992; Diaz and Flores, 2008; Smith, 2008)
There are currently no known positive impacts of brown four-eyed opossums on human populations.
Brown four-eyed opossums are occasionally blamed for the destruction of crops. (Nowak, 2005)
Currently, brown four-eyed opossums are considered a species of least concern according to the IUCN Red List of Threatened Species. These animals are likely widespread but rarely seen, they may have a large population and they are found in a variety of protected areas. (Brito, et al., 2012; Reid, 2009)
Due to the physical variations of this species in different ranges, it has been suggested that what is known as one species may in fact be several. Currently, brown four-eyed opossums have 5 recognized subspecies including M.n columbianus, M.n. modestus, M.n myosuros, M.n nudicaudatus and M.n tschudii. (Brito, et al., 2012; Gardner and Dagosto, 2008; Miranda, et al., 2009)
Leila Siciliano (author), Animal Diversity Web Staff.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
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.
uses smells or other chemicals to communicate
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.
parental care is carried out by females
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
an animal that mainly eats all kinds of things, including plants and animals
breeding is confined to a particular season
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.
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.
Bergallo, H. 1994. Ecology of a small mammal community in an Atlantic forest area in southeastern Brazil. Studies on Neotropical Fauna and Environment, 29:4: 197-217.
Bossi Paolinetti, D., H. de Godoy Bergallo. 1992. Parasitism by cuterebrid botflies (Metacuterebra apicalis) in Oryzomys nitidus (Rodentia: Cricetidae) and Metachirus nudicaudatus (Marsupialia: Didelphidae) in a southeastern Brazilian rainforest. Journal of Parasitology, 78:1: 142-145.
Diaz, M., D. Flores. 2008. Early reproduction onset in four species of Didelphimorphia in the Peruvian Amazonia. Mammalia, 72: 126-130.
Emmons, L. 1990. Brown four-eyed opossum Metachirus nudicaudatus. Pp. 19-20 in L Emmons, ed. Neotropical Rainforest Mammals: A Field Guide, Vol. 1. Chicago: The University of Chicago Press.
Fernandes, F., L. Cruz, E. Martins, S. dos Reis. 2010. Growth and home range size of the gracile mouse opossum Gracilinanus microtarsus (Marsupialia: Didelphidae) in Brazilian cerrado. Journal of Tropical Ecology, 26:2: 185-192.
Freitas, S., D. Astua de Moraes, R. Santori, R. Cerqueira. 1997. Habitat preference and food use by Metachirus nudicaudata and Didelphis aurita (Didelphimorphia, Didelphidae) in a restinga forest at Rio de Janeiro. Revista de Biologia Tropical, 57:1: 93-98.
Gardner, A., M. Dagosto. 2008. Tribe Metachirini. Pp. 35-39 in A Gardner, ed. Mammals of South America: Marsupials, Xenarthrans, Shrews, and Bats, Vol. 1. Chicago: University of Chicago Press.
Gentile, R., R. Cerqueira. 1995. Movement patterns of five species of small mammals in a Brazilian restinga. Journal of Tropical Ecology, 11:4: 671-677.
Helder-Jose, H., E. Freymuller. 1995. A morphological and ultra structural study of the paracloacal (scent) glands of the marsupial Metachirus nudicaudatus Geoffroy, 1803. Acta Anatomic, 153: 31-38.
Miranda, C., R. Vieira Rossi, J. de Sousa e Silva Junior, M. Guimaraes Moreira Lima, M. Persio Dantas Santos. 2009. Mammalia, Didelphimorphia, Didelphidae, Metachirus nudicaudatus, municipality of Jose de Freitas, State of Piaui, northeastern Brazil: Distribution extension. Checklist, 5:2: 360-363.
Moraes Junior, E. 2004. Radio tracking of one Metachirus nudicaudatus (Desmarest, 1817) individual in Atlantic Forest of southeastern Brazil. Boletin do Museu de Biologia Mello Leitao, 17: 57-64.
Nowak, R. 2005. Genus Metachirus. Pp. 75-76 in R Nowak, ed. Walker's Marsupials of the World, Vol. 1. Baltimore: The John's Hopkins University Press.
O'Connell, M. 2006. American Opossums. Pp. 808-813 in D MacDonald, S Norris, eds. The Encyclopedia of Mammals, Vol. 1. London: The Brown Reference Group.
Reid, F. 2009. Brown four-eyed opossum Metachirus nudicaudatus. Pp. 45 in F Reid, ed. A Field Guide to the Mammals of Central America and Southeast Mexico, Vol. 2nd Ed. Oxford: Oxford University Press.
Richard-Hansen, C., J. Vie, N. Vidal, J. Keravec. 1999. Body measurements on 40 species of mammals from French Guiana. Journal of Zoology, 247: 419-428.
Robinson, J., K. Redford. 1986. Body size, diet, and population density of Neotropical forest mammals. The American Naturalist, 28:5: 665-680.
Smith, P. 2008. Brown four-eyed opossum Metachirus nudicaudatus (E. Geoffroy St Hilaire, 1803). Fauna Paraguay Handbook of the Mammals of Paraguay, 19: 1-9.
Solari, S., V. Pacheco, L. Luna, P. Velazco, B. Patterson. 2006. Mammals of the Manu Biosphere Reserve. Fieldiana Zoology, 110: 13-22.