Metachirus nudicaudatus

Geographic Range

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.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

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.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest

Physical Description

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.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

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.

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

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 attached to their mother’s mammae for a period of time, juvenile brown four-eyed opossums likely ride on their mother’s back during nightly excursions.

• Parental Investment
• altricial altricial
• female parental care female parental care

Lifespan/Longevity

The maximum lifespan of brown four-eyed opossums is estimated at 3 to 4 years. Their longevity may be impacted by the frequency with which they are hit by cars.

Behavior

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 .

• Key Behaviors
• terricolous
• nocturnal nocturnal
• motile motile
• solitary solitary

Home Range

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.

Communication and Perception

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 young has been observed pulsating her body against her leafy nest, which gave her the appearance of a much larger animal. Due to her 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.

• Communication Channels
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

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.

• Primary Diet
• omnivore omnivore

• Animal Foods
• birds
• mammals
• amphibians
• reptiles
• eggs
• insects
• terrestrial non-insect arthropods
• mollusks

• Plant Foods
• seeds, grains, and nuts
• fruit

Predation

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.

Ecosystem Roles

Brown four-eyed opossums are known to carry a wide variety of parasites including botflies, fleas, ticks, nematodes, trematodes, cestodes and acanthocephalan worms.

Economic Importance for Humans: Positive

There are currently no known positive impacts of brown four-eyed opossums on human populations.

Economic Importance for Humans: Negative

Brown four-eyed opossums are occasionally blamed for the destruction of crops.

• Negative Impacts
• crop pest

Conservation Status

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.

Other Comments

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 .

Additional Links

Encyclopedia of Life

Contributors

Leila Siciliano Martina (author), Animal Diversity Web Staff.

References

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