Marmosops fuscatusgray-bellied slender mouse opossum

Geographic Range

Dusky slender opossums (Marmosops fuscatus) are native to the Neotropical region. Their geographic distribution is restricted to habitats in the Andes mountains in northern Venezuela and parts of Colombia, as well as the island of Trinidad. (Cerqueria, 1985; "Encyclopedia of Life", 2019; Gardner, et al., 2005; Pérez-Hernandez, et al., 2015)


Dusky slender opossums primarily occupy wet montane forest habitats. They are partially arboreal, but prefer to live on or near the forest floor. They prefer areas with sufficient vegetative cover, in which they can hide from predators and search for prey. Dusky slender opossums do not migrate, but will move between areas depending on levels of precipitation and predation. Dusky slender opossums have been reported between 650 and 2,400 m above sea level. ("Dusky Slender Opossum", 2012; Pérez-Hernandez, et al., 2015)

  • Range elevation
    650 to 2400 m
    2132.55 to 7874.02 ft

Physical Description

Dusky slender opossums are small marsupials. They have brown or grey-brown dorsal fur and white ventral fur that is grey at the base. Their faces are light brown with black eye rings, and their tails are hairless and grey or brown in olor. Dusky slender opossums weight between 41 and 110 g, and are 12.0 to 15.5 cm long, from head to rump. Dusky slender opossums have prehensile tails that are as long or longer than their bodies, between 14.8 and 18.2 cm long, which they use to climb vegetation. On average, males are slightly larger than females, but no other sexual dimorphism is present. (Döring, 2022; "Encyclopedia of Life", 2019; Nihranz and L., 2013; Wilson and Mittermeier, 2015)

  • Sexual Dimorphism
  • sexes alike
  • male larger
  • Average mass
    45 g
    1.59 oz
  • Average length
    13.28 cm
    5.23 in


Dusky slender opossums are polygynandrous, meaning both males and females have multiple mates. To attract mates, male dusky slender opossums produce clicking vocalizations. Females care for young without the help of males. Females reproduce multiple times throughout their life, usually producing one litter per year. However, there are reports of females producing up to three litters in one year. ("Encyclopedia of Life", 2019)

Female dusky slender opossums gestate young in utero for an average of 12 days. They give birth to altricial young, approximately 1 to 2 cm in length and weighing approximately 0.13 g. Newborns crawl from the birth canal into a pouch on the belly of their mother. Juvenile dusky slender opossums, also called joeys, spend roughly 2 months in the pouch of their mother, where they latch onto a nipple and feed on milk. After weaning, juveniles are dependent on their mother for another 3 months. Both female and male dusky slender opossums reach sexual maturity at 5 to 8 months old. ("Encyclopedia of Life", 2019)

  • Breeding interval
    Females have a litter of young approximately once per year.
  • Breeding season
    Opossums tend to breed from September through March.
  • Range number of offspring
    1 to 13
  • Average gestation period
    12 days
  • Average weaning age
    2 months
  • Average time to independence
    5 months
  • Range age at sexual or reproductive maturity (female)
    8 to 12 months
  • Range age at sexual or reproductive maturity (male)
    8 to 12 months

There is limited information regarding parental investment in dusky slender opossums specifically. However, with other species in the genus Marmosops, females play an important role in the success of their offspring, while males exhibit no parental investment beyond the act of mating. After giving birth, females carry their young, also called joeys, in their pouch for another 2 months. Newborn opossums must crawl from the birth canal into the pouch, and often mothers will make their journey to the pouch as easy as possible without directly helping them. For example, mothers will lick the ventral hairs that lead into their pouch to mat them down so that joeys do not lose their grip.

If a female has a litter size greater than the number of teats available, then the young that do not immediately attach to the teats will die. While in the pouch, joeys will essentially only sleep and eat. Joeys are fully weaned after around 2 months, after which they vacate the pouch. However, weaned young remain with their mothers for approximately 3 more months before becoming independent. During this time, mothers protect their young and help them obtain food that more closely resembles the diet of an adult. Dusky slender opossums reach full independence at about 5 months old, after which they are also considered sexually mature.

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


Because of their relatively small size and short reproduction cycle, species in the genus Marmosops have short lifespans; they usually survive 1 to 2 years in the wild. However, they have been known to survive up to 4 years in captivity. (Döring, 2022)

  • Typical lifespan
    Status: wild
    1 to 2 years
  • Average lifespan
    Status: captivity
    4 years


Dusky slender opossums are solitary animals except during the breeding season. Males are territorial during the breeding season and can become violent towards competing males when searching for mates. Although they live in forests, dusky slender opossums do not frequently climb trees, but prefer to stay in understory foliage. Dusky slender opossums are crepuscular and nocturnal, often emerging around 7 pm with another spike in activity closer to 3 am. (Pérez-Hernandez, et al., 2015; Saldaña, et al., 2019)

Home Range

Dusky slender opossums stay in one general area, but are nomadic. They will stay in areas that have abundant food and water and leave when they feel resources are not as available. No exact home range or territory sizes are reported for dusky slender opossums. (Cerqueria, 1985; Döring, 2022; Pérez-Hernandez, et al., 2015)

Communication and Perception

Dusky slender opossums use various noises to ward off potential predators, such as hisses, growls, and screeches. They also communicate acoustically when attracting mates, using specific clicking calls. Beyond these sounds, dusky slender opossums tend to stay relatively quiet. In addition to mating calls, dusky slender opossums rely on olfactory cues to attract or locate mates, producing chemicals from specialized scent glands. Dusky slender opossums have strong night vision, but their color vision is not as developed. (Nihranz and L., 2013)

Food Habits

Dusky slender opossums are generalist omnivores and will opportunistically feed on what is available in their habitat. However, the majority of their diet consists of insects, non-insect arthropods, flowers, flower parts, fruits, and small vertebrates. (Pérez-Hernandez, et al., 2015)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • fruit
  • flowers


There is limited information regarding the natural predators of dusky slender opossums. They likely serve as prey for larger carnivores, including foxes, coyotes, and snakes. To avoid detection by predators, dusky slender opossums spend much of their time in vegetative clutter. However, if directly threatened by a predator, dusky slender opossums can also defend themselves by playing dead. When doing so, their lips draw back to bare their teeth, their saliva begins to foam around their mouths, and their anal glands secrete a foul smell. This is an automatic, involuntary response to stressful situations. Dusky slender opossums regain consciousness anywhere between a few minutes and a few hours after this response is triggered. (Döring, 2022)

Ecosystem Roles

Ecologically, opossums are important for their role in the food chain. They eat smaller animals and insects and serve as prey for other carnivorous animals like coyotes, foxes, and even large snakes. Dusky slender opossums also play a role in seed dispersal of native plants through endozoochory - they eat fruits and seeds and disperse them in their excrement. (New World Encyclopedia contributors, 2008)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

In many regions of the world, opossums (order Didelphimorphia) are bought and sold as food items. They are also used to produce "opossum oil", which is high in fatty acids and is often used as a topical treatment for arthritis. Their role in ecosystems is also important to humans. For example, they control populations of insects that are potential crop pests and disease vectors. Furthermore, they are a source of food for large carnivores. Given these ecosystem services, fluctuations in the size of their populations can have effects on higher and lower trophic levels. (New World Encyclopedia contributors, 2008)

Economic Importance for Humans: Negative

Opossums (order Didelphimorphia) can carry diseases, including tuberculosis, leptospirosis, and spotted fever, which can be transmitted to humans and domestic animals. Most of these zoonotic diseases are spread from urine and feces. However, for the most part, dusky slender opossums avoid developed areas and conflict with humans in general. (Somma, 2021)

Conservation Status

Dusky slender opossums are currently considered data deficient by the IUCN Red List. However their populations appear to be decreasing due to habitat loss and degradation by human developments. Dusky slender opossums and are not listed in the CITES appendices, U.S. Federal List, and State of Michigan List. Further research is required to determine the conservation status of dusky slender opossums throughout their range.

Other Comments

There are a few generic names for Marmosops fuscatus, the two most common being "dusky slender opossums" and "gray-bellied slender mouse opossums".


Paige Swygert (author), Colorado State University, Galen Burrell (editor), Special Projects.



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

World Map


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 coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

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

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal


uses smells or other chemicals to communicate


a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease


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 mainly eats leaves.


A substance that provides both nutrients and energy to a living thing.


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


an animal that mainly eats fruit


An animal that eats mainly plants or parts of plants.


An animal that eats mainly insects or spiders.


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.


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


generally wanders from place to place, usually within a well-defined range.


an animal that mainly eats all kinds of things, including plants and animals


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scent marks

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

seasonal breeding

breeding is confined to a particular season


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


lives alone


uses touch to communicate


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


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.


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