Monodelphis adusta

Geographic Range

Monodelphis adusta occupies a range of South American countries spanning from northern Venezuela, Panama, and Columbia, down to Ecuador, Peru, and Bolivia, but has also been found in southwest Mato Grosso, Brazil.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

Given the rarity of this species, not a lot is known about the preferred habitats of the sepia short-tailed opossum. The habitats they have been found in are frequently forested, and the location of the traps most successful in capturing the opossums suggest they are probably terrestrial. They appear most often in montane rainforests of medium elevations (1050-2200m), but have been found across a wide range of elevations, from lowland forests of 100-500m in a semi-deciduous submontane forest in Brazil, to locations from 200m-2350m above sea level near Cusco, Peru in the subtropical highland climate of the Andes mountains, and the sky islands of northern Venezuela. They have been found to have a wide distribution with low local densities. Although little is known of the specific habitat preferences for this species, they seem to prefer primary forests over secondary. The only reports on habitat flora are from Bolivia, where two captured M. adusta were found in different areas of secondary forest, each with a different floral composition. The first had a moister understory, with the most prominent plants including Podocarpus sp. , Chusquea sp. , Miconia theaezans , Weimmania spp. , and Juglans boliviana , as well as abundant lichens, mosses, ferns and bromeliads. The second opossum was found in a drier, rockier area consisting of Ficus sp. , Podocarpus sp. , Brunellia sp. , Cecropia spp. , Inga sp. , Aniba coto , Ocotea sp. , and Nectandra sp .

They are able to withstand some amount of habitat degradation and have been found throughout fragmented habitat, from the edge to the interior.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest

Physical Description

Sepia short-tailed opossums are smaller than most short-tailed ( Monodelphis ) opossums. Their body length ranges from 93-125 mm and their body mass ranges from 17-33 g (average 26 g). Their tails are nearly naked and semi-prehensile.

A distinguishing feature of the sepia short-tailed opossum is the lack of a stripe on their dorsal surface and uniform coloration, which is often dark brown with more brown-gray fur on their ventral surfaces. Their fur is short and smooth, and their ears are small.

Their skull is flattened, especially in the frontal region, and they have small, low auditory bullae. Sexual dimorphism does occur within this species, with males being larger than females. The head-body length of males ranges from 93-125 mm, with an average of 99 mm observed in Brazil, and 110 mm observed in Peru. The average head-body length of females is 107.5 mm. Tails are shorter than the body length in this species, as is characteristic of all Monodelphis species, with tail lengths ranging from 40-63mm in both sexes, with averages of 56mm and 55mm for females and males, respectively.

Other measurements (mm) for males (average) are as follows: hindfoot 15-17(16), ears 11-14(12), condylobasal length 25.7-30.9(28.4), maxillary toothrow 11.4, molar length 5.8-6.3(6.1), width of M3 1.9-2.2(2.1), least interorbital breadth 5.4, palatal length 14.0-16.6(15.3), palatal breadth 8.8-10.0(9.4), and zygomatic breadth 13.2-16.6(15.2). Female measurements (mm) include: hindfoot 15.0, condylobasal length 27.5, maxillary toothrow 10.9, molar length 6.0, least interorbital breadth 5.5, and zygomatic breadth 14.5. The dental formula for this specific Monodelphis species has not been reported, but other species within this genus are known to have the formula 5/4 1/1 3/3 4/4.

Like all other members of Monodelphis , M. adusta lacks a marsupium.

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

• Sexual Dimorphism
• male larger

Reproduction

There is nothing known about the reproductive behavior of Monodelphis adusta . Sexual size dimorphism does exist however, which is similar to other didelphid species. Because other didelphid species have been found to be polygynous, it is possible that M. adusta is also polygynous.

Nothing is known about reproduction in M. adusta . Since they are small marsupials, it can be assumed that they will have a short gestation period, yielding highly altricial young and that they will have a relatively long lactation period, which is characteristic of this group.

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual

Nothing is known about the level of parental care given to M. adusta young, but if they do possess altricial young as most small marsupials do, young will be provided nourishment and care by their mothers. Because of their lack of a marsupium, the young must attach to the mother’s nipple until they are able to travel on the mother’s back. Nothing is known about the level of paternal care.

Lifespan/Longevity

The lifespan in the wild of sepia short-tailed opossums is not known, but in captivity they have lived 4.1 years.

Behavior

Little is known about the behavior of M. adusta . It is possible that they are solitary and asocial, which is the case for other Monodelphis species. M. adusta lives at low densities, suggesting that they do not live in large groups. They are terrestrial and less arboreal than other opossum species, but their tails are semi-prehensile, suggesting that they still may be able to climb.

• Key Behaviors
• motile motile

Home Range

Little is known about the home ranges and territories of M. adusta . It is likely that they are terrestrial, but may have some ability to climb trees. Because of their wide population distributions and low population densities, they are likely solitary.

Communication and Perception

There is nothing known about communication in Monodelphis adusta , however other Monodelphis opossums have been found to communicate via clicks or barks when threatened. Other opossum species have also been found to use auditory and visual sensations. Since M. adusta possess vibrissae, it is possible that they use tactile sensations.

• Perception Channels
• tactile tactile
• chemical chemical

Food Habits

Monodelphis adusta are thought to be omnivores, with diets consisting of invertebrates, fruits and small vertebrates. Two wild caught M. adusta from Bolivia had 90% invertebrate and 10% plant material in their intestines, however there have been no further in-depth studies on the diets of M. adusta to support these findings.

• Primary Diet
• omnivore omnivore

Predation

The specific predators of sepia short-tailed opossums are not known, but common predators of opossums include mammalian carnivores and birds of prey. It is possible that their cryptic colouration may help them avoid predation.

Ecosystem Roles

It is not known what role M. adusta plays within the ecosystem. These opossums can be hosts to the trematode Podospathalium pedatum . This parasite was recently discovered in the intestine of a male M. adusta in Peru.

• Ecosystem Impact
• parasite parasite

Economic Importance for Humans: Positive

There are no known positive effects that Monodelphis adusta has on humans.

Economic Importance for Humans: Negative

There are no negative effects known that Monodelphis adusta has on humans.

Conservation Status

The population of Monodelphis adusta is considered to be stable and there are no major threats that are known for these opossums. Furthermore, because of their wide distribution, large population, tolerance to habitat alteration and prevalence of habitats in protected areas, there are no major conservation concerns for these opossums.

Additional Links

Encyclopedia of Life

Contributors

Kathryn Kroeker (author), University of Manitoba, Jane Waterman (editor), University of Manitoba, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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Solari, S. 2007. New species of Monodelphis (Didelphimorphia: Didelphidae) from Peru, with notes on M. adusta (Thomas, 1897). Journal of Mammology , 88/2: 319-329. Accessed October 01, 2015 at http://www.jstor.org/stable/4498661 .

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