Gracilinanus aceramarcaeAceramarca gracile mouse opossum

Geographic Range

Aceramarca opossums (Gracilinanus aceramarcae) are found in the Andes Mountains of north and central South America, in southeastern Peru and northwestern Bolivia. These animals have been trapped near the Aceramarca River and in the Unduavi Valley, near La Paz, Bolivia. (Creighton and Gardner, 2008; Patterson and Solari, 2008; Voss, et al., 2009)


Aceramarca opossums are found in montane rainforests in the Andes Mountains. They are also found in mossy cloud, bamboo and elfin forests, as well as sphagnum bogs and pajonales at elevations ranging from 2,530 to 3,350 meters. This species has been documented near streams in the Unduavi Valley and near the Aceramarca River. (Creighton and Gardner, 2008; Patterson and Solari, 2008; Voss, et al., 2009)

  • Range elevation
    2,530 to 3,350 m
    to ft

Physical Description

Aceramarca opossums are small, pouchless marsupials with long, reddish-brown dorsal pelage and grayish-orange ventral pelage. Their gray snout is very narrow and they have a buff colored chin. These animals are adapted for an arboreal lifestyle, as evidenced by their extremely long tail. Their total body length is about 245 mm, including a tail length of about 142 mm and hind feet that are about 16 mm long. In general, Aceramarca opossums have a tail-to-body ratio of 1.5. On average, this species weighs about 23 grams. Aceramarca opossums are occasionally mistaken for their relatives, agile (Gracilinanus agilis) and wood-sprite opossums (Gracilinanus dryas); however, Aceramarca opossums have longer fur with more prominent guard hairs and smaller molars than the other species. Other members of genus Gracilinanus are sexually dimorphic, where males are larger than females; however, it is not known whether this applies to Aceramarca opossums as well. Members of the genus Gracilinanus may grow lifelong, these species are short-lived; however, the rare individuals that survive multiple years tend to be noticeably larger. In general, the temperature and metabolic rate of didelphids tends to be lower than similarly sized placental mammals. (Creighton and Gardner, 2008; Diaz, et al., 2002; Pires, et al., 2010; Voss, et al., 2009)

  • Average mass
    23 g
    0.81 oz
  • Average length
    245 mm
    9.65 in


Didelphids engage in a polygynous mating system. There is very little information specific to Aceramarca opossums; however, the extreme competition among males for breeding females may cause a massive amount of stress. Other members of genus Gracilinanus are considered partially semelparous because many of the males die shortly after breeding. This trend is considered only partial because a few males do survive to a second or even third breeding season. (Cooper, et al., 2009; Fernandes, et al., 2010; Martins, et al., 2006a)

There is very little information specifically regarding the reproductive behavior of Aceramarca opossums. Much more research has been conducted on their close relative, Brazilian gracile opossums. It is not known whether these species share all reproductive traits, however, it is not unlikely that these species share at least some reproductive traits. Brazilian gracile opossums begin mating when they are about 1 year old. This species reproduces seasonally; females are receptive during the end of the cool dry season, from August to September. Several pregnant and lactating females have been captured in September to December. Brazilian gracile opossums’ strategy of synchronous estrous means that their young are born in October to December, during the first half of the warm wet season when insect prey are most populous. This likely optimizes the female’s ability to capture food while caring for young. Litters are composed of 6 to 14 individuals, with an average of 11 offspring. Weaning begins at about 2 to 3 months of age, when the young weigh about 8 to 10 grams. (Martins, et al., 2006b; Martins, et al., 2006a; Pires, et al., 2010)

Genus Gracilinanus is composed of pouchless marsupials. Both attached and unattached young usually stay near their mother; however, older offspring may stay behind in the nest while their mother forages. Brazilian gracile opossum, a close relative of Aceramarca opossums, wean their offspring when they are about 2 to 3 months old, during the warm wet season. (Hershkovitz, 1992; Martins, et al., 2006a; Pires, et al., 2010)

  • Parental Investment
  • female parental care
  • pre-weaning/fledging
    • protecting
      • female
  • pre-independence
    • protecting
      • female


There is currently no information regarding the lifespan of Aceramarca opossums specifically, however, other members of genus Gracilinanus typically live 1 to 2 years. Likewise, other members of this genus are considered partially semelparous; most males do not survive to a second breeding season. Among Brazilian gracile opossums, a close relative of Aceramarca opossums, males invest so much in competing for mates that they often show fur loss, poor body condition and are more likely to become infested with parasites after the beginning of the breeding season. Although females also have a short lifespan, they survive to a second year more frequently than males. In general, offspring from the preceding season replace the adults each year. (Cooper, et al., 2009; Martins, et al., 2006b; Martins, et al., 2006a; Pires, et al., 2010)


Members of genus Gracilinanus are solitary and nocturnal; they typically only come together for breeding. While member of this genus may forage in a similar location, they do not interact. These animals are mostly arboreal, but may forage on the ground. Other members of this genus are known to enter torpor when the temperature is colder than 20°C. (Cooper, et al., 2009; Hershkovitz, 1992; Pires, et al., 2010)

Home Range

There is currently no information regarding the home range size of Aceramarca opossums. However, their close relative, Brazilian gracile opossums have home range sizes of approximately 1,400 meters squared for males and 1,200 meters squared for females. (Fernandes, et al., 2010; Pires, et al., 2010)

Communication and Perception

There is very little information regarding the communication or perception of genus Gracilinanus. Members of this genus may produce a variety of sounds defensively or when they are startled, these sounds include hissing, growling and screeching. It has been suggested that arboreal marsupials are more vocal and have more adept vision than their non-arboreal counterparts; however, no conclusive studies have been conducted. (Bradshaw, et al., 1998; Delciellos and Vinicius, 2009; Hershkovitz, 1992)

Food Habits

Very little is known about the feeding habits of Aceramarca opossums. Other members of genus Gracilinanus are primarily insectivorous, consuming mostly beetles, ants and wasps. In addition, other members of the genus also eat fruits, especially during the dry season and are important seed dispersers. Although these species are arboreal, most forage on the ground. (Cooper, et al., 2009; Creighton and Gardner, 2008; Hershkovitz, 1992; Martins and Bonato, 2004; Martins, et al., 2006b; Martins, et al., 2006a; Pires, et al., 2010; de Carmargo, et al., 2011)

  • Animal Foods
  • insects
  • Plant Foods
  • fruit


There is currently no information regarding the predation of Aceramarca opossums specifically, however, general predators of genus Gracilinanus may include various owls, snakes and lizards. Similar species are predated upon by white-tailed hawks, crab-eating foxes, oncillas, maned wolves, margays and jaguarundis. Likewise, the remains of unidentified members of genus Gracilinanus have also been recorded in the scat of ocelots, coatis and striped owls. (Bianchi and Mendes, 2007; Bianchi, et al., 2011; Ferreira, et al., 2013; Granzinolli and Motta-Junior, 2006; Hershkovitz, 1992; Motta-Junior, et al., 2004; Pires, et al., 2010)

  • Known Predators
    • owls (Strigiformes)
    • snakes (Serpentes)
    • lizards (Lacertilla)

Ecosystem Roles

Aceramarca opossums are likely insectivores and seed dispersers. There is currently no specific information regarding parasitism of the species, however, other members of genus Gracilinanus are known to be hosts of a variety of nematodes, lice and botfly larvae. (Cooper, et al., 2009; Creighton and Gardner, 2008; Cruz, et al., 2009; Feijo, et al., 2008; Martins and Bonato, 2004; Martins, et al., 2006b; Martins, et al., 2006a; Pires, et al., 2010; Puttker, et al., 2008; Torres, et al., 2007; Torres, et al., 2009; de Carmargo, et al., 2011)

Economic Importance for Humans: Positive

Positive impacts of Aceramarca opossums on human populations are currently not known.

Economic Importance for Humans: Negative

Negative impacts of Aceramarca opossums on human populations are currently not known.

Conservation Status

Aceramarca opossums are currently listed as a species of least concern according to the IUCN Red List of threatened species. Although this species is rarely seen and has not been studied thoroughly, it is believed that they have a large population size. Likewise, much of their habitat is found in protected areas. (Patterson and Solari, 2008)


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



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

World Map


uses sound to communicate


Referring to an animal that lives in trees; tree-climbing.

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


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.

female parental care

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.


An animal that eats mainly insects or spiders.


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


having more than one female as a mate at one time


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

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


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.


Bianchi, R., S. Mendes. 2007. Ocelot (Leopardus pardalis) predation on primates in Caratinga Biological Station, southeast Brazil. American Journal of Primatology, 69: 1173-1178.

Bianchi, R., A. Rosa, A. Gatti, S. Mendes. 2011. Diet of margay, Leopardus wiedii, and jaguarundi, Puma yagouaroundi (Carnivora: Felidae) in an Atlantic rainforest, Brazil. Zoologia, 28:1: 127-132.

Bradshaw, S., W. Burggren, H. Heller, S. Ishii, H. Langer, G. Neuweiler, D. Randall. 1998. Hearing: The Brain and Auditory Communication in marsupials. Berlin: Springer.

Cooper, C., P. Withers, A. Cruz-Neto. 2009. Metabolic, ventilatory, and hygric physiology of the gracile mouse opossum (Gracilinanus agilis). Physiological and Biochemical Zoology, 82:2: 153-162.

Creighton, G., A. Gardner. 2008. Genus Gracilinanus. Pp. 43-50 in A Gardner, ed. Mammals of South America: Marsupials, Xenarthrans, Shrews, and Bats, Vol. 1. Chicago: University of Chicago.

Cruz, L., F. Fernandes, A. Linhares. 2009. Prevalence of larvae of the botfly Cuterebra simulans (Diptera, Oestridae) on Gracilinanus microtarsus (Didelphimorphia, Didelphidae) in southeastern cerrado from Brazil. Revista Brasileira de Entomologia, 53:2: 314-317.

Delciellos, A., M. Vinicius. 2009. Jumping ability in the arboreal locomotion of didelphidmarsupials. Mastozoologia Neotropical, 16:2: 299-307.

Diaz, M., D. Flores, R. Barquez. 2002. A new species of gracile mouse opossum, genus Gracilinanus (Didelphimorphia: Didelphidae), from Argentina. Journal of Mammalogy, 83:3: 824-833.

Feijo, I., E. Torres, A. Maldonado Jr, R. Lanfredi. 2008. A new oxyurid genus and species from Gracilinanus agilis (Marsupialia: Didelphidae) in Brazil. Journal of Parasitology, 94:4: 847-851.

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: 185-192.

Ferreira, G., E. Nakano-Oliveira, G. Genaro, A. Lacerda-Caves. 2013. Diet of the coati Nasua nasua (Carnivora: Procyonidae) in an area of woodland inserted in an urban environment in Brazil. Revista Chilena de Historia Natural, 86: 95-102.

Granzinolli, M., J. Motta-Junior. 2006. Small mammal selection by the white-tailed hawk in southeastern Brazil. The Wilson Journal of Ornithology, 118:1: 91-98.

Hershkovitz, P. 1992. The South American gracile mouse opossums, genus Gracilinanus (Gardner and Creighton, 1989) (Marmosidae: Marsupialia) a taxonomic review with notes on general morphology and relationships. Field Zoology, 70: 1-56.

Martins, E., V. Bonato. 2004. On the diet of Gracilinanus microtarsus (Marsupialia: Didelphidae) in an Atlantic rainforest fragment in southeastern Brazil. Mammalian Biology, 69:1: 58-60.

Martins, E., V. Bonato, C. da Silva, S. dos Reis. 2006. Partial semelparity in the Neotropical didelphidmarsupialGracilinanus microtarsus. Journal of Mammalogy, 87:5: 915-920.

Martins, E., V. Bonato, C. da Silva, S. dos Reis. 2006. Seasonality in reproduction, age structure and density of the gracile mouse opossums Gracilinanus microtarsus (Marsupialia: Didelphidae) in a Brazilian cerrado. Journal of Tropical Ecology, 22:4: 461-468.

Motta-Junior, J., C. Alho, S. Belentani. 2004. Food habits of the striped owl in southeast Brazil. Journal of Raptor Research, 38: 777-784.

Patterson, B., S. Solari. 2008. "Gracilinanus aceramarcae" (On-line). IUCN Red List of Threatened Species. Accessed April 25, 2013 at

Pires, M., E. Martins, M. Silva, S. dos Reis. 2010. Gracilinanus microtarsus (Didelphimorphia: Didelphidae). Mammalian Species, 42:1: 33-40.

Puttker, T., Y. Meyer-Lucht, S. Sommer. 2008. Effects of fragmentation on parasite burden (nematodes) of generalist and specialist small mammal species in secondary forest fragments of the coastal Atlantic forest, Brazil. Ecological Research, 23: 207-215.

Torres, E., A. Maldonado Jr, R. Lanfredi. 2009. Spirurids from Gracilinanus agilis (Marsupialia: Didelphidae) in Brazilian pantana wetlands with a new species of Physaloptera (Nematoda: Spiruridae). Veterinary Parasitology, 163: 87-92.

Torres, E., A. Maldonado Jr, R. Lanfredi. 2007. Pterygodermatites (Paucipectines) jagerskioldi (Nematoda: Rictulariidae) from Gracilinanus agilis and G. microtarsus (Marsupialia: Didelphidae) in Brazilian pantanal and Atlantic forest by light and scanning electron microscopy. Journal of Parasitology, 93:2: 274-279.

Voss, R., D. Fleck, S. Jansa. 2009. On the diagnostic characters, ecogeographic distribution, and phylogenetic relationships of Gracilinanus emiliae (Didelphimorphia: Didelphidae: Thylamyini). Mastozoologia Neotropical, 16:2: 433-443.

de Carmargo, N., R. Cruz, J. Ribeiro, E. Vieira. 2011. Frugivory and potential seed dispersal by the marsupialGracilinanus agilis (Didelphidae: Didelphimorphia) in areas of cerrado in central Brazil. Acta Botanica Brasilica, 25:3: 646-656.