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Gracilinanus emiliaeEmilia's gracile mouse opossum

By Leila Siciliano Martina

Geographic Range

Emilia’s opossums (Gracilinanus emilia) are found near the Amazon River in South America and have been reported in the following locations: Columbia, Peru, Venezuela, Guyana, Suriname, French Guiana and northeastern Brazil. (Brito, et al., 2008; Creighton and Gardner, 2008; Voss, et al., 2009)

Habitat

Depending on an individual’s location within their range, Emilia’s opossums may be found within different habitat types. Populations within Venezuela, Peru and Brazil are typically found in coastal, lowland or Atlantic rainforests. Populations in Argentina and Paraguay are found in savannahs, primary or secondary gallery forests and some lowland rainforests. This species can also be found in the montane forests of the Andes Mountains. Emilia’s opossums are arboreal, but also likely forage on the ground. (Brito, et al., 2008; Creighton and Gardner, 2008; Voss, et al., 2009)

Physical Description

Emilia’s opossums are rarely seen, in fact; their species description is based on fewer than a dozen confirmed specimens. They are small, pouchless marsupials with bright, reddish-brown dorsal pelage, white ventral pelage and an extremely short and narrow rostrum. These animals are adapted for an arboreal lifestyle, as shown by their extremely long, unicolor tail. They have a total body length of 217 mm, including a tail length of about 142 mm; in general, their tail-to-body ratio is 1.64 to 1.96. This extremely long tail is what distinguishes this species from other members of their genus. Their hind feet are about 13 mm long. This species weighs 10 to 14 grams on average. Other members of genus Gracilinanus are sexually dimorphic, where males are larger than females; however, it is not known whether this applies to Emilia’s opossums. 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)

  • Range mass
    10 to 14 g
    0.35 to 0.49 oz
  • Average length
    217 mm
    8.54 in

Reproduction

Didelphids engage in a polygynous mating system. There is very little information specific to Emilia’s 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 Emilia’s 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, given their similar behavior and somewhat similar range, 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. Their 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., 2006a; Martins, et al., 2006b; 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 Emilia’s 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
    • provisioning
      • female

Lifespan/Longevity

There is currently no information regarding the lifespan of Emilia’s 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 Emilia’s 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, the offspring from the preceding season replace the adults each year. (Cooper, et al., 2009; Martins, et al., 2006a; Martins, et al., 2006b; Pires, et al., 2010)

Behavior

Members of genus Gracilinanus are solitary and nocturnal; they typically only come together for breeding, these animals may forage in a similar location, but do not interact. Emilia’s opossums are arboreal, but may forage on the ground. Other members of their genus are known to enter torpor when the temperature is colder than 20°C. (Brito, et al., 2008; Cooper, et al., 2009; Hershkovitz, 1992; Pires, et al., 2010)

Home Range

There is currently no information regarding the home range size of Emilia’s 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 Vieira, 2009; Hershkovitz, 1992)

Food Habits

Very little is known about the feeding habits of Emilia’s opossums. Other members of genus Gracilinanus are primarily insectivorous, consuming primarily 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., 2006a; Martins, et al., 2006b; Pires, et al., 2010; de Camargo, et al., 2011)

  • Animal Foods
  • insects
  • Plant Foods
  • fruit

Predation

There is currently no information regarding the predation of Emilia’s 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 de Cassia 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

Emilia’s 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; Feijo, et al., 2008; Martins and Bonato, 2004; Martins, et al., 2006a; Martins, et al., 2006b; Pires, et al., 2010; Puttker, et al., 2008; Torres, et al., 2007; Torres, et al., 2009; de Camargo, et al., 2011)

Economic Importance for Humans: Positive

There are currently no known positive impacts of Emilia’s opossums on human populations.

Economic Importance for Humans: Negative

There are currently no known negative impacts of Emilia’s opossums on human populations.

Conservation Status

Due to the sparse data on this species, the IUCN Red List of Threatened Species is not able to evaluate Emilia’s opossums, listing them as simply, ‘data deficient’. (Brito, et al., 2008)

Contributors

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

Glossary

Neotropical

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

World Map

acoustic

uses sound to communicate

arboreal

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

endothermic

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

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

insectivore

An animal that eats mainly insects or spiders.

iteroparous

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).

motile

having the capacity to move from one place to another.

mountains

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.

nocturnal

active during the night

polygynous

having more than one female as a mate at one time

rainforest

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

semelparous

offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.

sexual

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

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Bianchi de Cassia, 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 Atlantic rainforests, 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.

Brito, D., D. Astuas de Moraes, D. Lew, P. Soriano, L. Emmons. 2008. "Gracilinanus emiliae" (On-line). IUCN Red List of Threatened Species. Accessed April 25, 2013 at www.iucnredlist.com.

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, Bats, Vol. 1. Chicago: University of Chicago.

Delciellos, A., M. Vieira. 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-Chaves. 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 morphological 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 opossum 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 Asio clamator in southeast Brazil. Journal of Raptor Research, 38: 777-784.

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 Camargo, 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.

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