Brazilian gracile opossums (Gracilinanus microtarsus) are found in southeastern Brazil in coastal rainforests from the Brazilian state of Minas Gerais, south to Santa Catarina. There have also been mixed reports of Brazilian gracile opossums found in Misiones Province, Argentina. (Brito, et al., 2008; Creighton and Gardner, 2008; Geise and Astua, 2009; Voss, et al., 2009)
Brazilian gracile opossums are found in seasonal lowland and pre-montane ecosystems. This species prefers Atlantic coastal rainforests and wet evergreen and deciduous forests in areas of moderate to high rainfall, however, they have also been found on eucalyptus plantations. Brazilian gracile opossums may also be found in cerrado habitats, which are characterized as tropical savannas. These animals are frequently referred to as ‘habitat generalists’, due to their ability to survive in fragmented habitats and human disturbed environments. This species is arboreal and is often found on tree branches and vines, although they forage on the ground. They may use tree hallows, abandoned internal tree nests and bamboo boxes for resting sites. (Brito, et al., 2008; Creighton and Gardner, 2008; Geise and Astua, 2009; Martins, et al., 2006a; Pires, et al., 2010; Puttker, et al., 2008; Voss, et al., 2009)
Brazilian gracile opossums are small, pouchless marsupials. These animals have long, uniformly reddish-brown dorsal pelage, with buff gray under fur. Among other members of their genus, Brazilian gracile opossums have notably redder fur than the others. Their faces are noticeably lighter than the rest of their body, with a dark, broad ring around their eyes, reaching their nose. These animals are adapted for an arboreal lifestyle, as shown by the elongated digits on their white feet. Likewise, they have a long, unicolor prehensile tail. Their total body length is about 230 mm, including a tail length of 131 mm, their tail-to-body ratio is 1.25. Their large hind feet are approximately 15 mm long. This species is small and sexually dimorphic. Females typically weigh 20 to 30 grams, whereas males weigh between 30 to 45 grams. Likewise, males grow at a faster rate, about 1.5 times as quickly as females; in addition, their tails, feet and ears tend to be larger. Members of 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. Female Brazilian gracile opossums in breeding condition tend to have a much higher metabolic rate than those not in breeding condition. Brazilian gracile opossums’ dental formula is as follows: I 5/4, C 1/1, P 3/3, M 4/4 with a total of 50 teeth. Due largely to their range overlap, Brazilian gracile opossums are often mistaken for their relative, agile opossums. In addition to their red dorsal pelage, Brazilian gracile opossums can be distinguished by their larger ears and the broadness of their ocular rings. (Cooper, et al., 2009; Creighton and Gardner, 2008; Diaz, et al., 2002; Fernandes, et al., 2010; Geise and Astua, 2009; Martins and Bonato, 2004; Martins, et al., 2006b; Pires, et al., 2010; Voss, et al., 2009)
Brazilian gracile opossums engage in a polygynous mating system, similar to other didelphids. The extreme competition among males for breeding females causes a massive amount of stress for this species. As a result, Brazilian gracile opossums are considered partially semelparous because many of the males die shortly after breeding. This trend is considered only partial because each year a few males survive to a second or even third breeding season. (Fernandes, et al., 2010; Martins, et al., 2006b)
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)
Brazilian gracile opossums are pouchless marsupials. Females typically have 6 to 14 young per litter, but are often found with 8 to 14 young attached. Both attached and unattached young usually stay near their mother; however, older offspring may stay behind in the nest while their mother forages. Females wean their offspring when they are about 2 to 3 months old, during the warm wet season. (Hershkovitz, 1992; Martins, et al., 2006a; Martins, et al., 2006b; Pires, et al., 2010)
This species has a short lifespan; in general, their life expectancy is about 1 to 2 years. Brazilian gracile opossums are considered partially semelparous; most males do not survive to a second breeding season. 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 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. (Martins, et al., 2006a; Martins, et al., 2006b; Pires, et al., 2010)
Brazilian gracile opossums are solitary and nocturnal; they typically only come together for breeding. However, there may be anywhere from 8 to 29 conspecifics within a given area, these animals may forage in a similar location, but do not interact. This species enters torpor when the ambient temperature is colder than 20°C; although, evidence suggests that they may enter a daily torpor, lasting up to 8 hours. Brazilian gracile opossums are arboreal and have been trapped on tree branches and vines, but also forage on the ground. This species nests in tree hallows, abandoned woodpecker nests and human-made bamboo boxes. These nests are filled with dry leaves and have an internal area for the animals to rest; however, it is unknown whether all animals use these nests or just reproductive females. (Creighton and Gardner, 2008; Martins and Bonato, 2004; Martins, et al., 2006a; Martins, et al., 2006b; Pires, et al., 2010)
Their home range is based on their body size; larger individuals have a larger range. Male home ranges average about 1,400 meters squared and female home ranges average 1,200 meters squared. The difference in home range size between the sexes can possibly be attributed to the larger male body size or to the competition between males for breeding females. (Fernandes, et al., 2010; Pires, et al., 2010)
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)
Brazilian gracile opossums are primarily insectivores; approximately 84% of their diet is composed of insects, of which 35% are beetles (including curculionid, meloid, scarabaeid, alleculid, tenebrionid, chrysomelid, and elaterid beetles). In addition to beetles, stomach content analyses indicate that they also feed on a variety of other insect prey, including termites, ants and wasps, cockroaches, crickets and grasshoppers, moths, dipterans, barkflies, and mayflies. Additionally, they eat snails and fruits from Brazilian nightshade, passion flower and from genus Miconia. They are also important dispersers of seeds from family Araceae. (Araujo, et al., 2010; Creighton and Gardner, 2008; Martins and Bonato, 2004; Martins, et al., 2006a; Martins, et al., 2006b; Pires, et al., 2010; Puttker, et al., 2008)
Brazilian gracile opossums are predated upon by crab-eating foxes, white-tailed hawks, oncillas, maned wolves, margays and jaguarundis. The remains of unidentified members of genus Gracilinanus have also been recorded in the scat of ocelots, coatis and striped owls. Additional predators may include various owls, snakes and lizards. (Ferreira, et al., 2013; Granzinolli and Motta-Junior, 2006; Hershkovitz, 1992; Motta-Junior, et al., 2004; Pires, et al., 2010; de Cassia Bianchi and Mendes, 2007; de Cassia Bianchi, et al., 2011)
Brazilian gracile opossums are insectivores and important seed dispersers for family Araceae. They may become infested with nematodes (Pterygodermatites jagerskioldi) and may be parasitized by botfly larvae (Cuterebra simulans), especially during the warm wet season. Males are at a much greater risk of parasites after the breeding season begins. Comparatively, Brazilian gracile opossums have relatively few nematodes; this may be because they rarely encounter parasite infested feces due to their arboreal lifestyle. (Araujo, et al., 2010; Creighton and Gardner, 2008; Cruz, et al., 2009; Lopes Torres, et al., 2007; Martins and Bonato, 2004; Martins, et al., 2006a; Martins, et al., 2006b; Pires, et al., 2010; Puttker, et al., 2008)
Brazilian gracile opossums have no known positive impacts on human populations; however, they are important seed dispersers in their habitat. (Pires, et al., 2010)
Brazilian gracile opossums have been found residing in Eucalyptus plantations; however, they are not known to cause any damage. (Pires, et al., 2010)
Brazilian gracile opossums are currently listed as a species of least concern on the IUCN Red List of threatened species. It is likely that this species has a relatively large population size and can survive in fragmented and human-disturbed habitats. (Brito, et al., 2008; Pires, et al., 2010; Puttker, et al., 2008)
Leila Siciliano (author), Animal Diversity Web Staff.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
living in landscapes dominated by human agriculture.
Referring to an animal that lives in trees; tree-climbing.
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.
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.
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.
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.
breeding is confined to a particular season
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.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
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.
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.
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.
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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