Gracilinanus agilis

Geographic Range

Agile opossums ( Gracilinanus agilis ) are found in central South America. This species has been reported in eastern Peru, central Brazil, eastern Bolivia, Paraguay and northeastern Argentina. However, reports regarding their presence in Peru and Argentina are mixed.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

Agile opossums are an arboreal species that have been found in both wet and dry forests; however, they are more common in dry and seasonally dry forests south of the Amazon in Brazil, Paraguay, Bolivia and Argentina. Their habitats include humid and evergreen forests in the lowland understory, at elevations up to 1,800 meters. Agile opossums have also been found in both caatinga and cerrado biomes, which are characterized by thorny bushes and gallery forests, respectively. In addition, this species is also tolerant of habitat degradation caused by humans. These animals are often found on vines and tree branches, 1.5 to 2 meters off the ground.

• Habitat Regions
• tropical tropical

• Terrestrial Biomes
• forest forest
• rainforest rainforest
• scrub forest scrub forest

Physical Description

Agile opossums are small, pouchless marsupials with reddish brown to dusky gray dorsal pelage and white to gray ventral pelage. They have a thin, dark ring around their eyes, which does not extend to their nose. These animals are adapted for an arboreal lifestyle, as evidenced by the elongated digits on their feet. Likewise, they have a long, hairy, grizzled-brown prehensile tail, which is about 123 mm long, with a tail-to-body ratio of about 1.4. Their approximate total body length is 212 mm and their large hind feet are approximately 15 mm long. This species is small and sexually dimorphic, where males are larger than females. Agile opossums weigh between 13 to 21 grams. 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. Agile opossums tend to have a body temperature of approximately 33 °C, with a basal metabolic rate similar to other marsupials. Due largely to their range overlap, agile opossums are often mistaken for their relative, Brazilian gracile opossums . In addition to their thinner ocular ring, agile opossums can be distinguished by their smaller ears and tails.

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

• Sexual Dimorphism
• male larger

Reproduction

Agile 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, agile opossums 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.

• Mating System
• polygynous polygynous

There is very little information specifically regarding the reproductive behavior of agile opossums; however, research has shown that a female may have up to 12 young with her at a time. 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 that they share a similar range and both are solitary, nocturnal and arboreal, it is not unlikely that these species share reproductive traits as well. 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. Weaning begins at about 2 to 3 months of age when the young weigh about 8 to 10 grams.

• Key Reproductive Features
• semelparous semelparous
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Agile opossums are pouchless marsupials . Females have been found with up to 12 young at a time. 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 agile opossums, wean their offspring when they are about 2 to 3 months old, during the warm wet season.

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

Lifespan/Longevity

This species has a short lifespan; in general, their life expectancy is about 1 to 1.5 years. Agile opossums are considered partially semelparous; most males do not survive to a second breeding season. Among Brazilian gracile opossums , a close relative of agile 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.

Behavior

Agile opossums are solitary and nocturnal; they typically only come together for breeding, 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. Agile opossums are arboreal and have been trapped on tree branches and vines 1.5 to 2 meters above ground, but also forage on the ground.

• Key Behaviors
• arboreal arboreal
• nocturnal nocturnal
• motile motile
• solitary solitary

Home Range

There is currently no information regarding the home range size of agile 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.

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.

• Communication Channels
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Agile opossums are primarily insectivorous, similar species ( Brazilian gracile opossums ) primarily consume beetles , ants and wasps . Agile opossums also consume fruits, especially during the dry season. They primarily eat pioneer plants from family Melastomataceae (including Melastomataceae albicans , M. cuspidate , M. ferruginata , M. pepericarpa , M. pohliana and Ossaea congestiflora ), members of the nightshade family ( Solanaceae ) and mistletoe (family Viscaceae ). Agile opossums are important seed dispersers. Most seeds are not damaged by the digestive process, aside from O. congestiflora . Interestingly, females are more important seed dispersers than males.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• insects

• Plant Foods
• fruit

Predation

Agile opossums are predated upon by white-tailed hawks . The remains of unidentified members of genus Gracilinanus have also been recorded in the scat of ocelots , coatis and striped owls . Likewise, their close relative, Brazilian gracile opossums are predated upon by crab-eating foxes , oncillas , maned wolves , margays and jaguarundis . Additional predators may include various owls , snakes and lizards .

Ecosystem Roles

Agile opossums are insectivores and important seed dispersers. Likewise, they are parasitized by a variety of nematodes including Pterygodermatites jagerskioldi , Spirura guianensis , Physaloptera herthameyerae and members of genus Gracilioxyuris . These parasites were recovered from the esophagus, stomach and intestines of agile opossums. It is hypothesized that this species is particularly vulnerable to parasitism due to their diet.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Although they are important seed dispersers within their habitat, agile opossums have no known positive impacts on human populations.

Economic Importance for Humans: Negative

There are no known negative impacts of agile opossums on human populations.

Conservation Status

Agile opossums are currently listed as a species of least concern according to the IUCN Red List of Threatened Species. Their large range, population size and their ability to live in human-altered habitats makes the outlook for this species positive and stable.

Additional Links

Encyclopedia of Life

Contributors

Leila Siciliano Martina (author), Texas State University.

References

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