There are two distinct ranges known for thick-tailed opossums, Lutreolina crassicaudata. One range is east of the Andes, between Bolivia and southern Brazil at the northern end, and central Argentina at the southern end. A second range, far to the north and including Guyana, eastern Venezuela, and eastern Columbia, has yielded fewer specimens.

Biogeographic Regions: neotropical (Native )

The basic body plan of L. crassicaudata is weasel-like. This species has short, rounded ears and a thick tail that is naked at the tip. The tail is prehensile, though not as much as in other didelphid species, and is 210 to 330 mm long. Adults have a head and body length of 200 to 400 mm. As adults, males tend to be larger than females, weighing between 455 and 1100 g, whereas females have been recorded as 176 to 800 g. Though there is no question that females do have a pouch, the amount of development of the pouch is unclear.

Coat color varies within the species. This appears to be a geographic variation, and may be due to differences in diet or climate. The upper part of the coat is generally pale yellow, buff, or dark brown, whereas the under part varies from a reddish-ochraceous to pale or dark brown.

Range mass: 176 to 1100 g.

Average mass: 432.6 g.

Range length: 466 to 781 mm.

Average length: 574.1 mm.

Sexual Dimorphism: male larger

Average basal metabolic rate: 2.265 W.

• Terrestrial
• Freshwater

L. crassicaudata occupies grassland, savanna grassland, and gallery woodland, and is often found near areas of permanent water. It is found in areas subject to periodic flooding, and is reportedly the most adapted didelphid to life on the pampas. It has been trapped at elevations up to 1700 m.

Range elevation: 1700 (high) m.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: savanna or grassland ; forest

Wetlands: marsh

Other Habitat Features: riparian

The species is omnivorous. Individuals are reported to feed on small mammals, birds, reptiles, fish, and insects. In a study of fecal samples to determine diet, crabs, beetles, vertebrates, and fruit were all found. Specimens included animals from the classes Aves and Diplopoda, and the orders Decapoda, Coleoptera, Hymenoptera, Lepidoptera, Orthoptera, and Opiliones. Plants were from the families Arecaceae, Cecropiaceae, Moraceae, Piperaceae, and Solanaceae. One successful captive diet included butterfish, meat, frogs, earthworms, shrimp, and mice.

Animal Foods: birds; mammals; amphibians; reptiles; fish; insects; terrestrial non-insect arthropods; terrestrial worms; aquatic crustaceans

Plant Foods: fruit

Primary Diet: omnivore

Though it has not been documented directly, L. crassicaudata exhibits the ecological requirements to be a seed disperser, especially for pioneer or secondary plants. To the extent that any predators rely on this species for food, these animals are likely to have some affect of predator populations.

Ecosystem Impact: disperses seeds

Predators and anti-predation behaviors for the species are not reported. However, we may assume that they fall prey to a number of small and large carnivores which inhabit the same habitats.

There is no information on the modes of communication in L. crassicaudata. However, it is likely that they are similar to other members of their family, which are known to communicate with a number of vocalizations and visual signals. In addition, opposums generally have tactile communication, between mothers and their young, between mates, and also between rivals. In many species of opposums, physical aggression is common, especially between males. It is likley that L. crassicaudata is similar.

Communication Channels: visual ; tactile ; acoustic

Perception Channels: visual ; acoustic

There is no information on longetivity in the wild. One captive specimen was reported to have survived for three years.

Range lifespan

Status: captivity: 3 (high) years.

Average lifespan

Status: captivity: 3.0 years.

There is no information on the mating system of L. crassicaudata. However, the sexual dimorphism in size that is found in adults is indicative of intermale competition for mates, and therefore suggests some level of polygyny.

L. crassicaudata is reported to breed twice annually, once in the spring and again after the first litter has become independent. Gestation is short, as is common for marsupials, and is believed to be two weeks. Litter sizes of seven and eleven have been reported, though little other information is available. Although reports indicate that the female has a well developed pouch, the young are reportedly raised in a nest of dry grass.

Breeding interval: Thick-tailed opossums breed twice annually.

Breeding season: The breeding season is in the spring and summer.

Range number of offspring: 7 to 11.

Average gestation period: 2 weeks.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average gestation period: 14 days.

Average number of offspring: 8.

There is no information available on the parental investment of L. crassicaudata. However, we can assume that like other didelphids, these animals produce altricial young. The mother, as in all mammals, is likely to be the principle care-giver to the offspring, and feeds them with milk. The amount of time the young spend in the pouch has not been documented, and the only information directly available about the juvenile lives of these animals is that they are reared in a nest. There is no information indicating that males play a significant role in parental care.

Parental Investment: no parental involvement; altricial ; female parental care ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)

There is no special conservation status for the species at this time.

CITES: no special status

IUCN Red List of Threatened Species: least concern

There are no known adverse affects of L. crassicaudata on humans.

At one time in Argentina, the animals were trapped, and their pelts were used for trimming garments. However, this practice has declined, since the color tends to fade from the hairs.

Positive Impacts: body parts are source of valuable material