Didelphis aurita is a Neotropical marsupial found along the Atlantic coast of Brazil to northeastern Argentina and southeastern Paraguay.

Biogeographic Regions: neotropical (Native )

Big-eared opossums closely resemble another Neotropical marsupial, common opossums. In fact D. aurita was once considered a subspecies of D. marsupialis. Didelphis aurita has prominent facial markings and a conspicuous black line down the center of its forehead. The ears are naked and black. Its fur is dirty yellow with black or gray tips. Didelphis aurita has a long, prehensile tail that is furred at the base. The fur at the base of the tail is about as long as the hind legs and is at least half black and half white with the black portion sometimes longer. Didelphis marsupialis does not have as much fur on the base of its tail and it usually has a shorter black part. This is one characteristic that can be used to distinguish between D. aurita and D. marsupialis, besides geographic location.

Male D. aurita tend to be larger than females. Adult males range from 1500g to 1880g during the reproductive season. Females in the reproductive season can weigh anywhere from 1000g to 1300g.

Range mass: 700 to 1880 g.

Range length: 310 to 390 mm.

Average basal metabolic rate: 611.34 cm^3 oxygen/hour.

Sexual Dimorphism: male larger

• Terrestrial

Didelphis aurita lives in Atlantic rainforests, secondary Atlantic forests, and Araucaria highlands. Didelphis aurita is also found in forests that have been fragmented by urban development and deforestation. There are two discrete seasons where it lives. A warm rainy season lasts from September to March and a cool dry season from April to August. The mean annual temperature is between 17 °C and 24 °C and the mean annual rainfall is from 1350 mm to 2000 mm.

Range elevation: 1000 (high) m.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: rainforest

Didelphis aurita is an opportunistic omnivore that mostly feeds on arthropods and fruit; but it also consumes other invertebrates and small vertebrates. Several kinds of invertebrates, fruits, and vertebrates have been identified through scat sampling, and even some rubbish has been found in animals that are surrounded by urban areas. Invertebrates:  Diplopoda, Opiliones, Coleoptera (Scarabaeoidea), Orthoptera, Gastropoda, Lepidoptera larvae, Hymenoptera (Formicidae), Isopoda, Crabs (Aegla) Fruit: 13 Families and 22 species identified. Most fruit is consumed during the wet season when it is most abundant. Vertebrates:  Turdus rufiventris, Liotyphlops beui, Philander frenata, fish, other small mammals.

Animal Foods: birds; mammals; reptiles; fish; insects; terrestrial worms; aquatic crustaceans

Plant Foods: fruit

Primary Diet: omnivore

Didelphis aurita and other South American marsupials are the preferred host of Ixodes loricatus, a tick species. Didelphis aurita preys upon many different kinds of insects and fruits. The latter may help seed dispersal.

Ecosystem Impact: disperses seeds

Information on specific predators of this species is not available, but some of the larger carnivores in that region that may feed on Didelphis aurita are ocelots, pumas, and jaguarundis. Another likely predator is jararaca. Bothrops jararaca is a venomous pitviper in a group commonly known as lanceheads. It is a nocturnal hunter and its close relative B. asper is known to feed on Didelphis marsupialis in Mexico and Guatemala.

In response to a predator, D. aurita may act like its relative Didelphis virginiana and "play possum" or feign death to fool a predator. Additionally, D. marsupialis is surprisingly resistant to the venomous bite of B. asper. Didelphis aurita may also have some resistance to venom of B. jararaca.

Known Predators:

• ocelots (Leopardus pardalis)
• mountain lions (Puma concolor)
• jaguarundis (Herpailurus yaguarondi)
• jararacas (Bothrops jararaca)

Didelphis aurita has a cervical scent gland. A scent-marking behavior can release the secretions of this sebaceous gland into environment where they are used for social communication.

Communication Channels: chemical

Other Communication Modes: scent marks

Perception Channels: visual ; acoustic

Little information is available on specific lifespans of Didelphis aurita, but its close relative D. marsupialis has an average life span of 2 years in the wild.

Range lifespan

Status: captivity: 7 (high) years.

Average lifespan

Status: wild: 2 years.

Average lifespan

Status: captivity: 4 years.

Didelphis aurita is considered to be promiscuous because non-territorial males’ home ranges overlap with several territorial females and other non-territorial males’ home ranges. Therefore, the females defend areas with sufficient resources and males seeking mates roam around looking for them. Licking and scratching of the cervical scent gland and vocalization help males find females.

Mating System: polygynandrous (promiscuous)

In the case of Didelphis aurita the breeding season coincides with the wet season. This is when fruit is most abundant. Like other marsupials, Didelphis aurita undergoes a brief gestation period and gives birth to tiny young that crawl into the mother’s pouch where they attach to a nipple and feed for about 100 days. At the time of weaning it is usually the end of the rainy season so there is still food available for the young. Females may synchronize their reproduction using photoperiod. Individuals born at the end of the current breading season are able to reproduce at the start of the next breading season. Using information from other South American Didelphids like Didelphis marsupialis the females can have 2 to 3 litters per breeding season with an average of 7.3 young per litter.

Breeding interval: Big-eared opossums have 2 to 3 litters each breading season.

Breeding season: July to March

Average number of offspring: 7.

Average gestation period: 14 days.

Range weaning age: 100 (high) days.

Range age at sexual or reproductive maturity (female): 170 to 336 days.

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

Average number of offspring: 6.2.

Female Didelphis aurita carry the young in their pouches until weaning which could be up to 100 days from birth. This provides protection and nutrition for the underdeveloped young.

Parental Investment: pre-weaning/fledging (Provisioning: Female, Protecting: Female)

Didelphis aurita is one of the most common marsupials in its home range. Didelphis aurita was trapped with the highest frequency in most of the studies that were conducted in coastal Brazil involving small mammals. However, deforestation rates in that area are high and only 5% of the original rainforest remains. This may pose a threat to big-eared opossums and other rainforest species in the future.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Ixodes loricatus is a tick that prefers marsupial hosts. As much as 26% of big-eared opossums may be infested with this tick, which is involved in the transmission of Lyme disease.

Negative Impacts: injures humans (carries human disease)

Possible economic benefits may be ecotourism because of its abundance in tropical rainforests.

Positive Impacts: ecotourism