Didelphis aurita
big-eared opossum

Didelphis aurita is a Neotropical marsupial found along the Atlantic coast of Brazil to northeastern Argentina and southeastern Paraguay. ("InfoNatura: Birds, mammals,, and amphibians of Latin America", 2003; Emmons, 1997)

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. (Caceres and Monteiro-Filho, 2001; Caceres, 2003; Cerqueira and Lemos, 2000; Emmons, 1997; Grelle, 2003; Leite, Costa, and Stallings, 1996)

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. (Caceres, 2003; Emmons, 1997; Hume, 1999)

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. (Caceres, 2003)

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. (Hagmann, 2003)

Didelphis aurita is scansorial, nocturnal, and solitary. It is mainly terrestrial, but its relatively long forelimbs and claws allow it to easily climb trees. It has been argued that D. aurita is exclusively terrestrial and it only goes into trees to escape flooding, but other studies have shown that using proper techniques, D. aurita can be trapped or tracked in trees as frequently as on the ground. This scansorial behavior may allow for some resource partitioning and alleviate some competition between D. aurita and other opossums in the area, like the terrestrial Metachirus nudicaudatus and the arboreal Caluromys philander. (Caceres, 2003; Cerqueira and Lemos, 2000; Cuhna and Vieira, 2002; Leite, Costa, and Stallings, 1996)

Home Range

The average home range size for female D. aurita is .6ha to 1.7ha in the non-reproductive season and 0.6 ha to 1.3 ha in the reproductive season when resources are more abundant. Females may also have a hierarchy for which female gets the best territory. Males have a much larger home range of 2.3 ha to 2.7 ha. (Caceres, 2003)

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. (Nogueira and Castro, 2003)

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. (Caceres and Monteiro-Filho, 2001; Caceres, 2003; Cuhna and Vieira, 2002; Hume, 1999; Leite, Costa, and Stallings, 1996)

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 pit viper 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. (Emmons, 1997; Greene, 1997; Mattison, 1999)

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. (Greene, 1997; Hagmann, 2003)

Didelphis aurita and other South American marsupials are the preferred host of Ixodes didelphidis, a tick species. Didelphis aurita preys upon many different kinds of insects and fruits. The latter may help seed dispersal. (Barros-Battesti et al., 2000)

Ixodes didelphidis 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. (Barros-Battesti et al., 2000)

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

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. (Cuhna and Vieira, 2002; Gentile et al., 2000; Grelle, 2003; Leite, Costa, and Stallings, 1996; Pires et al., 2002)