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, et al., 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)
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. (Caceres, 2003; Nogueira and Castro, 2003)
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. (Eisenberg and Redford, 1999; Gentile, et al., 2000; Gentile, et al., 1995)
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. (Gentile, et al., 1995)
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, et al., 1996)
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, et al., 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 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. (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 loricatus, 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)
Possible economic benefits may be ecotourism because of its abundance in tropical rainforests.
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. (Barros-Battesti, et al., 2000)
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, et al., 1996; Pires, et al., 2002)
Matthew Wund (editor), University of Michigan-Ann Arbor.
Patrick Cusick (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
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.
uses smells or other chemicals to communicate
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
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.
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
an animal that mainly eats all kinds of things, including plants and animals
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
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.
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
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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