Monodelphis domestica Brazilian Short Tailed Opposum Class: Mammalia. Order: Didelphimorphia. Family: Didelphidae. Other names: Rainforest opossum, gray short-tailed opossum.

Physical Description: Short tailed opossums look much like mice in appearance. They are covered in dense, short, gray-brown fur that is very soft. Their prehensile tail is sparsely haired except for the base which is well-furred. They have large, naked ears. Most tend to be pale gray with whitish feet and tiny curved claws; under parts are dirty white to pale gray with an orange tinge. Tail tends to be darker on the upper part. Females have no pouch although they are marsupials. Newborn opossums cling to the nipples, which are arranged in a circle on the abdomen. Later they ride on the back and flanks of the mother. Males average 3- 5 oz., females 2.8- 3.5oz.; length 4-8” long.

Diet in the Wild: Small rodents, insects, scorpions, earthworms, carrion, seeds, fruit.

Diet at the Zoo: Mealworms, carnivore diet, mixed veggies, pinkie mice, insectivore diet, apples, oranges, bananas.

Habitat & Range: Primarily terrestrial. Found in deciduous forest and in and around houses and agricultural land of South America (Brazil and adjoining countries of Bolivia, Paraguay, and Chile).

Life Span: 2-3 years in the wild, up to 6 years in captivity.

Perils in the wild: Carnivores, birds of prey, snakes.

Physical Adaptations: They have opposable toes; on their hind feet they have a big toe that is opposable like the human thumb. Pads on their feet and toes enable them to climb up smooth surfaces, as well as tiny claws They have 50 teeth, which they may show when frightened. Cryptically colored and secretive, thereby avoiding some predation. Their fur is short thick, and very soft. Do not have good eyesight, but have excellent senses of smell and hearing. Gray short-tailed opossums vocalize when threatened or approached by a possible mate. A series of chirps or barks is used to advertise threat level. Olfaction plays an important role in the lives of gray short-tailed opossums; scent marking is used for territorial purposes and for assessment of reproductive condition of females.

Behavioral Adaptations: Nocturnal. The only socialization is during mating, other than that, they are completely solitary animals. 09/04/2012

Short tailed opossums are not very well adapted for arboreal life, however they are great climbers. When two animals meet there is no interaction unless they venture too close to one another. This usually precipitates threat displays which consist of open mouth and hissing. The animals then go their separate ways. If aggression does ensue (more likely among the males), hissing becomes a growl and then a screech.

Reproduction and Development: Nests are built in hollow logs and in fallen tree trunks that bridge streams or among rocks. The female builds a compact, complicated nest, carrying nesting material with her tail. They produce up to 4-5 litters annually. Litters of five to twelve young are born after a gestation of 14-15 days. Unlike most marsupials, the female does not have a pouch, meaning their young actually gestate outside of the mother's body. The mother will spend the majority of her time in the nest; young still attach to a teat the way other marsupials do, they are simply not contained in a pouch. A female has a circle of teats on her abdomen. Babies attach themselves to the teats, teats swell in the babies' mouths to keep them attached, then release and walk around on their own. At around 4 weeks of age, the young will begin to wander, only around the nest at first. When the mother leaves the nest, the babies will cling onto the mother's back and ride around with her. The babies will be weaned at about 8 weeks of age. Short Tailed opossums are sexually mature at about 4 to 5 months of age. Mating behavior is strongly tied to olfaction. Males habitually mark their surroundings with a chemical mark produced by a sternal gland. This scent serves as an advertisement to females and a warning to males. When a male and a receptive female meet, a precopulatory dance of sniffing, chasing, biting, and licking ensues (one of the two animals is often wounded in the precopulatory aggressive dance). At the completion of this dance, the male immobilizes the female's hind legs and begins copulation, which lasts from 4 to 7 minutes. The majority of mating takes place with the animals laying on their right sides.

Additional Information: The species M. domestica received its Latin name because of its habit of living in human dwellings where it consumes rodents and insects. It is considered a welcomed guest by the locals. Like humans, short tailed opossums are one of the only mammals that develop skin cancer from sunlight alone - other animals need combinations of sunlight, genes, and chemical carcinogens. Modern opossums have retained many primitive metatherian characteristics, and have not evolved much since the original didelphids. It has been calculated that the rate of karyotypic evolution (number of changes per million years) in metatherians is far less than that of placental mammals. The gray short-tailed opossum was the first marsupial to have its genome sequenced.

Conservation Status: Least Concern.

Conservation Efforts: N/A

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Glossary: List of definitions of the most important recurrent technical terms used in the text.

Didelphids – members of the marsupial family Didelphidae, or American opossums. Restricted to North and South America, most are omnivorous or carnivorous and can be found in various habitats and elevation ranges.

Karyotypic evolution – change in the number, size, and morphology of chromosomes in a species over time – can be used to determine evolutionary relationships among mammals, and to determine common ancestors.

Marsupials – mammals belonging to the Metatheria infraclass characterized by premature birth and continued development outside the womb. After a short gestation period, females produce live, but tiny and underdeveloped young, which then travel from the birth canal to the anterior abdomen of the mother, where they attach to the mammary gland and develop for several weeks to several months, depending on the species. Some marsupials have a pouch that covers the teats and serves to carry the young.

Metatherian – marsupial animals within the Mammalia class are categorized into the infraclass known as Metatheria.

Nocturnal – active at night. Nocturnal animals typically sleep during the day and are active at night, and have a suite of adaptations for nocturnal survival, such as a heightened sense of hearing, smell, and sometimes even eyesight.

Olfaction - sense of smell, or the act of smelling.

Sternal gland – or parasternal lymph nodes, are placed at the anterior ends of the intercostals spaces, by the sides of the internal mammary artery.

Sources: Cincinnati Zoo & Botanical Gardens http://www.handsonexotics.com/wp-content/uploads/2012/10/HOE-23.jpg http://www.brandywinezoo.org/opossum_gray.html http://animaldiversity.ummz.umich.edu/accounts/Monodelphis_domestica/ http://www.iucnredlist.org/details/40514/0 www.elpasozoo.org/docs/Volunteer_Training_Docs/MAMMAL%2520FACTS_Grey-Short- tailed%2520Opossum.pdf

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