Opossums are common in the eastern US but are rare in the west. Strangely enough, the so-called Virginia opossum (Didelphis virginiana) occurs in Tucson and other parts of Arizona. This is the only species of marsupials that occurs in the US. (Marsupials nurse their young in pouches. The kangaroo is probably the best known marsupial.)
An amusing decription written in early Spanish colonial times quoted in an article in Scientific American, describes an opossum as “a monstrous beast with a snout like a fox, a tail like a marmoset, ears like a bat, hands like a man, and feet like an ape, bearing her whelps about with her in an outward belly much like a large bag or purse.” (Source)
According to Wikipedia:
Virginia opossums can vary considerably in size, with larger specimens found to the north of the opossum’s range and smaller specimens in the tropics. They measure 13–37 in long from their snout to the base of the tail, with the tail adding another 8.5–19 in. Weight for males ranges from 1.7 to 14 lb and for females from 11 ounces to 8.2 lb. They are one of the world’s most variably sized mammals, since a large male from northern North America weighs about 20 times as much as a small female from the tropics. Their coats are a dull grayish brown, other than on their faces, which are white. Opossums have long, hairless, prehensile tails, which can be used to grab branches and carry small objects. They also have hairless ears and a long, flat nose. Opossums have 50 teeth, more than any other North American land mammal, and opposable, clawless thumbs on their rear limbs.
Opossums have 13 nipples, arranged in a circle of 12 with one in the middle. Perhaps surprisingly for such a widespread and successful species, the Virginia opossum has one of the lowest encephalization quotients of any marsupial. Its brain is one-fifth the size of a raccoon’s.
Opossums are mainly nocturnal and omnivorous. A large part of their diet is insects and other invertebrates, but they also eat the eggs of chickens and wild birds, fruits and berries, pet food left out in the yard, and garbage.
According to an article in the Journal of Mammology (November, 1952), an adult female opossum was captured (December, 1949) at the Rincon Stock Farm on Fort Lowell Road in Tucson. The following May, an adult male was found about four miles from the Farm. The author of this paper speculates that these animals were introduced from elsewhere, although he does mention that wild opossums lived in eastern New Mexico at the time.
A more recent article (2011) in the Western North American Naturalist journal reports opossums in Yavapai County, Arizona. The paper’s abstract reads:
The Virginia opossum (Didelphis virginiana) is the only marsupial native to the United States. In recent times, D. virginiana has expanded its range through natural movements and anthropogenic introductions. Didelphis virginiana has been present in southern Arizona owing to range expansion by the Mexican subspecies (D. v. californica) and anthropogenic introductions of the eastern subspecies (D. v. virginiana). Here, we document the recent collection of an opossum in central
Arizona. We also discuss how it possibly moved there and report on its stomach contents at the time of collection.
There are also reports of opossums in the Phoenix area.
Opossums react to a threat by feigning death, hence the saying “playing possum.” Opossums, like most marsupials, have unusually short lifespans for their size and metabolic rate. The Virginia opossum has a lifespan in the wild of only about two years.
There is some North American mythology about opossums. “In North America, Opossum sometimes appears in legends as a buffoon or braggart, whose habit of playing dead stems from embarrassment over having made a fool of himself. In Central America and parts of southern Mexico, Opossum occasionally plays the role of a trickster or an animal hero who escapes from danger by using his wits. Opossums are also symbols of fertility in some Mexican tribes, and a drink made with an opossum’s tail is still used by some Nahuatl women as folk medicine to help deliver babies. In some South American tribes, Opossum plays a more important mythological role as the Fire-Bringer.” Read more here.