At about the size of a house cat, the Virginia opossum is both stout and sluggish. It is characterized by its marsupium (pouch), dental formula (50 teeth is more than any other mammal in Kansas), white face with an elongate muzzle, long, scaley, prehensile tail, mostly naked ears and feet that, in cold weather, are pink, coarse, grizzled body hair, and hind feet with opposabable thumbs that have flat nails rather than claws.
The Virginia opossum is the only mammal in the United States with a marsupium. That feature, and the dental formula and hind feet, make it impossible to confuse the opossum with any other species in Kansas.
One reason the Virginia opossum has been so successful is its ability to survive in a variety of habitats although it is most abundant in areas characterized by the presence of deciduous trees. together with skunks, rabbits, and raccoons, it is one of the mammals that is killed most often by vehicles. It's sluggish, plantigrade movement is evolutionarily primitive. Likewide, movement in trees is slow and clumsy, even with the assistance of a prehensile tail Opossums swim strongly but slowly. In habitats with deciduous trees, opossums often live in hollowed out trunks. On the prairie, opossums dig dens or assume occupancy of dens abandoned by other animals. Their vocal repertoire consists of a hiss, a growl, and a screech in agonistic encounters and a metallic click emitted in a variety of situations. When threatened, they combine the hiss, and growl with baring of teeth and, sometimes, the extrusion of a rgreenish secretion from two anal glands. If the threat is strong, they "play dead" quite effectively. Opossums are active throughout the year. They are almost strictly nocturnal, spending much of the time between dusk and dawn out of their dens. When temperatures are especially cold during winter, they remain in their dens for days at a time. Social behavior in the species is primitive at best.
The sight of reflected light from the eyes of a night-roaming opossum is the usual encounter with this mammal. There are many times, however, when opossums can be seen during the day as they move through forests, especially on dark, overcast winter days. When suddenly approached or struck by a sharp blow, opossums will frequently appear to go into shock and with eyes closed will remain motionless for a time, "playing possum"; they will eventually revive and continue on their way. In severely cold weather opossums are inactive, and remain in their dens. Den sites are in cavities of standing trees, in hollow logs on the ground, or in depressions under fallen trees where dried grasses and leaves from the nest. Cavities in cliffs and rocky outcrops, when available, also provide protection.
Adults may attain the following dimensions: total length 643-860 mm; length of tail 253-378 mm; length of hind foot 53-75 mm; length of ear 45-52; weight 5-8 lb but may be 13 lb or more. Virginia opossums are short-lived. Females, for example, are 6 to 12 months old when reproduction begins and usually have only one successful reproductive season. The oldest known Virginia opossum, a male from Maryland, was 36 months old when last captured.
Another reason the Virginia opossum has been so successful is its unspecialized diet. Although the bulk of the items eaten are insects, carrion, and small animals of various kinds, it also consumes fruits, grains, and other vegetation.
Opossums are eaten by a variety of carnivores, but coyotes, dogs, and large owls are the most effective natural predators on opossums. However, the greatest source of mortality almost certainly is the automobile.
To compensate for their short longevity and rapid population turnover, opossum are prolific breeders. Breeding typically begins during the first two weeks of January and may extend into September. Gestation lasts 12 or 13 days. Neonates are little more than advanced embrhyos that pull themselves from the vulva to the pouch, where they attach firmly to a teat. There are 13 nipples, and any young in excess of that number starve. The young remain attached to nipples for 55 to 60 days, and weaning occurs at 95-105 days. Females normally produce two litters per year.