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Virginia opossum
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What is a Virginia opossum?
The Virginia opossum (Didelphis virginiana) is the only marsupial found north of Mexico. They are native to regions from southern Canada to northern Costa Rica, but have been introduced to western Canada and the Pacific coast.
These opossums are about the size of a house cat, with males growing up to 100 cm (40 inches) long. They have a long head, pointed snout, rounded naked ears, and a scaly, prehensile tail about half their total length. Virginia opossums are omnivores, eating almost anything from fruits and insects to small mammals and carrion. They are known for "playing possum" when threatened, and have a protein in their blood that neutralizes toxins.
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Why is the Virginia opossum called a marsupial?
The Virginia opossum is called a marsupial because it belongs to the infraclass Metatheria, also known as Marsupialia, a mammalian group characterized by premature birth. After a short gestation period of only 12–13 days, the Virginia opossum gives birth to as many as 25 young, who then instinctively crawl into their mother's pouch. The newborns attach themselves to their mother’s nipples (usually 13), which then swell and become firmly fastened to the mouth tissues of the young. They continue to develop in this state for weeks or months. The pouch, or marsupium, is a flap of skin covering the nipples, although it is not a universal feature among all marsupials.
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Where does the Virginia opossum live?
The Virginia opossum (Didelphis virginiana) is the only marsupial found north of Mexico. They live from southern Canada to northern Costa Rica. Some Virginia opossum populations in western Canada and along the Pacific coast down to northern Baja California, Mexico, were introduced from the eastern United States. The Virginia opossum can be found together with the common opossum (D. marsupialis) in eastern and southern Mexico and in Central America.
Virginia opossums are able climbers and can occupy different habitats as long as water is available. They typically den under stumps, in hollow trees and logs, and in buildings and rock piles. They seem to prefer holes in the ground dug by other animals, such as woodchucks.
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What does the Virginia opossum eat?
The Virginia opossum is not a picky eater. Its diet includes almost anything, such as insects, small mammals, eggs, nestlings, fruit, earthworms, birds, reptiles, amphibians, and carrion. They also commonly eat snakes, even poisonous ones, because they are immune to pit viper venom. The Virginia opossum has adapted to various habitats with available water, and they den under stumps, in hollow trees and logs, and in buildings and rock piles.
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How does a Virginia opossum carry and care for its young?
The Virginia opossum breeds from midwinter to late autumn, with one or two litters annually. After a gestation of only 12 to 13 days, as many as 25 young may be born, though the average is seven or eight.
The newborns are blind, naked, and weigh only 0.13 gram. Using their clawed forelimbs, they instinctively crawl toward their mother’s fur-lined pouch and attach to a nipple. The young remain attached to the nipple for 50 to 55 days, after which they are carried in the pouch or cling to the mother’s fur. At about 100 days old, they are fully weaned and independent.
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How does the Virginia opossum protect itself from predators?
The Virginia opossum has a few interesting adaptations that help it survive encounters with predators. If surprised, it may feign death, or "play possum," appearing lifeless to a potential predator. This unlearned, reflexive behavior includes motor inhibition and unresponsiveness to external stimuli.
Additionally, the Virginia opossum has a special protein in its blood called lethal toxin-neutralizing factor (LTNF). This protein can detoxify a wide variety of poisons, including the venom of snakes, bees, and scorpions.
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Virginia opossum, (Didelphis virginiana), the only marsupial (family Didelphidae, subfamily Didelphinae) found north of Mexico. The Virginia opossum occurs from southern Canada to northern Costa Rica. Populations in western Canada and along the Pacific coast south to northern Baja California, Mexico, originated as introductions from the eastern United States. The Virginia opossum (Didelphis virginiana) and the common opossum (D. marsupialis) can be found together in eastern and southern Mexico and in Central America.
Male Virginia opossums may grow to 100 cm (40 inches) but average about 76 cm (30 inches) in total length (including the tail); females average about 72 cm (28 inches). The size of a house cat, males average about 3 kg (6.6 pounds), females about 2 kg (4.4 pounds). The Virginia opossum is the only member of the genus that stores body fat, and older males may exceed 6 kg (13.2 pounds) in the fall of the year. Virginia opossums have a long head and pointed snout, rounded naked ears, and a scaly, nearly hairless, prehensile tail that is about half of their total length. Their fore and hind feet have five toes, all with sharp claws except for the clawless, thumblike, opposable innermost toe on the hind feet. The Virginia opossum, like all members of the family Didelphidae, has 50 teeth, and the last premolar is the only tooth that is replaced (that is, preceded by a milk tooth) in the adult.
Its ears, eyes, eye rings, and feet and the basal one-third to one-half of the naked tail are black. The toes and the tips of the ears usually are white in northern populations and black in Mexico and Central America. The face is white in northern populations and dusky brown or blackish in populations from Texas southward but always with a white cheek patch—a characteristic used to identify this species where it occurs together (sympatry) with the common opossum. The coarse coat of long guard hair overlying the shorter, dense underfur may be either pale gray (gray phase) or mainly black (black phase). Rare in the north, black-phase individuals are more common in the southern United States and farther south. The albinotic colour phase is a rare and unusual colour pattern, often misinterpreted as albino (true albinos have white fur and pink eyes and skin), in which the fur is white but the colour of the eyes, eye rings, feet, and basal portion of the tail is dark brown or black.
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Virginia opossums eat almost anything, including fruit, insects, earthworms, eggs, nestlings, birds, reptiles, amphibians, small mammals, and carrion. They commonly prey on snakes, including poisonous species, and are immune to pit viper venom. Able climbers, opossums occupy a variety of habitats as long as water is available. They den under stumps, in hollow trees and logs, and in buildings and rock piles. They seem to prefer holes in the ground dug by other animals, such as woodchucks. If caught on the ground and not able to escape, a Virginia opossum may become catatonic. Most body functions remain normal, but the animal appears to be unconscious or dead. This behaviour has given rise to the expression “playing possum.” Fat opossums were once a popular food in the southern United States, and possum hunting was a popular sport. Although they are still trapped, their fur has a low market value.
The Virginia opossum breeds from December through August, depending on the latitude. Two litters per year are normal, but in colder northern regions the young from the second litter rarely survive the winter. Gestation is 12–13 days. As many as 25 young may be born in each litter, but the maximum number raised by the mother is determined by the number of teats (normally 13) in the pouch, and the average number of pouch young is usually 7 or 8. Born blind and naked and weighing about 0.13 gram (0.0046 ounce) apiece, these tiny, larvalike young crawl upward using their forelimbs as they seek the mother’s fur-lined pouch. Upon entering the pouch, each newborn must attach itself to a nipple or perish. Each pouch young remains firmly attached to the nipple for the first 50–55 days of life. Thereafter, until weaned and independent, the young either travel in the pouch or cling to the fur of their mother’s back. A short time after the first litter becomes independent, the female breeds again. Each of the female’s nipples, which have become enlarged and elongated by the first litter, develops a small projection (papilla) to which the newborn from the second litter attaches.
The myth that the opossum gives birth through its nose probably begins from the female’s habit of licking the pouch and surrounding fur just before the young are born. In addition, the birth canal is divided, and the male has a bifurcated penis—an anatomical curiosity that is responsible for a myth that opossums breed through the nostrils and that reinforces the false belief that females give birth through the nose. The notion that the mouth of the young fuses to its mother’s nipple is also false. Transverse plates develop on the roof of the mouth to anchor the young to the nipple. If the mouth is not carefully detached from the nipple before the young can open its mouth on its own, the skin of the nipple may be torn and bleed—hence the notion that the mouth and nipple had grown together.
The life span of Virginia opossums is short. Most reproductive females are under a year of age, and few live long enough to breed a second year. The oldest documented free-living Virginia opossum was a three-year-old male from Maryland.
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