| Virginia opossum | |||
|---|---|---|---|
| |||
| General information | |||
| Universe | Real Life | ||
| Aliases | Possum Virginia possum North American opossum/possum | ||
| Classification | Didelphis virginiana | ||
| Species type | Opossum | ||
| Homeworld | Earth | ||
| Intelligence | Non-sapient | ||
| Biochemistry | Carbon-based | ||
| Biological information | |||
| Lifespan | Wild: 2 years Captivity: 4 years | ||
| Reproduction | Sexual, viviparous | ||
| Average height | 20-27 in (50.8-68.58 cm) at shoulder | ||
| Average weight | ♂: 1.7 to 14 lb (0.8–6.4 kg) ♀: 11 ounces to 8.2 lb (0.3–3.7 kg) | ||
| Average length | Snout to tail base: 13–37 in (35–94 cm) Tail: 8.5–19 in (21.6–47 cm) | ||
| Locomotion | Quadrupedal | ||
| Feeding behavior | Omnivorous | ||
| Prey | Ticks Carrion Eggs Fish Frogs Reptiles Young rabbits Meadow voles Mice Rats Grasshoppers Crickets Beetles Birds Snakes Lizards Crayfish Other Virginia opossums Raspberries Blackberries Apples Acorns Beechnuts Vegetables | ||
| Predators | Owls Red foxes Domestic cats Domestic dogs Humans Other Virginia opossums | ||
| Lineage information | |||
| Related species | Big-eared opossum Common opossum White-eared opossum Guianan white-eared opossum Andean white-eared opossum | ||
| Cultural information | |||
| Sociocultral characteristics | |||
| Scientific taxonomy | |||
| Planet | Earth | ||
| Domain | Eukaryota | ||
| Kingdom | Animalia | ||
| Subkingdom | Eumetazoa | ||
| Infrakingdom | Bilateria | ||
| Superphylum | Deuterostomia | ||
| Phylum | Chordata | ||
| Subphylum | Vertebrata | ||
| Infraphylum | Gnathostomata | ||
| Superclass | Tetrapoda | ||
| Class | Mammalia | ||
| Subclass | Theria | ||
| Infraclass | Marsupialia | ||
| Superorder | Ameridelphia | ||
| Order | Didelphimorphia (Opossums) | ||
| Family | Didelphidae | ||
| Subfamily | Didelphinae | ||
| Tribe | Didelphini | ||
| Genus | Didelphis (Large American opossums) | ||
| Species | D. virginiana | ||
| Other information | |||
| Status | Least Concern | ||
| Creator | God (debated) | ||
The Virginia opossum (Didelphis virginiana), also called the North American opossum is the only marsupial native to North America.
Description[]
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 (35–94 cm) long from their snout to the base of the tail, with the tail adding another 8.5–19 in (21.6–47 cm). Weight for males ranges from 1.7 to 14 lb (0.8–6.4 kg) and for females from 11 ounces to 8.2 lb (0.3–3.7 kg). 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.
The dental formula of an opossum is 5.1.3.4/4.1.3.4. No other mammal in North America has more than 6 upper incisors, but the Virginia opossum has 10.
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.
Tracks[]
Virginia opossum tracks generally show five finger-like toes in both the fore and hind prints. The hind tracks are unusual and distinctive due to the opossum's opposable thumb, which generally prints at an angle of 90° or greater to the other fingers (sometimes near 180°). Individual adult tracks generally measure 1.9 in long by 2.0 in wide (4.8 × 5.1 cm) for the fore prints and 2.5 in long by 2.3 in wide (6.4 × 5.7 cm) for the hind prints. Opossums have claws on all fingers fore and hind except on the two thumbs (in the photograph, claw marks show as small holes just beyond the tip of each finger); these generally show in the tracks. In a soft medium, such as the mud in this photograph, the foot pads clearly show (these are the deep, darker areas where the fingers and toes meet the rest of the hand or foot, which have been filled with plant debris by wind due to the advanced age of the tracks).
The tracks in the photograph were made while the opossum was walking with its typical pacing gait. The four aligned toes on the hind print show the approximate direction of travel.
In a pacing gait, the limbs on one side of the body are moved simultaneously, just prior to moving both limbs on the other side of the body. This is illustrated in the pacing diagram, which explains why the left-fore and right-hind tracks are generally found together (and vice versa). However, if the opossum were not walking (but running, for example), the prints would fall in a different pattern. Other animals that generally employ a pacing gait are raccoons, bears, skunks, badgers, woodchucks, porcupines, and beavers.
When pacing, the opossum's 'stride' generally measures from 7 to 10 in, or 18 to 25 cm (in the pacing diagram the stride is 8.5 in, where one grid square is equal to 1 in2). To determine the stride of a pacing gait, measure from the tip (just beyond the fingers or toes in the direction of travel, disregarding claw marks) of one set of fore/hind tracks to the tip of the next set. By taking careful stride and track-size measurements, one can usually determine what species of animal created a set of tracks, even when individual track details are vague or obscured.
Behavior[]
"Playing possum"[]
If threatened, an opossum will either flee or take a stand. To appear threatening, an opossum will first bare its 50 teeth, snap its jaw, hiss, drool, and stand its fur on end to look bigger. If this does not work, the Virginia opossum is noted for feigning death in response to extreme fear. This is the genesis of the term "playing possum", which means pretending to be dead or injured with intent to deceive.
In this inactive state it lies limp and motionless on its side, mouth and eyes open, tongue hanging out, and feet clenched. Fear can also cause the opossum to release a green fluid from its anus with a putrid odor that repels predators. Heart rate drops by half, and breathing rate is so slow and shallow it is hardly detectable. Death feigning normally stops when the threat withdraws, and it can last for several hours. Besides discouraging animals that eat live prey, playing possum also convinces some large animals that the opossum is no threat to their young. "Playing possum" in response to threats from oncoming traffic often results in death.
Diet[]
Opossums are omnivorous (sometimes said to be insectivorous) and eat a wide range of plant-based food, as well as animal-based food like small invertebrates, carrion, eggs, fish, amphibians, reptiles, birds, small mammals, and other small animals.
Insects such as grasshoppers, crickets, and beetles make up the bulk of animal foods. Opossums eat up to 95% of the ticks they encounter. and are estimated to eat up to 5,000 ticks per season, helping to prevent the spread of tick-born illnesses, including Lyme disease and Rocky Mountain spotted fever.
Small animals include young rabbits, meadow voles, mice, rats, birds, snakes, lizards, frogs, fish, and crayfish. The Virginia opossum has been found to be very resistant to snake venom. Attracted to carrion on the side of the highway, opossums are at an increased risk of being hit by motor vehicles.
Plant foods are mainly eaten in late summer, autumn, and early winter. These include raspberries, blackberries, apples, acorns, beechnuts, and vegetables. Persimmons are one of the opossum's favorite foods during the autumn. Opossums in urban areas scavenge from bird feeders, vegetable gardens, compost piles, garbage cans, and food dishes intended for dogs and cats.
Opossums in captivity are known to engage in cannibalism, though this is probably uncommon in the wild. Because of this, placing an injured opossum in a confined space with its healthy counterparts is inadvisable.
Seasonal behaviors[]
The Virginia opossum is most active during the spring and summer. It does not hibernate but reduces its activity during the winter. It may not leave its den for several days if the temperature drops below -7 to -4 degrees C. Both males and females are at greater risk of injury during breeding season. Males extend their range in search of mates which puts them at greater risk of injury from motor vehicles and predators due to unknown territory. Females carrying young are slower moving and have to forage earlier in the evening and later into the night, also increasing their risk of injury from motor vehicles and predation.
Reproduction[]
The breeding season for the Virginia opossum can begin as early as December and continue through October with most young born between February and June. A female opossum may have one to three litters per year. During the mating season, the male attracts the female by making clicking sounds with his mouth. The female's estrus cycle is 28 days and lasts 36 hours. Gestation lasts 11–13 days and the average litter size is 8–9 infants, although over 20 infants may be born. Opossums have a very high mortality rate of their young; only one in ten offspring survive to reproductive adulthood.
Newborns are the size of a honeybee. Once delivered through the median vagina or central birth canal, newborn opossums climb up into the female opossum's pouch and latch onto one of her 13 teats. The young remain latched for two months and in the pouch for 2+1⁄2 months. The young then climb onto the mother's back, where she carries them for the remainder of their time together. It is during this time that the young learn survival skills. They leave their mother after about four or five months.
Like all female marsupials, the female's reproductive system is bifid, with two lateral vaginas, uteruses, and ovaries. The male's penis is also bifid, with two heads, and as is common in New World marsupials, the sperm pair up in the testes and only separate as they come close to the egg.
Lifespan[]
Compared to other mammals, including most other marsupials except dasyuromorphians, opossums have unusually short lifespans for their size and metabolic rate. The Virginia opossum has a maximal lifespan in the wild of only about two years. Even in captivity, opossums live only about four years. The rapid senescence of opossums is thought to reflect the fact that they have few defenses against predators; given that they would have little prospect of living very long regardless, they are not under selective pressure to develop biochemical mechanisms to enable a long lifespan. In support of this hypothesis, one population on Sapelo Island, 5 miles (8 km) off the coast of Georgia, which has been isolated for thousands of years without natural predators, was found by Dr. Steven Austad to have evolved lifespans up to 50% longer than those of mainland populations.