Virginia opossum [1] Temporal range: Middle Pleistocene – present (~600,000–0 YBP) [2] | |
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North American opossum in winter | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Infraclass: | Marsupialia |
Order: | Didelphimorphia |
Family: | Didelphidae |
Genus: | Didelphis |
Species: | D. virginiana |
Binomial name | |
Didelphis virginiana (Kerr, 1792) | |
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Range of habitat, showing both historic, native range and introductions in the west; these areas are currently expanding northward (e.g., into Wisconsin and Minnesota). [5] | |
Synonyms | |
Didelphis marsupialis virginiana [6] |
The Virginia opossum (Didelphis virginiana), also known as the North American opossum, is a member of the opossum family found from southern Canada to northern Costa Rica (making it the northernmost marsupial in the world). Commonly referred to simply as the possum, [7] it is a solitary nocturnal animal about the size of a domestic cat, and a successful opportunist.
Opossums are familiar to many North Americans as they frequently inhabit settled areas near food sources like trash cans, pet food, compost piles, gardens or housemice. Their slow, nocturnal nature and their attraction to roadside carrion make opossums more likely to become roadkill.
The Virginia opossum is the original animal named "opossum", a word which comes from Algonquian wapathemwa, meaning "white animal". Colloquially, the Virginia opossum is frequently just called a "possum". [8] The term is applied more generally to any of the other marsupials of the families Didelphidae and Caenolestidae. The generic name (Didelphis) is derived from Ancient Greek: di, "two", and delphus, "womb". [9]
The possums of Australia, whose name derives from their similarity to the American species, are also marsupials, but of the order Diprotodontia.
The Virginia opossum is known in Mexico as tlacuache, tacuachi, and tlacuachi, from the Nahuatl word tlacuatzin.
This section needs additional citations for verification .(September 2018) |
The Virginia opossum's ancestors evolved in South America, but spread into North America as part of the Great American Interchange, which occurred mainly after the formation of the Isthmus of Panama about 3 million years ago. Didelphis was apparently one of the later migrants, entering North America about 0.8 million years ago. [10] It is now found throughout Central America and North America from Costa Rica to southern Ontario and is expanding its range northward, northwesterly and northeasterly at a significant pace. [8]
Its pre-European settlement range was generally as far north as Maryland; southern Ohio, Indiana and Illinois; Missouri and Kansas. The clearing of dense forests in these areas and further north by settlers allowed the opossum to move northward. Elimination of the opossum's main predators in these areas also contributed to their expansion. Since 1900, it has expanded its range to include most of New England (including Maine); New York, extreme southwestern Quebec; most of southern and eastern Ontario; most of Michigan and Wisconsin; most of Minnesota, southeastern South Dakota and most of Nebraska.
Areas such as Rhode Island and Waterloo Region and Simcoe County in southern Ontario rarely had sightings of opossums in the 1960s, but now have them regularly; some speculate that this is likely due to global warming causing winters to be warmer. [11] Some people speculate the expansion into Ontario mostly occurred by opossums accidentally being transferred across the St. Lawrence, Niagara, Detroit and St. Clair rivers by motor vehicles or trains they may have climbed upon. As the opossum is not adapted to colder winters or heavy snow, its population may be significantly reduced if a colder winter with heavier snow occurs in a particular northern region.
The Virginia opossum was not originally native to the West Coast of the United States. It was intentionally introduced into the West [8] during the Great Depression, probably as a source of food, [12] and now occupies much of the Pacific coast. Its range has been expanding steadily northward into British Columbia.
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 33–55 cm (13–22 in) long from their snout to the base of the tail, with the tail adding another 25–54 cm (9.8–21.3 in). Males are slightly larger, with an average body length of 40.8 cm (16.1 in) with an average tail length of 29.4 cm (11.6 in), while females are 40.6 cm (16.0 in) long with a 28.1 cm (11.1 in) tail. Weight for males ranges from 2.1–2.8 kg (4.6–6.2 lb) and for females from 1.9–2.1 kg (4.2–4.6 lb). [13]
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, [14] and opposable, clawless thumbs on their rear limbs. Opossums have 13 nipples, arranged in a circle of 12 with one in the middle. [15] [16]
The dental formula of an opossum is 5.1.3.44.1.3.4. [17] 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. [18] Its brain is one-fifth the size of a raccoon's. [19]
This section needs additional citations for verification .(March 2018) |
Virginia opossum tracks generally show five finger-like toes in both the fore and hind prints. [20] 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). If the opossum was not walking (perhaps running), 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.
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. [21] If this does not work, the Virginia opossum is noted for feigning death in response to extreme fear. [22] This is the genesis of the term "playing possum", which means pretending to be dead or injured with intent to deceive. [23]
In this inactive state it lies limp and motionless on its side, mouth and eyes open, tongue hanging out, and feet clenched. [21] Fear can also cause the opossum to release a green fluid from its anus with a putrid odor that repels predators. [22] [24] Heart rate drops by half, and breathing rate is so slow and shallow it is hardly detectable. [21] Death feigning normally stops when the threat withdraws, and it can last for several hours. [21] [24] Besides discouraging animals that eat live prey, playing possum also convinces some large animals that the opossum is no threat to their young. [22] "Playing possum" in response to threats from oncoming traffic often results in death. [25]
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. [26]
Insects such as grasshoppers, crickets, and beetles make up the bulk of the animal foods eaten by opossums. [27] It has been stated that opossums eat up to 95% of the ticks they encounter [25] [28] and may 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. [28] This interpretation has been challenged. [29] A widely publicized 2009 study by the Cary Institute indicated that Virginia opossums in a laboratory setting could eat thousands of ticks per week grooming. [30] [31] However, subsequent studies of the stomach contents of wild Virginia opossums have not found any ticks in their diet. [32]
Small animals include young rabbits, meadow voles, mice, rats, birds, snakes, lizards, frogs, fish, crayfish, gastropods, and earthworms. [33] [34] [35] [36] [37] The Virginia opossum has been found to be very resistant to snake venom. [38] [28] Attracted to carrion on the side of the highway, opossums are at an increased risk of being hit by motor vehicles. [24]
Plant foods are mainly eaten in late summer, autumn, and early winter. [27] These include raspberries, blackberries, apples, acorns, beechnuts, seeds, grains, bulbs, and vegetables. [27] [37] Persimmons are one of the opossum's favorite foods during the autumn. [39] Opossums in urban areas scavenge from bird feeders, vegetable gardens, compost piles, garbage cans, and food dishes intended for dogs and cats. [27] [33]
Opossums in captivity are known to engage in cannibalism, though this is probably uncommon in the wild. [40] Because of this, placing an injured opossum in a confined space with its healthy counterparts is inadvisable.
The Virginia opossum is most active during the spring and summer. [27] It does not hibernate but reduces its activity during the winter. [26] [41] It may not leave its den for several days if the temperature drops below −7 to −4 °C (19 to 25 °F). [27] Both males and females are at greater risk of injury during breeding season. [42] Males extend their range in search of mates which puts them at greater risk of injury from motor vehicles and predators as they venture into unfamiliar territory. [42] 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. [42]
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. [42] A female opossum may have one to three litters per year. [42] During the mating season, the male attracts the female by making clicking sounds with his mouth. [42] The female's estrus cycle is 28 days and lasts 36 hours. [42] Gestation lasts 11–13 days and the average litter size is 8–9 infants, although over 20 infants may be born. [42] Opossums have a very high mortality rate of their young; only one in ten offspring survive to reproductive adulthood. [43]
Newborns are the size of a honeybee. [27] 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. [42] The young remain latched for two months and in the pouch for 2+1⁄2 months. [42] The young then climb onto the mother's back, where she carries them for the remainder of their time together. [42] It is during this time that the young learn survival skills. [42] They leave their mother after about four or five months. [44]
Like all female marsupials, the female's reproductive system is bifid, with two lateral vaginae, uteri, and ovaries. [45] 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. [45] Males have three pairs of Cowper's glands. [46]
Compared to other mammals, including most other marsupials except dasyuromorphians, opossums have unusually short lifespans for their size and metabolic rate. [47] [48] The Virginia opossum has a maximal lifespan in the wild of only about two years. [49] Even in captivity, opossums live only about four years. [50] 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. [51] 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. [51] [52]
An early description of the opossum comes from explorer John Smith, who wrote in Map of Virginia, with a Description of the Countrey, the Commodities, People, Government and Religion in 1608 that "An Opassom hath an head like a Swine, and a taile like a Rat, and is of the bignes of a Cat. Under her belly she hath a bagge, wherein she lodgeth, carrieth, and sucketh her young." [53] [54] The opossum was more formally described in 1698 in a published letter entitled "Carigueya, Seu Marsupiale Americanum Masculum. Or, The Anatomy of a Male Opossum: In a Letter to Dr Edward Tyson", from Mr William Cowper, Chirurgeon, and Fellow of the Royal Society, London, by Edward Tyson, M.D. Fellow of the College of Physicians and of the Royal Society. The letter suggests even earlier descriptions. [55]
Opossums are not considered dangerous to humans. [56] Though their open-mouth hiss when frightened is often mistaken as rabid behavior, opossums are naturally resistant to rabies due to their low body temperature. Opossums can however host parasites and carry diseases such as tuberculosis, leptospirosis, and tularemia, among others. [57]
Like raccoons, opossums can be found in urban environments, where they eat pet food, rotten fruit, and human garbage. They also are considered a common predator of poultry farming in North America. [58] [59] Research suggests that proximity to humans causes an increase in body size for opossums living in or near urban environments. [60] Though sometimes mistakenly considered to be rats, opossums are not closely related to rodents or any other placental mammals.
The opossum was once a favorite game animal in the United States, particularly in the southern regions which have a large body of recipes and folklore relating to it. [61] Their past wide consumption in regions where present is evidenced by recipes available online [62] and in books such as older editions of The Joy of Cooking . [63] A traditional method of preparation is baking, sometimes in a pie or pastry, [64] though at present "possum pie" most often refers to a sweet confection containing no meat of any kind.[ citation needed ]
Around the turn of the 20th century, the opossum was the subject of numerous songs, including "Carve dat Possum", a minstrel song written in 1875 by Sam Lucas. [65]
Although it is widely distributed in the United States, the Virginia opossum's appearance in folklore and popularity as a food item has tied it closely to the American Southeast. In animation, it is often used to depict uncivilized characters or "hillbillies". Not surprisingly, then, the Virginia opossum is featured in several episodes of the hit TV show The Beverly Hillbillies , such as the "Possum Day" episode in 1965. [66] The title character in Walt Kelly's long-running comic strip Pogo was an opossum. In an attempt to create another icon like the teddy bear, President William Howard Taft was tied to the character Billy Possum. [67] [68] The character did not do well, as public perception of the opossum led to its downfall. In December 2010, a cross-eyed Virginia opossum in Germany's Leipzig Zoo named Heidi became an international celebrity. [69] She appeared on a TV talk show to predict the 2011 Oscar winners, similar to the World Cup predictions made previously by Paul the Octopus, also in Germany. [70]
The Perelman Building in Philadelphia, Pennsylvania, an annex of the Philadelphia Museum of Art, was formerly the Fidelity Mutual Life Insurance Company Building. Built in the late 1920s its facade is decorated with polychrome sculptures of animals symbolizing various attributes of insurance, including a possum to represent "protection".[ citation needed ]
Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of the defining features of marsupials is their unique reproductive strategy, where the young are born in a relatively undeveloped state and then nurtured within a pouch on their mother's abdomen.
The Tasmanian devil is a carnivorous marsupial of the family Dasyuridae. It was formerly present across mainland Australia, but became extinct there around 3,500 years ago; it is now confined to the island of Tasmania. The size of a small dog, the Tasmanian devil became the largest carnivorous marsupial in the world following the extinction of the thylacine in 1936. It is related to quolls, and distantly related to the thylacine. It is characterised by its stocky and muscular build, black fur, pungent odour, extremely loud and disturbing screech, keen sense of smell, and ferocity when feeding. The Tasmanian devil's large head and neck allow it to generate among the strongest bites per unit body mass of any extant predatory land mammal. It hunts prey and scavenges on carrion.
Opossums are members of the marsupial order Didelphimorphia endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North America in the Great American Interchange following the connection of North and South America in the late Cenozoic.
The common brushtail possum is a nocturnal, semiarboreal marsupial of the family Phalangeridae, native to Australia and invasive in New Zealand, and the second-largest of the possums.
The squirrel glider is a nocturnal gliding possum. The squirrel glider is one of the wrist-winged gliders of the genus Petaurus.
Quolls are carnivorous marsupials native to Australia and New Guinea. They are primarily nocturnal and spend most of the day in a den. Of the six species of quoll, four are found in Australia and two in New Guinea. Another two species are known from fossil remains in Pliocene and Pleistocene deposits in Queensland. Genetic evidence indicates that quolls evolved around 15 million years ago in the Miocene, and that the ancestors of the six species had all diverged by around four million years ago. The six species vary in weight and size, from 300 g (11 oz) to 7 kg (15 lb). They have brown or black fur and pink noses. They are largely solitary, but come together for a few social interactions such as mating which occurs during the winter season. A female gives birth to up to 30 pups, but the number that can be raised to adulthood is limited by the number of teats (6–7). They have a life span of 1–5 years.
The eastern cottontail is a New World cottontail rabbit, a member of the family Leporidae. It is the most common rabbit species in North America.
The water opossum, also locally known as the yapok, is a marsupial of the family Didelphidae. It is the only monotypic species of its genus, Chironectes. This semiaquatic creature is found in and near freshwater streams and lakes from Mexico through Central and South America to Argentina and is the most aquatic living marsupial. It is also the only extant marsupial species in which both sexes have a pouch. The now extinct thylacine, commonly referred to as the Tasmanian tiger, also exhibited this trait.
Didelphis is a genus of New World marsupials. The six species in the genus Didelphis, commonly known as Large American opossums, are members of the opossum order, Didelphimorphia.
The gray four-eyed opossum is an opossum species found in Guyana, Suriname, French Guiana, and northern Brazil, at altitudes from sea level to 1600 m, but generally below 1,000 metres (3,300 ft). Its habitats include primary, secondary and disturbed forest. It is one of many opossum species in the order Didelphimorphia and the family Didelphidae.
The bare-tailed woolly opossum is an opossum from South America. It was first described by Swedish zoologist Carl Linnaeus in 1758. The bare-tailed woolly opossum is characterized by a gray head, brown to gray coat, orange to gray underside and a partially naked tail. It is nocturnal and solitary; there is hardly any social interaction except between mother and juveniles and in mating pairs. The opossum constructs nests in tree cavities, and its litter size ranges from one to seven. Gestation lasts 25 days, and the juveniles exit the pouch after three months; weaning occurs a month later. The bare-tailed woolly opossum inhabits subtropical forests, rainforests, secondary forests, and plantations; its range extends from northern Venezuela to northeastern and southcentral Brazil. The IUCN classifies this opossum as least concern.
The common opossum, also called the southern or black-eared opossum or gambá, and sometimes called a possum, is a marsupial species living from the northeast of Mexico to Bolivia, including Trinidad and Tobago and the Windwards in the Caribbean, where it is called manicou. It prefers the woods, but can also live in fields and cities.
The gray short-tailed opossum is a small South American member of the family Didelphidae. Unlike most other marsupials, the gray short-tailed opossum does not have a true pouch. The scientific name Monodelphis is derived from Greek and means "single womb" and the Latin word domestica which means "domestic". It was the first marsupial to have its genome sequenced. The gray short-tailed opossum is used as a research model in science, and is also frequently found in the exotic pet trade. It is also known as the Brazilian opossum, rainforest opossum and in a research setting the laboratory opossum.
The eastern pygmy possum is a diprotodont marsupial of south-eastern Australia. Occurring from southern Queensland to eastern South Australia and also Tasmania, it is found in a range of habitats, including rainforest, sclerophyll forest, woodland and heath.
The boodie, also known as the burrowing bettong or Lesueur's rat-kangaroo, is a small, furry, rat-like mammal native to Australia. Once common throughout the continent, it is now restricted to a few coastal islands. A member of the rat-kangaroo family (Potoroidae), it lives in burrows and is active at night when it forages for fungi, roots, and other plant matter. It is about the size of a rabbit and, like most marsupials, carries its young in a pouch.
The western pygmy possum, also known as the southwestern pygmy possum or the mundarda, is a small marsupial found in Australia. Genetic studies indicate its closest relative is probably the eastern pygmy possum, from which its ancestors diverged around eight million years ago.
The red-legged pademelon is a species of small macropod found on the northeastern coast of Australia and in New Guinea. In Australia it has a scattered distribution from the tip of Cape York Peninsula in Queensland to around Tamworth in New South Wales. In New Guinea it is found in south central lowlands.
Derby's woolly opossum, or the Central American woolly opossum, is an opossum found in deciduous and moist evergreen forests of Central America, from southern Mexico to western Ecuador and Colombia. It was first described by English naturalist George Robert Waterhouse, and named in honor of Edward Smith-Stanley, 13th Earl of Derby. Derby's woolly opossum is the largest in its genus, with a total length of 60 to 70 centimetres and weight between 200 and 400 grams. The coat is brown and the underside white-buff to golden-brown. The opossum is nocturnal, arboreal (tree-living) and solitary. Diet consists of fruits, nectar, small invertebrates and vertebrates. The time when breeding takes place varies geographically. The litter size ranges from one to six. The IUCN classifies this opossum as least concern.
The Woodlark cuscus is a species of marsupial in the family Phalangeridae endemic to Papua New Guinea, specifically on Madau and Woodlark Island, a part of the Milne Bay Province of Papua New Guinea. It happens to be the largest mammal living on Woodlark Island but it is also found on the neighboring island of Alcester, 70 kilometers south of Woodlark Island.
Textbooks, encyclopedias, and science publications favor opossum, but when it comes to general speech and writing, possum is and has been the far more common choice.
Opossums are frequently encountered as corpses along highways. Some biologists believe that many die as they feed on road-killed animals – a favorite food. Others believe that the opossums' small brain (5 times smaller than that of a raccoon[sic - erroneous logic]) suggests that they may just be too dumb to get out of the way of vehicles!