Virginia opossums are full-bodied marsupials, with short legs and thick bodies. Their fur is typically grayish, but it may range from a reddish, brownish or even blackish hue. Within their fur, this species has long white tipped guard hairs. Their coloration may vary based on the range of the population; for instance, northern populations tend to have lighter guard hairs, thicker under fur and a more grizzled appearance, whereas southern populations generally appear darker and have thinner under fur. Albinism has been reported in this species. The fur of their face tends to be lighter than the rest of their body; typically it is pale grayish-white. They have large delicate ears, which are mostly furless, making frost bite to that region extremely common. Likewise, their long tails are also common victims of frost bite. Although there is fur at the base of their tail, it is largely hairless throughout. Virginia opossums’ tails are very long, they tend to be about 93% as long as their head to body length. This species is terrestrial, but they are also very good climbers. They have a prehensile tails that is used as an additional limb and is crucial for climbing. Their dark feet are also specialized for climbing and include an opposable toe. Although there is some disagreement regarding sexual dimorphism, adult male Virginia opossums tend to be slightly larger than adult females. Males often weigh between 2.1 to 2.8 kg, whereas females generally range between 1.9 to 2.1 kg. These may be under-estimates, as some sources claim Virginia opossums’ body weight ranges from 3 to 6 kg. Weights can vary based on the animal’s habitat; populations in urban areas tend to weigh 34% more than those from rural areas. Body and tail length estimates also vary; males have an average body length of 40.8 cm, with a tail length of 29.4 cm, whereas female body lengths average 40.6 cm, with a tail length of 28.1 cm. However, other published estimates suggest body length may range from 33 to 55 cm, with a tail length of 25 to 54 cm. Virginia opossums have the following dental formula: 5/4, 1/1, 3/3, 4/4. (Burnie, et al., 2001; Christiansen, 2006; Gipson and Kamler, 2001; Hoffmeister, 2002; Hossler, et al., 1994; McManus, 1974; McRuer and Jones, 2009; Wright, et al., 2012)
Virginia opossums (Didelphis virginiana) have an expanding range throughout Central and North American. Currently, Virginia opossums can be found from Costa Rica to southern Ontario, Canada. In the United States they are found east of the Rocky Mountains and along the west coast. This species is limited by extreme cold and deep snow. This species has not always been found so far north, before Europeans settled in North America the furthest north that Virginia opossums were found was Kentucky, Indiana and Ohio. In the 1970’s, it was predicted that this species would not venture beyond Vermont and New Hampshire, of course now they are found in Canada. Virginia opossums are more adapted to tropical environments, so it is not surprising that they are ill-equipped for extreme cold. During the very cold seasons, Virginia opossums modify their behavior to stay warm and may use the shelter offered by human structures, although opossums found in northern regions frequently have frost bite. (Cuaron, et al., 2012; Harmon, et al., 2005; Hossler, et al., 1994; Kanda, 2005)
Virginia opossums are found in many habitats; however, they typically prefer areas near a water source, such as a stream or swamp. These animals may live in woodlands and thickets but are very often found within human altered areas. They are successful in urban environments because they are small, nocturnal and have many young. Virginia opossums make nests in brush piles, hallow trees and drainage areas. They can be found from near sea level to 3,000 meters in elevation. (Cuaron, et al., 2012; Hoffmeister, 2002; McManus, 1974; Wright, et al., 2012)
Didelphid marsupials engage in a polygynous mating system, in which males vie for females. Male Virginia opossums have scent glands on their chest, which emits a musky odor and stains their fur; this is most commonly seen near the beginning of the breeding season. Females have a 29.5 day estrous cycle, upon entering estrous, breeding begins almost immediately. Mating behavior is one of the only social behaviors displayed by Virginia opossums, after mating; females become aggressive and solitary again. (Christiansen, 2006; Fernandes, et al., 2010; Holmes, 1992a; McManus, 1974)
Virginia opossums are ready to begin breeding within the first year of their life, around 6 months for females and 8 months for males, but typically do not begin breeding until 10 months of age. This species has a long breeding season, however, the exact months of the breeding season varies based on an individual’s location. In populations found at 44° N latitude, the breeding season lasts from February to September, whereas at 30°N latitude, the breeding season typically lasts from January to August. Likewise, the number of litters per year varies based on the climate. In northern regions, Virginia opossums average only one litter per year, in warmer climates, the number of litters may increase to 3 per year. After an extremely short gestation period of 12 to 13 days, 4 to 25 altricial “honey bee-sized” young are born, although females generally have only 13 mammae, some of which may be nonfunctional. The offspring weigh between 0.13 to 0.20 grams and are generally about 14 mm long. Although newborns are highly under-developed, the young do have muscular front legs, allowing them to climb to the mothers pouch. Many young will not survive the trip to the pouch, those who do, remain attached to the mammae for approximately 50 to 70 days, females averages about 8 pouch-young per litter. After the period spent within the pouch, young remain with their mother, either staying in the den while she forages, or riding on her back. Young begin eating solid food at about 85 days old and are fully weaned between 93 to 105 days old. After this period, young are typically independent, although some will stay in the weaning den with their mother until they are about 120 days old. About 60% of the young will not survive once they are fully independent. (Burnie, et al., 2001; Christiansen, 2006; Feldhamer, et al., 2007; Hoffmeister, 2002; Holmes, 1992b; Hossler, et al., 1994; McManus, 1974; O'Connell, 2006; Rademaker and Cerqueira, 2006)
Virginia opossums provide very little parental care; males offer no parental care, while females offer moderate care. After breeding, the female’s pouch emits a musky odor and becomes stained in a brownish-orange color due to scent glands located within; this likely helps newborn opossums find their mothers pouch. While young are residing within, females often lick both the pouch and their young. This licking behavior led to the mistaken idea that Virginia opossums breed with their noses and afterward, the young get to their mother’s pouch by crawling from her nostrils. Although a female with pouch-young may become very protective of her pouch, once her young are removed, females show little interest. Female Virginia opossums lactate for about 15 weeks. Most young Virginia opossums become solitary after weaning, however, some may remain with their mother in the weaning den until they are about 120 days old. (Holmes, 1992b; Kimble, 1997; McManus, 1974; McRuer and Jones, 2009; Porter, 1956)
Virginia opossums do not live very long; wild individuals typically only survive about 1.5 to 2 years. Early in life, young opossums have a very high mortality rate. Many of these altricial young never arrive in their mothers pouch, afterward; about 60% of those who do reach the pouch will perish once they are weaned. Many adult animals die during the cold season. Females may live slightly longer than males; however, they are no longer able to have young after 2 years of age. Captive opossums typically live longer; they generally survive to be 3 to 4 years old; however, there are reports of captive Virginia opossums surviving until they are 8 to 10 years old. (Christiansen, 2006; Gipson and Kamler, 2001; Harmon, et al., 2005; Hossler, et al., 1994; McManus, 1974; McRuer and Jones, 2009; O'Connell, 2006; Woods II and Hellgren, 2003)
Virginia opossums are solitary, nocturnal and terrestrial; however, they are also very good climbers and may den in trees. They begin their nightly activities around dusk and remain active until dawn; this may vary slightly throughout the year. These animals do not hibernate; however, they reduce their activity during the bitter cold seasons. When they are active, males travel greater distances, while females shows greater variation in their movement. Although this species is from Neotropical regions, they are able to survive into Canada by changing their behavior when it is cold and using their fat stores when food is scarce. During times of extreme heat, these animals spread saliva on their skin to help them cool down. Their ability to survive so far north is partially due to their ability to thrive in human altered environments. Virginia opossums use a variety of denning sites including buildings, hallow trees or abandoned burrows. They fill their den with dry leaves or shredded paper. Virginia opossums change denning sites often; the only time they remain in the same den for long periods is while they have young. When male Virginia opossums meet it often leads to an aggressive interaction, this may involve a ‘dance’ in which they lash their tails and reach with their front legs. However, captive individuals raised together may interact non-aggressively. Virginia opossums are famous for entering a catatonic state when they are alarmed; this is commonly known as “going opossum”. During this behavior the animal becomes motionless, this may last as little as a minute, or it may continue up to 6 hours. ‘Going opossum’ is rare and is most frequently seen in young opossums. Instead, it is more common for a threatened adult to bare their teeth and stand their ground, or flee. Virginia opossums have a reputation for being slow and clumsy; however, they turn often when pursued to avoid being captured and their quadrupedal plantigrade stance allows them to run 7.1 to 7.4 km per hour. Virginia opossums may also climb or swim to escape a perceived threat. (Allen, et al., 1985; Cuaron, et al., 2012; Hoffmeister, 2002; Hossler, et al., 1994; Kimble, 1997; Ladine and Kissell Jr, 1994; McManus, 1974; McRuer and Jones, 2009)
Virginia opossums’ home range size varies based on an individual’s range, their habitat, the available resources and their gender. In general, their home range size is thought to be about 12.5 to 38.8 hectares; females generally have a smaller home range. In Georgia home range sizes range between 7.2 to 94.4 hectares, in Texas home range sizes vary from 0.12 to 23.47 hectares and in urban environments females averaged 18.8 hectares and males averaged 37.3 hectares. Males are believed to keep larger home ranges because their reproductive success is based solely on their ability to find mates, whereas female success is based on the accessibility of food items. Their home ranges are oval shaped and often overlap with a water source. Virginia opossums were once considered nomadic but more recent research shows that an individual maintains a fairly constant home range throughout their life. (Allen, et al., 1985; Gehrt, et al., 1997; Gipson and Kamler, 2001; Harmon, et al., 2005; McManus, 1974; O'Connell, 2006; Wright, et al., 2012)
Virginia opossums use scent and sound signals to communicate with their young, mates and potential threats. Scent glands help newborns locate their mother’s pouch. Male Virginia opossums have scent glands on their chest that emit a musky odor and stain their fur, usually just before mating season begins. Males find females using scent; they can even identify specific females based on scent alone, while females are able to determine whether a scent belongs to a male or female, they cannot determine specific males. During aggressive encounters, Virginia opossums may produce an excretion from their anal glands. In addition, females maintain contact with their young through a series of clicks, lip smacking and bird-like sounds. When threatened, these animals may hiss, growl or screech. During the breeding season, mates may communicate with a series of metallic sounding clicks. Virginia opossums likely have sharp hearing. They have sensitive whiskers, which assists in their movement in the dark. Their vision is likely similar to cats, with adept night vision. While they likely have keen eyesight, their ability to recognize color is limited. Their ability to recognize specific tastes is likely also limited. (Christiansen, 2006; Holmes, 1992a; Kimble, 1997; Kolb and Wang, 1985; McManus, 1974; O'Connell, 2006)
Virginia opossums are opportunistic feeders, meaning they will eat almost anything available to them. These animals eat a variety of foods based on the season, their habitat and their range. Their diets include vertebrates, invertebrates, plant material, fruits, grains, carrion, garbage and pet food. During the colder seasons, they eat more small vertebrates, whereas in the warmer seasons they eat more invertebrates, plant material, fruits and seeds. Virginia opossums eat different quantities of these foods based on how available they are, in some locations items such as gastropods, reptiles and amphibians may be more available. (Christiansen, 2006; Hopkins and Forbes, 1980; McManus, 1974; McRuer and Jones, 2009)
Virginia opossums are hunted by a variety of species including owls, domestic dogs, coyotes, red foxes, raccoons, bobcats and large snakes, among others. They are also hunted and trapped by humans. Virginia opossums are unaffected by the venom of a variety of snakes from Family Viperidae including eastern and western diamondback rattlesnakes, copperheads, cottonmouth moccasins and Korean mamusi. Virginia opossums may have a better chance of survival in urban environments partially because there are fewer predators. (Harmon, et al., 2005; Hossler, et al., 1994; Ladine and Kissell Jr, 1994; Werner and Vick, 1977)
Virginia opossums are omnivorous. They consume a variety of vertebrates, invertebrates, plant material and carrion. Virginia opossums are important seed dispersers; they redistribute undamaged seeds from the genera Asimina and Diospyros, among others. These animals also carry many internal and external parasites. Virginia opossums are known carriers of at least 24 internal and 13 external parasites. Although they are not immune, it is unusual for this species to carry the rabies virus. (Baker, et al., 1995; Durden and Nixon, 1990; McManus, 1974; McRuer and Jones, 2009; Monet-Mendoza, et al., 2005; Rejmanek, et al., 2009; Willson, 1993)
Virginia opossums are often seen a pest species. In Portland, Oregon as much as 9% of an opossum’s diet was garbage and another 9% was pet food. This means they likely knocked over trash cans and ate food intended for cats and dogs. Virginia opossums are also farm pests because they may eat chickens. (Cuaron, et al., 2012; McRuer and Jones, 2009)
Given that Virginia opossums often live in urban and suburban areas, interaction with humans is common. These animals are hunted for sport and food. Some cultures believe that Virginia opossum meat has medical properties. For instance, eating their meat in a soup is believed to help inflammation, colitis, gastritis and skin infections. Likewise eating cooked Virginia opossum meat is believed to prevent heart attacks, using an ointment made of opossum fat is believed to treat epilepsy and infusing opossum bones in water is believe to treat allergies, dermatitis and coughing. Virginia opossums’ pelts may also be sold commercially. Although it is illegal in many states, Virginia opossums are sometimes kept as pets. In such situations, these animals may be successfully litter trained and adapt to the diurnal lifestyle of their owners. Obesity is common among captive Virginia opossums. (Alonso-Castro, et al., 2011; Cuaron, et al., 2012; Jacobo-Salcedo, et al., 2011; McManus, 1974; McRuer and Jones, 2009)
Virginia opossums are currently listed as a species of least concern according to the IUCN Red List of Threatened Species. This animal’s ability to adapt to human altered habitats has made it extremely successful and widespread. Virginia opossums do not merely tolerate human settlements; they flourish and have a greater survival rate near them. (Cuaron, et al., 2012; Harmon, et al., 2005; Wright, et al., 2012)
Leila Siciliano Martina (author), Animal Diversity Web Staff.
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