Virginia Opossum (Didelphis virginiana)

Virginia opossums are relatively hardy, stout, robust individuals with short legs and thick bodies.

They have large, delicate ears, which are predominately furless, making frost bite to that region extremely common.

Although there is some disagreement regarding sexual dimorphism in the Virginia opossum, adult males tend to be slightly larger than adult females. Male Virginia opossums also possess a sexually dimorphic sternal scent gland on their chest, which emits a musky odor and stains their fur.

Weight ranges from 1.9-2.8 kilograms, with females usually reaching a weight of 1.9-2.1 kilograms and males between 2.1-2.8 kilograms. These may be under-estimates, as some sources claim Virginia opossums’ body weight ranges from 3 to 6 kilograms. Weight measurement can range based on the animals chosen habitat as populations in urban areas tend to have a body mass that is approximately 34% larger than rural conspecifics.

Body and tail length estimates also vary. Males have an average body length of 40.8 centimeters with a tail length of 29.4 centimeters, whereas female body lengths average 40.6 centimeters with a tail length of 28.1 centimeters. However, other published estimates suggest body length may range from 33 to 55 centimeters, with a tail length of 25 to 54 centimeters.

The average heart rate of a normal Virginia opossum is approximately 200 beats per minute.

The Virginia opossum’s pelage is typically grayish, but it may range in color from a reddish, brownish, or even blackish hue. Within their fur, this species has long, white-tipped guard hairs. The fur of the face tends to be lighter than the rest of the body and is typically pale grayish-white. Albinism has also been reported in this species.

The Virginia opossum’s coloration may vary based on the range of the population and tends to be light gray in the north and a dark gray in the southern part of its range. Northern populations tend to have lighter guard hairs, thicker under fur, and a more grizzled appearance. The denser underfur serves a thermoregulatory function and tends to be white, but may have dark coloring on the tips. Southern populations generally appear darker and have thinner under fur. The guard hairs tend to be darker, giving the animal a darker overall appearance.

The Virginia opossum has a relatively small brain case, and the corpus callosum is absent in this species. The average length of an adult opossum’s skull is 11 centimeters.

The adult dental formula of the Virginia opossum is i 5/4, c 1/1, p 3/3, m 4/4, with 50 teeth in total.

Virginia opossum vertebral numbers remain fixed throughout growth and maturation: 7 cervical, 13 thoracic, 6 lumbar, 2 sacral, and 26 to 29 caudal.

The Virginia opossum has a long, hairless, and scale-like prehensile tail that is a common victim of frost bite. Although there is fur at the base of the tail, it is largely hairless throughout. Virginia opossum’s tails are very long and tend to be about 90-93% as long as their head to body length.

Virginia opossums have a fairly short lifespan. Females may live slightly longer than their male counterparts; however, they are no longer reproductively viable after 2 years of age. Wild individuals typically only survive about 1.5 to 2 years. Captive individuals typically have a longer lifespan and 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. Among adult animals, the vast majority of deaths occurred during the cold season.

SEXUAL DIMORPHISM

Larger Males with Chest Scent Glands

BODY LENGTH

33-55 cm. / 12-22 in.

SKULL LENGTH

11 cm. / 4 in.

TAIL LENGTH

25-54 cm. / 9-21 in.

BODY MASS

1.9-6 kg. / 4.1-6.2 lb.

DENTAL FORMULA

I ⁵⁄1, C ¹⁄1, P ³⁄3, M ⁴⁄₄, ×2 = 50

LIFESPAN

1.5-7 yr.

LOCOMOTION

Plantigrade

The Virginia opossum was first described by Kerr in 1792 with the scientific name Didelphis virginiana.

The Virginia opossum is categorized in the New World marsupial genus, Didelphis, with five other extant species of large American opossums: White-eared opossum (Didelphis albiventris), Guianan white-eared opossum (Didelphis imperfecta), Brazilian common opossum (Didelphis aurita), Andean white-eared opossum (Didelphis pernigra), and common opossum (Didelphis marsupialis). Didelphis solimoensis is an extinct species of the genus.

The Virginia opossum is the largest species in the genus, Didelphis, and the only marsupial and opossum to be found in North America north of Mexico.

Four subspecies of Virginia opossum are currently recognized by Integrated Taxonomic Information System (ITIS): D. v. virginiana (Eastern), D. v. californica (North Mexican), D. v. pigra, and D. v. yucatanensis (Yucatán).

KINGDOM

Animalia

PHYLUM

Chordata

CLASS

Mammalia

ORDER

Didelphimorphia

FAMILY

Didelphidae

GENUS

Didelphis

SPECIES

Virginia

SUBSPECIES (4)

D. v. virginiana (Eastern), D. v. californica (North Mexican), D. v. pigra, D. v. yucatanensis (Yucatán)

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. The possums of Australia, whose name is derived from a similarity to the opossums of the Americas, are also marsupials, but of the order Diprotodontia.

The name opossum 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.

The Virginia opossum is known in Mexico as tlacuache, tacuachi, and tlacuachi, from the Nahuatl word tlacuatzin.

ALTERNATE

Common Opossum, North American Opossum, Possum

GROUP

Grin, Passel

MALE

Jack

FEMALE

Jill

YOUNG

Joey

The Virginia opossum is the only living marsupial found in the United States.

Virginia opossums are not ubiquitous throughout the United States. The species is typically found east of the Rocky Mountains and along the west coast as they are restricted by low winter temperatures and snow depth. This climatic limitation of temperature is the Virginia opossum’s only limitation.

Due to the recent expansion of the species’ northern and western range, the Virginia opossum has been noted as one of the most successful mammal species in history. They have a wide range throughout Central and North America, which continues to expand, and can currently can be found from Costa Rica to southern Ontario, Canada.

The movement of this Neotropical species northward has been the subject of research. In the 1970’s, a scientific model hypothesized that this species would not venture beyond Vermont and New Hampshire.

Prior to European settlement, the opossum’s range was limited in the north to Kentucky, Indiana, and Ohio. Today, they are mostly found in the south and northeastern regions of the United States and are widely distributed throughout all of Mississippi.

EXTANT

Belize, Canada, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, United States

The Virginia opossum is found in a fairly wide range and variety of habitats, ranging from relatively arid to mesic environments. They may live in dry and arid environments, woodlands, thickets, forests, shrublands, and even human-altered artificial terrestrial areas.

Virginia opossum prefer wet areas, however, especially woodlands and thickets near streams and swamps, also in suburban areas.

This species has been extremely successful due to their ability to thrive in urban areas. This is assisted by their small body size, nocturnal habits, and high reproductive output. Their opportunistic denning and feeding habits have also led to the success of the species, especially in areas of habitat fragmentation. High reproductive potential further contributes to increasing population size. Abandoned burrows, buildings, hollow logs, and tree cavities are generally used for den sites.

Virginia opossum can be found from near sea level to 3,000 meters in elevation.

FOREST

Temperate, Subtropical/Tropical Dry, Subtropical/Tropical Moist Lowland, Subtropical/Tropical Mangrove Vegetation Above High Tide Level, Subtropical/Tropical Swamp, Subtropical/Tropical Moist Montane

SHRUBLAND

Temperate

ARTIFICIAL/TERRESTRIAL

Plantations, Rural Gardens, Urban Areas, Subtropical/Tropical Heavily Degraded Former Forest

Virginia opossums are solitary and their social behavior is not well developed, with the exception of mating. Mating behavior is one of the only social behaviors displayed by Virginia opossums. After mating, females resume their aggressive, solitary disposition.

Most encounters between adult opossums are usually hostile and aggressive. Many defensive techniques and behaviors have been noted and studied in the opossum. During aggressive encounters, Virginia opossums use olfactory and auditory signals to communicate with their potential aggressors, including discharging an excretion from two anal glands. In response to threatening stimuli, the animal will also hiss, growl, and bare teeth. Aggressive encounters between males may involve a dance in which they lash their tails and reach with their front legs. However, captive individuals raised together may form non-aggressive hierarchies in which females are dominant.

The Virginia opossums is almost exclusively nocturnal and begins its nightly activities around dusk. It remains active until dawn, but this may vary slightly throughout the year.

The Virginia opossum’s perception channels are specialized for its nocturnal behavior. The opossum likely has acute hearing. While they likely have keen eyesight, their ability to recognize color is limited. Their vision is likely similar to cats (Felis catus), however, they have a rod to cone ratio of 50:1, as opposed to a cat’s ratio of 10:1. They also have sensitive vibrissae, which assist in their movement in the dark. Their ability to recognize specific tastes is likely also limited.

These animals do not hibernate; however, they reduce their activity during the bitter cold seasons. During their active period, males travel greater distances, whereas females shows greater variation in their movement.

Given their tropical beginnings, it is not surprising that these neotropically evolved individuals are ill-equipped for extreme cold, with inadequate thermoregulatory abilities and poorly insulated fur. Instead, the northward migration and survival of Virginia opossums is likely facilitated by their metabolism of fat stores, behavioral modification during extreme temperatures, and the shelter offered by human structures. However, reports of frostbite or mortality due to starvation are common for northern populations at the edge of this species’ boundaries.

The Virginia opossum has a much lower amount of expanded energy due to thermoregulation than any other placental mammal. The opossum is a homeotherm that can maintain its body temperature at ambient temperatures that are lower than zero degrees Celsius. Many thermoregulatory measures are taken by the opossum in low temperatures. The species has been known to use shivering, vasoconstriction, piloerection, and even avoidance of the low temperatures. This species copes with extreme heat by spreading its saliva as a cooling mechanism. Sweat glands have proved to be nonfunctional and skin glands are located on the ventral side of males. Signs of temperature regulation were first noted in young at the age of 55 to 60 days old, at which the young are still living in the pouch of the female. At 95 days of age young Virginia opossums were found to be able to hold a deep body temperature constant at ambient temperatures as low as five degrees Celsius for a time period of two hours.

Virginia opossums are most famous for entering a defensive catatonic state, commonly known as going opossum. This behavioral trait is one of the opossum’s most noted and described. During this death feigning behavior, the animal becomes motionless. This trait allows the opossum to greatly decrease mortality due to predation. Feigning death has been described as the animal becoming very still or freezing and somewhat curling its body and falling onto its side. The tail is tucked between the legs and the mouth is drawn back and the tongue extends out of the mouth. The eyes have been noted to remain open but slightly less than when not feigning death. Reactions to tactile stimulation are reduced during this display. This behavior may last as little as a minute or it may continue up to six hours. This behavior is relatively rare and is most frequently displayed in young opossums. Instead, it is more common for a threatened adult to bare their teeth and stand their ground, or flee. Likewise, Virginia opossums may also climb or swim to escape a perceived threat.

Virginia opossums are terrestrial; however, they are also very adept climbers and may den in trees. Arboreal locomotion of the opossum is facilitated mainly by the prehensile tail, used as an additional limb, and the friction ridges that are found on the plantar surfaces on the bottom of their dark feet. The opossum also possesses an opposable hallux on the hind feet, specialized in climbing, that aids somewhat in arboreal locomotion. This hallux does not bear a claw, unlike the other digits. The hind foot is also used to carry out extensive grooming. Arboreal locomotion is typically slow.

The Virginia opossum uses three main types of locomotion, which includes arboreal, terrestrial, and aquatic.

It has been noted that the opossum will employ swimming but mainly as an escape mechanism. The Virginia opossum has been described as a strong swimmer and has been noted to have no fear of water. It can float with relative ease. All accounts state that immediately after entering the water the opossum would engage in underwater swimming. It has also been noted that the opossum will dive and travel under water up to a distance of 15 feet without surfacing to breath. The species engages in two different types of swimming. The swimming technique used most often resembles terrestrial locomotion used by the animal and the other has been described as “similar to that of a pacing horse.” The toes are usually spread apart during swimming, and the tail has been noted to move from side to side. The animal controls the closing of its nostrils with ease and has been observed resting while completely submerged under water. The eyes may also remain open during under water swimming. The opossum was also examined upon exiting the water with the pouch carrying the young sealed so tightly that it could not be opened. This may prove previously stated knowledge to be true that a mother opossum can close her pouch so tightly that water may not enter. Shivering has been recorded in response to swimming in low temperature water. It has been stated that large bodies of water, especially cold water, might serve as a distribution barrier due to the opossum’s rapid exhaustion and shivering response. The species is known to defecate in the water while engaging in swimming activities.

Virginia opossums have a reputation for being extremely slow and clumsy; however, they are known to show directional turns when pursued to avoid being captured.

Their quadrupedal plantigrade stance allows them to run 7.1 to 7.4 kilometers per hour. Likewise, Virginia opossums may also climb or swim to escape a perceived threat. When threatened, these animals may hiss, growl or screech.

It is very difficult to estimate Virginian opossum home range due to their excessive movement. Virginia opossums were once considered a nomadic species, but more recent research has shown that an individual maintains a fairly constant home range throughout their lifespan. The home range kept by Virginia opossums varies greatly. This may depend on their range, their habitat, the availability of resources, and their gender. The home ranges are more often oval-shaped, rather than circular, and often overlap with a water source. In general, their home range size is thought to be about 12.5 to 38.8 hectares. Females generally have a smaller home range than males. 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. One study provided a home range of approximately 11.5 acres, but that is only an estimation. A study conducted in Georgia found that home range size may be between 7.2 to 94.4 hectares and a study in Texas found home range sizes from 0.12 to 23.47 hectares. Likewise, home range sizes in urban environments averaged 18.8 hectares for females and 37.3 hectares for males. ion.

CIRCADIAN RHYTHM

Nocturnal

Virginia opossums are extremely opportunistic omnivorous feeders and eat a variety of foods based on the season, their habitat, and their range. Their diets include vertebrates, invertebrates, plant material, fruits, grains, pet food, garbage, and carrion.

Stomach content analyses have been conducted on Virginia opossums throughout the United States, generally their diet is composed of 14 to 27% mammal tissues, 10 to 18% fruits, seeds and bulbs, 6 to 11% grasses and leaves, 3 to 13.5% insects, 5.5 to 9% earthworms and 3 to 5% birds. Other food items were found more specific to an animal’s location and included up to 22.5% reptiles and amphibians, 10% gastropods, 9% pet food, 9% garbage and up to 5% carrion.

During the colder seasons, small vertebrates tend to make up a larger portion of their diet, whereas in the warmer seasons, they consume more invertebrates, plant material, fruits, and seeds.

Because of their love of garbage, pet food, and even poultry, Virginia opossums are often seen as a pest species. Stomach content analyses in Portland, Oregon found that as much as 9% of an opossums diet was composed of garbage, likewise, another 9% of their diet was pet food. Virginia opossums are also seen as farm pests due to their proclivity for poultry.

PREFERENCE

Generalist

STYLE

Forager

Didelphid marsupials, including Virginia opossums, engage in a polygynous mating system, in which males vie for reproductive females.

The Virginia opossum 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.

Although males typically only participate in breeding for one year, they are technically not semelparous because most ranges involve 2 to 3 breeding seasons per year. However, in one study, among approximately 12,000 trapped Virginia opossums, no adult males were found. The reproductive system of the male is composed of a scrotum and a hemipenis. Males also possess a sexually dimorphic sternal scent gland on their chest, which emits a musky odor and stains their fur. This is most commonly observed near the onset of the breeding season.

Female Virginia opossums experience an approximately 29.5 day estrous cycle. Upon entering estrous, breeding begins almost immediately. The female reproductive system is composed of three vagina, two vagina, which receive the sperm and are laterally placed, and a centrally placed median vagina, which serves the purpose of a birth canal.

During the breeding season, mates may use olfactory and auditory signals to communicate with each other, including emitting a series of metallic sounding clicks. Research suggests that males are able to identify particular females based on scent alone, whereas females are able to distinguish between the genders but are not able to discern among individual males.

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.

Virginia opossums nest in varied denning sites including brush piles, hollow trees, and drainage areas. They may also use buildings or abandoned burrows. Virginia opossums fill their den with substrate including dry leaves or shredded paper. They change denning sites often only remaining in the same den for long periods only while they are weaning young. One study showed that one in every four dens in the range was occupied by the opossum. The fact that more dens were always available than were in use proves that den factors place no limitation on the opossum. The preferred dens were usually covered with woody cover or another type of protection.

Virginia opossums invest little in parental care. Males provide no parental care, while females offer moderate care. Although a female with pouch-young may become very protective of her pouch, once her young are removed, she shows little interest. Female Virginia opossums typically continue lactating for about 15 weeks, over which time, the composition of the milk becomes modified.

After an extremely short gestation period of 12 to 13 days, four to 25 young are born. Even though female Virginia opossums can have up to 25 offspring, they generally only have 10-17 teats, but 13 mammae is the most common, some of which may even be nonfunctional. This is because only eight of the young will survive to the mother’s pouch. Once there, the young will remain attached to the mammae for approximately 50 to 70 days.

Virginia opossum offspring are born altricial and honey bee-sized. They typically weigh between 0.13 to 0.20 grams and are generally about 14 millimeters long.

After breeding, the female Virginia opossum’s pouch takes on a brownish-orange hue and emits a musky odor due to scent glands located within. This likely assists newborn opossums in finding their mother’s pouch.

Although the newborn offspring are highly under-developed in many regards, the young do possess muscular front legs, allowing them to climb to the mother’s pouch. Scent glands help the neonates locate their 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.

While young are residing within, female Virginia opossums are often observed licking at the pouch and their offspring. This practice led to the mistaken idea that Virginia opossums breed with their noses and afterward, the young crawl from the female’s nostrils into her pouch.

Virginia opossums use olfactory and auditory signals to communicate with their young. In addition, females maintain auditory contact with their young through a series of clicks, lip smacking, and bird-like sounds.

After the period spent within the pouch, Virginia opossum young remain with their mother, either staying in the den while she forages, or riding on her back. After ten days of age, young develop the means to fight infection. The young begin eating solid food at around 85 days old and are fully weaned between 93 to 105 days old. After this period, young are typically independent and adopt a solitary lifestyle, although some will stay in the weaning den with their mother until they are about 120 days old.

Early in life, young opossums have a very high mortality rate. Many of these altricial young never arrive in their mothers pouch, with an average of 8 young surviving the expedition to the pouch out of a total litter of 4 to 25 individuals. Afterward, about 60% of those who do reach the pouch will perish once they are weaned and become fully independent.

Virginia opossums become sexually mature within the first year of their life, around 6 months for females and 8 months for males, but typically begin breeding around 10 months of age.

BREEDING SEASON

January-September

BREEDING INTERVAL

4-12 Months

ESTROUS CYCLE

29.5 Days

PARENTAL INVESTMENT

Maternal

GESTATION

12-13 Days

LITTER

4-25

MAMMAE

10-17

POUCH LIFE

50-70 Days

WEANING

93-105 Days

INDEPENDENCE

93-120 Days

SEXUAL MATURITY

6-10 Months

Virginia opossums are important seed dispersers and redistribute undamaged seeds from the genera Asimina and Diospyros, among others.

These animals are also carriers for a wide variety of 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 be a carrier of the rabies virus.

Virginia opossums may be predated upon by a variety of species including owls, domestic dogs (Canis lupus familiaris), coyotes (Canis latrans), red foxes (Vulpes vulpes), northern raccoons (Procyon lotor), bobcats (Lynx rufus) and large snakes, among others. They may also be hunted or trapped by humans.

Virginia opossums are immune to the venom of a variety of snakes from the family, Viperidae, including eastern and western diamondback rattlesnakes, copperheads, cottonmouth moccasins and Korean mamusi.

The opossum may have a better chance of survival within more urban environments due partially to the lower predation risk.

Given the frequent urban habitation of Virginia opossums, interaction with humans is almost inevitable. These animals are unfortunately hunted for business, sport, and food.

Some cultures believe that Virginia opossums’ 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 composed 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.

FOOD

Local

WEARING APPAREL, ACCESSORIES

Local

The Virginia opossum is common and widespread throughout its known range.

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.

FRAGMENTATION

Not Fragmented

There are no major threats to the Virginia opossum.

Opossums are hunted and trapped for food and fur in certain areas of their range, but the mortality is mostly caused by collision with motor vehicles.

There are no specific measures in place to protect the Virginia opossum, as it likely occurs in a number of protected areas throughout its range.