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Opossums 1
Ruthe Smith and Joe Schaefer2The Virginia opossum (Didelphis virginiana) is an interesting animal ( Figure 1 ), though it can be a nuisance to man, a detriment to some wildlife, and has a name difficult to spell. True, they are not the cutest critters to ever to visit our backyards, but believe it or not, they are closely related to the adorable koala.
Description
The opossum ranges in size from 4 to 13lb (2 to 6kg), about the size of a house cat. The body is 15 to 20in (37 to 50cm) long, with a tail 9 to 20 in (24 to 50cm) long. Opossums have a cone-shaped head and a pointed snout ( Figure 1 ). Their overall color is gray--with slight variations. Opossums have a scaly, rat-like, prehensile tail they use with their opposable thumbs ( Figure 2 ) to grasp small branches and other objects. Opossums also have more teeth (50) than any other North American mammal.
Figure 1. The Virginia opossum is the only North American marsupial. Credit: Drawing: Hygnstrom et al., 1994. .
Range and Habitat
Opossums inhabit most of the eastern country-region United States and can be found throughout Florida. Probably due to human activity, their range is expanding northward. They can exploit man-made structures for shelter and eat garbage and road kill.Opossums use a variety of habitats: forests, grasslands, agricultural lands, and suburban areas. They are nocturnal (active at night), resting during daylight hours. Dens for daytime use include just about anything that provides shelter from the sun and poor weather. Opossums have been found in tree stumps, hollow logs, road culverts, attics, and even gopher tortoise burrows.
Figure 2. Opossum tracks. Notice the opposable thumb. Credit: Drawing, Hygnstrom et al., 1994. Feeding
Opossums are known as opportunistic feeders. They will eat many different items including bird eggs, chickens, moles, and earthworms, insects, snakes, grass, fruit, pet food, and garbage. Carrion (animals that are already dead) also is a favorite food item.
Reproduction
The Virginia opossum is the only North American marsupial. Like other marsupials--such as kangaroos and koalas--opossums give birth to relatively underdeveloped young which then climb along the females belly to a pouch called a marsupium. Within the pouch, the young attach themselves to one of 13 milk-providing nipples and do not let go for about 60 days. The average litter size is seven. Opossums have 1 to 2, and rarely 3, litters per year during the period from January to July.Newborns are about 1/2 inch long (1.3cm) and weigh 0.0046oz (0.13gm). After they emerge from the pouch they often ride on their mother's back when she goes outside the den. Opossums are short-lived; a 3-year old animal is considered elderly.
Playing Possum
When threatened by a potentially dangerous animal or person, opossums usually hiss and snarl at first. If these defense tactics do not scare off the intruder, they may lie down, open their mouth, and remain "lifeless" for several minutes. This is where the phrase "playing possum" came from. Many predators do not eat animals that are already dead so they may leave the opossum alone if it appears lifeless.
Importance
In the past, opossums have been hunted for fur, food, and because they were once thought to be significant predators to waterfowl. Opossums build up heavy layers of fat and the meat is considered too greasy for some tastes. Its use as food is generally more popular in southern states.Dead opossums can be seen frequently along highways. These animals are not fast enough to avoid high-speed cars, and vehicle collisions cause many deaths for this species in urbanizing areas. They also are prey to larger predators such as bobcats, coyotes, and domestic dogs.
Although opossums are nest predators, there is no evidence to suggest that they have a detrimental impact on wildlife populations. They may be helpful in reducing venomous snakes and removing dead animals from human populated areas. Adult opossums are immune to the venom of copperheads, rattlesnakes, and cottonmouths.
Opossums, like most other animals, are susceptible to infection by the rabies virus; however, very few rabid wild opossums have been documented. Extremely high doses of the virus have been required to experimentally infect opossums as they seem to be highly resistant to the disease. Even though they do not often carry rabies, opossums can still deliver a nasty bite.
Nuisance Problems
Opossums are called generalists because they will eat just about anything they can find. This can cause problems in areas where humans exist.Opossums will get into garbage cans; and eat pet food and cultivated fruits and vegetables. They may prey on poultry and their eggs, and enter homes through ripped screens or vent and duct systems.
To alleviate these problems and keep the opossum outside where it belongs, you can fasten garbage can lids with a rubber strap or bungee cord from hardware stores, and repair or cover holes in screens or building foundations. Do not leave pet food out at night. If the problem is extreme, you can surround your gardens with electric fencing.
You may lawfully live-trap the animals yourself. Sardines and cat food are effective baits. Once an animal is caught, however, another problem is created--what to do with it. Trapping and relocating wildlife is seldom biologically sound. Areas that appear suitable as release sites probably are not. Relocation to occupied areas causes problems for both the relocated animal and the resident population of the same species. In many respects, the soundest biological decision is to humanely destroy the nuisance animal. Relocation permits from the Florida Game and Fresh Water Fish Commission and permission from the landowner are required to transport and release any native wildlife species, and these permits are seldom issued for the reasons noted above.
Legal Aspects
The use of leg-hold and quick-kill (conibear) traps are illegal unless previously approved by a special permit from the Florida Game and Fresh Water Fish Commission. Chapter 39-24.002 of the Florida Administrative Code allows the taking of opossums in areas where the discharge of firearms is not prohibited at night throughout the year with the use of a light and a .22 caliber rifle or .410 gauge shotgun (with shot no larger than No. 6). Check local ordinances for restrictions on discharging firearms in your area.Suggested Reading
Gardner, A.L. 1982. Virginia opossum. In Wild Mammals of North America: Biology, Management, and Economics, J.A. Chapman and G.A. Feldhamer, Eds., Pp. 3-36. Baltimore, MD: The Johns Hopkins University Press. 1147 pp.Hall, E.R. and K.R. Nelson. 1959. The Mammals of North America, Vol. 1. New York: Ronald Press Co. 546 pp.
McManus, J.J. 1974. Didelphis virginiana. Mammalian Species 40:1-6.
Endnote
Drawings are reprinted from Hygnstrom, Scott E, Timm, Robert M, and Larson, Gary E., Eds. Prevention and Control of Wildlife Damage. 2 vols. 1994. University of Nebraska-Lincoln.
Footnotes
1. This document is WEC28, one of a series of the Wildlife Ecology and Conservation Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date June, 1991. Revised September, 2002. Reviewed September, 2002. Revised December, 2006. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.2. Ruthe Smith, former wildlife assistant, and Joe Schaefer, Ph. D., urban wildlife specialist, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.
U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.
Copyright Information
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