Opossums |
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History and Biology: The opossum, Didelphis virginiana , is the only marsupial native to America . It is commonly called the possum and is found throughout the eastern half of the United States and along the west coast. It is absent in large areas just west of the Rocky Mountain region and in the extreme northern regions. They prefer wooded areas near stream banks and irrigation levees, but also frequent anthropogenic structures such as, under houses, porches, and steps, also, plenum spaces, road culverts, and in barns. They are good climbers and may find harborage in any available shelter. The possum is about 12 inches high and 33 inches long from the nose tip to the tail tip. It is mostly light gray to black and usually has pinkish to white coloring dorsally on the head, nose, and feet. They have a dense underfur with protruding guard hairs that give it a rough straggly appearance. They have five toes on each foot, with an opposable and clawless thumb (hallux) on the hind feet. The tail is hairless and is a well developed prehensile organ. It is used to hang from tree limbs. Being a marsupial, the female has a well developed marsupium (pouch) for the newborn. Opossums prefer to live in brushy areas next to bodies of water, but they are found in a variety of industrial, suburban, and rural habitats such as brushy areas, stream banks, rocky outcrops, culverts, storm drains, industrial storage yards, homes, barns, and farmyards. They are nocturnal and seem to sluggishly wonder aimlessly over an area in search of food. When food is available, their nightly travel may be limited to a few hundred yards. The opossum dens in any shelter available such as, hollow logs, hollow trees, rock crevices, drainage pipes, culverts, crawlspaces beneath structures, attics, outbuildings, and burrows dug by other animals. Opossums typically produce one litter per year of 7 to 9 (average 6) young. After breeding, gestation is only 13 days. At birth, the young are the size of a kidney bean. The undeveloped young wiggle their way to the marsupium (pouch), enter, and attach themselves to one of 13 mammary glands where they complete development in about 4 to 6 weeks. Opossums are nocturnal and omnivorous and feed on anything such as, insects, grubs, rodents, snakes, frogs, carrion, fruit, berries, nuts, mushrooms, eggs, nestlings, and human refuse. They frequent highways for dining on road kills. Public Health Damage: Opossums may become a nuisance in and around human structures. They may den beneath structures, porches, and in attics. Their excretions accumulate and may become malodorous and obnoxious to humans and other animals. They frequently raid uncovered garbage cans and tear open garbage bags. Night time foraging often arouses dogs, causing them to bark and disturb the neighborhood. Opossums may be a reservoir for zoonotic diseases such as tularemia, leptospirosis, relapsing fever, murine typhus, Rocky Mountain spotted fever, and occasionally rabies. Structural Damage: Opossums inhabit the dwellings of humans, industrial yards, and farming operations. They can be inhibiting to the operations of these structures, especially if nesting in a plenum space. Their scats and dietary remains can become an eyesore and odiferous. They can increase in numbers if not controlled and removed from anthropogenic structures. Agricultural Damage: Opossums may threaten the health of humans and livestock in the United States because they may be a reservoir for potentially transmittable disease to both humans and livestock such as, tularemia, leptospirosis, relapsing fever, murine typhus, Rocky Mountain spotted fever, listeriosis, distemper, Q-fever, histoplasmosis, microfilariasis, and rabies. They also may do damage by defacement of agricultural buildings and equipment with scats, and dietary debris. Additionally, they do damage through the consumption and contamination of agricultural seed and grain products in the field, storage facilities, and wholesale and retail outlets. Environmental Damage: Because of its commensal relationship with humans and its potential for inquisitive investigations into structures and food supplies, the opossum is a constant public health and property damage problem. In nature, opossums feed on small mammals, birds, and eggs and may have a negative impact on the population richness and densities of native songbird and small mammal species. Economic Damage: Economic damage from the opossum is difficult to assess when you consider the intangible costs of the impact of zoonotic diseases on the public health of humans, livestock, domestic animals, and wildlife. Additionally, it is also difficult to determine the real cost of equipment and structural damages from defacement. Also, there is a significant cost to American consumers and business from the consumption and contamination of seed, grain, fruits, nuts, and vegetables damaged by the opossum. It is difficult to evaluate the damage to populations of smaller native songbird and small mammal species. References: Mallis, A. 1997. Handbook of Pest Control: The behavior, Life History, and Control of Household Pests, Eighth Edition. Mallis Handbook and Technical Training Company. Bennett, G. W., Owens, J. M., and Corrigan, R. M., 1988, Truman's Scientific Guide To Pest Control Operators, Harcourt Brace Jovanovich, Inc., One East First St. , Duluth , MN . 55802 |
