In the United States and Canada, the only species found is the Virginia opossum, and it is generally referred to as a "possum" - but should not be confused with the suborder Phalangeriformes, which are arboreal marsupials in the Eastern Hemisphere also called "possums" because of their resemblance to Didelphimorphia.
The word "opossum" is borrowed from the Powhatan language and was first recorded between 1607 and 1611 by John Smith (as opassom) and William Strachey (as aposoum). Both men encountered the language at the British settlement of Jamestown, Virginia, which Smith helped to found and where Strachey later served as its first secretary. Strachey's notes describe the opossum as a "beast in bigness of a pig and in taste alike," while Smith recorded it "hath an head like a swine ... tail like a rat ... of the bigness of a cat." The Powhatan word ultimately derives from a Proto-Algonquian word (*wa·p-aemwa) meaning "white dog or dog-like beast."
Didelphimorphs are small to medium-sized marsupials that grow to the size of a house cat. They tend to be semi-arborealomnivores, although there are many exceptions. Most members of this order have long snouts, a narrow braincase, and a prominent sagittal crest. The dental formula is: teeth. By mammalian standards, this is an unusually full jaw. The incisors are very small, the canines large, and the molars are tricuspid.
As a marsupial, the female opossum has a reproductive system that includes a bifurcated vagina, a divided uterus and a marsupium, which is her pouch. The average estrous cycle of the opossum is about 28 days. Opossums do possess a placenta, but it is short-lived, simple in structure, and, unlike that of placental mammals, not fully functional. The young are therefore born at a very early stage, although the gestation period is similar to that of many other small marsupials, at only 12 to 14 days. Once born, the offspring must find their way into the marsupium to hold on to and nurse from a teat. Baby opossums, like their Australian cousins, are called joeys. Female opossums often give birth to very large numbers of young, most of which fail to attach to a teat, although as many as thirteen young can attach, and therefore survive, depending on species. The young are weaned between 70 and 125 days, when they detach from the teat and leave the pouch. The opossum lifespan is unusually short for a mammal of its size, usually only one to two years in the wild and as long as four or more years in captivity. Senescence is rapid.
The species are moderately sexually dimorphic with males usually being slightly larger, much heavier, and having larger canines than females. The largest difference between the opossum and non-marsupial mammals is the bifurcated penis of the male and bifurcated vagina of the female (the source of the term "didelphimorph," from the Greek "didelphys," meaning double-wombed). Opossum spermatozoa exhibit sperm-pairing, forming conjugate pairs in the epididymis. This may ensure that flagella movement can be accurately coordinated for maximal motility. Conjugate pairs dissociate into separate spermatozoa before fertilization.
An opossum playing dead, or "playing possum"
Opossums are usually solitary and nomadic, staying in one area as long as food and water are easily available. Some families will group together in ready-made burrows or even under houses. Though they will temporarily occupy abandoned burrows, they do not dig or put much effort into building their own. As nocturnal animals, they favor dark, secure areas. These areas may be below ground or above.
Juvenile opossum hissing defensively
When threatened or harmed, they will "play possum", mimicking the appearance and smell of a sick or dead animal. This physiological response is involuntary (like fainting), rather than a conscious act. In the case of baby opossums, however, the brain does not always react this way at the appropriate moment, and therefore they often fail to "play dead" when threatened. When an opossum is "playing possum", the animal's lips are drawn back, the teeth are bared, saliva foams around the mouth, the eyes close or half-close, and a foul-smelling fluid is secreted from the anal glands. The stiff, curled form can be prodded, turned over, and even carried away without reaction. The animal will typically regain consciousness after a period of a few minutes to four hours, a process that begins with slight twitching of the ears.
Some species of opossums have prehensile tails, although dangling by the tail is more common among juveniles. An opossum may also use its tail as a brace and a fifth limb when climbing. The tail is occasionally used as a grip to carry bunches of leaves or bedding materials to the nest. A mother will sometimes carry her young upon her back, where they will cling tightly even when she is climbing or running.
Threatened opossums (especially males) will growl deeply, raising their pitch as the threat becomes more urgent. Males make a clicking "smack" noise out of the side of their mouths as they wander in search of a mate, and females will sometimes repeat the sound in return. When separated or distressed, baby opossums will make a sneezing noise to signal their mother. The mother in return makes the clicking sound and waits for the baby to find her. If threatened, the baby will open its mouth and quietly hiss until the threat is gone.
Opossums eat dead animals, insects, rodents and birds. They also feed on eggs, frogs, plants, fruits and grain. One source notes their need for high amounts of calcium. Thus possums eat the skeletal remains of rodents and roadkill animals. Opossums also eat dog food, cat food and human food waste.
Opossums are also notable for their ability to clean themselves of ticks, which they then eat. Some estimates suggest they can eliminate up to 5,000 ticks in a season.
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Opossums are found in North, Central, and South America. The Virginia opossum lives in regions as far north as Canada and as far south as Central America, while other types of opossums only inhabit countries south of the United States. The Virginia opossum can often be found in wooded areas, though its habitat may vary widely. Opossums have been moving north in recent years.
In Dominica, Grenada, Trinidad, Saint Lucia and Saint Vincent and the Grenadines the common opossum or manicou is popular and can only be hunted during certain times of the year owing to overhunting. The meat is traditionally prepared by smoking, then stewing. It is light and fine-grained, but the musk glands must be removed as part of preparation. The meat can be used in place of rabbit and chicken in recipes. Historically, hunters in the Caribbean would place a barrel with fresh or rotten fruit to attract opossums that would feed on the fruit or insects.
In northern/central Mexico, opossums are known as "tlacuache" or "tlacuatzin". Their tails are eaten as a folk remedy to improve fertility. In the Yucatán peninsula they are known in the Yucatec Mayan language as "och" and they are not considered part of the regular diet by Mayan people, but still considered edible in times of famine.
^ abcSiebert, Jr., Frank T. (1975). "Resurrecting Virginia Algonquian from the Dead: The Reconstituted and Historical Phonology of Powhatan". In Crawford, James Mack (ed.). Studies in Southeastern Indian Languages. University of Georgia Press.
^Vieira, Emerson R.; De Moraes, D. Astua (2003). "Carnivory and insectivory in Neotropical marsupials". Predators with Pouches: the biology of carnivorous marsupials. Csiro Publishing. pp. 267-280. ISBN978-0-643-06634-2.
^Prevosti, Francisco J.; Forasiepi, Analía; Zimicz, Natalia (2011). "The Evolution of the Cenozoic Terrestrial Mammalian Predator Guild in South America: Competition or Replacement?". Journal of Mammalian Evolution. 20: 3-21. doi:10.1007/s10914-011-9175-9.
^Cenizo, Marcos; Soibelzon, Esteban; Magnussen Saffer, Mariano (2015). "Mammalian predator-prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): New ichnological and taphonomic evidence". Historical Biology. 28 (8): 1026-1040. doi:10.1080/08912963.2015.1089868.
^Mellor, D. J.; Lentle, R. G. (2015). "Survival implications of the development of behavioural responsiveness and awareness in different groups of mammalian young". New Zealand Veterinary Journal. 63 (3): 131-40. doi:10.1080/00480169.2014.969349. PMID25266360.
^Moore, H.D. (1996). "Gamete biology of the new world marsupial, the grey short-tailed opossum, monodelphis domestica". Reproduction, Fertility, and Development. 8 (4): 605-15. doi:10.1071/RD9960605.
^Hamilton, W. J., Jr. (1958). "Life history and economic relations of the opossum (Didelphis marsupialis virginiana) in New York State". Cornell Univ. Agric. Exp. Sta. Memoirs. 354: 1-48.CS1 maint: multiple names: authors list (link)
^Silva, Andréa Leme da (2008). "Animais medicinais: Conhecimento e uso entre as populações ribeirinhas do rio Negro, Amazonas, Brasil". Boletim do Museu Paraense Emílio Goeldi. Ciências Humanas. 3 (3): 343-357. doi:10.1590/S1981-81222008000300005.
^Pinto, Angélica Auxiliadora da Costa; Maduro, Cice Batalha (2003). "Produtos e subprodutos da medicina popular comercializados na cidade de Boa Vista, Roraima". Acta Amazonica. 33 (2): 281-290. doi:10.1590/1809-4392200332290.
^ abcdefgGoin, Francisco J.; Pardinas, Ulyses F. J. (1996). "Revision de las especies del genero Hyperdidelphys Ameghino, 1904 (Mammalia, Marsupialia, Didelphidae. Su significacion filogenetica, estratigrafica y adaptativa en el Neogeno del Cono Sur sudamericano". Estudios Geologicos. 52 (5-6): 327-359. doi:10.3989/egeol.96525-6275.
^Goin, Francisco J.; de los Reyes, Martin (2011). "Contribution to the knowledge of living representatives of the genus Lutreolina Thomas, 1910 (Mammalia, Marsupialia, Didelphidae)". Historia Natural. 1 (2): 15-25. JSTOR20627135.
^Martínez-Lanfranco, Juan A.; Flores, David; Jayat, J. Pablo; d'Elía, Guillermo (2014). "A new species of lutrine opossum, genus Lutreolina Thomas (Didelphidae), from the South American Yungas". Journal of Mammalogy. 95 (2): 225. doi:10.1644/13-MAMM-A-246.
^Cozzuol, Mario A.; Goin, Francisco J.; de los Reyes, Martin; Ranzi, Alceu (2006). "The oldest species of Didelphis (Mammalia, Marsupialia, Didelphidae) from the late Miocene of Amazonia". Journal of Mammalogy. 87 (4): 663-667. doi:10.1644/05-MAMM-A-282R2.1.
^ abcGoin, Francisco J. (1997). "New clues for understanding Neogene marsupial radiations". Vertebrate Paleontology of the Miocene in Colombia. A History of the Neotropical Fauna. Smithsonian Institution Scholarly Press. pp. 185-204. ISBN978-1-56098-418-4.
^ abPavan, Silvia Eliza; Rossi, Rogerio Vieira; Schneider, Horacio (2012). "Species diversity in the Monodelphis brevicaudata complex (Didelphimorphia: Didelphidae) inferred from molecular and morphological data, with the description of a new species". Zoological Journal of the Linnean Society. 165: 190-223. doi:10.1111/j.1096-3642.2011.00791.x.
^Voss, Robert S.; Pine, Ronald H.; Solari, Sergio (2012). "A New Species of the Didelphid Marsupial Genus Monodelphis from Eastern Bolivia". American Museum Novitates. 3740 (3740): 1. doi:10.1206/3740.2.
^Goin, Francisco J.; Montalvo, C.I.; Visconti, G. (2000). "Los marsupiales (Mammalia) del Mioceno Superior de la Formacion Cerro Azul (Provincia de La Pampa, Argentina)". Estudios Geologicos. 56 (1-2): 101-126. doi:10.3989/egeol.00561-2158.
^Goin, Francisco J. (1997). "Thylamys zettii, nueva especie de marmosino (Marsupialia, Didelphidae) del Cenozoico tardio de la region Pampeana". Ameghiniana. 34 (4): 481-484.