November 3, 2017

Virginia Opossum (Didelphis virginiana)

Posted by: Naturalist Team

Virginia Opossum (Didelphis virginiana)

A common mammal species throughout the Eastern and Midwestern US, the Virginia Opossum is the only marsupial to live North of Mexico.  They range from southern Canada to northern Costa Rica with some populations found in California presumably brought there by travelers as a food source during the depression.  Although they are also commonly referred to as just possums in Georgia, the term possum is technically used to refer to a specific suborder of arboreal marsupials found only in Australia, and Opossum refers to new world marsupials found in North and South America. The term opossum was actually borrowed from the Algonquian name for them, aposoum, meaning “white dog”. The average Virginia Opossum is about 2 feet in length weighing around 8 pounds; female opossums are smaller than males, with male opossums ranging 12 to 15 pounds. They have a very short lifespan, typically only surviving a year in the wild. Like most marsupials the female Virginia Opossum has a pouch which is lined with fur where the young develop. A female Opossum can give birth to as many as 20 young, which at birth are not much larger than a honeybee, about a half an inch in length. Upon their birth they must crawl to the pouch of the female and attach themselves to one of the 13 teats within the mother’s pouch. After about 60 days the young will leave the pouch and travel on their mothers back until about 100 days of age where they are then independent and can forage on their own. Virginia Opossums are generally nocturnal, being most active at night, and spend much of their time in the trees, utilizing their furless prehensile tail as a fifth limb to help them navigate their arboreal habitat. They are an opportunistic omnivore, eating anything they can find including fruits, nuts, and carrion, as well as predating on small mammals and reptiles.

Recent studies have found that Opossums play an important role in regulating disease transmission in the habitats where they exist. Researchers experimentally found that half of all ticks introduced to mice were able to attach and feed, while only 3.5% of ticks introduced to opossums would attach. The study found that those ticks that failed to attach where eaten by the opossums during grooming. In field surveys they found that the average opossum carries about 200 ticks, and if that is 3.5% of the ticks that try to feed on an opossum, then the average opossum eats up to or more than 5,500 ticks. These same researchers hypothesize that the removal of opossums can have a profound effect on tick populations and increase transmission of ailments such as Lyme disease to other creatures, including people.

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