Blog Post Jennifer Errick May 2, 2018

The Only Marsupial in U.S. National Parks

National parks are some of the most biodiverse places in the country. Only one kind of marsupial can be found anywhere in the U.S. park system, however. Do you know which one?

It’s true that wombats, wallabies, kangaroos and koala bears are regular sights in national parks — if you happen to be in Australia. Australia boasts the most diverse population of marsupials in the world, with more than 200 different species roaming, climbing and hopping about the continent, out of about 334 such species worldwide.

In the United States, it’s a different story. The only marsupial anywhere in the country is the Virginia opossum (Didelphis virginiana). These two- to three-foot-long mammals are the only animals north of Mexico that carry their young in pouches, a characteristic of marsupials that allows their babies to more fully grow and develop before living independently from their mothers. All other mammals have placentas, which nourish the young while still in the womb. After an opossum’s babies are developed enough to live outside its pouch, the mother will continue to carry the young on her back for another month or two while they nurse.

Though the opossum is the only animal of its kind in this part of the world, it has a wide range and a robust population. It is most strongly associated with the Southeast, where it appears in folklore and even traditional recipes, but it is common throughout the country east of the Rockies. It also lives along the Pacific Coast, is widespread in Central America and has been expanding its range northward into parts of Canada. Thus, national park visitors can find them everywhere from Cuyahoga Valley to the Everglades to Olympic — and many, many places in-between.

Although opossums prefer forested habitats, part of their success comes from their ability to adapt to urban and suburban environments. These natural omnivores will feed on everything from worms and eggs to fruits and grains, and the shy, nocturnal creatures can often be found rummaging through trash bins in search of their next meals. They have a particular fondness for persimmons when the fruit is in season. Although sometimes viewed as pests, opossums voraciously feed on ticks, slowing the spread of Lyme disease.

How did the Virginia opossum evolve to be the only creature of its kind in the United States, when so many similar species live on the other side of the world?

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Scientists believe that modern marsupials, including the opossum, may have actually descended from ancestors that originated in North America. Around 65 million to 68 million years ago, many of these ancestor species went extinct and some migrated to South America, a continent that is now home to about 100 different marsupial species. At that time, South America, Antarctica and Australia were connected as one large landmass; all of Australia’s marsupials may have evolved from a single species that crossed over from South America, whereas the Virginia opossum is believed to have migrated north much later, roughly 3 million years ago. The Virginia opossum is one of the oldest surviving mammals on the planet, having existed for about 65 million years or more, since around the time the dinosaurs went extinct.

Fun fact: Opossums are one of very few mammals with prehensile tails, meaning they can independently grasp objects with them. This helps the animals gather nesting materials and keep their balance by holding on to tree branches and other objects as they climb.

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