CROW Case of the Week: Baby Opossums

The Virginia opossum (Didelphis virginiana) is not limited to the Cavalier State. It can be spotted in much of the United States east of the Rocky Mountains, but also found on the West Coast as well as Mexico, Central America and parts of western Canada. 

The Virginia opossum is the continent’s only marsupial, an animal sporting a pouch, like a kangaroo or a koala. It has a triangular head and a long pointed snout with grayish fur all over except for its ears, tail and feet. In fact, while a possum doesn’t hibernate in winter, it often takes shelter during extremely cooler weather due to its risk of getting frostbite on those furless body parts. 

No need to worry about these frisky mammals, though. They are survivors, since the species has been around for at least 70 million years, making them one of the Earth’s oldest creatures. Their resiliency is due to their protective behavior of running, growling, urinating and even defecating when approached by a predator. If that doesn’t work, they’ll “play possum” by rolling over, stiffening up, slowing up their breathing and surrendering to a catatonic state to deceive attackers. However, the lifespan of an opossum is unusually short for a mammal of its size. Ordinarily, it lives for only one to two years in the wild and as long as four or more years in captivity. 

Female possums have the potential to have three litters of babies per year, ranging from seven to 25 babies per litter. At CROW, the Virginia opossum is one of the more common babies seen at the clinic. Often times, their mothers are victims of being struck by a vehicle or other life-ending trauma. Without a mother to care for them, the babies are raised at CROW to have a shot at growing up and being released in the wild. With sometimes as many as 50 or more infant possums at the clinic, staff and students are kept busy with around-the-clock care.

“The youngest opossum babies require feedings every two to three hours, which typically works out to six feeds per day,” said Dr. Robin Bast, CROW’s staff veterinarian. “In some cases, this means their earliest feeding is at 6 a.m . and the last feeding as late as 11 p.m . As they grow and start to eat semi-solid foods on their own, we decrease the number of feedings they get per day.”

Due to the large amount of infant possums at the clinic, there is a designated room to care from them. It is dedicated in the memory of a longtime CROW volunteer and supporter, according to Dr. Bast. 

“We have a room that is almost exclusively used for raising baby opossums and houses neonate and juvenile opossums. In 2018, it has housed over 230 patients so far,” she said. “The room was dedicated in Ann Arnoff’s memory this fall, and state-of-the-art incubators were installed for the tiniest babies thanks to donations by the Spohr Charitable Trust.” 

Unlike other wild mammal babies, opossums cannot be nipple-fed due to their many sharp teeth and must be tube-fed until they are old enough to be transitioned to solid food. Once the opossums are eating a solid diet of various foods and have reached a certain size, they are moved to an outside enclosure until they are big enough to be released.

“Young opossums start to transition from formula onto solid food between four and seven weeks of age, when their eyes are open and their fur thickens,” added Dr. Bast. “The baby opossums typically stay indoors until approximately 12 weeks of age and weighing about 150 grams. Then, they spend a few weeks in outdoor enclosures until they are ready for release at around 15 weeks old and weighing around 300 grams.”

 

CROW Case of the Week stories are written by Bob Petcher and appear weekly in the Island Sun and River Weekly Newspapers.

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