Virginia Opossum: American marsupials that have been barely altered since the dinosaur era

With bead-like eyes, large ears, a hairless tail and short, stocky legs, the opossum is a distinctive marsupial. Despite their strange appearance, these animals have a rich evolutionary history and have little change for millions of years. Their incredible ability to adapt to a variety of environments, food sources and predators has helped them survive from the dinosaur era to today.

The Virginia Opossum is the only opossum species found in the US and Canada. The opossum has the minimum brain-to-weight ratio of North American mammals.

The earliest known parents of modern opossums lived over 65 million years ago at the time of the dinosaur extinction. A 2009 study published in PLOS One found that Peradectids, a family of marsupials known primarily in North America and Eurasia, were the closest relatives of living oposums. Like modern opossums, Peradectid had a skull similarly shaped on its hind legs with an opposite thumb. These have remained largely unchanged for millions of years. The earliest opossum fossils date back to the early Miocene period about 20 million years ago.

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One important reason Opossums has survived for so long is that the changes are adaptable. These marsupials eat almost everything, including fruits, insects, small animals, and animal corpses. They can live anywhere from forests to city backyards. And although they are mostly nocturnal, if there is a lack of food, they can sometimes be seen in the sunlight.

Opossums also resist snake venom, especially rattlesnakes and other pit vipers. This resistance is due to a protein known as lethal toxin neutralizing factors found in the blood, and can neutralize a variety of toxins in snake venom. This allows opossums to prey on venomous snakes, which would otherwise be a threat.

The opossum gives birth to an underdeveloped young man, which craves and nurses for about 8 weeks as it grows. The young opossum then rides on his mother’s back for several weeks until he becomes independent at 12 weeks of age.

When threatened, the opossum can groan, bare teeth, or climb nearby trees to escape. When escape is impossible, they resort to “playing and dead,” a defensive mechanism known as tanotosis.

This response is not a conscious decision, but a physiological response to extreme stress. It makes the opossum seem completely stationary and lifeless. This behavior is often accompanied by a significant decrease in the heart and respiratory rate, a decrease in body temperature, and the release of dirty absorbent fluid from the anal glands. Together, these cues show predators that the opossum is already dead, often causing them to lose interest and move on. Therefore, by “playing a possum”, the animal can survive the encounter.