Opossums - A Fast Life and Success That Starts in the Pouch
Alerted by the cries, the mother opossum quickly nosed in from the side. As she struggled to calm her babies, to mop up the bright chaos we’d inadvertently thrown her way, we quietly retreated and closed the garage door.
A few weeks later, we were saddened to see, in the middle of our driveway, the corpse of the mother opossum. There were no signs of injury or disease. As it turned out, the opossum had simply followed her species’ ruthless recipe for success in an overwhelmingly placental world: grow up fast, give birth to one or two large broods, and then, at a time of life when most comparably sized mammals have just reached their prime, stop playing possum — and die of old age.
The Virginia opossum, Didelphis virginiana, is one of the more familiar and widespread mammals in the United States, found coast to coast, up into Canada and down into Costa Rica, in fields and sheds, city parks and the alleys of Brooklyn, and all too often as roadkill on the sides of highways. The opossum is generally lumped together in the public mind with raccoons, squirrels, skunks and other workaday wildlife of more or less housecat dimensions, but scientists emphasize that Didelphis is a fundamentally different breed of animal, as singular in its evolutionary history as it is solitary in its habits.
For one thing, it’s our own private Australia, the United States’ sole living example of a marsupial mammal — a mammal that gestates its young in a pouch, or marsupium, rather than in a uterus, as we placental mammals do. For another, new [...]
It doesn't seem too difficult to figure out why mammals would be more successful than marsupials (if numbers equate to success of a type or specie), but it's also not at all surprising that examples of many types would survive through various ages even if they weren't as effective or efficient as other models.
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