The Virginia Opossum, Didelphis virginiana
One of the most unusual mammals that can be encountered along the river
is Didelphis virginiana, the Virginia opossum (sometimes called the American
opossum). This is North
America's only representative of the order Marsupialia, the marsupial
mammals, so called because of the external abdominal pouch called the
marsupium within which the young develop. These are ancient animals
with fossil remains known from 70 million years ago. This means relatives
of the opossum in your backyard roamed the Earth with the great dinosaurs! Today Marsupials mainly occur in
Australia (kangaroos, wallabies, etc.), and many people don't realize
that we have a marsupial mammal here in New England, the shy and unassuming
'possum.
Opossums are covered with short silvery fur interspersed with longer course
white-tipped hairs. Each foot has five toes equipped with a sharp claw
except for the inner toe of the hind foot which has no claw and is opposable
like the human thumb. This greatly aids the animal in climbing trees, a
major part of its lot in life. The tail is bare and prehensile, allowing the
possum to stabilize itself in the tree branches, though they do not swing from
their tails like monkeys. Generally shy and slow
moving, the opossum relies on stealth and a nocturnal lifestyle to avoid
danger. When an opossum does find itself in danger it is not (quite)
defenseless, as we'll see in a moment.
Opossums have large mouths which contain a number of sharp jagged teeth.
(These look more dangerous than they
are but no wild animal should be handled in any event, rabies being endemic
to our area.) In response to a threat however, an opossum is more likely to
resort to a different tactic than biting, they pretend to be dead. This is
actually quite comical to see, the animal will open its mouth and loll out
it's tongue, looking for all the world like it is actually dead. Since many
predators will only eat live prey this tactic of "playing possum" must be
moderately successful.
Opossums will often live in hollow trees, bedding down during the day in
dry leaves and debris and venturing out at night to hunt for food.
They will eat a wide variety of things, insects, eggs and corn being among
their favorites. They have also been accused of stealing chickens. The animal
pictured here is a young opossum that was living
about ten feet up in a tree beside a cornfield near the Fort River in
Hadley, MA. Its hollow in the tree was filled to overflowing with corn cobs,
one of the reasons that it was discovered and made famous, a fate it would
probably have gladly done without. After a bit of ignominy in the back of a
pickup truck 
it was released and
climbed away happily, none the worse for wear.
The dried leaves and corncobs from its nest have yielded quite a few interesting
insects, but that's another story.
Contributed by Sean Werle, Dept. of Entomology, UMASS Amherst.
Possum links
