Didelphis virginiana Photo Fiona Sunquist ©
If someone asks you to name a mammal with a pouch, odds are you’d say ‘kangaroo’. But you’d also be right if you said ‘opossum’.
Opossums grow throughout their short lives, resulting in considerable size and weight differences; they range from about 1 kg (2.2 lbs) to 6 kg (13 lbs) and males are larger and heavier than females.
About the size of a domestic cat, they have a pointed nose with long, highly sensitive whiskers, thin, leaf-like ears and a nearly naked, prehensile tail that is black at the base and pinkish for the remainder. Opossums often wrap their tails around branches when they climb to help them balance, but contrary to popular belief, they rarely hang by their tails. Whenever you see a photograph of an opossum hanging by its tail you can be fairly sure it is because the photographer posed it that way,
Opossum feet are adapted for climbing, and all the toes, except the opposable thumb on the hind foot have claws. Females have a fur-lined pouch on the abdomen.
Opossums are found in a variety of forested habitats and survive well in suburban areas where they are often considered pests because of their habits of raiding garbage cans. They spend the day resting in tree cavities, hollow logs or underground burrows and emerge after sunset to search for food. They eat practically anything, including fruit, insects, worms, small vertebrates, carrion, garbage and pet food.
In Florida opossums begin to breed in January. The young are born in an embryonic state after a 13-day gestation. The bee-sized babies emerge from the birth canal and make their own way to the mother’s pouch where they attach their mouths to a nipple. Micro-barbs on the babies’ lips and tongue fit into small grooves on the nipples, essentially sealing each young to a teat. The usual litter size in Florida is seven.
The young grow fast; by 65 days their eyes are open, they are well furred and about the size of large mice. They can be detached from the nipple and will crawl about on the mother’s fur as she rests. The pouch becomes crowded and it is difficult for the mother to walk with all the young in the pouch. At this stage some of the babies begin to ride on the mother’s back, grasping wedges of her fur in their mouth and feet. This is a hazardous time of their lives – babies regularly fall off and get left behind. Wildlife rescue services get many phone calls from distressed homeowners who find squawking baby opossums in the back yard after the family dog has chased the mother.
When the young are about 80 days old the litter becomes too cumbersome for the mother to carry, and she leaves them in a den while she forages. By 100 days of age the young are weaned and on their own, and the female has a new litter in the pouch. The youngsters begin to forage around the den, gradually expanding their range, but they are extremely vulnerable at this age; Great horned owls, foxes, snakes and other predators kill 90% of newly independent young.
Although they can live to be three or, rarely four years old in captivity, the majority of wild opossums live less than two years. But despite their short lifespan and ‘primitive’ system of reproduction, Virginia opossums are one of the most successful mammals in North America. Before European settlement of North America, the northern limits of their range were Kentucky, Indiana and Ohio, but the species is now found as far north as the Great Lakes and Canada. Opossums are abundant in Florida and frequently seen, especially as road kill.
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