Population, Conservation Status, Threats:
Considered least concern by the IUCN, with populations that appear to be increasing. Mortality is primarily due to collisions with cars and sometimes trapping for fur or as nuisances, but opossums are overall well-adapted to living in and around humans, and benefit from suburban expansion.
Physical Description:
Opossums are the only species of marsupial native to North America. They are a mid-sized, fairly round mammal, with a prehensile tail, agile paws, large ears and a narrow snout. Their paws, tail, and ears are all hairless - they are sometimes mistaken for rats due to these characteristics. Their fur is overall a ticked gray, but white on the face and black on the legs. Recently, it has been noted that they fluoresce under black light - what purpose this feature serves is yet unknown.
Opossum range from Montana Field Guide. In Colorado, they are only found on the eastern plains.
Habitat:
Virginia opossums are adaptable and capable of surviving in a wide variety of habitats, from deserts to marshlands and even urban areas, but they appear to prefer thickly-forested woodland with ample water supply.
Behavior:
Opossums are solitary and nocturnal, and unlike many other animals, do not appear to occupy a permanent home range, instead spending their time wandering far and wide for food. They are skilled climbers, due in part to the opposable thumbs found on their back feet, as well as their prehensile tails capable of wrapping around branches for stability. Notably, opossums are resistant to rabies, apparently due to their relatively low body temperature. The opossum's most distinctive behavior is its tendency to feign death when threatened, lying limp and motionless with its mouth open and tongue lolling, producing a foul-smelling anal gland secretion.
Diet:
Opossums are opportunistic omnivores, taking advantage of any and all food sources they may come across. Carrion, fruits and nuts, invertebrates, bird and reptile eggs, small vertebrates, and fungi are all fair game. In urban and suburban areas, garbage, cat and dog food, and even seed and suet meant for wild birds may supplement their diet.
Reproduction:
Females usually produce two litters each year, but may produce a third in warmer climates. Gestation lasts just under two weeks, after which an average of 6-9 young - called joeys - are born, though litters of up to 20 have been reported. As is the case with other marsupials, the young are born tiny (just half of an inch long) and helpless, and must climb into the mother's pouch immediately after birth to nurse and continue developing. Neonatal mortality is high, and females only have 13 nipples, limiting the maximum of young that can survive from a litter. After around two months in their mother's pouch, young are developed enough to leave, though they continue to cling to their mother's fur for transport, safety, and warmth. Joeys are weaned at around 100 days, and become independent soon thereafter.
Associated Species:
Opossums are credited as being a primary predator of ticks, thereby lessening tick population densities and, subsequently, the occurrence of Lyme disease, in areas with large possum populations. Great horned owls and coyotes predate upon opossums. Raccoons and opossums share diet requirements, nocturnal lifestyles, and both benefit from human settlement, and so can often be found inhabiting the same environments at the same times.
Illustration by Willow Sedam