Gray four-eyed opossum

Gray four-eyed opossum
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Didelphimorphia
Family:	Didelphidae
Genus:	Philander
Species:	P. opossum
Binomial name
Philander opossum (Linnaeus, 1758)
Subspecies
P. o. canus P. o. fuscogriseus P. o. melanuris P. o. opossum
Gray four-eyed opossum range

The gray four-eyed opossum, Philander opossum, is an opossum species from Central and South America, ranging from southern Mexico to Peru, Bolivia and southwestern Brazil, at altitudes from sea level to 1600 m, but generally below 1,000 metres (3,300 ft). Its habitats include primary, secondary and disturbed forest. It is one of many opossum species in the order Didelphimorphia and the family Didelphidae.

Description

It has a sharply defined white spot above each eye, hence the common name. Its prehensile tail is bicolored, with a pale distal part and a longer proximal darker gray part, and is naked at the end. Its testicles drag on the ground behind it as it walks. Its dorsal fur is gray, while its ventral fur, throat, and cheeks are cream-colored. Adults have ears that are black except at the base. Wild specimens weigh 200–674 grams (7.1–23.8 oz), while captive specimens can weigh up to 1.5 kilograms (3.3 lb). Body length ranges from 22.0 to 33.1 centimetres (8.7 to 13.0 in) with a tail in a similar size range, 19.5 to 35.5 centimetres (7.7 to 14.0 in).

Behavior

The species is nocturnal, solitary and partly arboreal. It is usually found in moist areas, often near streams, although it wanders in many different vegetation types. It is a good swimmer.

Gray four-eyed opossums do not have a well defined territory, and home range stability depends on the availability of adequate resources. They are omnivorous, feeding on small animals and vegetation, such as leaves, seeds, and fruits.

The gray four-eyed opossum doesn't "play dead" like the American Virginia opossum. Instead it displays aggression and fights with potential predators. Some displays of aggression include opening the mouth wide and hissing loudly. It is known to be "the fiercest fighter of the opossums". The gray four-eyed opossum is a nocturnal animal but can be active during the day. Although it is terrestrial, it is very good at climbing and swimming. This opossum is scansorial and has agile and swift movements; it seems to be more alert compared to other didelphids. The gray four-eyed opossum is pretty solitary and doesn't do much interacting with other opossums of its kind other than during mating.

The gray four-eyed opossums build nests in hollow trees, tree forks, fallen logs and in ground burrows. These nests are made out of dry leaves. They roll up into a ball while sleeping and although their eyes are actually closed, the white patches of fur above their eyes gives them the appearance of an awake animal.

Scapular Morphology

The shape and morphology of the scapula of the gray four-eyed opossum is highly influenced by forces acting upon the scapula during the early postnatal stages of its life.

Reproduction

Not much is known on how the gray four-eyed opossums conduct their mating rituals but they are in the family Didelphidae and so most likely to be polygynous. This means males compete with other males. There are no courtship displays or pair bonds formed in didelphids.

Reproduction of the gray four-eyed opossum is typically done seasonally, with more young being born during the rainy season when there is an abundance of fruit. During the dry season, less babies are born due to the lack of fruit available. With litter sizes averaging between 4 to 5 young, and with each female producing between 2 to 4 litters per year, success may seem high. Sadly this is not the case. Many young die while nursing in mom's pouch. This death rate is especially high during the dry season. A huge factor that determines survival of young is the mothers age. There are a large number of deaths when the female is less than 11 months.

The average gestation period for the gray four-eyed opossum is between 13 to 14 days, and each young weighs about 9 grams (0.32 oz) when they are born. They nurse in their mother's pouch until they are 68 to 75 days old. Once weaned, they stay in their mother's nest for 8 to 15 days before their mother becomes aggressive and basically kicks them out.

Diet

The gray four-eyed opossum has an omnivorous diet containing fruits, nectar, insects, small mammals (such as mice), birds, reptiles, amphibians, crustaceans, snails, and earthworms. Its diet varies depending on the season.

With such a varied diet, the gray four-eyed opossum will both encounter and eat venomous snakes. While the bites of these venomous snakes may be harmful to most animals, the gray four-eyed opossum is able to overcome the toxic affects due to its immunity to the toxins. The immunity to these toxins were initially thought to come from an immune response leading to the production of antibodies, but this is not the case. The immunity comes from toxin-neutralizing proteins found in opossum serum. These proteins are produced by the opossum prior to any encounter with a venomous snake, thus this immunity is not learned but inherited.