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Gray and Black "Four-eyed" Opossums
P. opossum (gray "four-eyed" opossum), from northeastern
Mexico to northeastern Argentina;
P. mcilhennyi (black "four-eyed" opossum), from central Peru.
Head and body length is 250-350 mm, tail length is 253-329 mm, and
adult weight in the wild is usually 240-400 grams. According to
Collins (1973), however, healthy, well-fed captive males weighed
800-1,500 grams and females, 600-1,000 grams.
The fur is rather straight and short in the gray (P. opossum)
but much longer in the black (P. mcilhennyi). The upper parts
are gray to black, with a white spot above each eye, and the
underparts vary from yellowish to buffy white. The white spots above
the eyes account for the vernacular name "four-eyed" opossum. The
tail, which is furred for about 50-60 mm from the rump and naked
toward the tip, is black or grayish black on its basal half and
white toward the end, with a pink tip. The body is slim and usually
lean, and the head is large, with an elongate, conical muzzle. The
ears are naked. The tail is slender, tapering, and prehensile.
Females have a distinct pouch. The number of mammae varies from five
to nine.
These opossums inhabit forested areas and are often found near
swamps and rivers. They are smaller and more agile than Didelphis
and quick in their actions. Although good climbers and swimmers,
they are mainly terrestrial. All 46 specimens taken in Venezuela by
Handley (1976) were caught in moist areas, nearly always on the
ground. They build globular nests, about 30 cm in diameter, in the
lower branches of trees or in bushes, and they may also inhabit
ground nests and burrows. They are thought to be mainly nocturnal,
though Husson (1978) stated that in Surinam they are as active in
the day as at night.
Their diet includes small mammals, birds and their eggs, reptiles,
amphibians, insects, freshwater crustaceans, snails, earthworms,
fruits, and probably carrion. Occasional damage to fruit crops and
cornfields has given them a bad reputation in certain areas. In
Panama, Fleming (1972) found maximum population densities of
0.55-0.65 per ha.
These opossums are not known to feign death when danger threatens,
like Didelphis, but will open the mouth wide, hiss loudly, and fight
savagely. When disturbed they may utter a long, chattering cry.
The gray four-eyed opossum (P. opossum) reportedly breeds all
year in some areas, possibly including Veracruz, Mexico, but is
seasonal in others (Hunsaker and Shupe 1977). Collins (1973) cited
records of females with pouch young being taken in Nicaragua from
February to October, in Panama from April to July, and Colombia in
June, September, and October. Jones, Genoways, and Smith (1974)
caught a female with six nursing young in March on the Yucatan
Peninsula. Phillips and Jones (1969) collected data indicating that
the main reproductive season in Nicaragua extended from March
through July. Litter size there averaged 6.05 (3-7). According to
Fleming (1973), the gray (P. opossum) is seasonally
polyestrous in Panama, with two or more litters probably being
produced by each female from January to November. Litter size
averaged 4.6 (2-7). Husson (1978) found females with young in
Surinam during January, March, and April. Litter size there ranged
from 1 to 7 but averaged only 3.4. These records support the
statement by Phillips and Jones (1969) that litter size tends to be
larger in the north. Collins (1973) reported that the small pouch
young of a female received on 7 May were weaned on 23 July, that
first estrus in females occurred at 15 months of age, and that
maximum known longevity for captives was only 2 years and 4 months.
Brown "Four-eyed" Opossum
The single species, M. nudicaudatus, is found from southern
Nicaragua to northeastern Argentina. Because of technical problems
of nomenclature, there has been recent argument regarding which
generic name properly applies to this species. Hershkovitz (1976,
1981) supported Metachirus, which has been in more general use,
while Pine (1973a) favored Philander Tiedemann, 1808, at least for
the time being. Hall (1981) followed Pine in applying Philander to
the brown "four-eyed" opossum, but Corbet and Hill (1986), Gardner
(1981), Honacki, Kinman, and Koeppl (1982), and Kirsch and Calaby
(1977) agreed with Hershkovitz. The generic designation Philander is
actually applicable to the gray and black "four-eyed" opossums and
is so employed here, again in accordance with Hershkovitz (1976,
1981) and his backers, rather than the name Metachirops, which was
used by Pine (1973a) and Hall (1981).
Head and body length is about 265 mm and tail length is
approximately 330 mm. A male and a female from Barro Colorado
Island, Panama Canal Zone, each weighed 800 grams. The back and
sides are brown, often dark cinnamon brown, and the rump may be
washed with black. The face is dusky, almost black in some
individuals, with a creamy white spot over each eye. These spots,
suggesting eyes, are usually smaller and more widely separated than
those of Philander. The underparts are buff to gray. The tail is
furred for a short distance basally. The pelage is short, dense, and
silky.
Although the common names and general appearance of Metachirus and
Philander are similar, the two are not closely related. Metachirus
may be distinguished externally by its brown coloration and longer
tail. Unlike the gray and black "four-eyed" opossums, the females of
Metachiruslack a pouch, having instead simple lateral folds of skin
on the lower abdomen, in which are located the mammae. Females with
five, seven, and nine mammae have been recorded (Collins 1973).
Kirsch (1977c) observed of didelphids, Metachirusis almost quiet
when held in the hand.
The brown "four-eyed" opossum lives in dense forests or in thickets
in open, brushy country. It builds round nests of leaves and twigs
in tree branches but occasionally males its shelter under logs or
rocks. Handley (1976) reported that all 18 specimens taken in
Venezuela were caught on the ground, mostly near streams or in other
moist areas. Members of this genus are completely nocturnal, rarely
moving from the nest until dark. The diet includes fruits, insects,
mollusks, amphibians, reptiles, birds, eggs, and small mammals.
Metachirus has been accused of damaging fruit crops in some areas.
Limited data indicate that this opossum is seasonally polyestrous
(Fleming 1973). It reportedly breeds November in Central America,
has litters of one to nine young, and probably has a maximum life
span of three to four years (Hunsaker 1977b). The single, 51-mm
young of a female obtained on 18 December was then already able to
stand alone. It later rode on its mother's back or hips and was
fully independent by early February (Collins 1973).
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