Caluromys philander
bare-tailed woolly opossum

Bare-tailed woolly opossums, Caluromys philander, are found in the rainforests of South America. The northern end of their range is delimited by the Venezuelan Andes and extends east along the South American coast line to north-central Brazil. It then continues south in an east-heading arc that rejoins the Atlantic Costal-forest around 15-degrees south latitude. Their range follows the coast to about 28-degrees south latitude, which is their apparent southern limit. Bare-tailed woolly opossums are found in the interior rainforest to about 55-degrees west longitude including parts of the Bolivian lowland rainforest. They range up to 1,800 m in elevation in primary and secondary growth forests and are also found on the island of Trinidad. (Eisenberg and Redford, 1999; Eisenberg, 1989; Emmons and Feer, 1997)

Bare-tailed woolly opossums are highly arboreal. In studies of habitat use and partitioning they were rarely, if ever, found on the ground and seldom found in the understory. They are found in both primary- and secondary-growth evergreen tropical rainforests. They are known from damage to orchards and banana plantations. The preferred habitat of C. philander is not clear, and varies dependent upon season, geographic locality, food availability, and reproductive status. These animals show a preference for denser canopy within their habitat, likely for concealment from predators. They nest in tree hollows lined with leaves or in leaf-nests in the canopy. (Eisenberg and Redford, 1999; Eisenberg, 1989; Grelle, 2003; Husson, 1978; Julien-Laferriere and Atramentowicz, 1990; Julien-Laferriere, 1999; Leite, et al., 1996)

Bare-tailed woolly opossums are medium-sized new-world arboreal opossums. Their weight ranges from 140 g to 390 g, with females being smaller than males. The average caloric intake for a 300 g individual is approximately 300 kJ/day. The body length, head to base of tail, is 160 mm to 279 mm and is always less than the length of the tail. The tail ranges from 250 mm to 405 mm in length. Outside ear length is 30 mm to 40 mm and hind foot length is 33 mm to 40 mm. The dental formula is I 5/4, C 1/1, P 3/3, M 4/4. The species has a distinctive post orbital process that can help distinguish it from other Neotropical marsupials. (Atramentowicz, 1995; Eisenberg and Redford, 1999; Eisenberg, 1989; Emmons and Feer, 1997; Husson, 1978; Schmitt and Lemelin, 2002)

The fur is generally soft and thick, with individuals in the lowlands having shorter coats than those in the uplands. The pelt has also been referred to as woolly, but all members of the genus Caluromys have a “woolly” pelt. The back is a reddish-brown with gray gradating in along the flanks. The belly is a yellowish-orange to gray color. The head is gray with three distinct dark-brown strips; one runs down the bridge of the muzzle from crown to nose and the other two extend from dark-brown eye-rings to the nose. The tail is furred for the first tenth to quarter of its length with a sharp demarcation between the furred and bare portions. The furless portion of the tail is cream to dark-gray or dark-brown in color, and is usually mottled with brown or white spots. Like many other Didelphidae the tail is also prehensile and helps with climbing, balancing, and grasping. (Atramentowicz, 1995; Eisenberg and Redford, 1999; Eisenberg, 1989; Emmons and Feer, 1997; Husson, 1978; Schmitt and Lemelin, 2002)

The eye-shine of bare-tailed woolly opossums is yellow and makes the eyes appear small. Females have a vestigial pouch, termed a marsupium, which is only present when they are carrying young. They also have seven mammae concealed by the marsupium. (Atramentowicz, 1995; Eisenberg and Redford, 1999; Eisenberg, 1989; Husson, 1978; Schmitt and Lemelin, 2002)

The mating system of C. philander is little understood. Individuals are solitary except when males are courting females. Courtship may simply occur through chance meetings as the territories of many individual overlap. (Eisenberg and Redford, 1999; Eisenberg, 1989; Julien-Laferriere, 1995)

Bare-tailed woolly opossums have up to 3 litters per year, but this is dependent upon resource availability. In one study, the breeding season was defined as beginning in September when there was an increase in the number of pregnant females concurrent with an increase in resource availability.

The average number of young varies greatly throughout the year dependent upon resource availability, habitat type, local conditions, as well as female age and mass. A female can have up to 7 young at once, but the average is 4.17 in the wild. There does not appear to be any additional cost to the female for large litters. It seems that the costs are borne by the young who are weaned at a smaller size in large litters than in small litters, indicating that regardless of litter size, female investment in any given litter is approximately constant.

Bare-tailed woolly opossums have a relatively short gestation period followed by an extended period of parental care. The gestation lasts only 24 days, and the young are born weighing less than 200 mg, with a length of 10 mm. This short time in utero is made up for by an extended period (up to 120 days) of pouch time. This period has two sub-periods, day 1 to 92, when the young are attached to the teat, and day 93 to weaning, when the young make short external excursions. The time in the pouch is followed by another 30 to 45 days in the mother’s nest. After this period the young leave the protection of the mother. The importance of leaving the maternal nest is demonstrated by the behavior of young in captivity. When young have not been removed after this period, they have been observed to cannibalize their mother.

Females reach sexual maturity around 270 days of age. The age of sexual maturity for males is not known. Little is known about the estrous cycle, but direct contact with males seems to induce fertility. This is hypothesized to result from pheromonal or behavioral cues from the male. (Atramentowicz, 1992; Atramentowicz, 1995; Guillemin, et al., 2000; Julien-Laferriere and Atramentowicz, 1990; Julien-Laferriere, 1995; Perret and Benmbarek, 1991)

In bare-tailed woolly opossums, care for the young is the singular responsibility of the female. After the short gestation period, the young are born quite undeveloped and altricial, requiring as much as 120 days in the marsupium to complete their development. Over the 144 to 159 days of care the mother protects and feeds them without any other assistance. Little is known about post dependence interactions. (Eisenberg and Redford, 1999; Eisenberg, 1989)

Little is known about the lifespan of bare-tailed woolly opossums. Captive animals have lived for up to five years and animals of a minimum age of 31 to 41 months were captured in a mark-recapture study. (Gewalt, 1990; Julien-Laferriere and Atramentowicz, 1990)

Bare-tailed woolly opossums are an arboreal species; they are rarely found in the understory and never on the ground. They prefer a dense upper-canopy for protection and nest in tree hollows or leaf nests within the canopy. They are nocturnal and tend to be more active for longer periods during the new moon apropos to the full moon. Nightly activity consists of foraging over their territory. Foraging duration lasts an average of 72.2 minutes followed by a period of rest and it is uncommon for more than two trees to be visited per night. C. philander has not been observed entering daily or seasonal torpor.

C. philander is not a very territorial species. Territories are loosely defended; male territories overlap and contain the territories of several females. Territory expanse depends on the sex and size of the individual and the level of resource availability. Depending on resource availability, population density ranges from 51 individuals per square-kilometer in primary forest to 151 individuals per square-kilometer in secondary forests. Encounters between individuals are agonistic and in lab studies a discreet social hierarchy was found to exist based on individual size with larger individuals being dominant. This limited the amount of overtly aggressive behavior during encounters, likely as a means of preventing unnecessary injury. Bare-tailed woolly opossums, however, are not docile and if attached or trapped they will bite. (Eisenberg and Redford, 1999; Eisenberg, 1989; Grelle, 2003; Julien Laferriere, 1997; Julien-Laferriere and Atramentowicz, 1990; Julien-Laferriere, 1995; Julien-Laferriere, 1999; Leite, et al., 1996)

The home range of a bare-tailed woolly opossum ranges from 1.3 hectares to 8.9 hectares with an average of 3.1 hectares for adults. This area may not be held exclusively by one individual and may overlap with the home ranges of several others. These areas may also be very liquid and transient. Juveniles exhibit a very high degree of dispersal from their natal territory. Adults exhibit similar characteristics with an average territory residency time of 7.7 months and a maximum residency of 21 months. Home range extent is dependent upon the age and sex of the individual; adults have larger home ranges than juveniles and females have larger home ranges than males. Home ranges have several core areas within them. The average number of core areas per territory is 4.4 and these seem to be based on food trees and not den sites. (Eisenberg and Redford, 1999; Eisenberg, 1989; Julien-Laferriere, 1995)

Bare-tailed woolly opossums are generally quiet animals; they move as silently as possible through the tree branches. Most of their communication occurs during intraspecific encounters. In these cases they hiss in a manner similar to other opossums unless it is an encounter between a courting male and receptive female. They are also known to make clicking sounds and in the suckling young this is believed to strengthen the bond between mother and young. When taken by a predator, bare-tailed woolly opossums are known to give a distress scream. (Eisenberg and Redford, 1999; Eisenberg, 1989; Emmons and Feer, 1997)

Given the feeding habits of bare-tailed woolly opossums, it is likely that they have a developed sense of smell to help them find ripe fruit and flowers. The eyes and ears are also large and likely help them navigate the night-time forest and capture insects. These attributes make it likely that the animals also use some sorts of visual communication (such as body postures) and chemical communication (such as pheromones hypothesized to be important in inducing ovulation). Tactile communication is undoubtedly important during mating, as well as between a mother and her young.

C. philander is omnivorous; the diet is composed of approximately 25 percent arthropods and 75 percent fruit, nectar, and tree gum. Because of the seasonal availability of food, the diet varies greatly throughout the year. During the wet-season, fruits and arthropods are much more abundant, whereas during drier periods, flowers and gums are much more common. Because of this, bare-tailed woolly opossums have a long colon and well developed caecum to help with the processing of fibrous material. They eat ripe fruit, and are able to determine ripeness by non-visual queues as they feed on brightly-colored as well as cryptically-colored fruit. (Julien-Laferriere and Atramentowicz, 1990; Julien-Laferriere, 1999; Leite, et al., 1996; Linares, 1998)

Beetles and butterflies are the primary arthropods they prey upon, but other insects are taken. Two tree-species make up their primary diet; these are Eperua falcate, for nectar, and Symphonia globulifera, for fruit and nectar. Sixty-four percent of the fruit intake for bare-tailed woolly opossums in French Guiana came from five tree-species: Symphonia globulifera, Tapirira guianensis, Dacryodes nitren, Licania robusta and Humiriastrum subcrenatum. Eighty-three percent of the nectar diet came from three tree-species: Eperua falcate, Symphonia globulifera, and Norantea guianensis. (Julien-Laferriere and Atramentowicz, 1990; Julien-Laferriere, 1999; Leite, et al., 1996; Linares, 1998)

Given the moderately small size of bare-tailed woolly opossums, they are a prey item for many species. Arboreal nocturnal snakes and cats, such as Leopardus wiedii, are suggested as predators. Additionally, raptors, such as Morphnus guianensis, and the Strigidae are implicated. (Husson, 1978; Julien Laferriere, 1997)

The role of bare-tailed woolly opossums in tropical forests is not specifically known. They likely play host to many parasites. They also likely aid some small-seeded fruit-bearing tree-species in the dispersal of seeds and in the pollination of other species. They certainly are important for forest-floor species, as they knock down fruit from the overstory. One final role is that of a tasty protein morsel for many species of arboreal predators. (Perret and Benmbarek, 1991; Schmitt and Lemelin, 2002)

The only obvious economic benefit from bare-tailed woolly opossums has been in research. They have been used to study primitive gait patterns and for a limited amount of evolutionary investigation. (Perret and Benmbarek, 1991; Schmitt and Lemelin, 2002)

There is some evidence that bare-tailed woolly opossums have done damage in banana plantations, but given their size and population density, this is very limited in scope. (Husson, 1978)

Bare-tailed woolly opossums are not listed as a species of conservation concern. They are small and able to adapt to various types of neotropical forests, are not involved in trade, or considered a pest to humans. However, as deforestation continues in neotropical regions, it is likely that this species will face growing pressure.

C. philander has a wide geographic range and is know by many common names. These are: bare-tailed woolly opossum (English), yellow opossum (German), Awari (Surinamese), philander or Wollige opossum (Dutch), comadreja lunuda cola desnuda or comadreja rabuda (Venezuelan), Mucura-chichica (Brazilian), kotori o mahihimi (Yanomami). Historically, the species was called both Philander philander and Didelphis philander; these names are no longer commonly used nor are they appropriate. (Emmons and Feer, 1997; Gewalt, 1990; Husson, 1978; Linares, 1998)