2. Derby's Woolly Opossum Caluromys derbianus French: Opossum de Derby / German: Derby-Wollbeutelratte / Spanish: Raposa lanuda de Derby Other common names: Central American Woolly Opossum, Derby's Pale-eared Woolly Opossum Taxonomy. Didelphys derbiana Waterhouse, 1841, type locality unknown. Restricted by A. Cabrera in 1958 to “ Valle del Cauca, Colombia.” Revision using modern techniques may change taxonomic status of subspecies of C. derbianus. Six subspecies recognized. Subspecies and Distribution. C.d.derbianusWaterhouse,1841—mostofPanama,WColombia,andWEcuador,inthelowlandsandPacificsideoftheAndes. C.d.aztecusThomas,1913—SMexico(Veracruz,Tabasco,Oaxaca,NWChiapas). C.d.centralisHollister,1914—SECostaRica,WPanama(Ncoast). C.d.fervidusThomas,1913—SMexico(ETabasco,NEChiapas,Campeche),Belize,andGuatemalatoHondurasandN&ENicaragua. C.d.nauticusThomas,1913—PacificcoastofPanama(BahiadeMuertos,Chiriqui,andCoibaI). C. d. pallidus Thomas, 1899 — C & W coast of Nicaragua, Costa Rica, and extreme W Panama (Pacific coast). Descriptive notes. Head—body 22.5-30 cm, tail 38.4-44.5 cm; weight 245-370 g. Dorsal fur of Derby’s Woolly Opossum is rich reddish-brown on shoulders, rump, and outer surfaces of legs and pale gray on lower legs. Sometimes a pale gray mid-dorsal stripe is present between shoulders. Head is pale gray, with a dark brown mid-rostralstripe, brown eye-rings, and gray cheeks. Tail length is ¢.160% of head-body length,tail has fur on 30-50% ofits length dorsally and ¢.25% ofits length ventrally, and difference between extent of dorsal and ventral fur is 6-5 cm or less. Naked part oftail is pale and mottled with brown spots, particularly in middle portion. Ventral fur is buffy white to golden tawny and long, dense, and woolly. Forefeet are creamy white, hindfeet are brown, and ears are naked and whitish or pink. Eyes in species ofthis genus are unique within the family Didelphidae in that they are not black but dark brown, with a black pupil. Designation of subspecies of Derby’s Woolly Opossumsis based on considerable geographical and non-geographical variation in fur color, with some specimens mainly or entirely pale gray, with less distinct facial markings. Sometimes younger specimens can be grayer than adults. Females have a complete pouch that opens forward. Actual number of mammae has not been reported, butlitters of four young have been observed. Derby’s Woolly Opossum has a 2n = 14, FN = 24 karyotype, with all biarmed autosomes and small acrocentric Xand Y-chromosomes. Y-chromosome has sometimes been described as a very small telocentric, and FN karyotypes varying from 20 to 24 have been reported. Skull size and shape of Derby’s Woolly Opossum are sexually dimorphic. Habitat. Primary and disturbed tropical humid forests from sea level to elevations of ¢.2500 m, as well as dry forests, gardens, and plantations. Food and Feeding. There are no studies focused directly on assessing diet of Derby’s Woolly Opossum. It is usually assumed that it feeds on insects and fruits, and it probably has a diet similar to that of the two other species in the genus: the Brown-eared Woolly Opossum (Caluromys lanatus) and the Bare-tailed Woolly Opossum (Caluromys philander). Occasionally, Derby’s Woolly Opossum has been seen visiting flowers of Mabea occidentalis (Euphorbiaceae), Ochroma pyramidale (Bombacaceae), Trichanthera gigantea (Acanthaceae), Kigelia pinnata (Bignoniaceae), and Marcgravia nepenthoides (Macgraviaceae) in Central America to feed on nectar, and it seemingly acts as a pollinator for some of these species. Captive individuals refused to attack adult live mice, but they readily accepted freshly killed ones. Young mice were eaten dead or alive, indicating that Derby’s Woolly Opossums may occasionally prey on small vertebrates in the wild. They manipulate food with their hands to bring it to their mouths, chewing one bite at a time. Feeding experiments in Panama showed that Derby’s Woolly Opossum prefers soft fruits such as Ficus insipida (Moraceae), Eugenia nesiotica (Myrtaceae), and Spondias mombin (Anacardiaceae) to hard-skinned fruits such as FE yoponensis or Lacmellea panamensis (Apocynaceae). Derby’s Woolly Opossums also feeds on insects such as grasshoppers and cicadas, when offered. Breeding. Female Derby’s Woolly Opossums make nests with dead leaves in tree hollows. Sexual maturity is reached at 7-9 months. Estrous females have been recorded all year long, with an estrous cycle of 16-39 days, usually ¢.27-29 days. Reported litter sizes in Nicaragua were 2—4 young, with an average of 3-3 young. Breeding of Derby's Woolly Opossums has been observed in January-September, and it is possible that they breed all year long. Activity patterns. Derby’s Woolly Opossums are strictly nocturnal in captivity. Captive individuals were most active in the middle of the night, although some individuals were active just before sunrise and after sundown. Movements, Home range and Social organization. Derby’s Woolly Opossums are arboreal, and they use theirtails for balance and grasping during arboreal locomotion, moving with a symmetrical gait, usually a trot sequence. They are probably essentially solitary, although there is no documentation of that. Known defensive behavior includes raising one forefoot while making a typical hissing sound and baring teeth. Agonistic vocalizations are squeals lasting 0-5 seconds, 3-6 kHz. Status and Conservation. Classified as Least Concern on The IUCN Red List. Although Derby’s Woolly Opossum may be affected locally by deforestation, because some populations are rapidly decreasing in Mexico and Ecuador due to forest loss, it is widely distributed, with presumably large populations, and it also occurs in several protected areas throughout its distribution. Apart from habitat loss, there are no major conservation threats to Derby’s Woolly Opossum. It was formerly hunted for its fur but apparently no longer. Bibliography. Abdala et al. (2006), Astua (2010), Astua & Leiner (2008), Biggers (1967), Biggers et al. (1965), Bucher & Hoffmann (1980), Cabrera (1958), Emmons & Feer (1997), Gardner (2005, 2007a, 2007e), Gribel (1988), Hall & Dalquest (1963), McNab (1982, 2005), Medellin (1991), Phillips & Jones (1968), Reig et al. (1977), de Souza et al. (2013), Steiner (1981), Tschapka & von Helversen (1999).

Published as part of Astúa, D., 2015, Didelphidae, pp. 129-186 in Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona :Lynx Edicions on pages 131-132, DOI: 10.5281/zenodo.6685333