Marmosops fuscatus (Thomas, 1896)

Astúa, D., 2015, Didelphidae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 129-186 : 185-186

102.

Dusky Slender Opossum

Marmosops fuscatus

French: Opossum sombre / German: Dunkle Schlankbeutelratte / Spanish: Marmosa esbelta oscura

Other common names: Dusky Slender Mouse Opossum, Gray-bellied Slender Mouse Opossum

Taxonomy. Marmosa fuscata Thomas, 1896 ,

“ Rio Abbarregas [= Rio Albarregas],” Merida, Venezuela, alt. 1630 metres.”

Three subspecies are recognized.

Subspecies and Distribution.

M.f.fuscatusThomas,1896—W&NVenezuela(CordilleradeMéridaandthecoast).

M.f.carriJ.A.Allen&Chapman,1897—TrinidadI.

M. f. perfuscus Thomas, 1924 — NC Colombia (Eastern Andes).

Descriptive notes. Head-body 12-15.5 cm, tail 14.8-18.2 cm; weight 41-104 g. The Dusky Slender Opossum has gray-brown dorsal fur. Head is similarly colored but paler between black eye-rings. There is no mid-rostral stripe. Cheeks are whitish. Tail length is c.120% of head-body length, and tail is robust, gray, paler toward distal end, and slightly pale below. Ventral fur is uniformly gray, frosted or yellowish. Fur is 6-10 mm long on back and slightly stiff. Females lack a pouch, but number of mammae is unknown. The Dusky Slender Opossum has a 2n = 14, FN = 24 karyotype, with all biarmed autosomes, a biarmed X-chromosome, and an acrocentric Y-chromosome. Skull size and shape are sexually dimorphic.

Habitat. Wet evergreen forests from near sea level to 2350 m, including montane wet forests and cloud forests, but also in clearings and gardens. Dusky Slender Opossums are frequently collected at sites near streams or other moist areas.

Food and Feeding. There is no specific information available for this species, but the Dusky Slender Opossum reportedly eats fruits and invertebrates.

Breeding. Sexual maturity of the Dusky Slender Opossum is reached at c.6 months old, and reported litter size is six young, although females were captured with 7-9 teats secreting milk, suggesting largerlitters may occur. Females raise 1-2 litters/year. Breeding season probably extends from May to January/February because lactating females were captured in November—-December and juveniles in September, November-December, and March in a secondary forest; lactating females were also captured in May-November in a humid pre-montane forest.

Activity patterns. There is no specific information available for this species, but the Dusky Slender Opossum is reported to be nocturnal.

Movements, Home range and Social organization. The Dusky Slender Opossum reportedly uses arboreal strata more than the ground, having been captured in both, but more frequently (c.70% of the time) in trees and vines than on the ground. Nevertheless, in another study, captures on the ground represented 93% oftotal captures, and released specimens always fled on the ground, even when placed on branches or vines. At a site in a pre-montane humid forest at ¢.700 m in elevation, male Dusky Slender Opossums moved an average of 30-9 m between captures, with a maximum distance of 63 m, and females moved an average of 58-5 m, with a maximum of 172 m. In contrast, in a secondary forest at 40 m in elevation, average distance moved between captures by a male was 85 m, with a maximum distance of 200 m. Densities of Dusky Slender Opossums in Venezuela are 25-325 ind/km?, with an average of 100 ind/km?®.

Status and Conservation. Classified as Data Deficient on The IUCN Red List. Conservation status of the Dusky Slender Opossum is unknown because of lack of recent information on its extent of occurrence, estimates of overall population size, and ecological requirements. It is possible that the Dusky Slender Opossum is actually under conservation threat because there are significant human impacts within much of its known distribution; native habitats are being converted into cultivated land and human settlement. Nevertheless, the Dusky Slender Opossum occurs in several protected areas.

Bibliography. Abdala et al. (2006), Astua (2010), Cordero (2001), Eisenberg (1989), Emmons & Feer (1997), Gardner (2005), Gardner & Creighton (2007a), Handley (1976), O'Connell (1979, 1989), Reig et al. (1977), Tate (1933).

Figures

76. Patagonian Opossum (Lestodelphys halli), 77. Karimi’s Fat-tailed Opossum (Thylamys karimii), 78. Dwarf Fat-tailed Opossum (Thylamys velutinus), 79. Elegant Fat-tailed Opossum (Thylamys elegans), 80. Pallid Fat-tailed Opossum (Thylamys pallidior), 81. Tate's Fat-tailed Opossum (Thylamys tatei), 82. Mesopotamian Fat-tailed Opossum (Thylamys citellus), 83. Dry Chaco Fat-tailed Opossum (Thylamys pulchellus), 84. Chacoan Fat-tailed Opossum (Thylamys pusillus), 85. Paraguayan Fat-tailed Opossum (Thylamys macrurus), 86. Argentine Fat-tailed Opossum (Thylamys sponsorius), 87. Buff-bellied Fat-tailed Opossum (Thylamys venustus), 88. Bishop's Slender Opossum (Marmosops bishop), 89. Junin Slender Opossum (Marmosops juninensis), 90. Delicate Slender Opossum (Marmosops parvidens), 91. Pantepui Slender Opossum (Marmosops pakaraimae), 92. Pinheiro’s Slender Opossum (Marmosops pinheiroi), 93. Handley’s Slender Opossum (Marmosops handleyi), 94. Gray Slender Opossum (Marmosops incanus), 95. Brazilian Slender Opossum (Marmosops paulensis), 96. Neblina Slender Opossum (Marmosops neblina), 97. Tschudi’s Slender Opossum (Marmosops impavidus), 98. Spectacled Slender Opossum (Marmosops ocellatus), 99. Creighton’s Slender Opossum (Marmosops creightoni), 100. White-bellied Slender Opossum (Marmosops noctivagus), 101. Narrow-headed Slender Opossum (Marmosops cracens), 102. Dusky Slender Opossum (Marmosops fuscatus), 103. Panama Slender Opossum (Marmosops invictus)

Subspecies and Distribution. M.f.fuscatusThomas,1896—W&NVenezuela(CordilleradeMéridaandthecoast). M.f.carriJ.A.Allen&Chapman,1897—TrinidadI. M. f. perfuscus Thomas, 1924 — NC Colombia (Eastern Andes).