Didelphis albiventris, Lund, 1840

Astúa, D., 2015, Didelphidae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 129-186 : 160-161

53.

Brazilian White-eared Opossum

Didelphis albiventris

French: Opossum a oreilles blanches / German: Stidopossum / Spanish: Zarigleya de orejas blancas de Brasil

Other common names: \ White-eared Opossum

Taxonomy. Didelphis albiventris Lund, 1840 ,

“ Rio das Velhas ,” Lagoa Santa , Minas Gerais, Brazil.

This species is monotypic.

Distribution. NE, C, & S Brazil, SE Bolivia, Paraguay, Uruguay, and Argentina as far S as Buenos Aires Province in the E and the Monte Desert ecoregion in the W.

Descriptive notes. Head-body 30-44.2 cm, tail 29-45 cm; weight 0.5-2.5 kg. Male Brazilian White-eared Opossums are larger than females, and there is sexual dimorphism in skull shape. Dorsal fur is gray to whitish, rarely blackish, consisting of two distinct layers. Underfur is usually white. Guard hairs are long, coarse, and gray-tipped or white-tipped. Head is white, with clearly marked eye mask from nose to near bases of ears. Cheeks are white, and there is a black line on center of forehead, narrowing to a point between eyes. Tail length is about the same as head-body length or slightly shorter, tail is basally furred, and rest oftail is naked and black on proximal one-half or more and white on the rest. Ventralfur is white, gray, or yellowish, paler than dorsum, and throat is white. Ears are large and white or mostly white with a black base. Females have a pouch, with eleven or more commonly 13 mammae, five or six on each side and a medial mamma. The Brazilian White-eared Opossum has a 2n = 22, FN = 20 karyotype, with all acrocentric autosomes, and acrocentric X-chromosome and Y-chromosome.

Habitat. Open and deciduous forest types, including areas of low and irregular rainfall such as the caatinga and Monte Desert habitats. Brazilian White-eared Opossums are very tolerant of habitat disturbance and easily coexist with humans, including in large cities. In the cerrado region, they occur in all major cerrado formations, gallery forests, and wet areas, and they can occur in the Atlantic Forest in contact zones between this and open formations.

Food and Feeding. Diet of the Brazilian White-eared Opossum is mainly composed of invertebrates, but small vertebrates and more than 20 species offruits are also consumed. In a disturbed area of south-eastern Brazil, its diet included mainly Hymenoptera, Coleoptera, and Diplopoda, but also rodents (Cavia, Necromys, Mus, and Rattus), small opossums ( Marmosa ), undetermined reptiles, and fruits of Cecropia (Urticaceae) , Acrocomia (Arecaceae) , and Miconia (Melastomataceae) . The Brazilian White-eared Opossum is considered an opportunistic consumer of fruits because it relies on invertebrates and vertebrates in the dry season. A variety offruits (e.g. species of Moraceae , Myrtaceae , Passifloraceae , Piperaceae , and Solanaceae ) are consumed, mainly in the wet season. It also seems that fruit consumption varies at an individual level. In southern Brazil, a similar diet was found, with invertebrate remains found in 100% of feces analyzed,fruits in 76%, and vertebrates in 58%. Vertebrates consumed included mammals, birds, reptiles, and fishes. Invertebrates included Isopoda, Decapoda, Blattodea, Coleoptera, Hemiptera, Hymenoptera, Lepidoptera larvae, Orthoptera, Opiliones, Diplopoda, and snails. A variety offruits were consumed, such as Syagrus (Arecaceae) , Cucumis , Melothria (Cucurbitaceae) , Erythroxylum (Erythroxylaceae) , Citrus (Rutaceae) , Leandra ( Melastomataceae ), Morus (Moraceae) , Psidium (Myrtaceae) , Passiflora (Passifloraceae) , Piper (Piperaceae) , Rubus (Rosaceae) , Cyphomandra, Solanum , Vassobia (all Solanaceae ), and unidentified Poaceae . The Brazilian White-eared Opossum opportunistically attacks bats (the Great Fruit-eating Bat, Artibeus lituratus, and the Little Yellow-shouldered Bat, Sturnira Lilium) entangled in mist-nets. Snake scales have been found in feces. It is immune to pit viper venom and successfully attacks and consumes pit vipers in captivity. The Brazilian White-eared Opossum has also been seen feeding on exudates of Tapira guianensis ( Anacardiaceae ) in north-eastern Brazil, using trees scratched by Common Marmosets (Callithrix jacchus) during the day. Brazilian Whiteeared Opossums are important disperses of seeds of several plant species. Nutritional contents of preferred diets, determined with cafeteria experiments in captivity where individuals were free to choose food items according to their needs, resulted in 20-9 g of proteins, 27-9 g of carbohydrates, 10-1 g oflipids, and 1-7% offibers per 100 g of dry matter.

Breeding. Female Brazilian White-eared Opossums make nests lined with grass, fur, and feathers in tree holes, logs, and palms. In Argentina, they also routinely use empty chambers in communal nests of monk parakeets (Myiopsitta monachus), where they can be opportunistic predators of eggs and nestlings. Sexual maturity is reached at 4-5-7 months. A female with very incomplete dentition, weighing only 320 g, was found with pouch young in March in Minas Gerais, Brazil; she probably was born early in that same breeding season, suggesting that these opossums may be able to produce two litters during a single breeding season. Gestation is estimated to last 13 days, and young are weaned at c¢.3-5 months of age in Argentina. Length of breeding season is variable and tends to be inversely correlated with latitude: populations at higher latitudes have shorter breeding seasons. They also have larger litters: populations at lower latitudes tend to invest in more and smaller litters because they have longer periods of time with higher resource availability, whereas populations at higher latitudes, which face shorter periods of suitable climate and resource availability, invest in fewer but larger litters. Female Brazilian White-eared Opossums usually show synchronous breeding. Reproductively active females in the Brazilian caatinga (c.7° S) were observed in November—-March. Breeding in the Brazilian cerrado (c.16° S) occurs during the wet season from July or August to April. In south-eastern Brazil (19° S), breeding is from mid-July to March; at 21° §, it is from late July to March, also coinciding with the wet season; in southern Brazil (25° S), itis from late July to April; and in Argentina at 34° S, it is either from late August to early March or, in another study at the same latitude, from mid-August to late February. In the Brazilian caatinga, a single litter was produced per breeding season, but at higher latitudes females had two litters during a breeding season. Average litter size in north-eastern Brazil (9-13° S) is 6-5 young, with 3-9 young in a single site. In central Brazil,litter size ranged from five to seven young; in south-eastern Brazil (19° S), itis seven young (with a maximum of ten); at 21° S, one study recorded an average of 6-2 young and another recorded 5-7 young. In a study at 23° S, average litter size was 7-3 young; in southern Brazil (25° S), nine young; mean litters of 6-9 young recorded in Argentina at 34° S, with as many as nine young perlitter (average of8-8 young was recorded in another study at the same latitude). Mean litters of 9-4 young, with a maximum of twelve young, have also been reported for Uruguay. Nevertheless, as many as 18 embryos have been reported, indicating that females may produce more newborns than actually survive. Onset of breeding in the Brazilian caatinga, at least in lowerlatitudes,is linked to average rainfall, but ultimately, variation in daylength would be the trigger for reproduction.

Activity patterns. The Brazilian White-eared Opossum is nocturnal, with the activity peak right after sunset, followed by a gradual decrease in activity. It has been seen feeding on palms at night.

Movements, Home range and Social organization. Brazilian White-eared Opossums appear to be mostly terrestrial, but they also use understory and are sometimes captured in traps set on trees. Males have been recorded at capture points at least 450 m apart in south-eastern Brazil. Estimated home ranges for the Brazilian White-eared Opossum vary greatly. Home ranges of 0-03-0-4 ha were recorded in an urban forest fragment in south-eastern Brazil; estimates in Argentina were 0-57 ha and 0-05-12 ha; and in an urban fragment in southern Brazil, home ranges were 0-66 ha for females and 0-69 ha for males. In the Brazilian caatinga, home ranges were 0-59 ha for females and 0-77 ha for males. In contrast, estimates of 3-2 ha for males and 1-5 ha for females, with a maximum of 7 ha for a male, were obtained in southern Brazil, with male-male, female—female, and male-female home range overlap recorded. The only study that used radio-telemetry yielded home range estimates of 3-8-6-8 ha in an Atlantic Forest fragment in north-eastern Brazil. Densities of Brazilian White-eared Opossums were 40-440 ind/km? in the Brazilian caatinga, 250 ind/km?in Argentina, and 200-600 ind/km?®in a gallery forest in central Brazil.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Brazilian White-eared Opossum has a wide distribution and presumably a large overall population;it is highly tolerant of habitat modification and human presence and occurs in several protected areas.

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Figures

65. Pygmy Opossum (Chacodelphys formosa), 66. Agricola’s Opossum (Cryptonanus agricola), 67. Chacoan Mouse Opossum (Cryptonanus chacoensis), 68. Guaiba Mouse Opossum (Cryptonanus guahybae), 69. Unduavi Mouse Opossum (Cryptonanus unduaviensis), 70. . Emilie’s. 9 Opossum.. Gracilinanus. (null), 71. Aceramarca Opossum (Gracilinanus aceramarcae), 72. Agile Opossum (Gracilinanus agilis), 73. Wood Sprite Opossum (Gracilinanus dryas), 74. Northern Gracile Opossum (Gracilinanus marica), 75. Brazilian Gracile Opossum (Gracilinanus microtarsus)

Distribution. NE, C, & S Brazil, SE Bolivia, Paraguay, Uruguay, and Argentina as far S as Buenos Aires Province in the E and the Monte Desert ecoregion in the W.