BROWN FOUR-EYED OPOSSUM Metachirus nudicaudatus FAUNA PARAGUAY

Metachirus nudicaudatus (E. Geoffrey St-Hilaire 1803)
TAX: Class Mammalia; Subclass Theria; Infraclass Metatheria; Order Didelphimorphia; Family Didelphidae; Subfamily Didelphinae (Myers et al 2006). A single species is recognised in this genus, defined by Burmeister in 1854. The specific name nudicaudatus is taken from the Latin meaning "naked tail". Gardner (2007) recognised five subspecies, that present in Paraguay being M.n.modestus O.Thomas (1923). However the species is in need of revision and one or more of the subspecies may in fact be separate species (Gardner 2007). There has been considerable debate as to which generic name should take precedence for this species. Pine (1973) argued that the colour description provided by Tiedemann (1808) in his description of Philander referred to the pouchless Brown Four-eyed Opossum and that Metachirops Matschie 1916 is the correct designation for the "Grey Four-eyed Opossums". This was based on the mistaken belief that Philander Brisson, (1762) was non-Linnean and therefore unavailable. Hershkovitz (1976) argued that the current use of Philander and Metachirus is correct and has been followed by most authors ever since. Synonyms adapted from Gardner (2007):
Didelphis nudicaudata Geoffroy St-Hilaire 1803:142. Type locality "Cayenne" French Guyana.
Didelphis myosuros Temminck 1824:38. Type locality "Brésil", restricted to Ipanema, São Paulo by Pohle (1927).
Didelphis nudicauda Lesson 1827:212. Incorrect spelling.
Philander nudicaudus Gray 1843:100. Name combination and incorrect spelling.
Didelphys [Metachirus] myosurus Burmeister 1854:135. Name combination and incorrect spelling.
Cuica myosuros Liais 1872:330. Name combination.
[Didelphys (Metachirus)] nudicaudata Trouessart 1898:1236. Name combination.
Metachirus tschudii JA Allen 1900:195. Type locality "Guayabamba" Amazonas, Peru.
Metachirus bolivianus JA Allen 1901:412. Name combination.
Metachirus nudicaudata Bertoni 1914:69. Incorrect gender.
[Didelphis (Metachirus)] tschudii Matschie 1916:268. Name combination.
[Didelphis (Metachirus)] bolivianus Matschie 1916:268. Name combination.
[Didelphis (Metachirus)] colombianus Matschie 1916:268. Name combination.
[Didelphis (Metachirus)] phaeurus Matschie 1916:268. Name combination.
Lutreolina nudicaudata Bertoni 1939:6. Name combination.
[Philander] nudicaudatus Pine 1973:391. Name combination.
ENG: Brown Four-eyed Opossum (Nowak 1991, Redford & Eisenberg 1992); Rat-tailed Opossum (Cimardi 1996).
ESP: Comadreja de anteojos (Massoia et al 2001); Cuica común (Emmons 1999, Redford & Eisenberg 1992); Zarigüeya de cuatro ojos marrón (Emmons 1999); Comadreja de cuatro ojos marrón (Massoia et al 2001); Guayquica amarilla (Massoia et al 2001), Cuica cola de rata, Guaiquica amarilla, Cuica amarilla, Cuica amarillenta, Guaquica (sic) amarillenta (Massoia et al (2006).
GUA: Yupatí (Massoia et al 2001), Guakí, Anguyá-guakí (Massoia et al 2006).
DES: Though this species bares a close physical resemblance to Philander the two genera are not closely related. Slender with a long, conical snout and short, dense, silky pelage. Head boldly-marked, dark blackish-brown with a small creamy-white patch above each eye and a larger creamy-white patch above each ear. Ears dark brown. Dorsally they are brownish with a cinnamon tinge and sometimes with a darker wash to the rump. Some individuals are more grey-brown with a cinnamon-orange tinge to the sides. Ventrally they are whitish or pale cream, extending up to the cheeks and being sharply demarcated from the dorsal colouration laterally. Tail long and mostly naked, being furred only for the basal 5-25mm and greyish in colouration with only sparse hairs along its length. The large feet are pinkish. Scrotum pink in males. The maruspium is lacking in females, though indistinct lateral folds in the abdomen may be present. Females possess a mean of 9 mammae, arranged in two rows of four with a median teat between them. CR - Skull is narrow and slender. Bony palate with two fenestrae. Mares & Braun (2000) give the following measurements for two males from Misiones, Argentina: Greatest Skull Length 58.7mm, 58mm; Condylobasal Length 54.6mm, 53.5mm; Interorbital Width 9.7mm, 9.8mm; Zygomatic Width 31.4mm, 30.6mm; Width of Braincase 18.5mm, 18.5mm; Palate Length 32.2mm, 31.5mm; Length of Nasals 28.5mm, 28mm; Width of Rostrum 9.6mm, 9.7mm; Mandibular Length 45.1mm, 43.3mm. DF: I5/4 C1/1 P 3/3 M 4/4 = 50. Upper P1 about half the size of P2. Mares & Braun (2000) give the following measurements for two males from Misiones, Argentina: Length of Upper Tooth Row 24.6mm, 24mm. CN: 2n=14. FN=24.
TRA: No information.
MMT: A large and robust, cat-like Didelphid, with tail slightly longer than the head and body (c118% HB length). Males are slightly larger than females. HB: Male 23.39cm (17-30cm), Female 22.29cm (15-26.5cm); TA: Male 30.77cm (22.7-37.3cm), Female 29.8cm (17.8-36.3cm); FT: Male 4.37cm (3.5-5.2cm), Female 4.14cm (3.4-4.7cm); EA: Male 3.54cm (2.8-4cm), Female 3.57cm (3.1-4.3cm); WT: Male 281.5g (102-480g), 235.9g (91-345g). (Eisenberg & Redford 1999). Unsexed sample TL: 57cm (46.9-63.8cm); HB: 26.17cm (21-33cm); TA: 30.84cm (24.2-39.5cm); FT: 4.41cm (3.9-5.2cm); EA: 2.96cm (2.2-3.9cm); WT: 225.56g (91-630g). (Massoia et al 2001, Emmons 1999, Redford & Eisenberg 1992). Mares & Braun (2000) give the following measurements for two males from Misiones, Argentina: TL: 57.2cm, 56.9cm; HB: 24.5cm, 24.7cm; TA: 32.7cm, 32.2cm; FT: 4.6cm, 4.1cm; EA: 3.5cm, 3.2cm. The following mean post-cranial measurements were noted by Carvalho et al (2000) for Brazilian specimens (n=3): Ulna 35.4mm; Forearm 40.8mm; Humerus 35.2mm; Tibia 49mm; Foreleg 50.3mm; Femur 39.3mm.
SSP: The only other species to share the "eyes" of Metachirus is Philander frenatus, which unsurprisingly is most easily distinguished by its greyish pelage. When viewed frontally note that the white spots above the eyes are smaller and more widely-spaced in this specoes. The second pair of "eyes" are much more extensive and located behind the ears, those of Philander being reduced and located in front of the ears. Note that the ears of this species are entirely dark, they being pale pinkish in Philander. The tail of Philander is proportionately shorter and furred at the base for the first 6 to 8 cm, as well as being bicoloured with a clearly demarcated tip - that of this species is naked to the base and either uniformly-coloured or becoming gradually paler along its length. Structurally the snout is more pointed and the legs are longer in this species. Note also that female Metachirus do not possess a pouch, whilst those of Philander do.
DIS: Widely distributed from Nicaragua south to Paraguay and northern Argentina. In Argentina the species is known only from the departments of Iguazú and Montecarlo in northeastern Provincia Misiones, with a possible record from Belgrano (Chebez 2009, Massoia et al 2006). It is found only in eastern Paraguay and is absent from the Chaco. Brown (2004) listed the following specimens from Paraguay Departamento San Pedro; Aca Poi (Wharton, 1950, USNM); Tacuati, Aca Poi, S bank Rio Ypané (Wharton, 1950, USNM); Departamento Caaguazú; Caaguazú. Summerfield Colony no. 1 1 (Wharton, 1953, USNM); Departamento Paraguari; Parque Nacional Ybycuí (Myers, 1978, UMMZ); Departamento Canendiyú; Curuguaty (Myers, 1978, UMMZ).
HAB: Generally in forested habitats, including secondary growth, edge habitats and low stature forest. In Minais Gerais, Brazil they were found in all forest types (Redford & Eisenberg 1992). Nowak (1991) states that the species occurs in dense forests and thickets in open, brushy country, but Emmons (1999) notes that they prefer mature forest with an open undergrowth. Moura et al (2005) found that 70% of specimens tracked avoided areas with dense canopy cover. Most specimens in Venezuela were trapped on the ground near streams (Nowak 1991). Stevens & Husband (1998) did not find the species within 80m of forest edge in the Brazilian Atlantic Forest, but Pires et al (2005) found no preference for forest interior over forest edge in a highly fragmented landscape in Rio de Janeiro State, Brazi. Pires et al (2002) stated that the species frequently moves between forest fragments with 10% of 22 recaptures showing evidence of interfragmentory movements and all movements being performed by males.
ALI: Omnivorous, consuming fruits, small vertebrates, birds eggs and invertebrates (Redford & Eisenberg 1992). This species is principally terrestrial and this is reflected in the diet. Cáceres (2004) studied fecal samples of 44 trapped individuals in southern Brazil and found the species to be principally insectivorous. Invertebrate remains were present in 100% of samples, composed of the following frequencies: Coleoptera 68%, Opiliones 64%, Diplopoda 50%, Hymenoptera (Formicidae) 39%, Orthoptera 23%, Blattaria 23%, Decapoda 14%, Lepidoptera larvae 7% and Pulmonata 5%. Vertebrate remains occurred in just 9% of samples, principally birds 5%, mammals 2% and reptiles 2%. Fruit remains were found in 7% of samples: Anthurium sp. 2%, Philodendron sp. 2% (both Araceae) and Nidularium sp. 2% (Bromeliaceae). In Rio de Janeiro State, Brazil Carvalho et al (1999) found Hymenoptera, Arachnida and termites in 75% of all fecal samples, Coleoptera in 50% of samples and Hemiptera and Diplopoda in 25% (n=4). Seeds were also present, notably those of Cecropia sp. The presence of seeds represents frugivory rather than granivory and Cáceres (2004) considered the species an occasional seed dispersers of certain plant species. Of the fruit seeds found in fecal samples by Cáceres (2004) the following percentage germination rate was recorded Anthurium sp. 88%, Philodendron sp. 22% and Nidularium sp. 77%. Santori et al (1995) studied fecal samples from the restinga of Brazil and considered the species principally insectivorous with a preference for Blattaria, Coleoptera, termites and ants, the latter apparently being taken opportunistically as no sign of nests were found in stomachs. Of 19 fecal samples 84.2% contained invertebrates, 26.3% contained vertebrate remains and 10.3% contained seeds. Of the six fecal samples containing vertebrate remains, one contained unidentified mammal remains and five contained reptiles (3 containing the Tropidurid lizard Tropidurus torquatus, 1 a species of Skink Mabuya sp. and the other an unidentified reptile). In order of prevalence the following invertebrate groups were found in samples: Blattaria 94.7%, Hymenoptera (Formicidae) 78.9%, Coleoptera 73.7%, Isoptera 68.4%, Arachnida 15.8% and Orthoptera 15.8%. The remaining groups were all present in one sample, representing 5.3% of the total sample: Diptera pupae, Hemiptera, Unidentified Hymenoptera, Myriapoda and Diplopoda. The presence of Dipteran pupae was considered a possible indication of scavenging behaviour. Seeds were found in three samples, two were unidentifiable, the third belonged to Pilosocereus sp. (Cactaceae). Cáceres (2004) and Morães Junior (2004) trapped animals in wire traps in southern Brazil using banana and cod liver oil as bait. Astúa de Morães et al. 2003 experimentally tested the proportions of protein, lipid, carbohydrate and fibre in the diet of adults (n=22) and juveniles (n=4) of this species under laboratory condtions. Mean proportions per 100g dry weight of food were: protein ad. 8.74g (+/-4.86), juv. 6.53g (+/-1.52); lipid ad. 1.91g (+/-2.30), juv. 1.04g (+/-0.07); carbohydrate ad. 12.88g (+/-10.27), juv. 3.40g (+/-1.99); fibre ad. 1.96% (+/-0.90), juv. 1.23% (+/-0.44). Santori et al (2004) described and illustrated the gut morphology of this species and associated it with dietary habits.
REP: Limited data available, but apparently polyestrous. Breeding occurs in November in Central America. Litter size ranged from 1 to 9 with a mean of 5. Juveniles are carried on the mothers back until able to stand alone (Redford & Eisenberg 1992, Nowak 1991).
BEH: Activity Levels Typically solitary, terrestrial and nocturnal in behaviour. Agile on the ground, they have powerful hindquarters that enable them to run rapidly. Cunha & Vieira (2002) used a spool and line technique to follow 19 individuals of this species in PN Serra dos Orgãos, Brazil and found that only one individual moved above and only once to a height of just 1m in over 3200m of paths followed. Emmons (1999) describes the species as furtive and shy and extremely difficult to observe because of their propensity to flee at the slightest disturbance. However she notes that the species seems to be more active and easier to see after rain. Locomotion Delciellos & Vieira (2006) studied arboreal locomotion of this species on horizontal branches in PN Serra dos Orgãos, Rio de Janeiro State, Brazil. A maximum velocity of 2.88 (+/-0.22) x body length/second was recorded on support branches of 5.08cm diameter, and a minimum velocity of 2.21 (+/-0.15) x body length/second was recorded on support branches of 2.54cm diameter. Minimum number of strides per second was 2.96 (+/-0.16) on support branches of 2.54cm and maximum number of stride lengths per second was 3.65 (+/-0.15) on support branches of 5.08cm diameter. Range of stride length was from 0.75 to 0.85 x body length. Delciellos & Vieira (2009) investigated climbing performance of this species on nylon ropes of three diameters 0.6cm, 0.9 and 1.25cm. Respective velocities (stride length x stride frequency) of 0.14 (+/-0.06), 0.30 (+/-0.20) and 0.39 (+/-0.39) were recorded for the three rope diameters. Number of strides per second respectively were 0.85 (+/-0.33), 0.97 (+/-0.47) and 1.09 (+/-0.64) for the three rope diameters. Stride length when related to body length was 0.18 (+/-0.09), 0.29 (+/-0.09) and 0.32 (+/-0.11) respectively. Home Range A female radio-tracked in Rio de Janeiro, Brazil for three nights during November 2001 covered a home range of 8.4ha, moving a mean of 549.9m (+/-49.5m) per night. It was exclusively nocturnal in behaviour, presenting activity peaks between 20.00h and 23.00h and with activity tailing off after 02.00h. (Morães Junior 2004). Vieira & Cunha (2008) found home range size and intensity of use to be correlated to body mass. Gentile & Cerquiera (1995) performed a mark-recapture study on this species in the Brazilian restinga at Barra de Maricá, Rio de Janeiro State, Brazil. Sampling a 4ha site they found that 71.8% of movements were within the range 41-200m from the original capture site. They considered the species to be highly mobile with local populations part of a metapopulation with a range not restricted to the sampling area. Gentile et al (2004) correlated population density with recruitment in Rio de Janeiro, Brazil. Roosts Loretto et al (2005) noted that the thriteen nests found during their trapping study where located on the ground in areas of undisturbed forest with deep litter layer and tall trees. Nests were spherical and built on the forest floor or between tree roots using leaves interwoven with roots. Entrance too nests were concealed but meausred 10 x 10cm. Nest sites appear to be changed at least every two months. Maximum lifespan is estimated at 3 to 4 years (Nowak 1991). Defensive Behaviour When disturbed runs rapidly and silently away across the forest floor (Emmons 1999). Loretto et al (2005) noted that all animals disturbed at the nest chose to run away, except for a female bearing young who gnashed the teeth, made clicking noises and hissed. The individual raised itself up and down against the roof of the nest creating a pulsating movement of an area of leaves much larger than the animal itself. They hypothesised that this defensive behaviour was exhibited only by females bearing young because of the risks associated with losing young when running rapidly through the forest. Morães Junior (2004) also stated that an animal disturbed at the nest grunted and gnashed its teeth but did not mention the reproductive condition of the animal. Considered the most aggressive opossum species by Enders (1935), who noted that an individual shipped live with a Philander of similar size totally dominated the other animal so that it showed signs of "being bitten severely about the head and neck" and was "totally cowed", whilst the Metachirus was unmarked. However Kirsh (1977) stated quite the opposite and described the species as almost quiet when handled. Enemies Husson (1978) reports the species as being preyed upon by Striped Owl in Surinam. An individual hit by a car in PN Iguazú, Misiones, Argentina was found on 23 October 1994 (Massoia et al 2006). Parasites Limardi (2006) listed the following ectoparasites from Brazilian specimens: Siphanoptera Adoratopsylla sinnuata (Ctenophthalmidae). Acari: Astigmata Didelphoecius validus and Metachiroecius brasiliensis (Atopomelidae). Thatcher (2006) noted the following endoparasites in Brazil: Trematoda Podospathalium pedatum (Alariidae). Cestoda Linstowia iheringi and Mathevotaenia bivittata (Anoplocephalidae). Nematoda Aspidodera subulata (Aspidoderidae); Cruzia tentaculata (Cruziidae); Physaloptera mirandai (Physalopteridae); Travassostrongylus orloffi, T.tertius and Viannaia pusilla (Trichostrongylidae). Acanthocephala Gigantorhynchus ortizi (Gigantorhynchidae). Longevity Considered to live 3 to 4 years (Hunsaker 1977).
VOC: Typically silent but threatened individuals grunt and gnash the teeth (Emmons 1999, Morães Junior 2004).
HUM: Occasional damage to fruit crops and cornfields has led to them receiving a bad reputation in parts of their range where they are more abundant (Nowak 1991). In Paraguay this species is rarely encountered and interviews with locals performed by Lowen et al (1996) failed to find any reference to the species. Its human impact in Paraguay is therefore minimal.
CON: Globally considered to be of Low Risk Least Concern by the IUCN, click here to see their latest assessment of the species. This species occurs in naturally low populations and is easily overlooked as a result of its furtive habits. It is likely under-recorded in Paraguay but has no doubt disappeared from large areas of its former range as a result of conversion of forest to agriculture. Population density near Manaus, Brazil was estimated at 25.6/km². Flores (2006) states that in Argentina the species is only found in indisturbed areas and classifies it as potentially vulnerable in that country. A similar conservation designation in Paraguay would seem correct.
Citable Reference: Smith P (2008) FAUNA Paraguay Online Handbook of Paraguayan Fauna Mammal Species Account 19 Metachirus nudicaudatus.
Last Updated: 30 June 2009.
References:
Allen JA 1900 - Descriptions of New American Marsupials - Bulletin AMNH 13: p191-199.
Allen JA 1901 - New South American Muridae and a New Metachirus - Bulletin AMNH 14: p405-412.
Astúa de Morães D, Santori RT, Finotti R, Cerquiera R 2003 - Nutritional and Fibre Contents of Laboratory-established Diets of Neotropical Opossums (Didelphidae) p225-233 in Jones M, Dickman C, Archer M Predators with Pouches: The Biology of Carnivorous Marsupials - CSIRO Publishing, Australia.
Bertoni A de W 1914 - Fauna Paraguaya. Catálogos Sistemáticos de los Vertebrados del Paraguay. Peces, Batracios, Reptiles, Aves y Mamíferos Conocidos hasta 1914 in Bertoni MS Descripción Física y Económica del Paraguay - M.Brossa, Asunción.
Bertoni A de W 1939 - Catálogos Sistemáticos de los Vertebrados del Paraguay - Revista de la Sociedad Cientifica del Paraguay 4: p3-60.
Brown BE 2004 - Atlas of New World Marsupials - Fieldiana Zoology 102.
Burmeister H 1854 Systematische Uebersicht der Thiere Brasiliens: Welche während einer Reise durch die Provinzen von Rio de Janeiro und Minas Geraës Gesammlt oder beobachtet wurden Vol 1 - G.Reimer, Berlin.
Cáceres NC 2004 - Diet of Three Didelphid Marsupials (Mammalia: Didelphimorphia) in Southern Brazil - Mammalian Biology 69: p430-433.
Carvalho FMV de, Delciellos AC, Vieira MV 2000 - Medidas Externas dos Miembros de Marsupiais Didelfidios: Uma Comparação com Medidas do Esqueleto Pós-Craniano - Boletim do Museu Nacional, Rio de Janeiro 438.
Carvalho FMV de, Pinheiro PS, Fernández FAS, Nessimian JL 1999 - Diet of Small Mammals in Atlantic Forest in Southeastern Brazil - Revista Brasileira de Zoociencias 1: p91-101.
Chebez JC 2009 - Otros Que Se Van - Editorial Albaros, Buenos Aires.
Cimardi AV 1996 - Mamíferos de Santa Catarina - FATMA, Florianopolis.
Cunha AA, Vieira MV 2002 - Support Diameter, Incline and Vertical Movements of Four Didelphid Marsupials in the Atlantic Forest of Brazil - Journal of Zoological Society of London 258: p419-426.
Delciellos AC, Vieira MV 2006 - Arboreal Walking Performance in Seven Didelphid Marsupials as an Aspect of Their Fundamental Niche - Austral Ecology 31: p449-457.
Delciellos AC, Vieira MV 2007 - Stride Lengths and Frequencies of Arboreal Walking in Seven Species of Didelphid Marsupials - Acta Theriologica 52: p101-111.
Delciellos AC, Vieira MV 2009 - Allometric, Phylogenetic and Adaptive Components of Climbing Performance in Seven Species of Didelphid Marsupials - Journal of Mammalogy 90: p104-113.
Eisenberg JF 1989 - Mammals of the Neotropics: Volume 1 The Northern Neotropics - University of Chicago Press, Chicago.
Eisenberg JF, Redford KH 1999 - Mammals of the Neotropics: Volume 3 The Central Neotropics - University of Chicago Press, Chicago.
Emmons LH 1999 - Mamíferos de los Bosques Húmedos de América Tropical - Editorial FAN, Santa Cruz.
Enders RK 1935 - Mammalian Life Histories from Barro Colorado Island, Panama - Bulletin of the Museum of Comparative Zoology 78: p385-502.
Flores DA 2006 - Orden Didelphimorphia in Bárquez R, Díaz, MM, Ojeda RA eds Mamíferos de Argentina, Sistemática y Distribución - SAREM, Buenos Aires.
Gardner AL 2007 - Mammals of South America Volume 1: Marsupials, Xenarthrans, Shrews and Bats - University of Chicago Press.
Gentile R, Cerqueira R 1995 - Movement Patterns of Five Species of Small Mammals in a Brazilian Restinga - Tropical Ecology 11: p671-677.
Gentile R, Finotti R, Rademaker V, Cerqueira R 2004 - Population Dynamics of Four Marsupials and its Relation to Resource Production in the Atlantic Forest of Southeastern Brazil - Mammalia 68: p109-119.
Geoffroy St.Hilaire E 1803 - Catalogue des Mammifères du Muséum National d´Histoire Naturelle - Paris.
Gray JE 1843 - List of the Specimens of Mammalia in the Collection of the British Museum - British Museum of Natural History, London.
Hunsaker D 1977 - The Biology of Marsupials - Academic Press, New York.
Husson AM 1978 - The Mammals of Suriname - Leiden, Germany.
Kirsch JAW 1977 - The Classification of Marsupials p1-50 in Hunsaker D ed The Biology of Marsupials - Academic Press, New York.
Lesson RP 1827 - Manuel de Mammalogie ou Histoire Naturelle des Mammifères - Roret, Paris.
Liais E 1872 - Climats, Géologie, Faune et Géographie Botanique du Brésil - Garnier Frères, Paris.
Limardi PM 2006 - Os Ectoparasitos de Marsupiais Brasileiros p27-52 in Cáceres NC, Monteiro-Filho ELA Os Marsupiais do Brasil:Biologia, Ecologia e Evolução - Editora UFMS, Campo Grande.
Loretto D, Ramalho E, Vieira MV 2005 - Defence Behaviour and Nest Architecture of Metachirus nudicaudatus Desmarest 1817 (Marsupialia, Didelphidae) - Mammlia 69: p417-419.
Mares MA, Braun JK 2000 - Systematics and Natural History of Marsupials from Argentina p23-45 in Reflections of a Naturalist: Papers Honoring Professor Eugene D Fleharty, Fort Hays Studies Special Issue 1.
Massoia E, Chebez JC, Bosso A 2006 - Los Mamíferos Silvestres de la Provincia de Misiones, Argentina - DVD-ROM.
Massoia E, Forasiepi A, Teta P 2000 - Los Marsupiales de la Argentina - LOLA, Buenos Aires.
Matschie P 1916 - Bemerkungen über die Gattung Didelphis L. - Sitzungsber. Gesells. Naturf. Freunde Berlin 1916: p259-272.
Morães Junior EA 2004 - Radio Tracking of one Metachirus nudicaudatus (Desmarest 1817) Individual in Atlantic Forest of Southeastern Brazil - Boletim Museu Biologia Mello Leitão 17: p57-64.
Moura MC, Capparelli AC, Freitas SR, Vieira MV 2005 - Scale Dependent Habitat Selection in Three Didelphid Marsupials Using the Spool and Line Technique in the Atlantic Forest of Brazil - Journal of Tropical Ecology 21: p337-342.
Myers P, Espinosa R, Parr CS, Jones T, Hammond GS, Dewey A 2006 - The Animal Diversity Web (online). Accessed December 2007.
Novak RM 1991 - Walker´s Mammals of the World 5th Ed Volume 1 - Johns Hopkins, Baltimore.
Pine RH 1973 - Anatomical and Nomenclatural Notes on Opossums - Proceedings of the Biological Society of Washington 86: p391-402.
Pires AS, Fernandez FAS, Schittini GM, Oliveira LC 2002 - Frequency of Movements of Small Mammals Along Coastal Atlantic Forest Fragments in Brazil - Biological Conservation 108: p229-237.
Pires AS, Koeler Lira P, Fernandez FAS, de Freitas D, Feliciano BR 2005 - Influence of Edge and Fire-induced Changes on Spatial Distribution of Small Mammals in Brazilian Atlantic Forest Fragments - Studies on Neotropical Fauna and Environment 40: p7-14.
Pohle H 1927 - Über die von Prof. Bresslau in Brasilien Gesammelten Säugthiere (Ausser den Nagethieren) - Abhandl. Senckenberg. Naturf. Gesell. Frankfurt 40: p239-247.
Redford KH, Eisenberg JF 1992 - Mammals of the Neotropics: Volume 2 The Southern Cone - University of Chicago Press, Chicago.
Santori RT, Astúa de Moraes D, Cerqueira R 1995 - Diet Composition of Metachirus nudicaudatus and Didelphis aurita (Marsupialia, Didelphoidea) in Southeastern Brazil - Mammalia 59: p511-516.
Santori RT, Astúa de Moraes D, Cerqueira R 2004 - Comparative Gross Morphology of the Digestive Tract in Ten Didelphidae Marsupial Species - Mammalia 69: p27-36.
Stevens SM, Husband TP 1998 - The Influence of Edge on Small Mammals: Evidence from the Brazilian Atlantic Forest Fragments - Biological Conservation 85: p1-8.
Temminck CJ 1824 - Deuxième Monographie sur le Genre Sarigue - Didelphis (Linn.) in Monographies de Mammalogie ou Description de Quelques Genres de Mammifères dont les espèces ont été Observeés dans les Différens Musées de l´Europe - G.Dufour et E d´Ocogne, Paris.
Thatcher VE 2006 - Os Endoparasitos dos Marsupiais Brasileiros p53-68 in Cáceres NC, Monteiro-Filho ELA Os Marsupiais do Brasil:Biologia, Ecologia e Evolução - Editora UFMS, Campo Grande.
Thomas O 1923 - New Subspecies of Metachirus - Annals and Magazine of Natural History Series 9 11: p602-607.
Trouessart EL 1898 - Catalogus Mammalium tam Viventium quam Fossilium. Fasciculus V: Sirenia, Cetacea, Edentata, Marsupialia, Allotheria, Monotremata - R.Friedländer & Sohn, Berolini.
Vieira MV, Cunha AdeA 2008 - Scaling Body Mass and Use of Space in Three Species of Marsupials in the Atlantic Forest of Brazil - Austral Ecology 33: p872-879.

ACKNOWLEDGEMENTS
Special thanks to Juan Carlos Chebez for providing important literature and Nilton Cáceres for very kindly reviewing texts and providing a copy of his book Os Marsupiais do Brasil.