RED-SIDED SHORT-TAILED OPOSSUM Monodelphis sorex FAUNA PARAGUAY

Monodelphis sorex (Hensel 1872)
TAX: Class Mammalia; Subclass Theria; Infraclass Metatheria; Order Didelphimorphia; Family Didelphidae; Subfamily Didelphinae (Myers et al 2006). Eighteen species are recognised in this genus, three are present in Paraguay. The scientific name Monodelphis is from the Greek meaning "single womb", sorex is Latin meaning shrew. The species is monotypic. This species suffers from a complicated taxonomic history. The species was originally described on the basis of immature specimens and as a result many immature specimens referred to in the literature are reliably identified. However adult female and half-grown males have in the past frequently referred to as Hensel´s Short-tailed Opossum Monodelphis henseli (Thomas 1888) and this name has continued to appear in recent works on South American mammals (eg. Redford & Eisenberg 1992, Hershkovitz 1992, Massoia et al 2009) perpetuating the confusion. Furthermore adult males have frequently been confused with M.dimidiata (Wagner 1847), and also attributed to two defunct taxa M.tricolor (Lund 1840) and M.touan (Shaw 1800), both of which are synonyms of the Guianan Short-tailed Opossum M.brevicaudata (Erxleben 1777) a species confined to northern Amazonian South America. As the only "red-sided" Monodelphis known from Paraguay this species is likely the "Micouré cinquième, ou micouré à queue courte" of de Azara (1801). If this is the case then the oldest name atrributable to the species is Monodelphis brevicaudis, Olfers 1818 and M.wagneri Matschie, 1916 is a synonym. Hershkovitz (1959) recognised M.brevicaudis as a valid species but assigned no specimens to the taxon and this was followed by Brown (2004) who went so far as to map the species for the Paraguayan Chaco (where M.sorex does not occur), though in her text she notes that the species is based on de Azara´s description and two lost specimens lacking locality data and that the name may require "reassignment". De la Sancha et al (2007) state that Monodelphis brevicaudis has variously been regarded to be a senior synonym of M.domestica or M.brevicaudata, but is now generally considered a synonym of M.sorex. The Tawny-headed Short-tailed Opossum Monodelphis scalops was reported erroneously for Paraguay by Contreras & Silveira Avalos (1995), though their written decription clearly refers to M.sorex, a fact confirmed upon examination of the specimen by de la Sancha et al (2007). Synonyms adapted from Gardner (2007):
Didelphis tricolor Lund 1840:19 not Didelphis tricolor E. Geoffroy St-Hilaire 1803.
Didelphys [Microdelphys] sorex Hensel 1872:122 Type locality "Rio Grande do Sul" restricted to "Taquara" by Cabrera (1958).
Didelphys (Peramys) henseli O.Thomas 1888:159 Type locality "Taquara, Rio Grande do Sul".
Peramys sorex O.Thomas 1888:380 Name combination.
[Didelphis (]Monodelphis [)] henseli Matschie 1916:271 Name combination.
[Didelphis (]Monodelphis [)] lundi Matschie 1916:271 Type locality "Lagoa Santa, Minas Gerais" based on D.tricolor Lund 1840.
[Didelphis (]Monodelphis [)] sorex Matschie 1916:272 Name combination.
Peramys henseli Cabrera 1919:42 Name combination.
P[eramys (Peramys)] sorex A. Mirando-Ribeiro 1936:404 Name combination.
Peramys henselii A. Mirando-Ribeiro 1936:409 Incorrect spelling.
P[eramys]. d.[imidiata]itatiayae A. Mirando-Ribeiro 1936:421 Type locality "Campo Bello, Rio de Janeiro".
Monodelphis henseli Cabrera & Yepes 1940:32 Name combination.
Monodelphis henseli Cabrera & Yepes 1940:32 First use of current name combination.
Monodelphis tricolor paulensis COC Vieira 1950:359 Type locality "Pirituba, subúrbio da cidade de Sao Paulo".
Monodelphis touan paulensis Cabrera 1958:9 Name combination.
Monodelphis henseley Tálice, Laffite de Mosera & Machado 1960:151 Incorrect spelling.
Monodelphis touan Olrog & Lucero 1981:68 Not Mustela touan Bechstein 1800.
Monodelphis henseli Ávila-Pires 1994:369 Name combination.
Microdelphis sorex Ávila-Pires 1994:369 Name combination.
Monodelphis brevicaudatus Chebez & Massoia 1996: 199 Not Didelphis brevicaudatus Erxleben 1777.
ENG: Red-sided Short-tailed Opossum, Southern Red-sided Opossum (Gardner 2007), Hensel´s Short-tailed Opossum (Redford & Eisenberg 1992), Shrewish Short-tailed Opossum (Canevari & Vaccaro 2007).
ESP: Colicorto rojizo (Canevari & Vaccaro 2007, Massoia et al 2000), Colicorto selvático (Canevari & Vaccaro 2007, Massoia et al 2000), Colicorto musaraña (Canevari & Vaccaro 2007, Emmons 1999), Musaraña (Massoia et al 2000), Colicorto de Hensel, Colicorto Misionero (Massoia et al 2009).
GUA: Guaiquiaca-aña (Canevari & Vaccaro 2007), Anguja (Massoia et al 2000), Mbicuré-í (Massoia et al 2000, Canevari & Vaccaro 2007).
DES: A small to medium-sized Monodelphis with short, rounded ears and tail approximately 50% of head and body length. Pelage short and smooth, lying flat against the body. Forehead, crown and dorsum dark brown, somewhat greyer on the head and deep reddish-chestnut on the rump. Sides of head to just above the eye orange-rufous. Flanks and sides reddish, sometimes with slight greyish tinge but always clearly demarcated from the dorsal colouration. Venter creamy-yellow to pale reddish. Feet reddish. Tail dark brown above and pale reddish below. Great sexual dimorphism in size with males up to 50% larger than females. Females lack a pouch and possess more mammae than any other mammal - 25-27, arranged with five central nipples and the remainder arranged in lateral lines. CR - The following cranial measurements are those provided by Contreras & Silviera Avalos (1995) for their male Paraguayan specimen: Greatest Length: 35.4mm; Minimum Postorbital Constriction: 5.6mm; Width of Brain Case: 13.9; Greatest Zygomatic Width: 20.5mm; Mandible Length: 27mm; Length of Nasals: 15.5mm; Palate Length: 17.4mm; DF: I5/4 C1/1 P 3/3 M 4/4 = 50. The following dental measurements are those provided by Contreras & Silviera Avalos (1995) for their male Paraguayan specimen: Length of Upper Tooth Row 16.9mm; Length of Upper Molar Row 9.9mm; Length of Lower Tooth Row 14.1mm; Distance across M3 10.1mm; Distance M1-M4 on Upper Tooth Row 5.7mm; Distance M1-M4 on Lower Tooth Row 7.2mm; CN: 2n=18.
TRA: No information.
MMT: A medium-sized Short-tailed Opossum. There is marked sexual dimorphism in size, with males up to twice the size and weight of females. TL: 14.48cm (11.9-21.5cm); HB: 9.38cm (7.8-13cm); TA: 5.1cm (3.6-8.5cm) approximately 50% of body length; FT: 1.52cm (1.5-1.55cm); EA: 0.88cm (0.53-1.1cm); WT: 48g; (Massoia et al 2000, Redford & Eisenberg1992, Emmons 1999). Contreras & Silveira Avalos (1995) gave the following measurements for a single male specimen wrongly identified by them as M.scalops: TL: 21cm; HB: 14.5cm; TA: 6.5cm; FT: 1.7cm not including claw, 1.9cm including claw; EA: 1.5cm; WT: 68g.
SSP: Intermediate in size amongst the three Monodelphis species currently documented for Paraguay, this is the only species that occurs in the Atlantic Forest. This species can be instantly separated from the other two species on account of its distinctive pelage colouration with reddish flanks contrasting with a grey-brown dorsal surface. Other Paraguayan species are uniformly coloured. Two additional species of possible occurrence in Paraguay are confusable with this species. The Tawny-headed Short-tailed Opossum Monodelphis scalops is clearly distinguishable by its uniformly tawny head, which lacks the brownish-grey crown and forehead of this species, and has grey rather than reddish flanks. The species has been recorded in Brazil and Misiones Province, Argentina and is likely present in the Atlantic Forest of Paraguay, though no confirmed records exist. The Yellow-sided Short-tailed Opossum Monodelphis dimidiata is of similar general patternation and size to this species. However the dorsal area is distinctly grey, not grey-brown as in this species and the flanks and side of the face are pale tawny-yellow, not reddish-brown. M.dimidiata has long, lax fur (except in old males), compared to the short, smooth fur of this species, and the feet are whitish or buffy as opposed to reddish in M.sorex. Furthermore M.dimidiata occurs in open, grassy habitats, not humid forests. The species is widespread in Argentina in the River Plate Basin, north to Provincia Salta and east through coastal Uruguay to Rio Grande do Sul, Brazil. It is apparently also present in Provincia Misiones, Argentina and its occurrence in Paraguay is considered possible, though it would represent a northern range extension.
DIS: An Atlantic Forest endemic species occurring in southern Brazil, south-eastern Paraguay and Misiones Province in Argentina (Departamentos Cainguas, Guaraní, Iguazú, Oberá, General Belgrano and Montecarlo and likely San Pedro - Massoia et al 2009). In Brazil the records are clustered in Minas Gerais, Sao Paulo and Rio Grande do Sul, though the species likely occurs more or less continuously between those points where suitable habitat occurs. In Paraguay there are specimen records from PN San Rafael, Departamento Itapúa and 12km W of Ciudad del Este area, Departamento Alto Paraná (Contreras & Silveira Avalos 1995).
HAB: Occurs in humid Atlantic forest in eastern Paraguay where it is the only Monodelphis so far reported. In Misiones it apparently tolerate considerable disturbance being found in capuera and cultivated areas close to forest (Massoia et al 2009).
ALI: Considered to be insectivorous by Canevari & Vaccaro (2007) and "principally carnivorous" by Massoia et al (2000). Casella & Cáceres (2006) published the first specifics on the diet of this species after studying stomach contents of animals (n=26) captured in western Paraná State, Brazil. They considered the species to be an opportunistic generalist feeder with a principally insectivorous diet supplemented with meat and fruit. Arthropods were the principal item in the diet with Coleoptera the single most prevalent group found in 92% of stomachs. Other animal items found in stomachs in order of prevalence were: Hymenoptera 80%, Blattaria 31%, Mammalia 31%, Orthoptera 30%, Decapoda 15%, Opiliones 15%, Acari 8%, other Crustacea 8%, Myriapoda 4%, Aves 4% and insect larvae 4%. Seeds were found in 8% of stomachs (Cecropia sp. and Rubus sp.) and unidentified plant material in 30% of stomachs. Of the 57 seeds found, 54 were intact and only 3 had been predated, suggesting that it was the fruit that had been consumed and indicating that the species may play a role in seed dispersal.
REP: No published information. The species has the largest number of mammae of any mammal (25-27) and in view of this Gardner (2007) suggested that the species may prove to be semelparous - a possibility supported by the high number of young individuals when compared to adults in specimen collections.
BEH: Avitivity Levels The species is terrestrial and crepuscular (IUCN 2008). No other published information. Enemies Ávila-Pires & Gouvêa (1977) mentioned a specimen of M.dimidiata taken from the oesophagus of a White-tailed Kite Elanus leucurus, but Gardner (2007) considers it more likely that it was this species - however White-tailed Kite is an open-country species that does not occur in Atlantic Forest and M.dimidiata is typical of grassland habitats (P.Smith pers.obs.). Massoia et al (2009) note that it is regular in pellets of Tyto alba in Misiones, Argentina. Parasites Notman (1923) described an ectoparasitic Staphylinid beetle Omaloxenus bequarti found on a Monodelphis collected at "Alto Itatiaya, Setto (sic) do Itatiaya, Brazil" which may have been this species. Fain (1979) reported M.dimidiata as the host of a Listrophid mite Didelphoecius paranensis, but Gardner (2007) believes that the correct identification of the host may actually be M.sorex.
VOC: No information.
HUM: This rare forest species has little impact on humans within its range.
CON: Globally considered to be Low Risk, Least Concern by the IUCN, click here to see their latest assessment of the species on account of a supposedly wide distibution and its occurrence in a number of protected areas. The species has recently been downgraded from its previous designation as vulnerable. The species is not listed by CITES. This species is considered endemic to the Atlantic Forest, one of the world´s most seriously threatened habitat types and is probably worthy of greater conservation concern. Canevari & Vaccaro (2007) consider the species to be vulnerable in Argentina and insufficiently known in Brazil. Flores (2006) consider the species vulnerable in Argentina but Massoia et al (2009) disagree and consider the species "undoubtedly the commonest Monodelphis of the Paranaense forest" in Argentina and likely more widespread than currently known. Population size in Paraguay is unknown but, as in other areas of the range, areas of available suitable habitat have declined alarmingly over recent decades. Though surveys have been insufficient to determine population sizes there is little doubt that the population is in decline as a result of habitat destruction. The species is present in PN San Rafael, but currently the reserve faces serious conservation issues, suffers from inadequate protection and a questionable legal status. It is presumably present in some of the Itaipú Reserves in Departamento Alto Paraná but deforestation in this area has been massive and huge areas of prime forest were lost as a result of the Itaipú dam project. Although the species obviously tolerates some degree of habitat disturbance, there is no doubt that the species is threatened in Paraguay, as with other species associated with the Atlantic Forest. It is apparently absent from the Mbaracayú Forest Reserve, Departamento Canindeyú, arguably Paraguay´s best protected Atlantic Forest reserve (Esquivel 2001).
Citable Reference: Smith P (2008) FAUNA Paraguay Online Handbook of Paraguayan Fauna Mammal Species Account 26 Monodelphis sorex.
Last Updated: 4 January 2009.
References:
Ávila-Pires FD 1994 - Mamíferos Descritos do Estado do Rio Grande do Sul, Brasil - Revista Brasileira de Biología 54: p367-384.
Bechstein JM 1800 - Thomas Pennant´s Allegemeine Uebersicht der Vierfüssigen Thiere. Aus dem Englischen Übersetzt und mit Anmerkungen und Zusätzen Versehen, von Johann Matthäus Bechstein - Weimar.
Brown BE 2004 - Atlas of New World Marsupials - Fieldiana Zoology 102.
Cabrera A 1919 - Genera Mammalium: Monotremata, Marsupialia - Museo Nacional de Ciencias Naturales, Madrid.
Cabrera A 1958 - Catálogo de los Mamíferos de América del Sur - Revista Museo Aregntino de Ciencias Naturales Bernadino Rivadavia Zoology 4: p1-307.
Cabrera A, Yespes J 1940 - Mamíferos Sud Americanos: Vida, Costumbre y Descripción - Historia Natural Ediar., Buenos Aires.
Canevari M, Vaccaro O 2007 - Guía de Mamíferos del Sur de América del Sur - LOLA, Buenos Aires.
Casella J, Cáceres NC 2006 - Diet of Four Small Mammal Species from Atlantic Forest Patches in South Brazil - Neotropical Biology and Conservation 1: p5-11.
Chebez JC, Massoia E 1996 - Mamíferos de la Provincia de Misiones in Fauna Misionera - LOLA, Buenos Aires.
Contreras JR, Silveira Avalos W 1995 - Incorporación del Pequeño Marsupial Monodelphis scalops, Thomas 1988, a la Mastofauna del Paraguay (Marsupialia: Didelphidae) - Notulas Faunisticas 70.
de Azara F 1801 - Essais sur l´Histoire Naturelle des Quadrupèdes de la Province du Paraguay Vol 2 - Pougens, Paris.
de la Sancha N, Solari S, Owen RD 2007 - First Records of Monodelphis kunsi Pine from Paraguay, with an Evaluation of its Distribution - Mastozoologia Neotropical 14: p241-247.
Emmons LH 1999 - Mamíferos de los Bosques Húmedos de América Tropical - Editorial FAN, Santa Cruz.
Erxleben JCP 1777 - Systema Regni Animalis per Classes, Ordines, Genera, Species, Varietates cum Synonymia et Historia Animalium. Classis 1 Mammalia - Lipisiae: Impensis Weygandianis.
Esquivel E 2001 - Mamíferos de la Reserva Natural del Bosque Mbaracayú, Paraguay - Fundación Moises Bertoni, Asunción.
Fain A 1979 - Les Listrophorides d`Amerique Neotropicale (Acarina: Astigmates) II: Famille Atopomelidae - Bull. Inst. Roy. Sci. Nat. Belgium 51: p1.158.
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 Vol 1: Marsupials, Xenarthrans, Shrews and Bats - University of Chicago Press, Chicago.
Geoffroy St-Hilaire E 1803 - Catalogue des Mammiferes du Muséum d´Histoire Naturelle - Paris.
Hensel R 1872 - Beiträge zue Kenntniss der Säugethiere Süd-Brasiliens - Abhandl. König. Akad. Wiss. Berlin 1872: p1-130.
Hershkovitz P 1992 - The South American Gracile Mouse Opossums, Genus Gracilinanus Gardner & Creighton, 1989 (Marmosidae: Marsupialia): A Taxonomic Review with Notes on General Morphology and Relationships - Fieldiana Zoology 70.
Lund PW 1840 - Fortsaettelse af Pattedryne - K. Danske Vidensk. Selskab. Naturv. Math. Afhandl. 3: p1-56.
Massoia E, Chebez JC, Bosso A 2009 - 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.
Mirando-Ribeiro A 1936 - Didelphia ou Mammalia-ovovivipara. Marsupiaes, Didelphos, Pedimanos ou Metatherios - Revista do Museu Paulista, Sao Paulo 20: p245-427.
Myers P, Espinosa R, Parr CS, Jones T, Hammond GS, Dewey A 2006 - The Animal Diversity Web (online). Accessed December 2007.
Notman H 1923 - A New Genus and Species of Staphylinidae Parasitic on a South American Opossum - AMNH Novitates 68.
Olrog CC, Lucero MM 1981 - Guía de los Mamíferos Argentinos - Ministerio de Cultura y Educación, Fundación Miguel Lillo, San Miguel de Tucumán, Argentina.
Redford KH, Eisenberg JF 1992 - Mammals of the Neotropics: Volume 2 The Southern Cone - University of Chicago Press, Chicago.
Shaw G 1800 - General Zoology or Systematic Natural History - Kearsley, London.
Tálice RV, Laffite de Mosera S, MachadoT 1960 - Observaciones sobre Monodelphis dimidiata - Actas y Trabajos del Primer Congreso Sudamericano de Zoología, La Plata 4: p149-156.
Thomas O 1888 - Diagnosis of Four New Species of Didelphys - Annals and Magazine of Natural History Series 6 1:158-159.
Vieira COC 1950 - Xenartros e Marsupiais do Estado de Sao Paulo - Arq. Zool. Estado Sao Paulo 7: p325-362.
Wagner JA 1847 - Beiträge zue Kenntniss der Säugthiere Amerika´s - Abhandl. Math.-Physik. König. Bayer. Akad. Wiss München 5: p121-208.