Proechimys roberti, J. A. Allen, 1899

Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Echimyidae, Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona: Lynx Edicions, pp. 552-604 : 574-575

42.

Robert’s Spiny-rat

Proechimys roberti

French: Rat-épineux de Robert / German: Robert-Kurzstachelratte / Spanish: Rata espinosa de Robert

Other common names: Roberto’s Spiny-rat

Taxonomy. Proechimys roberti Thomas, 1901 ,

“Rio Jordao, SW. Minas Geraes [sic], Altitude 960 metres,” Araguari, Minas Gerais, Brazil .

Proechimys roberti is a member of the guyannensisspecies group. It includes ors, boimensis, and arescens as synonyms. Monotypic.

Distribution. Amazonian lowlands of E Brazil S of the Amazon River, extending S to the cerrado biome in EC Brazil, primarily in the Rio Tapajos, Rio Xingu, and Rio Tocantins-Araguaia fluvial systems of Para, Maranhao, Tocantins, Minas Gerais, Goias, and Mato Grosso states.

Descriptive notes. Head-body 200-230 mm, tail 160 mm; weight 170-240 g. Robert's Spiny-rat is moderately sized, similar in size to the Guyenne Spiny-rat ( P. guyannensis ), with which it shares a number of morphological attributes, but it has a distinctly shorter tail (average c.70% of head-body length). Dorsal color ranges from reddish brown in the northern part ofits distribution in Amazonia proper to pale buff at the southern terminus of its distribution in dry forests and gallery forests of cerrado—a difference in color that reinforced specific status of Robert’s Spiny-rat when O. Thomas described onis in 1904 from near the mouth of the Amazon a few years later. Venter is white from chin to inguinal region, but white of inner thighs is discontinuous, broken by dark ankle bands, with pale surface of hindfeet. In many specimens, brownish patch extends from tarsusto lateral toes. Pads on plantar surface of hindfoot are only moderately developed, but thenar and hypothenar are present and sub-equal in size. As in the Guyenne Spinyrat, tail of Robert’s Spiny-rat is very sparsely covered with short hairs so that is appears naked to the eye. Scales are large, defining 9-10 annuli/cm. Pelage is stiff to the touch, although much softer in southern samples; aristiform development is, however, moderate; spines are relatively short (20 mm in length) and narrow (0-6-0-8 mm in width), and each terminates in long whip-like tip. Difference in softness of pelage between Amazonian and cerrado specimens is mostly in aristiform density, not in any appreciable difference in spine width or other features. Skull of Robert’s Spiny-rat is medium-sized but rather narrow, with distinctly narrowed, tapering rostrum, similar in most respects to that of the Guyenne Spiny-rat. Slight temporal ridges extend posteriorly onto parietals from supraorbital ledge in older individuals, but most specimens lack ridges altogether. Incisive foramina cannot be distinguished from those of the Guyenne Spiny-rat by any single feature. They are relatively wide and ovalto teardrop in shape, with little or no posterolateral flange so that anterior palate is either flat of only weakly grooved; premaxillary part of septum is short, less than one-half the opening, and either connected to very attenuate maxillary part or separated from the latter entirely; maxillary part is non-keeled, so that anterior palate is without medial ridge; and vomer might be visible ventrally but not always. Floor of infraorbital foramen is eitherflat or with only hint of groove formed by weakly developed lateral flange. Mesopterygoid fossa is intermediate in width, with angle averaging 64—67°; it penetrates posterior palate to anterior one-half of M®. Postorbital process of zygomais weakly to moderately developed and formed completely by squamosal. Three folds characterize all upper cheekteeth except M?, which may have only two. Number of folds on lower cheekteeth is more variable, with three (occasionally four) on P, and either two (usually) or three on each lower molar; counterfold count 3-3-3-3(2)/3(4)-2(3)-2(3)-2(3). As with otherspecies of spiny-rats whose populations occur in various forest types, southernmost samples of Robert’s Spiny-rat in the drier cerrado forests typically have simpler teeth, with higher proportions of individuals with only two folds on lower molars. Baculum of Robert’s Spiny-rat is relatively short (5-4—6-1 mm) and narrow (proximal width 1-7-2-3 mm; distal width 1:3-1-8 mm), with general features as described above for the Guyenne Spiny-rat, except specimens from the southern part of its distribution tend to be smaller in length and width. Chromosomal complement is 2n = 30 and FN = 54-56, with minor regional differences in numbers of small biarmed vs. uniarmed autosomal pairs.

Habitat. Well-drained forests, cerrado gallery forests, sometimes creek-side and gallery forests, but more commonly primary forests from near sea level to elevations of c.1000 m. Robert’s Spiny-rat may be sympatric with Cuvier’s Spiny-rat ( P. cuvieri ) in primary forests. Some have suggested that Robert’s Spiny-rat favors microhabitats with abundant babassu palms ( Attalea speciosa , Arecaceae ). Sympatry with Goeldi’s Spinyrat ( P. goeldii ) has been documented along southern margins of the Amazon River in eastern Brazil and also with the Long-tailed Spiny-rat ( P. longicaudatus ) in dry forests of cerrado in central Brazil.

Food and Feeding. There is no information available for this species.

Breeding. There is no information available for this species.

Activity patterns. There is no specific information available for this species, but Robert’s Spiny-rat is probably nocturnal and terrestrial.

Movements, Home range and Social organization. There is no information available for this species.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Robert’s Spiny-rat is widespread and occurs in a diverse set of forested habitats, some of which are in protected parks or indigenous areas, including Chapada dos Veadeiros and Brasilia national parks. Although much of eastern Amazonian and southern cerrado parts of its distribution have been severely impacted by forest loss, Robert’s Spiny-rat is not believed to be declining. Additional studies on distribution, habitat, abundance, ecology, and conservation threats to Robert’s Spiny-rat are needed.

Bibliography. Alho (1981), Allen (1916a), Bonvicino, Lindbergh & Maroja (2002), Bonvicino, Otazu & Vilela (2005), Eisenberg & Redford (1999), Ellerman (1940), Emmons (1990, 1997a), Gardner & Emmons (1984), Hershkovitz (1948), Machado et al. (2005), Moojen (1948), Patton (1987), Patton & Gardner (1972), Patton & Leite (2015), Patton & Reig (1989), Ribeiro (2006), Thomas (1901a, 1904b), Valim & Linardi (2008), Weksler et al. (2001), Woods & Kilpatrick (2005).

Figures

12. Broad-headed Spiny-rat (Clyomys laticeps), 13. Guiara (Euryzygomatomys spinosus), 14. White-spined Spiny-rat (Irinomys albispinus), 15. Elias’s Spiny-rat (Trinomys eliasi), 16. Rigid-spined Atlantic Spiny-rat (Trinomys paratus), 17. Yonenaga’s Spiny-rat (Trinomys yonenagae), 18. Elegant-spined Atlantic Spiny-rat (Trinomys setosus), 19. Moojen’s Spiny-rat (Trinomys moojeni), 20. Pau Brasil Spiny-rat (Trinomys mirapitanga), 21. Rio de Janeiro Spiny-rat (Trinomys dimidiatus), 22. Sao Paulo Spiny-rat (Trinomys thering), 23. Gracile Atlantic Spiny-rat (Trinomys gratiosus), 24. Sao Lourenco Punare (Thrichomys laurentius), 25. Jacobina Punare (Thrichomys inermis), 26. Lagoa Santa Punare (Thrichomys apereoides), 27. Pantanal Punare (Thrichomys pachyurus), 28. Foster’s Punare (Thrichomys fosteri), 29. Painted Tree-rat (Callistomys pictus), 30. Coypu (Myocastor coypus), 31. Armored Rat (Hoplomys gymnurus)

Distribution. Amazonian lowlands of E Brazil S of the Amazon River, extending S to the cerrado biome in EC Brazil, primarily in the Rio Tapajos, Rio Xingu, and Rio Tocantins-Araguaia fluvial systems of Para, Maranhao, Tocantins, Minas Gerais, Goias, and Mato Grosso states.