Proechimys steerei, Goldman, 1911

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 : 573

39.

Steere’s Spiny-rat

Proechimys steerei

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

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Taxonomy. Proechimys steerei Goldman, 1911 ,

“Rio Purus, a southern tributary of the Amazon, in north-western [Amazonas], Brazil.” Restricted by E. A. Goldman in 1912 to “Hyutana-han [= Huitanaa], a small village of rubber gatherers, on the north side of the Rio Purus, in the upper part ofits course.”

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Proechimys steerei is a member of the goeldii species group. It includes kermiti, pachita, hilda, rattinus, and lminalis as synonyms.

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Monotypic.

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Distribution. Amazon Basin in E Peru (S of the Rio Maranon), NW Bolivia, and W Brazil, largely S of the Amazon River and E to beyond the Rio Purus, but extending N of the Amazon River in the Imeri region W of the lower Rio Negro.

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Descriptive notes. Head—body 215-493 mm,tail 120-207 mm; weight 300-800 g. Steere’s Spiny-rat is one of the largest species of terrestrial spiny-rats. Its ears and hindfeet are large, and tail is c.65% of head-body length, bicolored dark above and pale below, and covered with fine hairs but with scales conspicuous to the eye. There are typically 8 annuli/cm. Dorsum is light reddish brown, only faintly streaked with darker hairs. Steere’s Spiny-rats vary in the degree to which they are darkened along midline, but in general, they lack dark midline characteristic of most specimens of the Napo Spiny-rat (P. quadruplicates). Venteris pure white, and texture of ventral fur is thicker and more velvety both to the eye and touch than in other species of Proechimys . Aristiform hairs of dorsum are distinctly narrow, short, and lax, markedly softer compared with all other sympatric species of Proechimys and the other two species in the goelditspecies group. Spines average only c¢.15 mm in length and 0-5 mm in width. Color of dorsal surface of hindfootis characteristic, with pale to dark brown outer band and whitish inner band along length of foot from tarsal joint to end oftoes. Skull of Steere’s Spiny-ratis large, with long and narrow rostrum and well-developed supraorbital ledge that extends onto parietals as weakly developed ridge. Incisive foramina are lyrate to oval in outline, with slightly to strongly flanged posterolateral margins that form grooves extending onto anterior palate; premaxillary part of septum is short, less than one-half the length of opening; maxillary part is distinctly narrow; both parts of septum are in contact in most specimens; and vomer usually is not visible. Groove is present on floor of infraorbital foramen, butlateral flange is only weakly developed. Mesopterygoid fossa is relatively broad (averaging 67°) but penetrates to midpoint of M’. Counterfold pattern is 3(4)-3(4)-3(4)—(3)4/4-3-3-3. Baculum is comparatively short (length 7-1-8-7 mm) and of moderate width (proximal width 2-5-2-9 mm; distal width 2-5-3-1 mm), with parallel or slightly concave sides; it is similar in size and shape to those of the Napo Spiny-rat and Goeldi’s Spiny-rat ( P. goeldii ). Phallus is remarkably small, particularly so for an animal as large as Steere’s Spiny-rat, with prepuce extending as narrow tube and terminating by characteristic tuft of hairs, rather than being rounded and blunt as in most male Proechimys . Chromosomal complement is 2n = 24 and FN = 40-42.

Habitat. Seasonally flooded rainforest in the dry season, such as blackwater igap6 and whitewater varzea, but margins of adjacent terra firma forest in the wet season, including secondary forests, abandoned garden plots, riverine margins, and flooded grass patches within forests at elevations of 50-400 m. Overits entire distribution, Steere’s Spiny-rat is the only species present in igapo or varzea.

Food and Feeding. Steere’s Spiny-rat feeds mainly on fruit, fungi, and seeds, with lesser amounts of plant material and arthropods. Consumption of sporocarps of micorrhizal fungi and seeds suggest that Steere’s Spiny-rat may play a key ecological role in seed and fungal dispersal in forests.

Breeding. Autopsy data from Steere’s Spiny-rats collected during a year-long survey along the Rio Jurua in western Brazil indicate that it has a higher reproductive output than most other species of Proechimys , perhaps correlated with ephemeral availability of its primary, seasonally flooded habitat. Both sexes reached sexual maturity at an early age, well before complete molt into their adult pelage; pregnant females, on average, were younger (based on tooth wear) than those of adjacent, terra firma species; almost all females participated in breeding with a large proportion (20%) exhibiting evidence of postpartum estrus (simultaneous pregnancy and lactation); and litter sizes were high for a species of Proechimys (mean = 3 young, range 1-7).

Activity patterns. Trapping records indicate that Steere’s Spiny-rat is terrestrial and nocturnal.

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. Steere’s Spiny-rat is widespread and specializes in riverine, seasonally flooded forest that is not under threat from agricultural expansion. It is part of the fauna in a number of protected parks and indigenous areas and is unlikely to be declining. Expansion of illegal gold mining along many major river systems through its distribution, especially in south-eastern Peru, might impact varzea habitat, and focused field studies are needed to assess this possible threat. Additional studies on distribution, habitat, abundance, ecology, and conservation threats to Steere’s Spiny-rat are needed.

Bibliography. Allen (1915a), Eisenberg & Redford (1999), Emmons (1982, 1990, 1997a), Gardner & Emmons (1984), Goldman (1911b, 1912a, 1912b, 1912c¢), Hershkovitz (1948), Janos et al. (1995), Moojen (1948), Patton (1987), Patton & Gardner (1972), Patton & Leite (2015), Patton & Reig (1989), Ribeiro (2006), Thomas (1911a, 1923b, 1924b, 1926b), Thomas & St. Leger (1926), 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. Amazon Basin in E Peru (S of the Rio Maranon), NW Bolivia, and W Brazil, largely S of the Amazon River and E to beyond the Rio Purus, but extending N of the Amazon River in the Imeri region W of the lower Rio Negro.