Hoplomys gymnurus
Creators: name: Don E. Wilson
name: Thomas E. Lacher, Jr
name: Russell A. Mittermeier
Publisher: name: Lynx Edicions
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Rodentia
Echimyidae
Hoplomys
Hoplomys gymnurus

description: 31.
Armored Rat
Hoplomys gymnurus
French: Rat-épineux cuirassé / German: Lanzenratte / Spanish: Rata acorazada
Taxonomy. Echimys gymnurus Thomas, 1897,
“Cachavi [= Cachabi], [Esmeraldas,] N. Ecuador,altitude 170 metres.” Restricted by R. A. Paynter, Jr. in 1993 to 00°58’N, 78°48’W.
Four subspecies are recognized.
Subspecies and Distribution.
H.g.gymnurusThomas,1897—NWEcuadorandSWColombia(Chocébioregion).
H.g.goethalsiGoldman,1912—SCostaRicatoWColombia;boundarywithgymnuruspoorlyunderstood.
H.g.trueiJ.A.Allen,1908—EHonduras,ENicaragua,andNCostaRica.
H. g. wetmoret Handley, 1959 — Isla Escudo de Veraguas (off NC Panama).
Descriptive notes. Head-body 212-320 mm, tail 114-240 mm; weight 220-820 g. The Armored Rat is large-bodied, with stout body, short and thick legs, relatively narrow and elongated hindfeet, nearly naked and proportionately shorttail (60-70% of head-body length), and short rounded ears. Most characteristic external features are broad, flat, and stiffen spines that cover dorsum from behind shouldersto flanks and rump. These spines are 26-33 mm in length and 1.7-2-2 mm in width, and they tend to obscure soft underfur. Spines are tipped black along mid-dorsum but may have pale tips on sides, which gives lateral aspect of skin distinct speckled pattern. As with other species of echimyids with well-developed spines (e.g. Lonchothrix, Mesomys, some Proechimys, and some Trinomys), those of Hoplomys extend down sides to junction with ventral fur. Color varies geographically, ranging from reddish orange dorsally in the southern part of the distribution to more yellowish in the north. Young Armored Rats are more typically dull brown dorsally. Individuals vary with regard to presence or absence of black ocular and crown areas. Venter is predominantly white, although there may be partial or complete dark brown collar across throat and buff lateral bands separating ventral from flank colors; some individuals have fully buffventer. Some Panamanian specimens are melanistic, almost black, with dark brown venters, variably spotted with white. Skull is conformed as in most non-fossorial eumysopine genera: relatively narrow in shape with elongated rostrum, concave interorbital region, and round cheekteeth with deeply oblique lateral folds that do not transect crown and become isolated as fossettes with wear. Prominent temporal ridges are present, supraorbital shelf is beaded, rostrum narrows toward tip, auditory bullae are very small, and floor of infraorbital foramen is typically flat, although slight groove that marks passage of infraorbital branch of maxillary nerve is present in some individuals. Size, flatness, and ridging of skull of Hoplomys increase with age (as judged by tooth eruption and wear), with growth apparently continuing well after all teeth are erupted and fully functional. As a result, skulls of “adults” exhibit considerable range in overall size—a characteristic of other eumysopine genera, most notably Proechimys and Trinomys. In the original description, Hoplomys was diagnosed by combination of its impressively broad and stiff dorsal spines and enamel pattern with all maxillary and mandibular cheekteeth possessing four well developed and obliquely positioned folds, a character that was contrasted with three folds typical of Proechimys. In nearly all craniodental and pelage characteristics, Hoplomysis either indistinguishable from or only at the extreme end of a continuum represented by the diverse species of Proechimys. For example, counterfold formula of Hoplomys does vary, particularly in lower molars (from 4/4, 4/4, 4/4, 4/4 to, rarely, 4/4, 4/3, 4/3, 4/3), and some species of Proechimys also exhibit four counterfolds on most, or all cheekteeth (most notably Tome’s Spinyrat, P. semispinosus, and the Napo Spiny-rat, P. quadruplicatus). Moreover, some species of Proechimys approach Hoplomys in aristiform spine development, such as the Guianan Spiny-rat (P. hoplomyoides), which has been placed in Hoplomys by some authors, and the Stiff-spined Spiny-rat (P. echinothrix), which has aristiform spines nearly as long and broad (22 x 1-4 mm, on average).
Habitat. Near streams in lowland and mid-elevation evergreen rainforest from Choco and Central American regions from sea level to elevations of ¢.1250 m. The Armored Rat might also occur in low-lying habitats such as palm swamps or wet cultivated areas. It is found in very moist habitats and primary or secondary rainforests. It occurs sympatrically with Tomes’s Spiny-rat in some areas. Compared with Tomes’s Spiny-rat, the Armored Rat is more associated with rocky habitats and mature moist and tall forests. Individuals occupy burrows systems near water, which are horizontal, might be 2 m long, and have nest chamber made of shredded vegetation.
Food and Feeding. The Armored Rat primarily feeds on fruits, seeds, and insects (e.g. beetles and orthopterans), and some green plant materials were found in some stomach contents.
Breeding. In central Panama, sex ratio of the Armored Rat was estimated at 1:1. It is sexually dimorphic with males 38% heavier than females. A maximum litter size of two young has been reported. The Armored Rat seems to be most reproductively active in April-August, but some pregnant females were collected in October and December in central Panama.
Activity patterns. The Armored Rat is nocturnal and terrestrial, and it occupies burrows as resting sites during the day.
Movements, Home range and Social organization. Local abundance of the Armored Rat appears highest in very moist and wet habitats, but it is less common than Tomes'’s Spiny-rat when the two morphologically similar taxa co-occur. Higher densities of Armored Rats were recorded in primary forest compared with secondary rainforest. Adult male and female Armored Rats were more closely associated than were those of sympatric Tomes’s Spiny-rat, suggesting monogamous or polygamous mating system. A mark-recapture study revealed a strong seasonal effect on density, being higher in May-June (1-69-2-89 ind/ha) and lower in October-December (0-69-0-89 ind/ha) in central Panama, which likely reflects reproductive seasonality keyed to variation in precipitation and ambient temperature.
Status and Conservation. Classified as Least Concern on The IUCN Red List. The Armored Rat is widespread and present in several primary and secondary rainforest habitats. Its distribution includes a number of protected parks, and overall it appears unlikely to be declining. Local people do hunt Armored Rats for food in central Panama. Additional studies on distribution, habitat, abundance, ecology, and conservation threats to the Armored Rat are needed.
Bibliography. Adler (2011), Adler et al. (1998), Alfaro (1896), Allen (1899b), Eisenberg (1989), Emmons (1990, 1997a), Goldman (1912a, 1912b, 1920), Gonzalez & Alberico (1993), Handley (1959), Patton (1987), Patton et al. (2015), Paynter (1993), Tesh (1970), Thomas (1897), Woods & Kilpatrick (2005).
description: Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Echimyidae, pp. 552-604 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on pages 567-568, DOI: 10.5281/zenodo.6623649