Proechimys semispinosus (Tomes, 1860)

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 : 571-572

36.

Tomes’s Spiny-rat

Proechimys semispinosus

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

Other common names: Gorgona Island Spiny-rat (gorgonae)

Taxonomy. Echimys semispinosus Tomes, 1860 ,

“Gualaquiza, SE Ecuador.” Amended by A. L. Gardner in 1983 to “Esmeraldas, province Esmeraldas, on the Pacific coast of Ecuador.”

Proechimys semispinosus is a member of the semispinosus-species group. As currently understood, it is polytypic; subspecies boundaries, and thus status, on the mainland of Colombia and Ecuador have not been fully ascertained. The form calidior named by O. Thomas in 1911 is considered a synonym of the nominate subspecies and the form chiriguinus named by Thomas in 1900 a synonym of panamensis, Echinomys semispinosus named by F. W. True in 1889 is included in the subspecies centralis. Ten subspecies recognized, but ranges poorly known and their validity needs to be properly assessed.

Subspecies and Distribution.

P. s. semispinosusTomes, 1860 — NWEcuador (EsmeraldasProvince).

P. s. burrusBangs, 1901 — SanMiguelI, PearlIs (offSCPanama).

P. s. centralisThomas, 1896 — EHonduras, E & CNicaragua, andN & ECostaRica.

P. s. colombianusThomas, 1914 — WColombia (Pacificlowlands).

P. s. goldmaniBole, 1937 — SWPanama (AzueroPeninsula).

P. s. gorgonaeBangs, 1905 — GorgonaI (offSWColombia).

P. s. ignotusKellogg, 1946 — IslaSanJosé, PearlIs (offSCPanama).

P. s. panamensisThomas, 1900 — SWCostaRicathroughmostofPanamaandpossiblyextendingintoNWColombia.

P. s. rosaThomas, 1900 — SWEcuador.

P.s. rubellus Hollister, 1914 — C Costa Rica (Angostura Valley, Cartago Province).

Descriptive notes. Head-body 290 mm, tail 240 mm; weight 0-26—c.1 kg. Tomes’s Spinyrat is moderately variable in weight geographically, larger in Central America and northern Colombia than in the southern part ofits distribution in Ecuador. Tail length also varies proportionally from ¢.63% of head-body length in the north to ¢.70% in the south. Dorsal color is rather consistently dark reddish brown, laterally speckled with black; sides are only slightly lighter but still contrasting sharply with uniformly white venter. Pale inner thigh stripe does not continue across ankle onto dorsal surface of hindfoot, which is uniformly dark. Plantar pads are well developed, and thenar and hypothenar pads enlarged and sub-equal in size. Tail is sharply bicolored, dark brown above and pale below, particularly in northern specimens but less bicolored in southern samples from north-western Ecuador. Hairiness of tail varies among individuals, with some moderately covered with elongated hairs such that tail scales are nearly hidden from view while other individuals from the same population have more typical sparsely haired tails. Scale annuli are well developed and usually obvious to the eye, averaging 7-8 annuli/cm. Dorsal pelageis stiff to the touch, but aristiform development also varies from north to south. These spines are of equal length (19-21 mm) in all populations, but vary in width and hencestiffness (0-9-1-1 mm in northern samples and 0-6-0-8 mm in southern ones). Nevertheless, each aristiform terminates in elongated, filamentlike, not blunt, tip. Skull is large and broad across zygomatic arches, and rostrum is elongated and narrowed. Tomes’s Spiny-rat is uniquely characterized among spiny-rats by its well-developed temporal ridges extending from supraorbital ledge across length of parietals. Only rarely is this ridge interrupted into anterior and posterior segments. Incisive foramina of most specimens are rather narrow, with almost parallel sides, or weakly lyre-shaped; posterolateral margins are usually strongly flanged, creating deep grooves extending onto anterior palate despite only moderate development of medial ridge; premaxillary part of septum is long, encompassing nearly entire length of opening; maxillary part varies from well developed to attenuate, is only weakly keeled at best, and is nearly always in contact with premaxillary part; and vomer is completely hidden from ventral view. Floor of infraorbital foramen has groove supporting infraorbital branch of maxillary nerve and is formed by well-developed lateral flange. Mesopterygoid fossa is of moderate width, but angle becomes broader from north to south (57-62°). In contrast to O’Connell’s Spiny-rat (PF. oconnelli ), post-orbital process of zygoma of Tomes’s Spiny-rat is moderately well developed and more commonly formed byjugal (especially in northern samples, less so in southern ones). Counterfold pattern is similar to that of species of the goelditspecies group, with four folds commonly present on all upper cheekteeth and M,, and less commonly on M, and even M,. Nevertheless, fold number decreases in samples from northern Colombia to southern Ecuador (subspecies rosa), where four folds are rare on all teeth and two folds may be found on M? and all lower molars. Therefore, counterfold formula is 4(3)-4(3)—4(3)-4(3-2) /4-4(3-2)-4(3-2)—4(3-2). Baculum is massive, long (length 8:5-9-7 mm), and broad (proximal width 4-2—4-9 mm; distal width 5-1-6:2 mm), with deeply concave margins, broadly expanded and thickened base, and wide distal part with well-developed apical wings separated by median depression. Chromosomal complements are 2n = 30 and FN = 54 in Costa Rica; 2n = 30 and FN = 50-54 in Panama, Colombia, and Ecuador; and 2n = 30 and FN = 56 in Pacific lowlands and Gorgona Island, Colombia.

Habitat. Primary lowland rainforest and secondary growth, mostly along riparian corridors and low-lying habitats, from sea level to elevations of ¢.500m. Tomes’s Spiny-rat enters tropical deciduous forest in the southern tip of its distribution. It has also been reported in disturbed habitats such as logged or otherwise fragmented forests.

Food and Feeding. Diet of Tomes’s Spiny-rat is mainly fruit and seeds, with lesser amounts of other plant material, insects, and fungi. Large seeds and palm nuts are usually carried to a secure feeding place such as a hole. Tomes’s Spiny-rat is an important disperser of several tropical fruit species.

Breeding. Pregnant Tomes’s Spiny-rats give birth to precocious young; litters are 1-5 young. In Panama, they breed throughout the year, with females potentially producing four successive litters.

Activity patterns. Tomes’s Spiny-rat is nocturnal, terrestrial, and solitary.

Movements, Home range and Social organization. Tomes’s Spiny-rats nest in burrows or cavities under logs, usually in dense vegetation. Insular populations were reported to have midto high density on five islands in Gatun Lake, central Panama. Male home ranges were estimated to be larger than those of females, but home ranges of both sexes overlapped extensively indicating no territoriality. Adults also had small home ranges with greater spatial overlap through rainy seasons when resources were most abundant. In general, degree of overlap was positively correlated with population density. In cases of high density, adults potentially shared diurnal resting sites such as burrows, which were not individual specific. A negative correlation between home range size and density suggested that abundance of food resources had an influence on home range size and degree of overlap. Mating system of Tomes’s Spiny-rat also varied with density and resource abundance, being mostly monogamous on lowdensity islands but polygynous or promiscuous on high-density islands. Seasonality was also a significantly correlated with home range and spatial overlap; overlap increased throughout the rainy season due to an increase in abundance of fruit, providing a greater chance of mating than in the dry season.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Tomes’s Spiny-rat is widespread and abundant; it is present in multiple forest types across its known distribution and occurs in several protected areas; and it is unlikely to be declining. Increased forest conversion with spread of large-scale agriculture oflarge parts ofits distribution, however, suggest that continued studies are needed to assess conservation status over the next few decades. Despite being common, few detailed population studies of Tomes’s Spiny-rat beyond those in central Panama have ever been undertaken.

Bibliography. Adler (1995, 1996, 1998, 2000, 2011), Adler & Beatty (1997), Adler & Kestell (1998), Adler & Lambert (1997), Adler & Seamon (1991), Adler, Endries & Piotter (1997), Adler, Tomblin & Lambert (1998), Alho (1981), Allen (1899b), Bangs (1901), Bole (1937), Cabrera (1961), Eisenberg & Redford (1999), Endries & Adler (2005), Gardner (1983), Goldman (1920), Hollister (1914a, 1914b), Kellogg (1946), Lambert & Adler (2000), Mangan & Adler (1999), McKee & Adler (2002), Moojen (1948), Patton (1987), Patton & Gardner (1972), Patton & Leite (2015), Patton & Reig (1989), Seamon & Adler (1999), Thomas (1882, 1900a, 1911b), Tomblin & Adler (1998), Tomes (1860), Travi et al. (2002), True (1889a).

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)

Subspecies and Distribution. P. s. semispinosusTomes, 1860 — NWEcuador (EsmeraldasProvince). P. s. burrusBangs, 1901 — SanMiguelI, PearlIs (offSCPanama). P. s. centralisThomas, 1896 — EHonduras, E & CNicaragua, andN & ECostaRica. P. s. colombianusThomas, 1914 — WColombia (Pacificlowlands). P. s. goldmaniBole, 1937 — SWPanama (AzueroPeninsula). P. s. gorgonaeBangs, 1905 — GorgonaI (offSWColombia). P. s. ignotusKellogg, 1946 — IslaSanJosé, PearlIs (offSCPanama). P. s. panamensisThomas, 1900 — SWCostaRicathroughmostofPanamaandpossiblyextendingintoNWColombia. P. s. rosaThomas, 1900 — SWEcuador. P.s. rubellus Hollister, 1914 — C Costa Rica (Angostura Valley, Cartago Province).