Transandinomys bolivaris, also known as the long-whiskered rice rat, is a rodent in the family Cricetidae. It is found in humid forest from northeastern Honduras to western Ecuador, up to above sea level. Since it was first described in 1901 from Ecuador, six scientific names have been introduced for it, but their common identity was not documented until 1998 and the species has long been known under the name Oryzomys bombycinus, described from Panama in 1912. The name Oryzomys bolivaris was used before it was moved to the new genus Transandinomys with Transandinomys talamancae (formerly Oryzomys talamancae) in 2006.
It is a medium-sized rice rat distinguished by its very long vibrissae (whiskers)—those above the eyes are up to long. The fur, which is soft and dense, is usually dark brown above and light gray below; it is darker in juveniles. The feet are long and the tail is about as long as the head and body. The skull is narrow and has a broad interorbital region (between the eyes). The species generally lives on the ground. Although it is rare, its conservation status is thought to be secure.
Taxonomy In 1901, Joel Asaph Allen described four new species of rice rat in the genus Oryzomys: three from Ecuador and the Peruvian Oryzomys perenensis. The three Ecuadorian species–Oryzomys bolivaris from Porvenir, Bolívar Province; Oryzomys castaneus from San Javier, Esmeraldas Province; and Oryzomys rivularis from Río Verde, Pichincha Province—were each based on a single specimen collected in 1899 or 1900.Allen, 1901, pp. 405–407; Musser et al., 1998, p. 271 He distinguished the three on the basis of coloration, size, and relative tail length.Musser et al., 1998, p. 273 Philip Hershkovitz listed all three among the many synonyms of "Oryzomys laticeps" (currently more narrowly defined as Hylaeamys laticeps) in a 1960 paper.Hershkovitz, 1960, p. 544
Edward Alphonso Goldman described Oryzomys bombycinus in 1912 from four specimens from Panama. He compared it to Oryzomys talamancae and placed it with the "Oryzomys laticeps group".Goldman, 1912, pp. 6–7 Three years later, he described Oryzomys nitidus alleni from Costa Rica as a subspecies of Oryzomys nitidus, without mentioning bombycinus. He revised Oryzomys of North America in 1918 and recognized Oryzomys bombycinus as the only member of its own group, with alleni as a subspecies distinguished by the proportions of the skull. He also mentioned that the group occurred in Ecuador and indicated that O. bombycinus probably reached Colombia. Goldman considered the group to be similar to O. talamancae, but suggested that bombycinus and alleni might only be subspecies of O. nitidus.Goldman, 1918, pp. 75–78 In 1939, Oliver Pearson added a third subspecies, O. b. orinus, from eastern Panama,Pearson, 1939, pp. 2–3 and in 1966 the species was first recorded from Colombia.Pine, 1971, p. 592 Ronald Pine reviewed Oryzomys bombycinus in 1971, when 59 specimens of it were known, and first recorded the species from Nicaragua and Ecuador.Pine, 1971, p. 590 He kept the three described subspecies—alleni from Nicaragua to western Panama, bombycinus from central Panama, and orinus from eastern Panama to Ecuador.Pine, 1971, fig. 1
Alfred Gardner and James Patton suggested in 1976 that Allen's O. rivularis may be the same species as O. bombycinus. They considered O. bolivaris as probably the same as O. nitidus and listed castaneus as a synonym of O. capito (equivalent to modern Hylaeamys megacephalus and closely related species plus Transandinomys talamancae).Gardner and Patton, 1976, pp. 39–41 In 1984, Benshoof and colleagues reported the first record of Oryzomys bombycinus from Honduras.Benshoof et al., 1984, p. 512 Guy Musser and Marina Williams reviewed O. talamancae in 1985 and included O. castaneus as one of its synonyms, though without having examined the holotype.Musser and Williams, 1985, p. 14 In the 1993 second edition of Mammal Species of the World, Musser and Michael Carleton used the name Oryzomys bolivaris for the species previously known as O. bombycinus, and in 1998, Musser and colleagues fully documented the allocation of the names bolivaris, castaneus, rivularis, bombycinus, alleni, and orinus to the same species, Oryzomys bolivaris.Musser et al., 1998, pp. 110, 273 They noted its similarity to O. talamancae, but did not attempt to determine phylogenetic relationships among the species they discussed.Musser et al., 1998, p. 323 In their limited material, they found geographic variation within the species inconsequential and they recognized no subspecies.Musser et al., 1998, pp. 148–149
In 2006, Marcelo Weksler published a phylogenetic analysis of Oryzomyini ("rice rats"), the tribe to which Oryzomys is allocated, using morphological and DNA sequence data. His results showed species of Oryzomys dispersed across Oryzomyini and suggested that most species in the genus should be allocated to new genera.Weksler, 2006, pp. 75–77 Later in the same year, he, together with Alexandre Percequillo and Robert Voss, named ten new genera for these species, including Transandinomys, which has Oryzomys talamancae (now Transandinomys talamancae) as its type species. They also included Oryzomys bolivaris in Transandinomys, so that it is now named Transandinomys bolivaris, although it had not been included in Weksler's phylogenetic study. The two species are morphologically similar, but they could identify only one synapomorphy (shared-derived trait) for them: very long superciliary vibrissae (whiskers above the eyes).Weksler et al., 2006, p. 26 Transandinomys is one of about 30 genera in Oryzomyini, a diverse assemblage of American rodents of over a hundred species,Weksler, 2006, p. 3 and on higher taxonomic levels in the subfamily Sigmodontinae of family Cricetidae, along with hundreds of other species of mainly small rodents.Musser and Carleton, 2005
Various authors have used the common name "long-whiskered rice rat" for this species,Pine, 1971, p. 570; Reid, 2009, p. 208 but several other names have been proposed. In 1918, Goldman named O. bombycinus bombycinus the "Long-Haired Rice Rat"Goldman, 1918, p. 77 and O. b. alleni the "Allen Rice Rat".Goldman, 1918, p. 78 Musser and Carleton, writing in the 2005 third edition of Mammal Species of the World, used "Long-whiskered Oryzomys",Musser and Carleton, 2005, p. 1146 the 2009 IUCN Red List gave "Bolivar Rice Rat", and Thomas Lee and colleagues used "Long-whiskered Trans-Andean Rice Rat" in 2010.Lee et al., 2010, p. 10
Description + MeasurementsMusser et al., 1998, table 25 Region nNumber of specimens measured. In some samples, the number varies by measurement. Head and body Tail Hindfoot Nicaragua 5 108.2 (99–119) 115.2 (99–126) 28.8 (27–32) Costa Rica,western Panama 9–13 118.7 (103–134) 113.2 (96–125) 30.3 (27–33) Central Panama 13–15 120.7 (111–140) 120.8 (111–130) 30.0 (27–33) Eastern Panama 5 116.8 (107–125) 117.6 (109–126) 28.0 (25–29) Colombia 8 127.4 (115–141) 121.3 (100–135) 30.5 (29–32) Ecuador 8–9 119.4 (111–133) 114.8 (100–127) 29.7 (28–32) Measurements are in millimeters and in the form "average (minimum–maximum)". Transandinomys bolivaris is a medium-sized rice rat with very long superciliary vibrissae (more than long and extending well beyond the ears when laid back against the head).Tirira, 2007, p. 199; Reid, 2009, p. 208 According to Fiona Reid's Mammals of Southeastern Mexico & Central America, it is distinguishable from any similarly sized rice rats by the length of these whiskers;Reid, 2009, p. 208 T. talamancae also has long superciliary vibrissae, but not as long as in T. bolivaris. In both species, the mystacial vibrissae (above the mouth) are also long and extend beyond the ears when laid back, but they are again much longer in T. bolivaris. The vibrissae are mostly dark, but translucent at the tips. Handleyomys alfaroi, a rice rat with which young T. bolivaris are often confused, is much smaller. In T. bolivaris, the cheeks may be light gray, buff, or reddish. The ears are dark brown to black and are sparsely haired.Musser et al., 1998, p. 121
The fur, which is soft, dense, and thick,Musser et al., 1998, p. 123 is dark brown to gray on the upperparts, grading to black on the midback and yellowish brown on the sides. The underparts are sharply different in color. There, the hairs are dark gray at their bases and white at the tips, so that the fur appears grayish white. The fur is shorter and darker than in T. talamancaeMusser et al., 1998, p. 128 and softer and thicker than in H. alfaroi.Musser et al., 1998, p. 143 Young animals have darker, finer, and softer fur. Pine separated the subspecies alleni and orinus on the basis of their darker fur,Musser et al., 1998, pp. 145–146 but Musser and colleagues could not confirm this pattern and found paler and darker specimens within the same geographical regions.Musser et al., 1998, p. 148
The tail appears naked and is shorter than or about as long as the head and body;Musser et al., 1998, p. 121; Tirira, 2007, p. 199 it is longer in T. talamancae.Musser et al., 1998, p. 427 Its coloration is variable; it is dark brown above and at the sides and light brown and often white to a greater or smaller extent below, and in some specimens the tail has the same color above and below. The scales on the tail are smaller than in T. talamancae.Musser et al., 1998, p. 129
The forearms are dark gray. The forefeet are unpigmented and ungual tufts of white hairs surround the equally unpigmented claws. The animal has long, narrow hindfeet, longer than in T. talamancae, with usually smooth soles (lacking squamae, which are present in T. talamancae). The three middle digits are much longer than the outer two. Six pads are present on the sole. The upper surface and the sides of the hindfeet are white and appear naked, although short, white hairs are present;Musser et al., 1998, p. 124 these hairs are longer in T. talamancae.Musser et al., 1998, p. 131 Ungual tufts of long, white or gray hairs are present around the claws,Musser et al., 1998, p. 124; Reid, 2009, p. 208 which are short and lack pigment.
Head and body length is , tail length , hindfoot length , ear length , and body mass . Females have four pairs of mammae, as usual in oryzomyines. Like most rice rats, T. bolivaris has twelve thoracic (chest) and seven lumbar vertebrae.Steppan, 1995, table 5 A study in Costa Rica found that there are 58 chromosomes, including many that are large and have two arms, and the fundamental number of arms is 80 (2n = 58, FN = 80), a highly differentiated karyotype. The karyotype of T. talamancae is variable, but has fewer chromosomes (34 to 54) and major arms (60 to 67).Musser et al., 1998, table 13 H. alfaroi has more chromosomes (60 to 62) and major arms (100 to 104).
Skull and teeth
The skull is relatively long and has a long, narrow rostrum (front region), broad interorbital region (between the eyes) and narrow braincase with almost vertically oriented walls at the sides and behind. It differs from that of T. talamancae in various proportions. Although the subspecies previously recognized in "Oryzomys bombycinus" have been separated by small differences in skull features, Pine rejected these on the basis of his much larger samples.Musser et al., 1998, p. 145 Musser and colleagues agreed, but noted that Colombian animals appeared to have larger skulls.Musser et al., 1998, p. 146 The zygomatic plates are broad and the zygomatic arches (cheekbones) behind them are nearly parallel to each other. The margins of the interorbital region contain prominent beads, which extend to the braincase as temporal ridges; these are usually less well-developed in T. talamancae.Musser et al., 1998, p. 135 Unlike in T. talamancae and H. alfaroi, the parietal bone is usually limited to the roof of the braincase and does not extend to the sides.Musser et al., 1998, pp. 135, 143; Weksler et al., 2006, p. 25