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Diagnosis: Small to moderately-sized salamander (males 26-57 mm SL, females 38-67 mm SL); moderate digital webbing; adults with 45-57 maxillary teeth; moderately long tail; high color variation (dorsum may be brown to light gray to black; mottling present or not; sometimes brick red to yellow middorsal field; often pink or red limbs and throat; venter may be brown with darker markings to black with sparse white spots).
Description: Bolitoglossa pesrubra is a common small to medium-sized species with moderate digital webbing. Adults are 60 to 131 mm in total length. Adult males measure 26 to 57 mm in standard length, while adult females measure 38 to 67 mm in standard length. Tail length is moderate, measuring about 49 to 51% of total length. Eyes are large and protruding. Adults have 45 to 65 maxillary teeth, extending to 3/4 the length of the eye, and 21 to 33 vomerine teeth. Adult males have 0 to 2 1/2 costal folds between adpressed limbs, while adult females have 1 to 3. Hands and feet are moderately webbed, with at least two phalanges on the longest two or three digits free of webbing. Subterminal pads are present. Head width is 14 to 17% of standard length, and leg length is 22 to 25% of standard length (Savage 2002).
Dorsal ground color varies from shiny brown to light gray to black, with or without dark brown to black mottling, or sometimes black with light spots. Paler areas are often reddish or pinkish. A broad brick-red to yellow middorsal field is sometimes present. Limbs and throat will often be pink or red. Venter may be brown with darker markings to black with scattered white spots or blotches (Savage 2002).
This species was first described by Taylor (1952), as B. pesrubra, and subsumed into B. subpalmata by Vial (1966); much of the literature on this species is under B. subpalmata. It was separated again from B. subpalmata by García-París et al. (2000). The taxon now considered B. pesrubra may still represent several species (Stuart et al. 2008).
The karyotype is 2N=26, NF (nombre fundamental, the number of chromosome arms)=52; all chromosomes are biarmed. No heteromorphism is present in sex chromosomes of this species (Kezer 1964; León and Kezer 1978).
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).
Costa Rica. Restricted to the central Cordillera de Talamanca, including the Fila Cedral, from 1,870-3,620 m asl (Savage 2002; García-París et al. 2000). Populations in the southern Talamanca are probably a different species. It is found in humid lower montane, montane, and sub-alpine zones, in forest as well as in disturbed areas such as road edges and garbage dumps (Stuart et al. 2008). Although the habitat is continuous it is quite heterogeneous at different elevations; the Sakira and Villa Mills areas are higher elevation cold and wet páramo habitat (6–9°C and 1,700–4,000 mm rain/year 6–9°C), with a moderate seasonal water deficit and primarily bamboo and shrubs for vegetation (García-París et al. 2000). In the lower elevation Salsipuedes area, the climate is mild and wet (12–15°C, 2,300–5,100 mm rain/year), with a small seasonal water deficit (García-París et al. 2000).
This is the only species of salamander currently known from the seasonally dry páramos of Central America (Kappelle and Savage 2005), though other salamander species have been found in South American páramo (e.g., Bolitoglossa hiemalis from Colombia (Lynch 2001).
This species is a nocturnal generalist, eating a wide variety of small arthropods (e.g., Coleoptera, Diptera, Collembola, Acarina; Mead and Boback 2002). It is active throughout the year, at temperatures ranging from 0 to 20°C (Savage 2002). At higher elevations, it is mostly terrestrial, hiding under surface debris or bark during the day and foraging for food at night on low vegetation and moss mats (Savage 2002). At lower elevations, B. pesrubra is semiarboreal; it can often be found hiding in bromeliads during the day (Savage 2002).
Egg clutches are made up of 13 to 38 eggs. Each egg measures about 5 mm in diameter and is surrounded by a vitelline membrane plus two gelatinous layers. In higher-elevation populations, on the continental divide in the Cordillera de Talamanca, clutches are laid under rocks and logs. Females from lower-elevation also make use of bromeliads or other plants with suitably large axils for clutch deposition sites. Clutch attendance is generally done by females but Vial (1968) found that in about thirteen percent of cases (four of thirty-one) the male tended the clutch. The parent attending the clutch coils around the eggs with the head and throat resting on top of the egg mass, and rotates the eggs every few days. Attendance is nearly continuous over the four to five months of embryonic development. Unattended clutches fail to develop. Development is direct (Vial 1968).
In the wild, individuals are estimated to grow slowly, about 3 mm per year, and to reach sexual maturity at 6 years for males and 12 years for females (Vial 1968). Under captive conditions, however, growth can be up to 5x as fast, with males reaching sexual maturity in about 1.5 years and females maturing at 3 years (Houck 1982). Prey availability may be the reason for the differing growth rates in captivity vs. the wild (Savage 2002). Longevity has been estimated to be about 18 years (Vial 1968).
In a six-month study (Vial 1968, as B. subpalmata), the species was found not to be very vagile; distances away from original capture sites ranged from 0.1 m to 50 m. Juveniles moved an average of 2.8 m, while females moved an average of 3.7 m and males moved an average of 5.4 m. Home ranges were 44 sq m on average (Savage 2002).
Population densities at high elevations are some of the highest recorded for salamanders; 9,297 individuals/ha at 3,200 m (Vial 1968). Densities are lower at lower elevations; at 2,438 m the population density dropped to 756/ha (Vial 1968). Population density also varied seasonally, with higher densities noted in the rainy months (May-November) and lower densities in the driest month (March).
This species is apparently toxic to predators; Thamnophis snakes were observed to be incapacitated or in serious discomfort after consuming B. pesrubra salamanders (Brodie et al. 1991). Tail displays are also used as a defense against predators, though this species rarely sheds its tail when seized by snakes (Ducey and Brodie 1991; Ducey et al. 1993). There are no snakes at the higher elevations occupied by B. pesrubra, and B. pesrubra salamanders from higher elevations were less likely to make tail displays when threatened (Ducey and Brodie 1991; Ducey et al. 1993).
Analysis of mitochondrial cytochrome b sequences showed strong phylogeographic structure among B. pesrubra populations, with three distinct phylogeographic units: Villa Mills, Sakira, and Salsipuedes (García-Paris et al. 2000). Average population heterozygosity for B. pesrubra is exceptionally high for vertebrates, at 0.23–0.28 (Hanken and Wake 1982). This is likely due to the combination of a nonmigratory life history (direct terrestrial development with no need to migrate to a water source), low vagility, small home ranges, and high philopatry (García-Paris et al. 2000).
Although this species achieves some of the highest densities ever recorded for salamanders (0.5 individuals/sq m, or 9,297/ha, at high elevations of 3,200 m; Vial 1968), B. pesrubra is growing increasingly rare and is estimated to have suffered more than a 30% population decline over the past fifteen years/three generations (Stuart et al. 2008). Declines are patchy and enigmatic; some populations have declined by up to 90%, e.g., at Cerro de la Muerte, where no animals were recorded in 2005 surveys; Lips and Donnelly 2005; and at Cerro Cuerici, Stuart et al. 2008; in other areas this species is still common (Stuart et al. 2008). B. pesrubra showed marked declines in 1987-1988 (Savage 2002), at a time when many other Costa Rican anuran species (especially Atelopus species) were also undergoing sudden population crashes (Pounds et al. 1997). Modeling predicts that the range occupied by this salamander is highly suitable for the amphibian chytrid fungal pathogen Batrachochytrium dendrobatidis (Bd) (Lötters et al. 2010). B. pesrubra can apparently tolerate disturbed habitat since it has been found at roadside edges and in garbage dumps (Stuart et al. 2008), implying that disease (such as chytridiomycosis) is likely to have played more of a role in its decline than habitat loss. It occurs within several protected areas, including Parque Nacional Chiripó, Parque Nacional Tapantí and Reserva Biológica Cerro las Vueltas (Stuart et al. 2008).