Description

Diagnosis: This salamander is a moderately large sexually dimorphic species (males average 52.7 mm SL, females average 76.3 mm SL) that is charcoal-gray with white flecking on the dorsum. Distinguished from other large black Bolitoglossa as follows: B. robusta has a cream-colored ring on the tail and more maxillary teeth; B. nigrescens has a more robust trunk, longer limbs, and a higher mean number of maxillary and vomerine teeth; B. magnifica is larger in size and has fewer maxillary and vomerine teeth; B. obscura has fewer maxillary and vomerine teeth; B. copia has more interdigital webbing and has white coloration around the jaws, gular region, and throat; B. anthracina has a narrower head and considerably more maxillary teeth (Hanken et al. 2005).

Description: Adult males measure 44.1-61.5 mm in SL (average 52.7 mm); females measure 69.9-82.7 mm (average 76.3 mm). The tail length is shorter than SL, with SL/TL ratio of 1.27 in males and 1.17 in females. The head is markedly rugose, and is broad in males but narrower in females. Snout is truncated. Nostrils are small. Nasolabial protuberances are small in females but are well developed in males. Mental glands in males are oval in shape and are wider than long. The postiliac gland appears as a large pale spot. Eyes are located within the jaw margins. 2-4 premaxillary teeth are present in both sexes; 20-49 maxillary teeth in males and 59-77 in females; 23-44 vomerine teeth in males and 48-53 in females. The premaxillary teeth of males are small and protrude through upper lip. The limbs are long. The limb interval is 1.5 in males and 2.0 in females. The hands and feet are large and digits have bluntly pointed digital tips. Webbing is less extensive in adults than in juveniles. The two distal-most phalanges of the longest digits of adults are free of webbing. The fingers are 3>2>4>1 in order of decreasing length, while toes are 3>4>2>5>1. All digits have well developed subterminal pads. Skin is rough or rugose and glandular (Hanken et al. 2005).

In life, the holotype was mottled charcoal, grayish black, and pale brown-black when first captured, but subsequently the coloration changed to dark blackish brown while the salamander was in captivity. Dorsum is flecked with numerous widely scattered gray to white spots. Venter is black with widely scattered white flecks. Proximal portions of the hind limbs are dark orange. Hands and feet are gray. Iris is dark brown. The mental gland is pigmented but paler than the ground color. Subadults and juveniles have small white patches on lateral and ventrolateral surfaces of the body. A subadult was light gray when captured, but turned to solid dark black in captivity with two white patches on the tail base ventrolaterally.

In preservative, the white flecks become obscure. Those that remain most prominent are found on the tail and close to the tail base (Hanken et al. 2005).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Costa Rica, Panama

View distribution map in BerkeleyMapper.

Bolitoglossa sombra is known from the Pacific slopes of the Cordillera de Talamanca of Costa Rica and western Panamá (from Cerro Frantizius to Las Tablas). It may occur near Santa Clara in western Panamá, but the identity of the single specimen from this locality has not been confirmed. It inhabits tropical premontane and lower montane rainforest at elevations ranging from 1500 to 2300 m asl. Salamanders were found 0.6-2.0 m above the ground, on moss-covered tree trunks, resting in a machete slice in a tree trunk, between mossy buttresses of a tree on top of leaf litter, on stumps, underneath moss on a tree trunk, in the leaf axil of a bromeliad, and on a concrete structure leading to an underground aqueduct (Hanken et al. 2005).

Life History, Abundance, Activity, and Special Behaviors
B. sombra is an agile and active salamander. One individual was found climbing rapidly up a tree trunk. This species uses its prehensile tail freely as it moves. On the Pacific slopes of Cerro Pando, it is sympatric with with B. compacta, B. marmorea, and Oedipina grandis. It is presumed to breed by direct development (Hanken et al. 2005).

Trends and Threats
It has a limited range and probably does not tolerate much habitat degradation, making it vulnerable to habitat destruction. However, it occurs within protected reserves: Parque Internacional La Amistad, including the Las Tablas protected area, in Costa Rica. Chytridiomycosis may be a threat (Stuart et al. 2008).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities

Comments

First described by Hanken et al. (2005). The specific name derives from the Spanish sombra, meaning "shadow", referring to the dark coloration of the body.

A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).

References

Hanken, J. Wake, D. B., and Savage, J. M. (2005). ''A solution to the large black salamander problem (genus Bolitoglossa) in Costa Rica and Panamá.'' Copeia, 2005(2), 227-245.

Stuart, S., Hoffmann, M., Chanson, J., Cox, N., Berridge, R., Ramani, P., Young, B. (eds) (2008). Threatened Amphibians of the World. Lynx Edicions, IUCN, and Conservation International, Barcelona, Spain; Gland, Switzerland; and Arlington, Virginia, USA.

Species Account Citation: AmphibiaWeb 2011 Bolitoglossa sombra: Shadowy Web-Footed Salamander <https://amphibiaweb.org/species/6433> University of California, Berkeley, CA, USA. Accessed Nov 22, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Nov 2024.

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