Description
Craugastor occidentalis is a frog with an adult snout-vent length range of 27.79 - 32.24 mm in males and 31.40 - 40.44 mm in females. There is a ‘Y-shaped’ supratympanic fold that extends onto the lateral surfaces of the dorsum. This fold is usually unbroken, but some individuals from Colima and Jalisco have been examined where this fold is broken. The dorsum is highly glandular, sometimes tubercles form a short longitudinal series of warts on the posterior half of the dorsum, and there are often dark blotches associated with individual glands. Most adults have open hourglass glandular ridging on the dorsum in addition to short linear ridging (Streicher et al. 2014).

Craugastor occidentalis can typically be differentiated from all other members of the C. rhodopis Species Group by a distinctive ‘Y-shaped’ supratympanic fold that extends onto the lateral surfaces of the dorsum (Streicher et al. 2014).

Individuals of this species typically possess a supratympanic dark stripe or patch. Dorsal ground color occurs in varying shades of grey, tan or brown. Extensive lip barring is common. Some individuals have a thin mid-dorsal stripe, white arms and/or a distinctive white upper labium. Bright red coloration on the axial and postaxial thigh surfaces has been observed in an individual from Guerrero (Streicher et al. 2014).

Males often had dark throats and proportionally larger tympana than females (Streicher et al. 2014).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Mexico

View distribution map in BerkeleyMapper.

This species is distributed in western Mexico across a wide range of elevations (15 - 2500 m). It occurs primarily in lowland tropical dry forests and high elevation pine-oak forests and is distributed as far north as the Mexican state of Sonora (Arenas-Monroy et al. 2012; Streicher et al. 2014).

Life History, Abundance, Activity, and Special Behaviors
The call consists a series of five high frequency bird-like chirps followed by 1 - 3 quieter single note peeps. The duration of the call is between 5 and 6 seconds. Males were observed calling from positions at forest floor level to approximately 3.5 m into the understory (Streicher et al. 2014).

Larva
Presumably direct-developing like other species of the genus Craugastor.

Trends and Threats
None listed at as of 2023.

Relation to Humans
Lives adjacent to some agricultural areas (IUCN 2020).

Comments
Bayesian and Maximum Likelihood analysis of 12s mtDNA found that C. loki is sister to C. rhodopis and together they are sister to C. occidentalis. However, the amount of sequence divergence within each species indicate that there may be more potential taxonomic subdivision (Streicher et al 2014).

Phylogenetic analyses of C. occidentalis have revealed evidence of a phylogeographic break in the species. The break between two divergent clades of C. occidentalis occurs more or less at the terminus of the Trans-Mexican Volcanic Belt (TMVB) in western Jalisco (Streicher et al. 2014). As such, the TMVB may have been a dispersal filter barrier for C. occidentalis, a finding that is consistent with patterns observed in other amphibian species inhabiting both sides of this geological boundary (e.g. Smilisca fodiens; Cox et al. 2012).

This species was originally described by Boulenger (1898) as Borborocoetes mexicanus. It was determined that a replacement scientific name was necessary because a different species in the same genus described earlier by Brocchi (1877) used the same specific epithet, mexicanus. Taylor (1941) provided the replacement name, Eleutherodactylus occidentalis, and is therefore credited as the species authority.

Parasites have been described from a population in Jalisco (Martínez–Salazar 2008).

References
Arenas-Monroy, J.C., González-Saucedo, Z.Y., Carbajal-Márquez, R.A. and Rodríguez, J.J. (2012). Geographic distribution: Craugastor occidentalis (Taylor’s Barking Frog). Herpetological Review 43(2), 298. [link]

Boulenger, G.A. (1898). Fourth report on additions to the batrachian collection in the Natural-History Museum. Proceedings of the Zoological Society of London 1898, 473–482. [link]

Brocchi, P. (1877). Sur quelques batraciens raniformes et bufoniformes de l’Amérique Centrale. Bulletin de la Société Philomathique de Paris. 1(7), 175–197. [link]

Cox, C.L, Streicher, J.W., Sheehy III, C.M., Campbell, J.A. and Chippindale, P.T. (2012). Patterns of genetic differentiation among populations of Smilisca fodiens. Herpetologica 68, 226–235. [link]

IUCN SSC Amphibian Specialist Group. (2020). Craugastor occidentalis. The IUCN Red List of Threatened Species 2020: e.T56801A3050260. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T56801A3050260.en. Accessed on 28 November 2023.

Martínez–Salazar, E.A. (2008). A new rhabdiasid species from Craugastor occidentalis (Anura: Brachycephalidae) from Sierra de Manantlan, Jalisco, Mexico. Revista Mexicana de Biodividad 79, 1. [link]

Taylor, E.H. (1941) Some Mexican frogs. Proceedings of the Biological Society of Washington 54, 87–94. [link]

Streicher, J.W., García-Vázquez , U.O., Ponce-Campos, P., Flores-Villela, O., Campbell, J.A. and Smith, E.N. (2014) Evolutionary relationships amongst polymorphic direct-developing frogs in the Craugastor rhodopis species group (Anura: Craugastoridae). Systematics and Biodiversity 12(1), 1–22. [link]

Species Account Citation: AmphibiaWeb 2023 Craugastor occidentalis: Western Leaf-litter Frog <https://amphibiaweb.org/species/3090> University of California, Berkeley, CA, USA. Accessed Sep 12, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 12 Sep 2024.

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