Description
Brachycephalus herculeus is a small, stout-bodied frog with adult male and female snout-vent length ranges of 11.8 - 14.7 mm and 13.9 - 15.2 mm respectively. The head is shorter than wide. In both the lateral and dorsal views, the short snout is rounded. The protuberant nostrils are oriented posterolaterally. The distinct canthus rostralis is straight and the loreal region is weakly concave. The mouth has a slight sigmoid shape. The eyes are about 60% of the head length and protrude in both the dorsal and lateral views. There is no tympanum. However, there are small, bulging parotid glands present immediately posterior to the eyes. The skin on the head and dorsum is ossified. The skin in general appears warty because of osteoderms scattered across the body and limbs, both dorsally and ventrally. The ventrolateral surfaces and area around the cloacal opening are also granular. The limbs are short and slender. The upper arm length is 78% of the forearm length. There are no metacarpal tubercles. Only fingers III and IV are distinct, with fingers II and V being vestigial. The tip of the smaller finger III is rounded while the IV is pointed. The tibia is shorter than the thigh, and the foot is longer than the thigh. There are no metatarsal tubercles. Toes II, III, and IV are distinct, but toe I is externally absent and toe V is vestigial. The relative toe lengths are II < III < IV with the tips of toes II and III being round and toe IV being pointed (Folly et al. 2024).

DIAGNOSIS:

Brachycephalus herculeus can be distinguished from similar species such as Brachycephalus ephippium by the combination of leaf-colored green wash (as opposed to it being absent or olive green) on the dorsum that does not extend to the flanks or sides of the head, plus the presence of osteoderms (Folly et al. 2024).

COLORATION:

In life, the dorsum is mostly orange with a green wash down the center of the head and body and on the dorsal surface of the hind limbs. The hands, feet, elbows, knees, and ankles are orange. The ventrum is bright orange-yellow. The osteoderms appear as small yellow bumps on the skin. The eyes are entirely black. In preservative, the body, hands, and feet are beige and limbs gray. There are paired gray blotches on either side of the vertebral column and a cream stripe below the eyes and the osteoderms appear as small white bumps (Folly et al. 2024).

VARIATION:

On average, females are about 2 mm larger in snout-vent length than males. The concentration of osteoderms can vary from individual to individual, as well as coloration in preservative, which can range from cream to gray on the dorsum, head, and limbs (Folly et al. 2024).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

View distribution map in BerkeleyMapper.

The entire Brachycephalus genus is endemic to the Brazilian Atlantic forest (Hedges et al. 2008). At the time of the species description, the distribution of B. herculeus was only known from the type locality, which is in Desengano State Park of Rio de Janeiro, southeastern Brazil. This area consists of montane rainforest and B. herculeus can be found between 1000 - 1200 m a.s.l. in leaf litter or other plant material on the ground (Folly et al. 2024).

Life History, Abundance, Activity, and Special Behaviors
This is a terrestrial, diurnal species that can be found active in leaf litter and occasionally in plants on or around the bases of trees. During the rainy season it is associated with sloping ground near trails (Folly et al. 2024)

Adult males exhibit advertisement calls, often calling unexposed from leaf litter and other surface objects. The call consists of a single repeating pulse note and can last for several minutes (Folly et al. 2024).

The exact timing of the breeding season is unknown, although an amplecting pair was found in February of 2011, suggesting that they likely breed during the rainy season, like other closely related species. The pair exhibited axillary amplexus but switched to inguinal when confronted (Folly et al. 2024).

This genus reproduces via is a direct development (Hedges et al. 2008).

Larva
This species is assumed to be direct developing, like other members of the genus (Hedges et al. 2008).

Trends and Threats
As an Atlantic Forest endemic species with an extremely narrow distribution, B. herculeus is likely greatly impacted by any habitat loss that occurs within its range (Bornschein et al. 2019). More research is needed to understand the population trends of this species and any threats it may face (Folly et al. 2024). As such, the IUCN does not currently have a conservation status listed for this species. However, this species does occur within a protected area, Parque Estadual do Desengano (Folly et al. 2024). On a broader scale, legislation such as the Brazilian Forest Act and the Atlantic Forest Act exist to mitigate the factors contributing to habitat loss in these areas (Calmon et al. 2011)

Possible reasons for amphibian decline

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

Comments

PHYLOGENETIC RELATIONSHIPS:

References
Folly, M., Condez, T. H., Vrcibradic, D., Rocha, C. F. D., Machado, A. S., Lopes, R. T., and Pombal Jr., J. P. (2024). A new species of Brachycephalus (Anura: Brachycephalidae) from the northern portion of the state of Rio de Janeiro, southeastern Brazil. Vertebrate Zoology, 74, 1–21. [link]

Hedges, S. B., Duellman, W. E., and Heinicke, M. P. (2008). New World direct-developing frogs (Anura: Terrarana): Molecular phylogeny, classification, biogeography, and conservation. Zootaxa, 1737(1), 1–182. [link]

Bornschein, M. R., Pie, M. R., and Teixeira, L. (2019). Conservation status of Brachycephalus toadlets (Anura: Brachycephalidae) from the Brazilian Atlantic Rainforest. Diversity, 11(9), 150. [link]

Calmon, M., Brancalion, P. H. S., Paese, A., Aronson, J., Castro, P., Da Silva, S. C., and Rodrigues, R. R. (2011). Emerging threats and opportunities for large‐scale ecological restoration in the Atlantic Forest of Brazil. Restoration Ecology, 19(2), 154–158. [link]

Species Account Citation: AmphibiaWeb 2024 Brachycephalus herculeus <https://amphibiaweb.org/species/9842> University of California, Berkeley, CA, USA. Accessed May 2, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 2 May 2025.

AmphibiaWeb's policy on data use.