Description
Micrixalus fuscus is a small frog with a snout-vent length (SVL) of 32 mm. The dorsum and venter has smooth skin. It has a pointed, prominent snout that is longer than the orbital diameter. The canthus rostralis is angular and this species has a flat loreal region that is vertical. The nostril is halfway between the eye and the snout tip. It has a glandular lateral fold and a fold from the eye to the shoulder. The tympanum is small and indistinct. The fingers are not webbed, but the toes are completely webbed. Subarticular tubercles are small and it has a small inner metatarsal tubercle. (Boulenger 1882).

Diagnosis: It is similar to M. phyllophilus, but can be distinguished by the absence of a papilla in the middle of the tongue and does not have bright pink coloration on the ventral sides of the thighs and belly as does M. phyllophilus (Boulenger 1882).

Coloration: M. fuscus has a light tan to dark reddish brown to nearly black dorsum with black marbling or spotting (Inger 1984). The flanks are darker. The venter is yellow-tan that can have brown reticulations (Boulenger 1882; Inger 1984). The throat may also be reticulated A white, black or tannish, thin dorsolateral fold is present and a light thigh stripe runs from the anus to the inside of the knee. A deep yellow thigh stripe is also present. (Inger 1984). Limbs have cross-barring patterns. The posterior part of the thigh is dark brown with a light stripe down the middle (Boulenger 1882). Females have bright yellow coloration in the groin and on the anterior of the thigh; the yellow tends to be duller in males. The dorsal sides of the feet are bluish-grey (Inger 1984).

Variation: Males are differentiated by large, cream-coloured nuptial pads and the presence of two internal vocal sacs with openings (Boulenger 1882; Inger 1984). Individuals vary widely in color pattern and amount of webbing on the feet. Webbing between the toes varies from three quarters to complete webbing (Inger 1984).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: India

View distribution map in BerkeleyMapper.

This species is endemic to southern Western Ghats of India (Biju et al. 2012).

M. fuscus inhabits areas in streams, streambanks, dead leaves, bare soil and some areas away from streams in evergreen forest and moist deciduous or moist semi-evergreen forest. It can also occur in secondary growth between 70 to 1000 m in elevation (Biju et al. 2012; Inger 1984).

Life History, Abundance, Activity, and Special Behaviors
M. fuscus is a diurnal frog. Males vocalize from 6 AM in the morning to 6 PM. Vocalizations are made from rocks and are characterized by a “krrik…krik” and followed by a “kichi…kichi…kichik” sound. Varying patterns in its repertoire are interspersed in the calls. A disturbed individual will produce a weak squeak (Vasudevan 2001).

This species uses “foot flagging” behavior in which the hind limb is brought behind the body and folded. It alternates legs for this display (Vasudevan 2001).

Males compete with each other by chasing away nearby callers and leaping onto the intruder's rocks (Vasudevan 2001).

Individuals have been found mating in a seepage area with flowing water. The eggs found were large and transparent (Inger 1984).

Trends and Threats
M. fuscus is threatened by habitat destruction. Forests of its habitat are converted for agricultural purposes (coffee and tea plantations). Overharvesting of wood, dam construction and infrastructure development are also threats to this species (Biju et al. 2004).

This species is protected by national legislation in several protected areas (Biju et al. 2004).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Urbanization

Comments
This species is considered a species complex of which M. herrei may be included (Biju et al. 2004).

This species was featured as Species of the Week, with the following News Highlight on December 6, 2021:

Foot-flagging or "dancing" in frogs is an elaborate courtship behavior, usually displayed by breeding males, in which the hind leg is raised above the head and rotated backwards. This behavior has been documented in eight separate frog genera, many of which are distantly related, and is believed to replace calls during sociosexual communication in species that live in noisy environments, such as waterfalls. These displays can be highly variable, with some species incorporating toe taps while others rotating both legs at the same time. Anderson et al. (2021) investigated the physiological mechanisms behind this behavior to better understand the convergent evolution of the trait. They found that androgen receptor messenger RNA (AR mRNA) was elevated in the thigh muscle of all foot-flagging species when compared to non-flagging species, but there was no statistical difference in AR mRNA in the central nervous system. These findings lend support to the hypothesis that selection in the endocrine system may be the mechanism of convergent changes in various suites of behavior. (Written by Ann Chang)

References

Boulenger, G.A. (1882). Catalogue of the Batrachia Salientia s. Ecaudata in the Collection of the British Museum, Ed. 2. Taylor and Francis, London.

Frost, D. (2011). Amphibian Species of the World: an Online Reference. Version 5.5.

Inger, R. F., Shaffer, H. B., Koshy, M., and Bakde, R. (1984). ''A report on a collection of amphibians and reptiles from the Ponmudi, Kerala, South India. Part 1.'' Journal of Bombay Natural History Society , 81(2), 406-427.

S.D. Biju, Sushil Dutta, Vasudevan Vasudevan, S.P. Vijayakumar, M.S. Ravichandran. Micrixalus fuscus. IUCN (2004). 2011 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 26 May 2012.

Vasudevan, Karthikeyan (2001). ''A foot flagging frog from the Western Ghats.'' Cobra (Chennai), 44 , 25-29.

Species Account Citation: AmphibiaWeb 2021 Micrixalus fuscus: Kalakkad Dancing Frog <https://amphibiaweb.org/species/4817> University of California, Berkeley, CA, USA. Accessed Oct 3, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 3 Oct 2024.

AmphibiaWeb's policy on data use.