Description

DESCRIPTION:

Platymantis biak is a moderate-sized frog in which females have a snout-vent length range of 37.4 - 42.4 mm, while males have a snout-vent length range between 32.3 - 39.9 mm. The head is wider than long, and males have heads that are broader than its body. Eye diameter among females can be anywhere from 3.8 - 3.9 mm, while males range from 4.0 - 5.7 mm. The foot length is slightly less than half the hand length. The fingers are slender and long, with the terminal discs moderately expanded compared to other species. This species possesses smooth skin as opposed to granular skin (Siler et al. 2010).

DIAGNOSIS:

Platymantis biak differs from similar species by its larger body size, and moderately expanded finger disc. More specifically, P. biak is distinguished from P. negrosensis and P. luzonensis by the absence of granular skin. Its terrestrial karst microhabitat preference sets this species apart from its predominantly arboreal relatives, such as P. negrosensis and P. luzonensis. Other Philippine limestone specialist include P. bayani, P. insulatus, P. paengi, and P. spelaeus, which all have similar mottled coloring but can be differentiated based on geographic location, the size of their digit discs, and patterning on their flanks (Siler et al. 2010).

COLORATION:

The coloration in preservative consists of both dark and light brown mottled blotches on the dorsal surface, with occasional blotches of brownish green. The temporal region usually ranges from dark brown to black with dark green blotches. The dorsal surface of the hands, fingers, and feet are usually covered in bands of light and dark brown, and a grayish-tan color. There is also a w-shaped pigmentation pattern present on the dorsal surface. A tan coloration is present on the belly, forearm, and hands. However, this coloration becomes darker brown in areas of the legs and feet (Siler et al. 2010).

VARIATION:

Variation exists in regards to the w-shaped pattern present on the dorsal surface of the body. In some specimens the w-shaped pattern is more evident than in others. Variation also exists in regards to body size. Females are usually larger and more robust than male specimens (Siler et al. 2010).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Philippines

View distribution map in BerkeleyMapper.

The general geographical distribution of P. biak is currently limited to the Central Luzon Island in the Philippines, specifically in the Biak Na Bato National Park. This species of forest frog demonstrates a preference for terrestrial karst microhabitats. It is typically found living in limestone caves, usually resting on top of limestone boulders or inside deep crevices (Siler et al. 2010).

Life History, Abundance, Activity, and Special Behaviors
Although assigned to a generally arboreal species group, P. biak is limited to terrestrial microhabitats.They are often perched and well camouflaged on the surface of limestone boulders found around the forest or inside caves (Siler et al. 2010).

Males have been observed calling from atop rocks (Siler et al. 2010).

This species is further characterized by its direct developing reproductive mode and is suspected to breed and deposit its eggs within the limestone crevices (Siler et al. 2010).

Trends and Threats
Platymantis biak has a “Near Threatened” IUCN Red List status (IUCN 2018). There is not enough research to determine whether the population is increasing or decreasing, but are threatened due habitat degradation and the species’ restriction to terrestrial limestone microhabitats, which makes it important for these environments to be preserved (Siler et al. 2010).

Possible reasons for amphibian decline

General habitat alteration and loss
Mining

Comments

PHYLOGENETIC RELATIONSHIPS:

Platymantis biak is a member of the P. guentheri group, which includes P. banahao, P. bayani, P. cornutus, P. diesmosi, P. guentheri, P. insulatus, P. luzonensis, P. negrosensis, and P. rabori. However, because of the number of undescribed species in the genus, the species’ exact phylogenetic relationships is unclear (Siler et al. 2010).

ETYMOLOGY:

The species epithet “biak” means crack or crevice in Tagalog. It is also a reference to Biak Na Bato National Park, where the frog was discovered. (Siler et al. 2010).

The common name, Luzon limestone forest frog, comes from Luzon island where Biak Na Bato National Park is located (Siler et al. 2010).

References

IUCN SSC Amphibian Specialist Group. (2018). "Platymantis biak." The IUCN Red List of Threatened Species 2018: e.T42862906A42862915. https://dx.doi.org/10.2305/IUCN.UK.2018-1.RLTS.T42862906A42862915.en. Accessed in February 2022.

Siler, C.D., Diesmos, A.C., Linkem, C.W., Diesmos, M.L., Brown, R.M. (2010). “A new species of limestone-forest frog, genus Platymantis (Amphibia: Anura: Ceratobatrachidae) from central Luzon Island, Philippines” Zootaxa 2482(1): 49–63 [link]

Species Account Citation: AmphibiaWeb 2022 Platymantis biak: Luzon limestone forest frog <https://amphibiaweb.org/species/7495> University of California, Berkeley, CA, USA. Accessed Dec 22, 2024.

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

AmphibiaWeb's policy on data use.