Kaloula rigida
Luzon Narrow-Mouthed Frog
family: Microhylidae
subfamily: Microhylinae
Conservation Status (definitions)
IUCN (Red List) Status Vulnerable (VU)
Other International Status None
National Status None
Regional Status None

Country distribution from AmphibiaWeb's database: Philippines


View distribution map using BerkeleyMapper.


From the Encyclopedia of Life account:


The genus Kaloula is part of a large group of narrow mouth frogs in the family Microhylidae. The approximately 65 genera of narrow mouth frogs occur in North and South America, Africa, Australia, and Souteast Asia. Of the ten subfamilies, the genus Kaloula is a member of the Microhylinae group.

Within the Philippines, the diversity of species in the genus Kaloula can be roughly broken down into three major ecomorphological groups. The first being the shrub frogs. This group consists of species historically believed to all be subspecies of Kaloula conjuncta. They have expanded toe disks used for an arboreal lifestyle. During the rainy season they will climb down and breed in ephemeral pools of water on the ground. Tadpoles within this group are pigmented. The group of shrub frogs has a large distribution throughout the Philippines. There are clear divisions between species with true K. conjuncta occurring throughout Luzon, K. negrosensis observed throughout the visayan islands, K. meridionalis observed in mindanao, and the type locality of K. stickelii occurring on samar.

The second group consists of burrowing frogs with narrow toe disks. These frogs burrow during the year except for the rainy season, when they surface and breed in pools on the ground. Tadpoles of this group also are pigmented. With the exception of Kaloula picta, which has dispersed throughout the Philippines, the other burrowing frogs have narrow ranges. Kaloula rigida occurs in North Luzon and Kaloula walteri occurs in Southern Luzon and Polillo Island. Kaloula pulchra has been recently introduced into the Philippines, and has now been observed at several localities on Luzon Island (Siler et al., 2011) in the northern Philippines.

The third group of species in the genus Kaloula have evolved a completely arboreal lifestyle. They spend their lives within tree-holes, have wide toe disks, and non-pigmented tadpoles (likely due to an absence of contact with the sun). The tadpoles complete their lifecycle within the tree hole itself. These frogs are recognized to possess restricted ranges, possibly due to their dependence on primary forest habitat. Two different species of tree hole frogs occur on Luzon. Kaloula kalingensis is restricted to the north, a new species spanning across central Luzon, and K. kokacii is recognized to occur in southeastern Luzon Island and on Catanduanes Island.

Author: Siler, Cameron

Type Locality

Balbalan, Kalinga, Mountain Province, Luzon", Philippines; Changes to provincial boundaries in the Philippines have resulted in this locality now being recognized as part of Kalinga Province in northern Luzon Island in the Philippines; type stored in the California Academy of Sciences; CAS 61475 (EHT 7681)

Author: Siler, Cameron

Faunal Affinity

Luzon Pleistocene Aggregate Island Complex (PAIC; Brown and Diesmos, 2002).

Author: Siler, Cameron


This species is only known from the mountains of northern Luzon Island in the Philippines.

Author: Siler, Cameron


Coloration in life reported as "deep lavender to purple, slightly iridescent; lighter lavender to brownish in groins and above limbs; dim traces of spots on limbs and a darker triangular area about anus; belly dirty light brown, mottled and reticulated with lighter color; chin and throat dark with fine reticulations of dirty white" in the type description by Taylor (1922).

Author: Siler, Cameron

Diagnostic Description

"Choanae large, partially concealed by overhanging jaw, separated from one another by a distance equal to diameter of choanae; two strong, transverse, palatal ridges immediately behind choanae, very narrowly separated medially; in front of esophagus a wide, dermal, transverse, palatal ridge, which is preceded bya second arched ridge; tongue broadly oval, entire; snout short, truncate; rounded on edge; loreal region nearly perpendicular; diameter of eye longer than its distance from end of snout; nostrils as far forward as tip of snout, which slopes backward and downward to mouth; tympanum small, dimly outlined, covered with skin; a distinct fold from behind eye to insertion of arm; a dim fold in front of tympanum and another short fold behind angle of jaw; skin above uniformly corrugated save on tip of snout and lores; belly more or less smooth; a dim suggestion of granulation on throat and chin and on inferior and posterior aspects of femur; tips of digits on hand slightly swollen, no wider than digits; subarticular tubercles moderately developed, large, rather flattened; carpal tubercles on foot large, flattened, not strongly differentiated; a round, outer metatarsal tubercle and an elongate, blunt-edged, inner tubercle; a small but distinct web between toes; leg brought forward the tibiotarsal articulation does not reach beyond insertion of arm; femur involved in body skin for more than half its length; males with internal vocal sacs." (Text taken from Taylor, 1922)

Author: Siler, Cameron