Phrynobatrachus kakamikro is a small species (SVL < 19 mm) of puddle frog known only from the type locality in western Kenya. Members of this genus are identified by the presence of a midtarsal tubercle, elongate inner metatarsal tubercle, and outer metatarsal tubercle. P. kakamikro is characterized by the absence of a number of characters present in closely related species, including a papilla on the tongue, digital discs, and femoral glands in males. Pedal webbing is considered rudimentary, and adult males exhibit a grey throat.

The specific name is a free neologism that reflects the type locality (Kakamega forest) and small size of the new species (Greek mikro(s) meaning small).

It is only known from the type locality in semi-humid western Kenya, 1,650 m above sea level (Schick et al., 2010).

The body is slender with the head narrower than body. Maxillary teeth are present, and vomerine teeth are absent. Tongue is as long as wide, free for about two thirds of its length, tip is bifurcated, and a papilla is present. Nostrils are closer to tip of snout than to anterior corner of eye, and the canthus rostralis is slightly concave from tip of snout to nostril and straight from nostril to eye. The horizontal eye diameter is larger than the distance from nostril to anterior corner of eye, and the tympanum is invisible. Dorsal skin is finely coarse and ventrally smooth. Manual webbing is absent. Fingertips may be slightly swollen but not expanded to digital discs. Pedal webbing is rudimentary with 3-3.75 digits free of webbing on digit IV. Toe tips may be slightly swollen but not expanded to digital discs. Dorsum is light brown with semi-regular dark brown markings on each side, and a light vertebral line may be present. The back of thighs is banded. Venter is translucent to cream, occasionally with dark marks in the pectoral region. In males the throat is grey, and small femoral glands are absent. The iris is golden brown.

Phrynobatrachus kakamikro is a miniature (snout–vent length < 19 mm) puddle frog species. Snout-vent lengths vary from 17.45-18.98 mm ( n = 3) in females; only a single preserved male with SVL of 16.2 mm was collected (Schick et al., 2010).

Phrynobatrachus kakamikro is a small species (SVL < 19 mm) of puddle frog known characterized by the absence of a number of characters present in closely related species, including a papilla on the tongue, digital discs, and femoral glands in males. Pedal webbing is considered rudimentary, and adult males exhibit a grey throat.

Phrynobatrachus inexpectatus, P. mababiensis (including its junior synonyms P. vanrooyeni, P. chitialaensis, P. broomi), P. minutus, P. parvulus (including its junior synonyms P. schoutedeni, P. ukingensis nyikae) and the P. scheffleri are morphologically most similar to P. scheffleri. Toe webbing in P. inexpectatus is almost absent and the throat of males is strongly suffused with dark grey pigment (Largen, 2001). Phrynobatrachus minutus and P. parvulus males in breeding condition can be distinguished by throat colour, yellowish and dark grey, respectively (versus light grey in P. scheffleri). Phrynobatrachus inexpectatus is slightly smaller than the new species (mean SVL 14.5 and 16.4 mm in males and females, respectively). P. minutus and P. parvulus males in breeding condition can be distinguished from this species by throat colour, i.e. yellowish and dark grey, respectively, versus light grey in P. kakamikro. Phrynobatrachus scheffleri possesses a papilla on the tongue and femoral glands (both absent in P. kakamikro). Femoral glands are also present in P. inexpectatus, P. minutus and P. parvulus. The following can be distinguished from P. kakamikro by having larger adult SVL: Phrynobatrachus acridoides (ca. 25 mm), P. auritus (> 35 mm), P. bullans (ca. 25 mm), P. dendrobates (> 30 mm), P. irangi (> 50 mm ), P. kreffti (> 35 mm), P. natalensis (> 24 mm), P. pakenhami (> 25 mm) and P. versicolor (> 25 mm). Phrynobatrachus graueri, P. kinangopensis, P. perpalmatus, and P. rouxi are of similar SVL, but display digital discs and a visible tympanum (both absent in P. scheffleri). In addition, the foot of P. kinangopensis and P. perpalmatus is well webbed (versus rudimentary webbing in P. kakamikro). Phrynobatrachus pallidus, P. rungwensis, P. ukingensis, P. ungujae and P. uzungwensis share similar SVL with P. kakamikro and exhbit an indistinct tympanum, but differ through presence of well developed digital discs. In addition, the throat is heavily pigmented in P. ukingensis, and P. uzungwensis exhibits extensive pedal webbing (vesus rudimentary webbing in P. kakamikro). Phrynobatrachus breviceps, P. keniensis, and P. stewartae exhibit more extensive pedal webbing (at maximum two and a half phalanges of fourth toe free of webbing versus three free of webbing in P. scheffleri).

This species was found in a small temporary pond in anthropogenic grass land on the forest edge (Schick et al., 2010).

At the type locality other species present included Hyperolius acuticeps, H. ituriensis, H. kivuensis, H. lateralis, H. viridiflavus, Kassina senegalensis, Xenopus victorianus, Ptychadena cf. mascareniensis, P. taenioscelis and Phrynobatrachus scheffleri (Schick et al., 2010).

This species was found active at night.

The advertisement call was recorded at the type locality from a non-collected specimen (Schick et al., 2010). The call consists of two notes, the first being a ‘buzz’ followed by a single ‘click.’ Individuals were observed calling while sitting in swampy areas on flooded vegetation. Syntopic P scheffleri were not heard calling. Phrynobatrachus kakamikro advertisement calls differ from those of P. scheffleri by having two notes (versus one), lower pulse rate and higher dominant frequency. Phrynobatrachus mababiensis has a higher and P. parvulus a lower pulse rate than this species.

Mitochodrial sequence data from 12S rRNA, valine-tRNA, and 16S rRNA fragment, as well as combined sequence data from mitochondrial and nuclear (RAG-1) genes indicate that P. kakamikro is sister species to P. mababiensis C from central Tanzania (Zimkus and Schick, 2010; Zimkus et al., 2010). This species falls within a larger group of puddle frogs from East African montane regions that also includes P. parvulus, P. inexpectatus, P. minutus, P. rungwensis, P. scheffleri, and P. uzungwensis (Zimkus et al., 2010).

This species has not yet been assessed by the IUCN, but Schick et al. (2010) suggest that it be categorized as Data Deficient due to the limited information available.