The throat is immaculate in specimens from the Caribbean lowlands in Limón Province; the throats are dusky laterally in most other specimens except some from the Meseta Central, in which the throats are heavily flecked with black. This variation occurs in males and females.
The color and pattern in life are highly variable. A composite description of living individuals (now KU 91718-41) from 6 kilometers east of Golfito, Puntarenas, Costa Rica, illustrates the variability: "Dorsum pale olive-green, fading to tan posteriorly, or tan all over with dark olive-green or dark brown spots on back and bars on limbs. Flanks dark brown with cream, greenish gray, or bluish gray mottling. Posterior surfaces of thighs dark brown with pale blue, pale green, or tan flecks. Iris creamy silver. Throats white with some brown flecks peripherally." (Duellman, Field notes, February 15, 1965.) A male from the Río Jorco, San José, Costa Rica, was dull olive-tan above with olive-green marks; the flanks were brown with pale tan flecks, and the posterior surfaces of the thighs were pale brown with cream-colored flecks. Six females from the same locality were reddish brown above with olive-brown or dark brown markings; one was uniform orange-tan, and another was dull olive-green with darker markings.
The color of the iris in living frogs varies from creamy silver to grayish yellow or bronze with a variable amount of black reticulation.
Natural History.—Smilisca sordida is not associated with any one type of vegetation; instead it lives in the vicinity of rocky streams having low gradients. Breeding takes place primarily in the dry season, when the water in the streams is clear and at a low level. Through most of the range of S. sordida showers, or even short heavy rains, occur in the dry season. After such rains the breeding activity is maximal. Breeding congregations have been found from December through April, but a few calling males and gravid females have been taken in June, July, and August. In the rainy season non-breeding individuals are found sitting on bushes near streams at night. Taylor (1952:843) found specimens in bromeliads by day.
Males usually call from rocks or gravel bars in, or at the edge of, streams. Some individuals perch in low bushes overhanging the streams, and some sit in shallows in the streams. Clasping pairs have been found on the banks of streams and in shallow water in streams.
The breeding call consists of one to six moderately short, rather high-pitched notes (duration 0.18 to 0.45 seconds) repeated at intervals of 12 seconds to several minutes. Each note is a vibrant rattle having 78 to 135 pulses per second and major frequences of about 1200 to 2600 cycles per second (Pl. 11C).
The tadpoles live in shallow parts of the streams, where they cling to the surfaces of small rocks and hide beneath leaves and rocks. A complete developmental series of tadpoles is not available; measurements of those stages examined are summarized in Table 12.
A typical tadpole in stage 36 of development (KU 68475 from 15 km. WSW of San Isidro el General, Costa Rica) has a body length of 11.7 mm., tail length of 22.8 mm., and a total length of 34.5 mm.; body about three-fourths as deep as wide; snout broadly rounded in dorsal view, sloping and rounded in lateral view; eyes widely separated, directed dorsolaterally; nostril slightly closer to eye than to tip of snout; mouth ventral; spiracle sinistral, about two-thirds distance from snout to posterior end of body and slightly below midline; anal tube dextral; caudal musculature heavy, straight; dorsal fin not extending onto body; fins deepest at about mid-length of tail; there depth of caudal musculature equal to depth of dorsal fin and half again as deep as ventral fin; musculature extending nearly to tip of tail; body reddish brown above and pale grayish brown with white flecks below; caudal musculature pale tan with brown flecks; a series of reddish brown dashes at base of caudal fin separated from others in series and from dashes on other side by creamy white; fins transparent with reddish brown flecks on posterior one-half of ventral fin and on all of dorsal fin (Fig. 14C). Mouth bordered by two rows of short, pointed papillae; lateral fold present; tooth-rows 2/3; upper rows equal in length; second upper row narrowly interrupted medially; three lower rows complete, nearly as long as upper rows, deeply indented medially; upper beak robust, inner surface not forming continuous arch with short lateral processes; lower beak deep, V-shaped; both beaks bearing short serrations (Fig. 15F).
Little variation occurs in structure. In some specimens the second upper tooth-row is complete; no individuals were found to have the row broadly interrupted medially.
The series of dark dashes on the dorsal edge of the caudal musculature is diagnostic of all stages studied. In life, tadpoles from 15 and 20 kilometers west-southwest of San Isidro el General, Costa Rica, had a tan body, often with an olive-tan tinge; the caudal musculature was tan; the flecks and dashes were dull red or reddish brown. Tadpoles from 6 kilometers east of Golfito, Costa Rica, had bodies with olive-green flecks. The caudal musculature was brown with bluish green flecks; the fins were transparent with reddish brown flecks. The belly was a silvery golden color. Tadpoles from Bajos de Jorco, Costa Rica, had brown bodies with bluish green flecks; the tail and fins had reddish brown flecks and dashes. The iris was a bronze color in specimens from all three localities, as well as in the young mentioned in the following paragraph.