Adult: Species description based on Savage (2002). Medium sized treefrog. Males to 45 mm; females to 62 mm. Males have a paired vocal sac. Dorsal: Dorsal surface tuberculate and is gray, tan or reddish brown in coloration. Darker blotches and markings may be present, as well as white or green flecks. Ventral: Ventral surface creamy white. Throat (i.e. vocal sac) of males is grey, whereas throat of females is white with some small brown flecks. Concealed surfaces: Posterior surface of the thigh is brownish with blue spots. Groin has similar blue spots, while the lateral surface posterior to the arm has yellow spots. Distinguishing characteristics: Snout very short and truncated in appearance. Eye: Iris brown with black reticulations. Extremities: Hand and feet moderately webbed. Toes with large terminal pads.
Breeding season: Breeding occurs during the dry season (Heyer 1976). Males call from the edges of forest streams (Nunes 1988). During amplexus, females construct shallow open depressions in which to lay their eggs (Malone 2004). Egg: Small, black eggs float on surface of water (Malone 2004). Tadpole: Although they breed in streams, tadpoles of S. sila are adapted to life in quiet pools (Heyer 1976). Bodies are fat and tails are less muscular with high tail fins, unlike more typical stream-dwelling species (Heyer 1976).
Habitat: Lowland rainforest to 970 m. Ecology: Adult Smilisca sila are depredated by bats (Trachops cirrhosus; Tuttle and Ryan 1982). Call: A low squawk, usually followed by one or more rattling secondary notes (Ibanez 1991). Males also produce aggressive calls (Ibanez 1991). Behavior and communication: Smilisca sila change calling behavior in response to availability of light in the environment (Tuttle and Ryan 1982, Nunes 1988). Frogs call more and produce more complex calls on moonlit nights, and are also less likely to call from concealed sites, such as under leaves (Nunes 1988). Tuttle and Ryan (1982) suggested than moonlight allows the frogs to detect and avoid bat predation. Males also prefer to call near waterfalls (Tuttle and Ryan 1982). The frequency of waterfall noise completely overlaps with that of the calls of S. sila, thus potentially further hindering detection by bats (Tuttle and Ryan 1982). Finally, frogs synchronize calling (Tuttle and Ryan 1982, Ibanez 1991), which lessens chances of bat predation because bats are less likely to respond to synchronized calls (Tuttle and Ryan 1982). Type locality: a small stream at north edge of the village of El Volcán, Chiriquí, elevation 1280 meters (Panama) Physiology: Smilisca sila has a much shorter latency to response to calls of other males than many of species of frogs thus studied (Ryan 1986). Ryan (1986) suggested that use of a different neural pathway decoupling call detection and call recognition may contribute to call overlap in this species. Diet: Tadpoles are scrapers and chewers, mostly eating algae from the surface of rocks and submerged plant matter in stream pools (Heyer 1976).