About Smilisca sila Duellman & Trueb, 1966
Adult Smilisca sila have a maximum snout–vent length of 45 mm (1.8 in) for males and 62 mm (2.4 in) for females. Their dorsal (upper) skin is tuberculate (bumpy) in texture, and has a gray, tan, or reddish-brown base color; individuals may also have white or green flecks, plus darker blotches and markings. The ventral (belly) surface is creamy white. Males have a paired gray vocal sac, which they use to produce their characteristic choruses, while females have a single white vocal sac with brown flecks. The underside of the thighs and groin is brown with blue spots, and the underside of the arm has yellow spots. Their irises are brown with a black net-like pattern. Both front and back toes are webbed and end in large toe pads. Adult Smilisca sila are very similar in morphology to its sister species, Smilisca sordida, but have a flatter snout and bumpier skin. Tadpoles of this species have a relatively round body, weak muscles, and broad, short tails adapted for living in small ponds. They have mouthparts specialized for scraping and chewing food. Smilisca sila occurs in the lowlands of southwestern Costa Rica, Panama, and northern Colombia. It prefers transitional zones between wet and dry lowland tropical forests near shallow rocky pools and stream banks, but can also be found in secondary forest, and sometimes in relatively open areas. This species is found at elevations ranging from 10 to 970 m. Breeding happens during the dry season from January to April at low elevations; at high elevations, breeding may occur during the rainy season. Females prefer to breed and lay eggs on gravel islands or banks alongside first-order streams. Males typically call from positions alongside streams that have ambient noise and overhanging vegetation, which can mask their calls from predators and provide hiding space if needed. Tadpoles live in clear pools and slow-moving water, staying near the bottom. Acoustic communication is the most common form of communication among anurans, and for male Smilisca sila, it is the main way to attract and communicate with females through advertisement calls. However, predators of this species – including the frog-eating bat Trachops cirrhosus and frog-biting midges of the genus Corethrella – also use these advertisement calls to locate Smilisca sila individuals to hunt or parasitize them. This creates a trade-off between individual mating success and higher predation risk, which has shaped how and when males choose to call. Males call more often, use more complex calls, and have a longer total calling period on moonlit nights than on moonless nights, because they can detect predators visually more easily when the night is bright. On dark, moonless nights, males hide in overhanging vegetation and produce shorter, simpler calls at a lower frequency.
