Caribbean National Forest
There are 16 native species of tree frogs or coquis in Puerto Rico, 13 of which occur in the Caribbean National Forest. Eleven of the 13 are endemic species, that is, they occur only in Puerto Rico. One species, the Burrow Coqui is found only in El Yunque's Cloud Forest. Only two coquis speciesthe Forest and Common Coquisactually produce the sound "co-kee," but in Puerto Rico the name "coqui" refers to all 16 species. Two of El Yunque's coqui species, the Web-footed and Mottled Coquis, are classified as threatened in Puerto Rico and have been proposed for federal listing as Threatened or Endangered. Causes of their decline are not clearly understood. The Web-footed Coqui inhabits mountain streams and is usually found near waterfalls. The Mottled Coqui inhabits montane forest and is found in mudbanks, logs and in or near moss. The coquis of El Yunque range in size from 15 mm in length, such as the diminutive Burrow Coqui, to 80 mm in length, such as the large Web-footed Coqui. Coquis vary in color from gray to brown to green to yellow.
Most tree frog species begin calling at sunset. Each species has a characteristic call. Tree frogs call to defend their territories, of which there are three types: shelter, feeding and mating. The most conspicuous calls are emitted by males in defense of their mating territory. Apparently, the call of the male coqui serves to discourage other nearby males from calling to attract females.
Coquis, unlike many other frogs, do not pass through a tadpole stage. The female lays the egg (about 28 per clutch) in a humid terrestrial environment. In at least five of the Puerto Rican species, the male broods and guards the eggs and females are aggressively forced away from the eggs soon after laying. At the end of the incubation period, a froglet, a tiny replica of the adult, emerges from each egg.
All coquis have disks or pads on the tips of their toes, which help them cling to slippery surfaces. Many species are arboreal, that is, they live in trees. Arboreal species tend to have larger toe pads, relative to their weight, than terrestrial species. One species, the Web-footed Coqui (E. karischmidti), has webbed toes for swimming.
On the coastal lowlands almost all coqui species are arboreal, while in the highland forest most are terrestrial. Nearly all the lowlands species have ranges extending high up into the mountains, but mountain species rarely range down to the coast.
Details mentioned in this article were accurate at the time of publication