The common coquí or coquí (Eleutherodactylus coqui) is a frog native to Puerto Rico belonging to the Eleutherodactylus genus of the Eleutherodactylidae family. The species is named for the loud call the males make at night. This sound serves two purposes. ‘CO’ serves to repel males and establish territory while the ‘QUI’ serves to attract females. Since the auditory systems of males and females respond preferentially to different notes of the male call, this is an example of a sex difference in a sensory system. The common coquí is a very important aspect of Puerto Rican culture and it has become an unofficial territorial symbol of Puerto Rico.
Since they are more famous for their sound rather than their appearance, you really do need to spend at least one night in a rainforest lodge like the ones in El Yunque just to have the experience of listening them sing.
And one more!