Identifying the symphony of sounds that occurs when the sun goes down can be a challenge. Among amphibians, rodents, reptiles and more, wordless dialogue is exchanged to express a variety of messages from warning signals to mating calls through the use of short and low chirps, long melodic trills and everything in between.
Frogs and Toads
Male eastern American toads produce a chirp-like mating call that can last up to 30 seconds, usually heard near bodies of water that serve as their breeding grounds. In the Pacific Northwest, typically nocturnal boreal toads can be found in wet environments emitting high nocturnal chirps reminiscent of young geese. Cliff chirping frogs are endemic to limestone-heavy areas of central and western Texas; they emit short, clear chirping noises late into the night that resemble those of a cricket. A musical, two-note chirp may be heard through the night from the male coqui frog, found throughout the southeastern United States, Hawaii and Puetro Rico; its call may reach 90 decibels.
Several nocturnal squirrel species are known to make chirping sounds during their active hours. The low chirps of northern flying squirrels are mainly heard in coniferous forests, while southern flying squirrels -- emitting a similar-sounding chirp -- inhabit mixed and deciduous forests. Both species are social, and although the northern flying squirrels commonly nest in small groups of up to eight members, louder noises are likely to be heard from the large dens of southern squirrels, numbering as many as 20 at a time.
Perhaps the most vocal reptiles, geckos can be found in warm-weathered habitats on all continents except Antarctica. Most are nocturnal, and nearly all species are vocal. Some species make a single chirp to ward off predators, like the high, bird-like call of the Mediterranean house gecko, while others make elongated noises consisting of many successive chirps. These are often heard during mating or in territorial situations, as evidenced by the calls of flying and turnip-tailed geckos. Several species have earned names expressing the sounds of their unique chirps, such as the “chee chak” gecko.
Bats use their chirps for survival in the dark, a feat known as echolocation. They emit many brief sounds, only a thousandth of a second each, and gauge the reverberations to navigate their flights as well as locate food. A bat may emit up 250 chirps per second as it nears an object during flight. Exceptionally high in frequency, these chirping sounds typically lie outside the range of the average human’s hearing ability.