The click of crickets in the evening or frogs croaking during the monsoons might sound random or even annoying, but they have a good reason for making these sounds. Scientists call it phonotaxis: the movement by an animal in response to a sound. It has mostly been observed among crickets, moths, frogs, and toads, among a few other creatures.
There are two types of phonotaxis: positive and negative. The purpose of positive phonotaxis is attraction. It usually happens when the females of a particular species – including those of crickets and frogs – are attracted to the sounds made by the males. Negative phonotaxis, on the other hand, serves to repel or warn, such as when the sound of a predator nearby signals to an animal that it needs to move away. Crickets in particular have been found to steer themselves away from low-intensity ultrasound typically associated with bats (which use it for echolocation).
In 1984, scientists found that Mediterranean house geckos (Hemidactylus turcicus) use positive phonotaxis to their advantage. The fields that these geckos inhabited were also home to male decorated crickets (Gryllodes supplicans), which used species-specific sounds to attract the females from their burrows. The geckos recognised and followed this call until they reached the burrow, where they consumed the female crickets.
