A summer night is often defined by a persistent, rhythmic sound emanating from the darkness—a chorus of high-pitched noises broadly classified as “chirping.” This nocturnal symphony is produced by a diverse cast of animals, ranging from tiny insects to amphibians and small mammals. Identifying the source can be challenging, as many creatures use acoustic signals for communication under the cover of night. Understanding which animals are responsible for this chatter, and the reasons behind their vocalizations, reveals the complex biological activity occurring just beyond our view.
The Primary Suspects: Crickets and Katydids
The most common source of the continuous summer night soundscape comes from two distinct groups of insects: crickets and katydids. Both belong to the order Orthoptera and rely on a process called stridulation to produce their calls, which involves rubbing specialized body parts together. The two, however, can be distinguished by the rhythmic pattern and acoustic quality of their songs.
Male crickets create their characteristic song by rapidly drawing a scraper on one forewing across a file of ridges on the underside of the other forewing. This action produces a clear, pure tone because their carrier frequencies are relatively low and consistent. The rate of this chirping is directly influenced by ambient temperature, as crickets are ectotherms and their muscle activity speeds up in warmer conditions.
Katydids produce a sound that is buzzier, raspier, or whiney, with less pure and higher carrier frequencies. Their nocturnal calls often manifest as a distinct, ticking-like sequence that is sometimes interpreted as sounding like their name, “kay-tee-did.” These insects wait until later at night than crickets to begin their songs, and they tend to inhabit trees and shrubs, contrasting with the ground-dwelling nature of many common crickets.
Amphibians and Other Nocturnal Callers
A number of amphibians and other animals produce sounds that are frequently mistaken for insect chirps. Many species of frogs, particularly smaller tree frogs, are active at night and produce high-pitched calls that can easily be confused with the rhythm of an insect. Unlike insects, amphibians produce sound through vocalization, using air sacs and their larynx to generate noise.
The Cliff Chirping Frog and the Rio Grande Chirping Frog, for example, are small anurans whose calls consist of sharp, high-pitched chirps, squeaks, and whistles. These species do not require standing water for their tadpole stage, allowing them to inhabit drier environments like yards and rocky areas. Another famous example is the Coqui Frog, native to Puerto Rico, whose loud, two-note call is an inescapable part of the tropical night soundscape.
Some small mammals also utilize chirping sounds for communication. Nocturnal flying squirrels, such as the Northern and Southern species, emit low chirps as a form of social communication within their nesting groups. Additionally, geckos, which are among the most vocal reptiles, use short chirps as both a defensive warning and a mating call in their warm-weather habitats.
Decoding the Nighttime Chorus: Sound and Purpose
These signals serve the dual purpose of attracting a mate and defending territory against rivals. In most species of both insects and amphibians, it is the male that produces the loud, repetitive call to advertise his presence to females seeking a mate. These calls are species-specific, allowing females to identify and locate a suitable partner from the background noise of the nocturnal environment.
The mechanisms used to create these sounds are fundamentally different, which aids in identification. An insect chorus features a rhythmic consistency tied to temperature, as stridulation is a mechanical process. In contrast, frog and toad calls, which use biological vocalization, tend to have a more distinct vocal quality. Paying attention to the pitch and the pattern—whether it is a steady mechanical rhythm or a complex vocal trill—allows for a more accurate identification of the unseen nighttime singers.