Frogs’ nocturnal calls are a common part of the natural world. These choruses, from soft chirps to booming croaks, reveal a fascinating aspect of amphibian life, deeply connected to their biology and environment.
Why Frogs Call at Night
Frogs primarily call at night for communication, mainly for reproduction. Male frogs produce specific advertisement calls to attract mates and establish territory. These calls signal a male’s presence and suitability to potential female partners. Calls also warn off rival males from breeding sites. Less frequently, frogs vocalize with release calls if accidentally grasped by another male, or produce distress calls when threatened.
Common Nocturnal Frog Species
Many frog species contribute to the nighttime symphony, each with a distinct vocalization. The Spring Peeper ( Pseudacris crucifer ) is a small tree frog known for its high-pitched “peep-peep-peep” call. These calls are loud for their size and can be heard in large choruses, particularly in early spring. Gray Treefrogs ( Hyla versicolor ) produce a musical, bird-like trill. They are common in wooded areas near water and can sing for hours.
American Bullfrogs ( Lithobates catesbeianus ) are recognized by their loud, low-pitched, two-part drone or bellow. Their calls can carry for a considerable distance, making them prominent in ponds and lakes. Green Frogs ( Lithobates clamitans ) emit a banjo-like “gunk” or “twang” sound. American Toads ( Anaxyrus americanus ), while technically toads, are frequently part of nocturnal choruses and produce a long, sustained, high-pitched trill.
Understanding Frog Call Types
Frog calls serve various specific purposes. Advertisement calls are unique to each species, helping females identify suitable mates and announcing a male’s presence to other males during the breeding season. Territorial calls are distinct vocalizations used by males to warn off rivals, indicating an occupied space. For instance, a male bullfrog may make a sharp, short call if another male approaches too closely.
Release calls are made by a male frog when mistakenly clasped by another male, signaling “let me go, I am not a female.” This sound is often a repetitive, squeaky noise. Distress or warning calls, while less common, occur if a frog is startled or threatened by a predator, such as the sharp squeak an American Bullfrog might make before escaping into water.
Environmental Factors Affecting Calls
External conditions significantly influence when and how intensely frogs vocalize. Temperature is a primary factor, as frogs are ectothermic animals whose body temperature depends on their surroundings. Many species have specific temperature ranges for calling, and warmer temperatures often lead to increased calling rates.
Humidity and the presence of water also play a large role. Rain events often trigger a surge in calling activity, creating ideal moist conditions for breeding. Increased humidity allows frogs to be more active and vocal for longer periods. The availability of standing water, such as temporary ponds and wetlands, provides essential breeding sites, which further encourages calling. The time of year, particularly the breeding season for each species, dictates the overall intensity and frequency of nocturnal choruses.