The sounds of the night often include a chorus performed by frogs, particularly in wetlands. While their calls are familiar, their purpose and identity often remain a mystery. This article explores frog vocalizations, explaining their functions and helping identify the voices in the nighttime soundscape.
The Language of Frogs: Why They Call
Frog calls serve specific biological purposes, primarily for communication. Male frogs vocalize to attract females for mating. These “advertisement calls” are unique to each species, allowing females to identify a suitable mate amidst a noisy chorus.
Male frogs also use “territorial calls” to defend their area from other males. These can be more aggressive, warning intruders. Frogs also make “distress calls,” which are loud, high-pitched sounds when threatened by a predator. This startling sound can cause a predator to release the frog, allowing escape.
A “release call” is produced by a male frog if mistakenly grasped by another male during breeding. This sound signals to the other male that it has latched onto another male or an unreceptive female, prompting release. These vocalizations are essential for a frog’s survival and reproduction.
Identifying the Night’s Choristers: Common Frog Calls
Many frog calls contribute to the nighttime chorus. The American Bullfrog produces a deep, resonant “jug-o-rum” or “rumm-rumm-rumm” call, reminiscent of a low bass note. This bellowing sound carries over long distances.
The Spring Peeper, a small treefrog, is known for its high-pitched, whistle-like “peep, peep, peep.” In large groups, these tiny frogs create a collective sound audible for miles. The Green Frog emits a single, banjo-like “gunk!” or “twang!” sound, sometimes heard in a short series.
Gray Treefrogs are recognized by their melodic trill, a loud, musical sound lasting about half a second and repeating every few seconds. Their relative, the Cope’s Gray Treefrog, produces a similar but faster, harsher trill. The Northern Leopard Frog’s call is a low, guttural snore-like rattle, like a small motorboat engine, often with chuckles or croaks.
When and Where Frogs Call
Frog calling activity is tied to specific times and environmental conditions. Most species are nocturnal, active and vocal after dusk, with peak calling in early night hours. This timing reduces predator encounters and allows calls to travel effectively.
Seasonal changes also influence when frogs call. For many species, calling is most frequent during breeding seasons, typically spring and early summer in temperate climates. Some species may call year-round in warmer regions or during specific rain events.
Frogs typically call from habitats near water, as most species lay eggs in aquatic environments. These include ponds, marshes, swamps, slow-moving streams, and temporary puddles. Environmental factors like temperature, humidity, and recent rainfall stimulate calling, with warmer, humid nights after rain often leading to active choruses.