The Tungara frog, Engystomops pustulosus, is a small amphibian found across Mexico, Central America, and northern South America. It is known for its complex mating calls and remarkable foam nests, showcasing adaptations for survival in tropical environments.
Physical Characteristics and Habitat
Tungara frogs are modest in size, typically measuring between 25 and 35 millimeters. Their warty, brown skin gives them a toad-like appearance.
These amphibians are common in tropical lowlands, inhabiting shallow pools and temporary ponds, particularly during the wet season. Their geographical range is extensive, spanning from Mexico through Central America, and into northern South America. Their mottled coloration provides camouflage, helping them blend into wetland and forest floor habitats and avoid predators.
The Iconic Mating Call
Male Tungara frogs produce a complex mating call to attract females. This vocalization is a two-part sound: a low-frequency “whine” followed by a series of shorter, high-frequency “chucks”. The number of these “chucks” can vary, with more complex calls including a greater number of these additional sounds. Females show a strong preference for calls that are more complex and have a lower frequency.
During the wet season, male frogs congregate in shallow pools and engage in loud choruses. To produce their calls, they inflate a large vocal sac beneath their chin, which amplifies the sound. These calls attract mates and signal male fitness.
Reproduction and Foam Nests
Reproduction begins with amplexus, where the male firmly grasps the female from above. As the female releases her eggs, she also secretes a protein-rich fluid from her oviducts. The male simultaneously fertilizes the eggs while rapidly beating his hind legs to whip the fluid into a frothy foam. This creates a unique foam nest that floats on the water.
These foam nests are crucial for the survival of the developing offspring, providing a protective barrier against desiccation and temperature fluctuations. Each nest contains between 100 and 200 eggs, which are encased within the moist, aerated foam. After about two days, the tadpoles hatch from their eggs and drop into the water below, where they begin to feed on detritus and other organic matter.
Life in the Wild
Tungara frogs are primarily insectivores, with their diet consisting mainly of small invertebrates. Adult frogs frequently consume termites, which are a significant food source in their habitat. Their diet also includes other small creatures such as snails, beetles, flies, and isopods. They are active hunters, using their sticky tongues to capture prey.
The loud and complex mating calls that are so effective at attracting females also present a significant risk to the male frogs. These vocalizations, along with the ripples they create on the water’s surface, can attract predators like the Fringe-lipped Bat (Trachops cirrhosus). These bats are known to use the frogs’ calls and the associated water disturbances to locate their prey through echolocation. Despite these predatory pressures, the Tungara frog remains a common and extensively studied species, particularly in regions like Panama.