During the breeding season, the males group together at night in temporary pools and call to attract mates. When a female chooses one of the males,
amplexus occurs at the edge of the water and the male creates a
foam nest in which the eggs are laid; the
tadpoles develop in the water and undergo
metamorphosis into juvenile frogs in about four weeks. The nests are resistant bio-foams that protect the fertilized eggs. After about four days, the tadpoles leave and the nest degrades but otherwise can last for up to two weeks. Female túngara frogs also exhibit elicitation behaviors that mainly serve to cause a potential mate to increase its sexual display intensity. Among all repeatable and noticeable locomotive behaviors that females exhibit, behaviors in which females clearly move closer to or farther from males are known as approach/retreat (AR) behaviors, while behaviors in which females do not move closer or farther are known as nonapproach/retreat (NAR) behaviors. Specifically, behaviors, elicitation behaviors are NAR behaviors that induce increase of number of chucks from males. Their primary role is manipulating male display, not acquiring mate. Elicitation behaviors vary with male chorus size, being more common in low density choruses than high density choruses due to its main purpose of producing more chucks. In high density choruses, increased production of chucks would not provide as much benefit than in low density choruses.
Mating call The primary mating behavior of túngara frogs is long-distance mating call consisting of two distinct call components: 'whine' and 'chuck'. Males produce a call that consists of a whine, and can also add up to seven short chuck sounds to their
mating call. A call consisting of both a whine and a chuck is considered a complex call. The chuck portion of the call is produced by vibrations of a fibrous mass suspended near the frog's
larynx, with larger masses allowing production of more chucks per whine. The main organ responsible for producing sound in túngara frogs is larynx supported by its fibrous mass hanging from the vocal cords and projecting from the larynx into the bronchi. As the trunk muscles around the lungs contract, the expelled air pushes through the larynx and vibrates the vocal cords/folds and the larynx, producing the sound. Air enters the buccal cavity, passes through the vocal slits, and inflates the
vocal sac. The inflation of vocal sac is also known to serve as a visual cue to receivers. Male túngara frogs produce chuck through their fibrous mass, and their fibrous mass is larger than other species and populations that do not produce chuck. Also, surgical excision of the fibrous mass inhibits the production of chuck despite the frog's attempt to produce complex call.
Mate choice Female preferences for calls play a significant role in túngara frog mating. They favor complex calls over simple calls, low frequency chucks over high frequency chucks, and conspecific whine over heterospecific whine. Females prefer the mating call of frogs who produce chucks with lower frequencies. If a female finds a male's call attractive, she will use the call, as well as ripples in the water caused by its production, to locate her new mate. Female choice for complex calls can be explained by the tuning of the túngara frog's inner ear organs: the amphibian papilla and the basilar papilla. The frequency that the basilar papilla is most sensitive to is 2130 Hz, and the chuck's dominant frequency is about 2500 Hz. The smaller the frequency difference between the male's chuck frequency and the tuning of the basilar papilla, the greater the neural excitation of the female. Thus, females prefer the lower frequency chucks that are closer to the tuning frequency of the basilar papilla. Female choice for low frequency chucks comes from female's preference for larger males providing reproductive benefit. The size difference between the mates determines the fertilization rate in that decrease in the size difference leads to decrease in the number of unfertilized eggs and increase in fertilization rate. Due to the tendency of female túngara being larger than male túngara frogs, larger males lessen the size gap with females and benefit the fertilization. And since larger males have larger larynxes, they produce lower frequency of sound (chuck and whine). Consequently, strong
sexual dimorphism can be observed in larynx size. Until about 16 mm snout-to-vent length, females and males have larynges of about the same size. However, above this point, males show strong positive allometric growth in larynx size until the plateau of growth at about 24 mm snout-to-vent length, around the time of the male's first call in the field. This shows that male reproductive behavior is triggered at the full development of the larynx. Female choice for conspecific whine comes from the lack of prediction between phylogenetic similarity of the túngara frog species and acoustic similarity of their calls. Also, shared common ancestry is suggested to lead to shared auditory and neural responses. Compared to the former female choice, female choice for conspecific whine has less significance due to the lack of overlap between the habitat of túngara frogs and the habitat of other
Physalaemus species, decreasing the instances of avoiding the calls of close relatives.
Male/male interactions Despite the benefit of satisfying the female choice and increasing mating success, complex calls also follow with a cost of increased risk of predation and parasitism because frog-eating bats,
Trachops cirrhosus, and blood-sucking flies,
Corethrella spp., prefer complex calls to simple calls. Males produce complex calls more often when there are other calling males nearby, forming what is known as a chorus. Males that use such calling strategies are able to maximize the possibility of finding a mate and minimize predation risk. Therefore, the males must find a strategy that resolves the conflict between natural selection and sexual selection. While portraying a trait that increases its attractiveness, the male must also remain inconspicuous through strategic variance of call complexity. When males are alone, they produce mostly simple calls, but when they are in choruses, they increase their call complexity and produce complex calls. Research suggests the relationship between the chorus size and the costs and benefits of frog chorusing behavior. The benefit of frog chorusing behavior is increased in larger chorus size because increase of chorus size leads to increase of operational sex ratio, probability of mating, and decrease of predation risk. While predation rate and chorus size do not have a correlation, predation risk and chorus size do have correlation. The cost of frog chorusing behavior is increased in smaller chorus size, as shown in the negative correlation between predation risk and chorus size. The tendency of acoustically orienting predators to attack choruses influences the individual's predation risk in a way that when the predator appears in the site of chorusing, the individual has a higher chance of getting attacked when there are not as many frogs in the site. The cost-benefit model of the frog chorusing behavior suggests the influence of the asymmetric benefits related to male size and behavior on the size of male túngara frogs in terms of joining the choruses. == Conservation ==