Poco se conoce sobre la estructura vocal del Caiman yacare del Pantanal brasileño. Llamadas agresivas de hembras adultas que cuidaban de los nidos fueron registradas durante enero y febrero y llamadas de socorro de caimanes jóvenes, en abril de 1992. Hembras adultas de C. yacare presentaron una vocalización agresiva más larga y compleja que en otras especies más grandes de Alligatoridae. Las vocalizaciones de los jóvenes caimanes también presentaron diferencias interespecíficas con otros cocodrilos y variaciones intraespecíficas entre grupos separados por pocos kilómetros. Se utilizó la Prueba de Mantel para comparar las distancias de Mahalanobis entre la estructura de las vocalizaciones de los jóvenes de acuerdo con sus grupos y las distancias geográficas donde ellos estaban. La distancia geográfica en sí no explica las diferencias en las vocalizaciones de jóvenes de diferentes grupos. Hembras adultas de C. yacare han respondido a grabaciones de llamadas de caimanes de grupos de otras regiones, así como a imitaciones de llamada de socorro. Se postula que las variaciones en las llamadas de socorro pueden estar asociadas con una baja especificidad en el reconocimiento de sonido por caimanes adultos que han respondido de la misma forma protectora a las más heterogéneas expresiones de peligro de los jóvenes.

The Paraguayan caiman (Caiman yacare) is the main Caimaninae species occurring in the Brazilian Pantanal Wetland. Despite the relative availability of works focused on biology and conservation of the Paraguayan caiman, almost nothing is known about its vocal structure and behavior. We recorded aggressive calls of adult caiman females guarding nests and, afterwards, the distress calls of the new born juvenile caimans in seasonally flooded areas of the Nhecolândia (Southern Pantanal). The results of both observations and sonographic analyses diverged from studies with other crocodilian species. Aggressive vocalization of adult females of the Paraguayan caiman was longer and more complex than the same vocalization of larger Alligatoridae species. Vocalizations of the young caimans presented interspecific differences with other crocodilian offsprings. Moreover, we found statistically significant intraspecific variation in the distress call structure among different pods, even separated by few kilometers. Differences in distress call structure were tested by Canonical Discriminant Analysis (CDA). We obtained the squared Mahalanobis distances between the acoustic multivariate spaces of each pod provided by the CDA and compared with the geographic distance between the bays of origin of each pod through Mantel Test. The geographic distance by itself did not explain the differences found in the structure of the vocalization of young caimans from different pods. The adult females of Paraguayan caiman positively responded to playbacks of calls from juvenile caimans from pods of other regions, as well as to rough imitations of distress call. Since the adult caimans showed protective responses to quite heterogeneous vocalizations of distress by juveniles, we hypothesized that the variation in the distress call pattern may be associated to a low specificity in sound recognition by adult caimans.

Estudos sobre o sucesso de acasalamento em anfíbios anuros mostram que determinadas características morfológicas e/ou comportamentais, como o tamanho, as vocalizações e o número de noites de participação no coro podem influenciar o sucesso reprodutivo dos machos. Este estudo teve como objetivos (1) descrever o comportamento reprodutivo de machos e fêmeas de Dendropsophus bipunctatus, (2) examinar o sucesso de acasalamento dos machos, bem como (3) verificar as preferências das fêmeas a certas propriedades acústicas exibidas por machos através de testes de playback. Durante as atividades de corte, machos apresentaram períodos de imobilidade seguidos de pequenos deslocamentos que pode ser interpretado como uma forma de aumentar suas chances de atrair uma fêmea, pois os sinais acústicos podem, dessa forma, ser emitidos em diferentes direções. Machos maiores ou mais pesados não obtiveram um maior número de fêmeas e o número de noites de participação no coro foi a única variável que foi significativamente correlacionada com o sucesso reprodutivo dos machos. Acasalamentos por classe de tamanho e massa foram observados nesta espécie e altas taxas de fertilização foram encontradas em todas as razões de tamanho e massa dos casais em amplexo coletados no campo. Os resultados dos experimentos com cantos (playback) mostraram que fêmeas exibem uma preferência por sinais acústicos emitidos a uma elevada taxa de repetição do que aqueles emitidos a uma baixa taxa.

Studies on sexual selection in anuran amphibians show that some morphological and/or behavioral characteristics, such as size, vocalizations, and chorus tenure can influence male mating success. The goals of this study were (1) to describe the breeding behavior of males and females of Dendropsophus bipunctatus, (2) to assess male mating success, and (3) to verify the female preferences for specific acoustical properties performed by males through the two-choice calls trials. During courtship activities, males performed a stationary calling position followed by frequent small switches of calling sites that could enhance mating success, as signals were emitted from different directions. Larger or heavier males did not obtain a larger number of females, whereas chorus tenure was the only variable significantly related to the reproductive success of males. We observed high percentage fertilization rate among all size and mass ratios of males and females, as well as size and mass assortative mating. The results of the two choice trials show that females of D. bipunctatus prefer signals produced at high call-rate than lower ones.

O extenso repertório vocal de Leptodactylus natalensis é descrito. Observações de campo foram feitas em três fragmentos florestais no Domínio Tropical Atlântico, localizados nas regiões Nordeste (Estado de Alagoas) e Sudeste (Estado do Espírito Santo) do Brasil. O repertório vocal de L. natalensis foi constituído de dez notas emitidas em unicidade ou em diferentes combinações. As diferentes vocalizações foram organizadas em três grupos distintos de acordo com o contexto social no momento da emissão. L. natalensis apresenta extensa diversidade de sinais acústicos sustentada pela variação na duração de cada nota, assim como no número e seqüência de emissão das diferentes notas.

The extensive vocal repertoire of Leptodactylus natalensis is described. The field observations were made at three forest fragments of the Tropical Atlantic Domain, in Northeast (State of Alagoas) and Southeast (State of Espírito Santo) regions of Brazil. The vocal repertoire of L. natalensis was constituted by ten notes emitted alone or in different combinations. The several vocalizations were organized in three distinct groups according to the social context in the moment of emission. L. natalensis presents extensive diversity of acoustic signals supported by variations in duration of each note, as well as in the number and sequence of emission of different notes.

The breeding activity of Physalaemus signifer (Girard, 1853) was monitored from July 1999 to July 2000 in a temporary pond in Palmital, Municipality of Saquarema, State of Rio de Janeiro, Atlantic Rain Forest, Brazil. Males were sexually actives only in four nights, arriving at the pond on the early rainy season. Males in amplexus were larger and spent more nights in the reproductive aggregation than solitary ones. The number of nights was correlated with the mass of the males. Males adopted satellite behavior as alternative tactic for mate acquisition. Changes between calling and satellite tactics were observed in different nights. Calling males were not larger and heavier than satellite ones. Satellite behavior seemed to be related with the order of arrival on the pond. Size and mass of males did not influence the results of fights. Resident males won the majority of agonistics combats. Three types of vocalizations are described: advertisement, territorial, and encounter calls.