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Neighbour-stranger discrimination is an important mechanism in social behaviour, as it allows the individual to avoid the high energetic costs of repeated agonistic interactions with neighbours. In some anuran species, the owners of territories respond more aggressively towards strangers than neighbours. Here, we investigated whether gladiator frog, Boana goiana, males discriminate between neighbours and strangers. This is a lek-breeding species; therefore, it does not defend fixed territories which are associated with a specific resource. We conducted a playback field experiment with a repeated-measures design, based on three treatments: (i) neighbour’s call in initial position, (ii) stranger’s call in initial position, and (iii) neighbour’s call in new position. We did not observe any systematic modification in the acoustic properties (call duration, dominant frequency, repetition rate) of the advertisement and short aggressive calls of B. goiana males given in response to our playback treatments. Our results indicate that B. goiana males do not exhibit vocally mediated ‘dear enemy’ relationships. We discuss the possible ecological and social factors that may have impeded the evolution of ‘dear enemy’ relationships in this species.

Anurans living in species-rich assemblages may experience acoustic niche overlap. To deal with potential masking interference during reproductive activity, species can present acoustic partitioning based on differences in calling period. Studies addressing this question in tropical assemblages have mainly focused on the seasonal scale, and little is known about nightly variation in calling. Here, we reported on phenology and abundance of five tropical anuran assemblages at both seasonal and daily scale and tested the effects of temperature and relative humidity on calling activity patterns of 19 species. Based on 420 hourly acoustic surveys, an overall peak of calling activity in between the first and fourth hour after sunset was identified by Rayleigh’s circular test, with a gradual decrease until sunrise. This nightly pattern was followed by most of the species in the assemblages and similarly observed for species presence and abundance of calling males. The acoustic niche overlap was greater than expected by chance within the assemblages, while no pattern of coincidence or segregation was found for the syntopic congeneric species (Dendropsophus, Boana and Leptodactylus). Moreover, the calling activity of the assemblages, measured as richness and diversity of calling species, was negatively influenced by air and water temperature and positively by relative humidity. Thus, climatic variables act as driver factors to determine calling activity and reproduction of anurans at daily scale. The absence of a segregation pattern at the assembly or genus levels in the calling activity over time indicates that the use of the acoustic temporal niche is not a limiting resource for Cerrado anurans.

Overcoming the Linnaean and Wallacean shortfalls is an urgent task for biologists. It has been estimated that only a small fraction of the biodiversity on Earth is known, while geographic ranges of already described species are poorly documented. We performed a systematic review and modeling on species descriptions of Brazilian amphibians to evaluate the taxonomic knowledge on this group, to estimate the number of new species that remain to be described, and to identify description trends and relevant information for guiding future studies. All descriptions made between 1758 and 2017 of amphibian species and anuran tadpoles in Brazil, the country with the richest amphibian fauna, were gathered and characterized (species, year of description, number of authors per article, and coordinates of the collecting site). We found 1,119 amphibian species reported occurring in Brazil. The number of descriptions of both amphibian species and anuran tadpoles, as well as the number of authors per article, has exponentially increased over time. Phylogenetic regression analysis revealed that species with smaller body length and distribution area were described later, and that these two species traits are also correlated. According to two predictive models and several scenarios, we estimated that at least 25% of the Brazilian amphibian species have not yet been described. Our findings highlight the maintenance of significant Linnaean and Wallacean shortfalls in the knowledge of Brazilian amphibian species, despite of the increasing research efforts. The northern (Amazon) and central region (Cerrado) of Brazil should be priority areas for herpetological research. Society and the scientific community must commit to a greater investment in biodiversity knowledge to improve conservation strategies before the described and undescribed species become extinct.

Advertisement calls are often used as essential basic information in studies of animal behaviour, ecology, evolution, conservation, taxonomy or biodiversity inventories. Yet the description of this type of acoustic signals is far to be completed, especially in tropical regions, and is frequently non-standardized or limited in information, restricting the application of bioacoustics in science. Here we conducted a scientometric review of the described adverstisement calls of anuran species of Brazil, the world richest territory in anurans, to evaluate the amount, standard and trends of the knowledge on this key life-history trait and to identify gaps and directions for future research strategies. Based on our review, 607 studies have been published between 1960 to 2016 describing the calls of 719 Brazilian anuran species (68.8% of all species), a publication rate of 10.6 descriptions per year. From each of these studies, thirty-one variables were recorded and examined with descriptive and inferential statistics. In spite of an exponential rise over the last six decades in the number of studies, described calls, and quantity of published metadata, as revealed by regression models, clear shortfalls were identified with regard to anuran families, biomes, and categories of threat. More than 55% of these species belong to the two richest families, Hylidae or Leptodactylidae. The lowest percentage of species with described calls corresponds to the most diverse biomes, namely Atlantic Forest (65.1%) and Amazon (71.5%), and to the IUCN categories of threat (56.8%), relative to the less-than-threatened categories (74.3%). Moreover, only 52.3% of the species have some of its calls deposited in the main scientific sound collections. Our findings evidence remarkable knowledge gaps on advertisement calls of Brazilian anuran species, emphasizing the need of further efforts in standardizing and increasing the description of anuran calls for their application in studies of the behav

In frogs, acoustic signals are the most important communication mechanism, since they may be used in several social contexts. In many anurans, the dominant frequency of calls is negatively related to body size, and in such species, this spectral parameter may be considered a good predictor of fighting ability. We experimentally investigated the vocal behavior of 30 male Hypsiboas goianus in central Brazil to answer the following questions: (1) Do males change the acoustic parameters of their calls in response to conspecific intruders? and (2) Does the acoustic behavior of H. goianus depend on the simulated body size of their opponent? We used playback of synthesized calls with high (3573 Hz) and low (3123 Hz) dominant frequency to simulate small and large males, respectively. Males reduced the rate of advertisement calling in response to playback but did not change vocal behavior in response to low-frequency and high-frequency playback. So, while males adjust their calling activity in response to simulated conspecifics, there was no evidence that they assess the fighting ability of their opponents through acoustic interactions.