62ª Reunião Anual da SBPC

C. Ciências Biológicas - 14. Zoologia - 6. Zoologia

THE ADVERTISEMENT AND RELEASE CALLS OF Rhinella jimi (ANURA, BUFONIDAE)

Adrian Antonio garda 1 Vinícius de Avelar São Pedro 1 Marília Bruzzi Lion 1

1. Universidade Federal do Rio Grande do Norte

INTRODUÇÃO:

Little is known about the reproductive biology of frogs from the R. marina group, even though they are commonly found living within or near houses in urban and rural areas and attain large sizes. Few studies have addressed the biology of species from the group in detail. Rhinella marina in Barro Colorado Island apparently reproduces in late dry season and early rainy season. Likewise, R. schneideri reproduces at the end of the dry season in São Paulo, Brazil, while R. rubescens reproduces during the dry season. This early offset of the reproductive period along with the explosive breeding pattern observed for most species may account for the lack of reproductive data on the group. One recently described species, R. jimi, is widespread in the Brazilian Northeast region and commonly found in country areas and on the outskirts of large cities. It is characterized by gland concentrations on the forearm, around the cloaca, and on the feet. Herein we provide a detailed description of the advertisement and release calls of R. jimi along with behavioural notes from reproductive males in the municipality of Natal, Rio Grande do Norte State, Brazil. We compare the results with the descriptions available for other species of the R. marina species group.

METODOLOGIA:

We recorded frogs on February 22, 2010, in a permanent pond located in the neighbourhood of Ponta Negra, municipality of Natal, Rio Grande do Norte State, Brazil (25M 257634, 935034, 34 m above sea level). This artificial pond emerged when constructors were digging in the area to build a drainage system for pluvial waters and accidently reached the water table. The male was stimulated to emit release call by gently compressing its sides between thumb and forefinger. We recorded individuals for five minutes each using a Marantz® PMD 660 digital recorder with a Sennheiser® ME62 omni-directional or with a Sennheiser® ME66 directional microphone. Calls were recorded using 44 kHz at 16 bit sampling size and saved in .wav format. Voucher specimens were collected, individually tagged, killed with 5% xylocain cream and preserved in 10% formalin. We constructed spectrograms in Raven® using the following parameters: FFT 512 (1024 for power spectruns), overlap 50, and DFT 512. To produce waveform figures we filtered background calls on the frequency ranges of R. granulosa (2500 - 4200 Hz). Air and water temperatures were measured after each recording.

RESULTADOS:

Behavioural patterns suggest that this species is a short, explosive breeder with males actively searching for mates in a scramble competition fashion. Release calls are formed by random combinations of notes that vary in the number of pulses (2-5) and amplitude, but with dominant frequency equal to the advertisement call of the individual. Advertisement calls are formed by trains of repeated pulsed notes with 6.29 ± 2.29 s duration and average dominant frequency of 600.59 ± 51.71 Hz. Calls were initiated by a rising phase composed of 15.65 ± 7.09 notes during which frequency and amplitude rose to before levelling out along the remaining of the call. The number of pulses per note (2-3) is within the range of several species in the group and the character might have a large intrapopulational variation. Rhinella jimi is also similar to R. cerradensis because of its high variation in call duration. However, comparisons are hampered because most call descriptions for members of the R. marina group do not quantify individual or population level variations in call traits.

CONCLUSÃO:

Advertisement calls are fundamental aspects of frogs' natural history, and most likely determinant for the ecology and evolution of the large toads of the R. marina group in South America. The lack of adequate descriptions and quantification of individual and population-level variations hampers the use of robust analyses needed to statistically identify such differences without inherent human bias involved in visual inspection of spectrograms. One example of such technique is the cross correlation analysis. Because calls are stereotyped and similar, such analysis would surely help identify real differences among these species. Given their wide distributions, potential hybridization zones, and documented hybridization among syntopic species, adequate sound descriptions are cumbersome to fully understand not only each species' biology but also the evolution of these large toads across South America.

Palavras-chave: Rhinella jimi, vocalização, comportamento.