Calls and calling behavior of the frog Leptodactylus natalensis (Amphibia: Anura: Leptodactylidae)

•Leptodactylus natalensis has a prolonged calling season, typically from May to September. Individuals occur in and call from the most forested patch of habitat on the campus of the Universidade Federal de Sergipe. Two kinds of calls were recorded and analyzed•advertisement and chirp calls. The function of the chirp call is unknown. The advertisement call has two carrier frequency bands, known to date for only two other species of Leptodactylus. The two carrier bands may correspond to different frequency tuning sensitivities in males and females, as females have slightly larger tympani than males, corresponding with their larger overall size. Published natural history information for the frog Leptodactylus natalensis Lutz, 1930, consists of comments on calling and microhabitat made by Lutz (1930) in his original description of the species and a recent study of some reproductive aspects, including the first description of the tadpole for the species (Oliveira & Lirio Júnior 1999). Calls of Leptodactylus natalensis have not been analyzed previously (Heyer 1994). One of us (CMC) had the opportunity to observe calling behavior and recorded the calls of L. natalensis. The purpose of this paper is to report these observations and describe the calls. Methods and Materials Observational data and recordings of Leptodactylus natalensis were made by CMC on the campus of the Universidade Federal de Sergipe, Sao Cristóvao, Sergipe, Brazil. Incidental information on calls at Santo Amaro das Brotas, Sergipe, was also obtained by CMC. Recordings were made from two individuals. Five recordings (USNM tape 323, cut 1) were made from specimen MZUSP 89945 (MZUSP = Museu de Zoología, Universidade de Sao Paulo collection), SVL (snout-vent length) 33.9 mm, on 22 June 1998, at an air temperature of 25°C, water temperature 24°C, the last recording completed at 1955 h. One recording (USNM tape 323, cut 2) was made from specimen MZUSP 89947, SVL 32.4 mm, also on 22 June 1998, air 25°C, water 24°C, the recording completed at 2030 h. It was not raining when these recordings were made, but a brief heavy rain occurred at 2100 h. Calls were recorded with a Sony TM5000 cassette recorder with a M 44 N(C) Beyer Dynamic Soundstar II microphone. Terminology follows that of Heyer et al. (1990), with the following clarifications. Carrier frequency is the frequency broadcast by the calling frog to the environment. Often, the carrier frequency embraces a range of frequencies loud enough to be heard by the intended receiver (male or female). The dominant frequency as used here is the single frequency value (or very narrow range of frequencies) that has the most sound energy in the call. Recordings were analyzed using "CaVOLUME 113, NUMBER 1 285 nary 2.1" software (Charif et al. 1995). Call rates and durations were measured from wave form displays, beginning and ending carrier frequencies from audiospectrogram displays, and dominant frequencies from spectral displays. Although the initiation of calls is clear on the wave form displays, the ends of the calls are not very distinct, perhaps due to the level of background noise and possible microphone ringing. Advertisement call rates were based on six calling sequences ranging from 7.8 to 15.2 sec from each of six recordings. Frequency data were taken from 10 consecutive calls from each of the six recordings; call duration and pulse data were taken on the same 10 calls for recordings 2 and 5 of MZUSP 89945 and for MZUSP 89947. Chirp call data are from the six chirps loud enough to analyze in the second recording of MZUSP 89945. Behavior and Calling Site Leptodactylus natalensis has a prolonged calling season coinciding with the rainy season, typically from May to September (also see Oliveira & Lirio Junior 1999). Calling starts around 1600 h. Calling activity is most intense around 1900 and continues until 2300 or 2400 h. However, on rainy days, especially at the beginning of the rainy season, males can be heard calling at 0800 h, and continuing throughout the day and night. Males do not call during hot and sunny days during the rainy season. The general site the frogs occupy on the campus is a small patch (100 X 400 m) of second growth (capoeira) on the right bank of the Rio Poxim, a seasonally partially flooded area (varzea) with many ponds. The site has 5-6 m high trees, many young palm trees, a thick grass ground cover, shallow litter, and white sand. The Leptodactylus natalensis were only heard calling from the capoeira•^never from the left bank of the Rio Poxim, which has more artificial open areas and patches of mangrove swamps. MZUSP 89945 was calling very close to the foot of a young palm tree surrounded by a pond with leaves in the water. The frog sat in the water, half submerged. A second male (MZUSP 89946) was about a half meter from the calling male. This second male was in a small burrow, with half the body exposed and uttered some "clicks" but no other calls. The "clicks" did not record adequately enough to analyze. MZUSP 89947 was near the foot of a small tree, at the edge of a little channel of rain water, hidden in grass. Leptodactylus natalensis infrequently jump when disturbed. Usually they take two or three steps backward and quietly hide under a leaf or other ground cover.