Release call and altitudinal distribution extension of Zachaenus carvalhoi Izecksohn, 1982 (Anura: Cycloramphidae) from Southeastern Brazil

Zachaenus carvalhoi is a small frog endemic to the Atlantic Forest of southeastern Brazil, known from a few localities in the states of Minas Gerais and Espírito Santo. The main information on the species is related to its distribution, natural history and advertisement call. Herein we describe the release call of Z. carvalhoi, and provide a new altitudinal record. On 21 October 2016, we hand-captured a male Z. carvalhoi (30.78 mm) vocalizing in a forest fragment in Cataguases, Minas Gerais State (-21.429022°S, -42.703334°W; 230 m a.s.l.). We simulated in laboratory a false axillary amplexus until a release call was emitted. The frog emitted four calls, which were recorded using a Tascan DR40 digital recorder with an internal microphone. Spectral and temporal parameters were measured using Raven Pro 1.5. The release call was composed of one to three notes (mean 0.11 ± 0.07, range 0.03–0.17 s; N=4). The mean note duration was 0.05 ± 0.01 s (0.03–0.07; N=8) and the mean interval between notes was 0.01 ± 0.01 s (0.002–0.03; N=4). The call presented up to 18 harmonics, with frequency modulation in six of eight notes analyzed. The peak of dominant frequency was 2056.6 ± 271.5 Hz (1500–2390.6), and coincides with the second harmonic in five notes, and with the third harmonic in three notes. The release and advertisement call differs on call duration (0.2–0.4 and 0.03–0.17, respectively) and spectral structure (pulsed and harmonic, respectively). However, both calls have similar dominant frequency, which is expected, since the calls are produced by the same morphological apparatus. In addition, our record provides the lowest altitudinal occurrence for the species (330 meters below the lowest known locality in Cariacica/ES - 560 m). Therefore, elevation might not be seen as a barrier to dispersal for this particular species.