Bioacoustics of Tympanoterpes merganota

Notes on natural history and adult behavior . Adults were most active between 8 a.m. and 1 p. m. During this period, individuals of both sexes were observed flying among small shrubs and resting on tree trunks. Upon approach, both singing males and females typically retreated, descending to the ground and hiding in the grass ( N = 4). When males were captured, they produced a highamplitude stress call, with spectral characteristics similar to the calling song of conspecific males. During the calling song production, males may emit sounds with their heads oriented downward ( Fig. 2d , Online Resource 3), although the most frequently observed posture in this species involves the head facing upward ( Fig. 2c , Online Resources 4, 5 and 6). During the first part of the calling song, males retract the abdomen while producing brief “click” sounds (Online Resources 4, 5 and 6). The signal amplitude (in dB) varies, with the first part of the calling song having a higher amplitude, between 45 and 48 dB, followed by the second part, which ranges between 68 and 70 dB. During the second part, males partially open their wings and expand the abdomen ( Fig. 2c , Online Resources 4, 5 and 6). The calling song is performed either individually or in chorus (gregarious behavior). During chorus emission, which consists of the continuous production of the second part of the calling song, the signal was heard between 9 a.m. and 1 p. m., primarily during periods of greater sunlight exposure. This acoustic activity was not detected when cloud cover reduced sunlight incidence. Males were observed producing signals on distinct plant species. In the PNMSH, they were observed producing signals on Disynaphia ligulifolia (Hook. & Arn.) R. M. King & H. Rob. ( Asteraceae ) ( Fig. 2f ), while in the PEI, they were observed producing signals on Baccharis dracunculifolia DC. ( Asteraceae ) ( Fig. 2a ). A single copulation was observed in the PNMSH ( Fig. 2e ). During the process, a male emitted the calling song while positioned on D. ligulifolia . Within less than 1 min, a female appeared on the same plant. The male continued to emit the calling song until the female approached. Once the female reached the male, copulation occurred and lasted approximately 2 min. No acoustic signals were produced after the initial physical contact between the individuals. During copulation, the pair remained in an end-to-end position. The calling song, copulation, and oviposition of the species were also recorded in Pedreira, São Paulo , Brazil ( Barbosa 2021 , 2024a , b). The calling song and the copulation position ( Fig. 2g ) were similar to those recorded in Viamão, Rio Grande do Sul , Brazil . An oviposition event, on a Pterocaulon lanatum Kuntze ( Asteraceae ) plant ( Fig. 2i ), was additionally recorded for the study ( Fig. 2h , Online Resource 7) ( Barbosa 2024b ).

Phenology . From September to January, according to the dry-pinned specimens labels, considering that the first number in “12–89” and “12/85” from DZUP and MZSP labels, respectively, refers to December, which seems most likely. Records found on the iNaturalist platform are from September to December, with a single record for May and June (Online Resource 1). Bioacoustics . The calling song ( N = 7) consists of two parts ( Fig. 4a ). The first echeme, part A, is formed by syllables reminiscent of clicks, totalling 36.4 ± 14.4 (15–73) in all. This part of the signal lasts approximately 1.9 ± 0.7 (0.14–3.02) s. The second echeme, part B, is composed of an echeme lasting about 6.8 ± 3.5 (2.6–15.4) s, with peak frequency of the 8.8 ± 0.5 (8.1–10.8) kHz ( Fig. 4b ). The rate of syllables is 114.71 ± 10.70 (101–130) per second at 23°C. The chorus signaling involves the continuous emission of the second part of the calling song ( Fig. 4c ). Additionally, there is an increase in amplitude in the second part. Its calling song is also in broad-range frequency, with F1 at 8.72 ± 0.4 (8.4–9.2) kHz, F2 at 15.87 ± 0.28 (15.5–16.2) kHz, and F3 at 22.52 ± 0.24 (22–22.8) kHz. It is noteworthy that F1 ranges between 7 and 10 kHz, with the most prominent value at 8.7 kHz. The stress call ( N = 7) consists of syllables lasting about 0.11 ± 0.08 (0.045–0.28) s ( Fig. 4d ). Each echeme contains 59 ± 36 (21–128) syllables. The stress call is like the calling song, but also exhibits broad-range frequency, with F1 at 8.32 ± 0.58 (7.8–8.9) kHz, F2 at 18.26 ± 1.49 (15.6–19.1) kHz, and F3 at 24.36 ± 0.81 (23.7–25.3) kHz ( Fig. 4e ). The acoustic repertoire of the species was described before in Acosta et al. (2025) .