Full Description

"We combined physiological and sound propagation approaches to estimate the communication range of the Lusitanian toadfish’s (Halobatrachus didactylus) advertisement sound, the boatwhistle (BW). We recorded BWs at different distances from vocalizing fish in a natural nesting site at ca. 2–3 m depth."

"It is a benthic species with an unusually rich vocal repertoire (Amorim et al., 2008) that produces sounds in both reproductive and agonistic contexts (dos Santos et al., 2000; Vasconcelos et al., 2010). During the breeding season, males aggregate in nesting areas close to the substrate and produce advertisement calls – the boatwhistle (BW) – to attract mates (Jordão et al., 2012; Vasconcelos et al., 2012). The BW is the most commonly produced acoustic signal in this species throughout the year (Amorim et al., 2006, 2008, 2010)."

"The recording obtained at 0.1 m was adjusted to a playback amplitude of 140 dB sound pressure level (SPL; re, 1 µPa), corresponding to the amplitude of BWs produced by a vocalizing nesting male (Vasconcelos and Ladich, 2008)."

"To represent the variability of the Lusitanian toadfish BW (Amorim and Vasconcelos, 2008), four different BWs were used as stimuli (Fig. 1), differing in duration (418–1006 ms) and dominant frequency [ca. 50–150 Hz; fast Fourier transform (FFT) 8192 points, Hamming window]. Each experimental subject was tested with two different BWs."

"The BWs (BW1–4) recorded in shallow waters of the natural toadfish breeding habitat suffered strong attenuation with distance (Figs 2 and 3A). When compared with the measurements of the reference hydrophone (0.1 m), the attenuation averaged 17 dB in the first 2.5 m. An additional 7 dB attenuation was found 5 m away from the vocal fish, and the progressive loss of sound energy was to about _35 dB at a distance of 15 m. From 5 m onward, the attenuation was almost constant, with an average of 2.1–2.7 dB per 2.5 m. As expected, the attenuation varied throughout the frequency range of the BW, with lower frequencies exhibiting a stronger attenuation with increasing distance (Fig. 3B,C)."

"BWs suffered strong attenuation with distance in the natural toadfish breeding habitat as expected for shallow water. Low-frequency sounds with wavelengths longer than the height of the water column are strongly attenuated in natural environments (Bass and Clark, 2003; Mann, 2006). Because BWs have fundamental frequencies of ca. 50–60 Hz (sound wavelength _≈25–30 m), water depth at our breeding study site (<5 m) will impact sound propagation."

"The present study points to the Lusitanian toadfish communication range being more limited by audition than affected by the background noise in the studied habitat."

Observation Environment Quotes

"The boatwhistles were recorded in the field 0.1 m away from the vocal male. "

"We made synchronous recordings of BWs produced by breeding territorial males in the natural nesting habitat (Air Force Base 6, Montijo, Portugal; 38°42_ N, 8°58_ W)."

Behaviour Description Quotes

"We combined physiological and sound propagation approaches to estimate the communication range of the Lusitanian toadfish’s (Halobatrachus didactylus) advertisement sound, the boatwhistle (BW). ' ' It is a benthic species with an unusually rich vocal repertoire (Amorim et al., 2008) that produces sounds in both reproductive and agonistic contexts (dos Santos et al., 2000; Vasconcelos et al., 2010)."

Sound Name Quotes

"We combined physiological and sound propagation approaches to estimate the communication range of the Lusitanian toadfish’s (Halobatrachus didactylus) advertisement sound, the boatwhistle (BW)."