Full Description

"Lusitanian toadfish males form aggregations during the breeding season and emit a tonal advertisement call (the boatwhistle) to attract mates to their nests. We test the hypothesis that the boatwhistle can convey information both on individual identity and motivation by checking how signal parameters vary with time. We study how the physical (tide level) and social (calling alone or in a chorus) environments and male calling rate affect this advertisement signal and how all these external and internal factors (environment, social and male motivation) blend to modulate the Lusitanian toadfish’s advertisement call. Boatwhistles of each male were very stereotyped in short periods of time (minutes), but intra-male signal variability greatly increased in a longer time scale (days). Nevertheless, significant differences among males could still be found even in a long time scale. Pulse period was the acoustic feature that most contributed to discriminate among males. Tide level and male calling rate modulated boatwhistle characteristics, and there was a differential effect of tide on call attributes depending on male calling rate. Social acoustic environment only affected calling rate. These results suggest that inter-individual differences in call characteristics and call plasticity may mediate both male– male assessment and mate choice."

"Here, we test the hypothesis that the advertisement call of the Lusitanian toadfish shows enough inter-male variability and intra-male plasticity to convey information of male identity and motivation in chorusing aggregations."

"The tonal phase (P2) of the boatwhistle is the longest and the most characteristic of boatwhistles in the Lusitanian toadfish and in other batrachoidids (Thorson and Fine 2002; Amorim and Vasconcelos 2008)."

"In conclusion, significant differences among male calls in a long time scale were still found, although to a lesser extent than in a short time scale."

"Males differed significantly in all five acoustic parameters and average correct classification of individuals based on their calls was high (86%) as shown by DFA, with P2 pulse period, sound duration and amplitude modulation being the best parameters to discriminate among males."

"When considering a longer time frame (up to a week) there were still significant differences among Lusitanian toadfish males for all five acoustic features, but these become more variable within a male (Table 1). With the exception of P2 pulse period, all other parameters showed high intra-male variability over a week. This variability of the Lusitanian toadfish advertisement calls in a longer time frame suggests that boatwhistles are being modulated by either external factors such as the physical or the social environment or by internal factors such as the internal physiological state of the male (Remage-Healey and Bass 2005)."

"Interestingly, the P2 pulse period was the least variable acoustic feature both within and between males and kept the CV w and CVb under 0.1, regardless of the time span considered."

"Tide level had a significant effect in boatwhistle duration and P2 pulse period, which showed lower values at low tide. Consequently, vocal conspicuity was reduced at low tide as the number of calling males (see “Material and methods”) and sound duration decreased."

"Nevertheless, males that were calling at a high rate showed a pronounced increase of the fundamental frequency (the inverse of the pulse period) with low tide thus increasing the chances of sound detection at low water levels (Mann 2006)."

"Social environment affected calling rate in the Lusitanian toadfish and chorusing males called at higher rates."

"Male calling rate also had a significant effect on acoustic features of boatwhistles. High-calling rate males produced on average longer boatwhistles with higher fundamental frequencies."

Observation Environment Quotes

"We deployed 60 artificial concrete shelters every 1.5 m in rows along the shoreline in an intertidal area of the Tagus estuary (Portugal, Montijo, Air-Force Base 6; 38°42_N, 8° 58_W). The shelters had a hemicylinder shape capped at one end (internal dimensions, 50 cm long, 30 cm wide and 20 cm high) and were readily occupied by toadfish in the breeding season. These nests were only exposed to air during spring low tides. The water level in the nesting area varied between 0 m and 2.8 m. Three groups of six to eight males (n=22) that spontaneously occupied these artificial concrete nests were recorded over a period of 8 days in June/July 2006 and 2007, during the peak of the reproductive season. Subject males had a mean total length of 42.9 cm (range, 37.9–47.7 cm) and a mean eviscerated weight of 1,207 g (857–1,612 g). Each male was recorded for an average of 35 h (11–56 h). Nests with the subject fish were placed 1.5 m apart in two rows and were at least 15 m apart from other nests that could be occupied by other males. Nests’ entrances were closed with a plastic mesh that allowed prey items to enter but prevented males from abandoning the nest during recordings."

Behaviour Description Quotes

"Lusitanian toadfish males form aggregations during the breeding season and emit a tonal advertisement call (the boatwhistle) to attract mates to their nests. We test the hypothesis that the boatwhistle can convey information both on individual identity and motivation by checking how signal parameters vary with time. We study how the physical (tide level) and social (calling alone or in a chorus) environments and male calling rate affect this advertisement signal and how all these external and internal factors (environment, social and male motivation) blend to modulate the Lusitanian toadfish’s advertisement call. Boatwhistles of each male were very stereotyped in short periods of time (minutes), but intra-male signal variability greatly increased in a longer time scale (days). Nevertheless, significant differences among males could still be found even in a long time scale. Pulse period was the acoustic feature that most contributed to discriminate among males. Tide level and male calling rate modulated boatwhistle characteristics, and there was a differential effect of tide on call attributes depending on male calling rate. Social acoustic environment only affected calling rate. These results suggest that inter-individual differences in call characteristics and call plasticity may mediate both male– male assessment and mate choice."

Sound Name Quotes

"Lusitanian toadfish males form aggregations during the breeding season and emit a tonal advertisement call (the boatwhistle) to attract mates to their nests. We test the hypothesis that the boatwhistle can convey information both on individual identity and motivation by checking how signal parameters vary with time. We study how the physical (tide level) and social (calling alone or in a chorus) environments and male calling rate affect this advertisement signal and how all these external and internal factors (environment, social and male motivation) blend to modulate the Lusitanian toadfish’s advertisement call. Boatwhistles of each male were very stereotyped in short periods of time (minutes), but intra-male signal variability greatly increased in a longer time scale (days). Nevertheless, significant differences among males could still be found even in a long time scale. Pulse period was the acoustic feature that most contributed to discriminate among males. Tide level and male calling rate modulated boatwhistle characteristics, and there was a differential effect of tide on call attributes depending on male calling rate. Social acoustic environment only affected calling rate. These results suggest that inter-individual differences in call characteristics and call plasticity may mediate both male– male assessment and mate choice."

"Here, we test the hypothesis that the advertisement call of the Lusitanian toadfish shows enough inter-male variability and intra-male plasticity to convey information of male identity and motivation in chorusing aggregations."