Stereotypy and variation of the mating call in the Lusitanian toadfish, Halobatrachus didactylus

Abstract

Signal attributes should show different degrees of variability depending on the information to be conveyed. Species identity is usually associated with stereotyped features of a signal, whereas other types of information such as individual quality and motivation are associated with signal plasticity. 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 malemale assessment and mate choice.

Fish Sounds and Mate Choice

“…In other words, only males with high fat reserves are able to contract sonic muscles in a sustained high rate during the emission of boatwhistles. This acoustic feature shows low intra-and interindividual variability in this species (coefficient of variation <8 %; Amorim and Vasconcelos 2008;Amorim et al 2011), inasmuch as it is constrained by the central pattern generator in the hindbrain (Bass and Baker 1990;Bass et al 2008), suggesting that males with higher body lipid levels are advertising their quality to females by sustaining sonic muscle contraction close to their physiological limit.…”

“…Part of these characteristics can also show some plasticity potentially relevant for individual assessment within a male chorus. For instance, sound duration and calling rate are modulated by the level of acoustic competition in the Lusitanian and in the Gulf (Opsanus beta) toadfishes (Thorson and Fine 2002a;Amorim et al 2011). For example, in the Gulf toadfish, chorusing activity increases after sunset and males tend to increase calling rate while decreasing call duration ( Fig.…”

Assessing acoustic communication active space in the Lusitanian toadfish

“…Congruently, tide level has been shown to influence the number of BWs produced by nesting males and the characteristics of these BWs. Males calling from nests in the upper infralitoral zone exhibited a marked circatidal rhythm, with a higher BW production in the high tide (Amorim et al, 2011). These changes in vocal behaviour probably reflect a strategy to minimize vocal activity costs, i.e.…”

A new concept in underwater high fidelity low frequency sound generation

“…[1][2][3][4][5] These signals are often pulsed low frequency sounds with fast transients. 6,7 Playback experiments, a widespread tool to study the function of animals' acoustic signals, 8 have been hampered in fish due to limitations of commercially available underwater loudspeakers, which do not reproduce fish sounds appropriately.…”