Full Description

"At the start of the breeding season, male oyster toadfish Opsanus tau (Linneaus) establish a territory where they produce an advertisement boatwhistle call to attract females to the nest site (Gudger 1910; Gray and Winn 1961; Winn 1972; Fish 1972)."

"Only sexually mature male toadfish produce the tonal boatwhistle advertisement call, while both males and females produce shorter broadband grunts during putative agonistic interactions (Fish 1954; Gray and Winn 1961)."

"Most previous studies on O. tau concentrate on the advertisement boatwhistle call, and while early literature eludes to possible variations in grunts (including ‘incomplete boatwhistles’ and the ‘growl’ described as single grunts produced almost continuously; Winn 1972) (Fish 1954; Winn 1967; Fish 1972), there is little information on the type, structure, acoustic characteristics, and behavioral contexts of grunts in this species."

"Toadfish grunts have been described historically as non-harmonic pulsed sounds that are produced by both males and females in presumably agonistic contexts throughout the year (Fish 1954; Gray and Winn 1961; Winn 1967)."

"Increased temperatures were associated with an increase in the fundamental frequency of boatwhistles of oyster toadfish, while boatwhistle duration was independent of water temperature (Fine 1978a; Edds-Walton et al. 2002)."

"A total of 3040 grunts were recorded from the group of 14 toadfish on 108 of the 121 days of the study period between May 23 and September 21, 2007. The majority of grunts (61%) were recorded from region 1 that contained 9 fish, followed by region 3 (26%; 3 fish) and region 2 (13%; 2 fish). Grunts were produced both day and night, and there was no difference in the number of grunts produced by time of day across the study period (data compared in 3 h time blocks; Kruskal-Wallis 1-way ANOVA on ranks, p>0.05). However, the number of grunts produced during hours of darkness (average rate=142.5 grunts/hr) was higher than during hours of light (average rate=102.4 grunts/hr) (MannWhitney Rank Sum test, p=0.02)."

"There was also a positive correlation between the number of grunt vocalizations and the number of boatwhistle vocalizations per day (Spearman Rank Order Correlation, r=0.36; p<0.001). Boatwhistle production was maximal at the end of June and beginning of July. Periods of boatwhistle production were accompanied primarily by grunt trains from fish within the same region as the calling individual. Grunts were classified into one of 4 different types based on their pulse structure: single grunts, net grunts, doublet grunts, and grunt trains (Fig. 1). A single grunt was defined as an individual grunt that was not part of a train or doublet and was the most common grunt type recorded (70% of all grunts). Single grunts had durations of 46–269 ms ( x=111.2±34.3 SD ms; n=327 analyzed) and broadband frequency components of ~ 40–250 Hz (Fig. 2). Single grunts were similar in duration to the first doublet grunt, but were longer than both the second doublet grunt and individual grunts within a train, and shorter than both net grunts and boatwhistles (Kruskal-Wallis 1-way ANOVA on ranks, p<0.001; Dunn’s tests, p<0.05) (Fig. 2). Frequencies of single grunts did not differ from the first or second doublet grunts, but were higher than grunts within a train and lower than boatwhistles (Kruskal-Wallis 1-way ANOVA on ranks, p<0.001; Dunn’s tests, p<0.05) (Fig. 2). Grunt trains were a series of 3 or more individual grunts in succession, accounted for 20% of all grunts recorded, and were most common during times of boatwhistle production. Both fixed-interval and variable-interval grunt trains were produced throughout the study period. Grunt trains contained 3 to 22 grunts ( x=6.9±5.4 SD; n=64 trains analyzed) that lasted 0.5–13.4 sec ( x train duration=4.3±3.1 SD sec) and in most cases the first grunt in a train was longer than the subsequent grunts. Individual grunts within a train were 36–249 ms in duration (x =81.1±29.7 SD ms;n=242 grunts in 64 trains) and had frequencies of 40– 250 Hz (Figs. 1, 2). These individual grunts within a train were similar in duration and fundamental frequency to the 2nd doublet grunt, but were shorter and had lower frequency components than all other grunt types and boatwhistles (Kruskal-Wallis 1-way ANOVA on ranks, p<0.001; Dunn’s tests, p<0.05) (Fig. 2). Doublet grunts were a series of 2 adjacent grunts separated by < 800 ms ( x interpulse interval=267.7± 202.1 SD ms; n=65 analyzed) where the first grunt was longer ( x duration=123.8±30.4 SD ms; n=65) than the second grunt ( x duration=65.7±13.1 SD ms; n=65), but both grunts had similar frequency components (40–200 Hz) (Figs. 1, 2). Doublet grunts, which composed 10% of all grunts, were recorded throughout the study period and from multiple individuals. Net grunts were individual grunts produced while the fish was restrained within a net underwater, and were made by both males and females in response to handling, but were not observed at any other time. Net grunts were longer ( x duration=176.8±66.4 SD ms; n=80 analyzed) and had higher frequency components (78–277 Hz) than all other grunt types, but were shorter and had lower fundamental frequencies than boatwhistles (Kruskal-Wallis 1-way ANOVA on ranks, p<0.001; Dunn’s tests, p<0.05) (Figs. 1, 2). Single grunts, doublet grunts and trains of grunts (grunt trains) were all produced throughout the study period from late May to late September, with a peak in production during July for all types (Fig. 3)."

"Vocalizations were produced across the range of temperatures measured (14–25°C) and the total number of grunts produced per day was correlated with average daily water temperature (Spearman Rank Order Correlation, r=0.36, p<0.001) (Fig. 4). In contrast, the total number of grunt vocalizations was not correlated with average daily light levels measured by the light probe positioned in the habitat (Spearman Rank Order Correlation, p=0.98). However, there was a positive correlation between the number of grunts per day and the total hours of daylight per day (i.e. daylength: sunrise to sunset) (Spearman Order Rank Correlation, r=0.29, p=0.001) (Fig. 4)."

"Toadfish net grunts differed in duration, frequency components, and structure compared to spontaneously produced grunts and boatwhistles. These net grunts also differed in fundamental frequency (O. tau, < 125 Hz; H. didactylus, ~260 Hz) and structure and duration (O. tau, single sound ~177 ms duration; H. didactylus, pair of sounds ~73 ms duration) from the handlinginduced ‘knocks’ described in the Lusitanian toadfish (dos Santos et al. 2000), but this may be due in part to the difference in swim bladder morphology between these two species. Net grunts in the present study were only recorded during restraint and handling, and not during natural interactions, but the behavioral context for this sound type may have been absent (e.g. predator presence)."

"The similarity in pulse structure among grunt types indicates that they are all based on a stereotyped pulse, whose temporal patterns or rate of production can be varied to produce different sounds."

"The incidence of grunt production was also higher at night when toadfish are known to be more active (Phillips and Swears 1981), which lends support to the idea of increased encounters."

"Single grunts and grunts within trains also decreased in duration with increasing temperatures."

"The correlation between grunt vocalizations and tidal amplitudes associated with the semilunar cycle in the absence of the physical cues of hydrostatic pressure, changing water depth, and current directions also suggests that toadfish have an endogenous semilunar rhythm or clock."

"Fig. 1 Sounds produced by the oyster toadfish Opsanus tau. Oscillograms (top) and sonograms (bottom) of each vocalization type are shown."

Observation Environment Quotes

"Sound recordings were made from a group of toadfish housed in an outdoor concrete rectangular raceway tank (1230 long x 120 wide x 150 high cm) at the Quissett campus of the Woods Hole Oceanographic Institute (WHOI), Woods Hole, MA."

Behaviour Description Quotes

"At the start of the breeding season, male oyster toadfish Opsanus tau (Linneaus) establish a territory where they produce an advertisement boatwhistle call to attract females to the nest site (Gudger 1910; Gray and Winn 1961; Winn 1972; Fish 1972)."

"Only sexually mature male toadfish produce the tonal boatwhistle advertisement call, while both males and females produce shorter broadband grunts during putative agonistic interactions (Fish 1954; Gray and Winn 1961)."

"The purpose of this study was to 1) identify and characterize the grunts produced by oyster toadfish and compare them with the advertisement boatwhistle, and 2) test for relationships between grunt vocalization characteristics and environmental parameters such as water temperature, light levels, daylength, and tidal and lunar cycles in a group of toadfish maintained in an outdoor habitat."

Sound Name Quotes

"At the start of the breeding season, male oyster toadfish Opsanus tau (Linneaus) establish a territory where they produce an advertisement boatwhistle call to attract females to the nest site (Gudger 1910; Gray and Winn 1961; Winn 1972; Fish 1972)."

"Only sexually mature male toadfish produce the tonal boatwhistle advertisement call, while both males and females produce shorter broadband grunts during putative agonistic interactions (Fish 1954; Gray and Winn 1961)."

"Most previous studies on O. tau concentrate on the advertisement boatwhistle call, and while early literature eludes to possible variations in grunts (including ‘incomplete boatwhistles’ and the ‘growl’ described as single grunts produced almost continuously; Winn 1972) (Fish 1954; Winn 1967; Fish 1972), there is little information on the type, structure, acoustic characteristics, and behavioral contexts of grunts in this species."

"A total of 3040 grunts were recorded from the group of 14 toadfish on 108 of the 121 days of the study period between May 23 and September 21, 2007."

"boatwhistles: sounds with an intital grunt-like segment 1 followed by a tonal segment 2 as described by previous studies (e.g. Gray and Winn 1961; Winn 1972; Edds-Walton et al. 2002). "

"Boatwhistle production was maximal at the end of June and beginning of July. Periods of boatwhistle production were accompanied primarily by grunt trains from fish within the same region as the calling individual. Grunts were classified into one of 4 different types based on their pulse structure: single grunts, net grunts, doublet grunts, and grunt trains (Fig. 1)."