Vocalization during Agonistic Behaviour in Cottus gobio L. (Cottidae): An Acoustic Threat Display

Agonistic behaviour in the river bullhead C. gobio consists of visual (raising gill covers and fins, lowering the head, darkening) and acoustic (single knock sounds and trains of knock sounds) threat displays, rarely followed by attacks and bites. This study investigates the relationship of vocalizations with size, dominance, territory dimensions and sex of the opponents. Four groups, each consisting of a big male, a small male and a female, were each investigated for three different days. The number of won contests of each individual, the numbers of each sound produced during these encounters and the tank part where encounters took place were determined. Subordinate fish emit fewer sounds but relatively far more trains of knock sounds than dominant ones. They produce relatively more sounds under shelters whereas dominants do this on uncovered areas. α-fish produce more calls during agonistic encounters with β-fish than Ω fish. In β-individuals no such difference was noted. Basically no sex related behaviour could be observed. In each area of the tank one individual won most contests (= territory). Dimensions of territories differed significantly between individuals in each tank (α-, β-, Ω-fish). In no case were all three individuals able to maintain territories. Relative sizes of fish correlate significantly with relative numbers of successful encounters and with territory dimensions. Furthermore, both parameters are positively correlated with the numbers of sounds emitted by an individual. Sound production in C. gobio functions as an acoustical threat display. Because of the high energy costs of sound emission underwater it might be a very effective method of assessing the fighting ability of an opponent.     

How boat noise affects an ecologically crucial behaviour: the case of territoriality in <Emphasis Type="Italic">Gobius cruentatus</Emphasis> (Gobiidae)

Gobius cruentatus emit sounds during agonistic interactions. In order to evaluate the effect of boat noise exposure on G. cruentatus territorial behaviour, we played a field-recorded diesel engine boat noise during aggressive encounters between an intruder and a resident fish in a laboratory-controlled tank. We tested two factors: role (resident vs. intruder) and condition (noisy vs. silent); the test animals underwent all the treatments in a round-robin design. Agonistic behavior of the residents was modified by boat noise: during the playback residents were more submissive and won less encounters than in the control (silent) condition. We suggest that sound production is an effective tool for territorial defense, since the impairment of acoustic communication due to the recreational boat noise diminished the ability of the resident to maintain its territory.     

Significance of Agonistic Vocalization in the Croaking Gourami (Trichopsis vittatus,Teleostei)

Trichopsis vittatus emits high amplitude sounds during agonistic encounters with conspecifics. The sound producing organ is derived from the structural components of the pectoral fins. The study involved muting a sample of subjects by removing two pectoral fin tendons without any further restriction in movements and behaviour. Mute and unaltered males were then placed together in pairs and the following agonistic behavioural elements were determined: attacks, lateral displays, sound production and frontal displays. Soniferous males had a higher probability of winning contests when size differences were small. In pairs with big size ratios, the larger males were more often successful. Besides visual and acoustical signals, lateral line stimuli seem to play no role in threatening displays. These results demonstrate that vocalization during agonistic encounters is important for becoming dominant in specific circumstances. Because of correlation between main frequencies and size, sound emission might be a very effective method of assessing the physical strength of an opponent.     

Agonistic interactions with asymmetric body size in two adult-age groups of the annual killifish Millerichthys robustus (Miller & Hubbs, 1974)

In this study, the author evaluated two adult age groups of the Mexican rivulus Millerichthys robustus with body size asymmetries to determine the strategies used by an annual killifish during agonistic interactions of different ontogenetic stages. To achieve this goal, the author first characterized the ethogram of agonistic interactions of M. robustus composed of seven behavioural units in males and five behavioural units in females. The author then analysed agonistic interaction strategies used by males and females with body size asymmetries in two groups of different adult ages that represent different ontogenetic stages: (a) just after sexual maturity was reached, at 5 weeks of age, and (b) near natural death, at 24 weeks of age. The agonistic behaviour patterns of M. robustus were compatible with the logic of mutual assessment. Large males had an advantage during their interactions in both age groups, winning all of the encounters. Nonetheless, there was more aggression in 5-week-old fish encounters. In addition, small 24-week-old fish were more aggressive than small 5-week-old fish. These changing strategies may be because of the cost–benefits required during a fight at each ontogenetic stage. In the female encounters, size did not predict winners, as both small and large fish won a similar number of encounters, and some contests remained unresolved regardless of age group. There was a tendency for small females of any age to risk more than males in fights to maintain reproductive fitness.     

Dominance status reversal based on pair-bond formation in the convict cichlid (Amatitlania nigrofasciata)

Dominant individuals have access to higher-quality resource; thus, reversing their dominance status would be important for subordinate individuals. Using the convict cichlid fish (Amatitlania nigrofasciata), this study examines whether forming a pair bond can reverse dominance status. Furthermore, I hypothesize that female convict cichlids will incur more dominance reversals from pair-bond formation than males. Dyadic, same-sex contests were conducted to determine dominant and subordinate individuals. Forced pairing of these individuals based on status was followed by polyadic, between-pair contests. The results indicate that individual dominance status does carry over into between-pair competition. Furthermore, dominance reversals do occur in convict cichlids and occur more frequently in females than in males. In addition, dominant males assist their mates during aggressive encounters, and these assists may account for subordinate females winning against dominant females during polyadic contests.     

Four type of sounds for one winner: vocalizations during territorial behavior in the red-mouthed goby <Emphasis Type="Italic">Gobius cruentatus</Emphasis> (Pisces Gobiidae)

During territorial encounters, the acoustic repertoire of Gobius cruentatus consists of four types of sound emissions: a tonal sound, a noisy tonal sound, a train of individual pulses, and a complex sound. The complex sound is made of two distinct elements, an initial tonal part followed by pulses. This is the largest acoustic repertoire described so far in gobiid fish during aggressive interaction. Sounds are emitted, mainly by the residents, when fish have already started the interaction but before the encounter is settled. Therefore, sounds seem to have a threatening function.     

Acoustic and visual adaptations to predation risk: a predator affects communication in vocal female fish

Predation is an important ecological constraint that influences communication in animals. Fish respond to predators by adjusting their visual signaling behavior, but the responses in calling behavior in the presence of a visually detected predator are largely unknown. We hypothesize that fish will reduce visual and acoustic signaling including sound levels and avoid escalating fights in the presence of a predator. To test this we investigated dyadic contests in female croaking gouramis (Trichopsis vittata, Osphronemidae) in the presence and absence of a predator (Astronotus ocellatus, Cichlidae) in an adjoining tank. Agonistic behavior in T. vittata consists of lateral (visual) displays, antiparallel circling, and production of croaking sounds and may escalate to frontal displays. We analyzed the number and duration of lateral display bouts, the number, duration, sound pressure level, and dominant frequency of croaking sounds as well as contest outcomes. The number and duration of lateral displays decreased significantly in predator when compared with no-predator trials. Total number of sounds per contest dropped in parallel but no significant changes were observed in sound characteristics. In the presence of a predator, dyadic contests were decided or terminated during lateral displays and never escalated to frontal displays. The gouramis showed approaching behavior toward the predator between lateral displays. This is the first study supporting the hypothesis that predators reduce visual and acoustic signaling in a vocal fish. Sound properties, in contrast, did not change. Decreased signaling and the lack of escalating contests reduce the fish’s conspicuousness and thus predation threat.     

Ontogenetic development of auditory sensitivity and sound production in the squeaker catfish <Emphasis Type="Italic">Synodontis schoutedeni</Emphasis>

Background  

Surveys of ontogenetic development of hearing and sound production in fish are scarce, and the ontogenetic development of acoustic communication has been investigated in only two fish species so far. Studies on the labyrinth fish Trichopsis vittata and the toadfish Halobatrachus didactylus show that the ability to detect conspecific sounds develops during growth. In otophysine fish, which are characterized by Weberian ossicles and improved hearing sensitivities, the ontogenetic development of sound communication has never been investigated. We analysed the ontogeny of the auditory sensitivity and vocalizations in the mochokid catfish Synodontis schoutedeni. Mochokid catfishes of the genus Synodontis are commonly called squeakers because they produce broadband stridulation sounds during abduction and adduction of pectoral fin spines. Fish from six different size groups - from 22 mm standard length to 126 mm - were studied. Hearing thresholds were measured between 50 Hz and 6 kHz using the auditory evoked potentials recording technique; stridulation sounds were recorded and their sound pressure levels determined. Finally, absolute sound power spectra were compared to auditory sensitivity curves within each size group.     

Vocal communication in the bicoloured white-toothed shrew<Emphasis Type="Italic">Crocidura leucodon</Emphasis>

Vocal sounds of 15 individuals ofCrocidura leucodon (Hermann, 1780) emitted during agonistic and amicable interactions in male-male, female-female and male-female dyadic encounters, and intraspecific cage groups, were studied. An analysis of spectral properties, along with an examination of context and function, were performed. The sounds registered during agonistic interactions showed an increase, then a decrease in frequency, often followed a complex undulating curve. The dominant frequency (DF) was 10.7±0.05 kHz, and duration (DU) was 104.2±4.4 ms. The calls emitted by shrews at investigation and grooming often ended with chirping notes (DF=4.8±0.2 kHz, DU=23.5±1.1 ms). While clustering and huddling up to the partner, the animals produced calls consisting of short notes with a very low intensity (DF=1.0±0.07 kHz, DU=35.2±0.8 ms). Based on these finding, it can be assumed that threatening sounds, emitted in agonistic encounters, allow shrews to avoid conflicts, while those, emitted when clustering and huddling up to the partner, contribute to maintenance of group cohesiveness. The variability of frequency ranges and intensity of sounds probably reflects the territorial and gregarious behaviour ofC. leucodon and adaptation to communication in variable acoustic environments.     

Wing-Click Sounds of Heliconius cydno alithea (Nymphalidae: Heliconiinae) Butterflies

Field-collected Heliconius cydno Doubleday females were observed producing audible wing clicks during encounters between conspecifics in greenhouses in a large insectary during the day and at roosting time. Occasionally, these females also were observed producing sounds in aggressive encounters with females of a close relative, H. erato (L). However, the wing-clicks were not observed subsequently from first-generation adults born in the greenhouses. The sounds were produced in short trains of 3–10 wing-clicks at the rate of 10 clicks/s. The individual clicks had a mean duration of 1.48 ms and a broad frequency spectrum, with a peak near 1075 Hz. This peak lies near the 1200-Hz frequency of maximal sensitivity measured previously for auditory neurons of H. erato. The production of these previously unreported sounds suggests that wing clicks may play a role in both intra- and interspecific communication among Heliconius species.     

Male—male aggression in the plethodontid salamander Desmognathus ochrophaeus

Aggressive encounters between pairs of male mountain dusky salamanders (Desmognathus ochrophaeus) were staged in the laboratory in the absence of any obvious limited resource. We observed aggressive interactions which sometimes escalated to biting. Physical injuries were inflicted during some aggressive encounters; however, the consequences of injury for future fitness are uncertain. Several behaviour patterns used in contests apparently functioned as threat displays, and these sometimes ended contests before they escalated to biting. We could detect no significant influences of three types of asymmetries among males in determining the winners and losers of contests (body size, recent mating experience and familiarity with the testing arena). Three cases of 'homosexual' courtship were observed. Both intermale aggression and intermale courtship may be interpreted as forms of competition for mates.     

Ontogeny of Acoustic and Feeding Behaviour in the Grey Gurnard, Eutrigla gurnardus

Although sound production in teleost fish is often associated with territorial behaviour, little is known of fish acoustic behaviour in other agonistic contexts such as competitive feeding and how it changes during ontogeny. The grey gurnard, Eutrigla gurnardus, frequently emits knock and grunt sounds during competitive feeding and seems to adopt both contest and scramble tactics under defensible resource conditions. Here we examine, for the first time, the effect of fish size on sound production and agonistic behaviour during competitive feeding. We have made sound (alone) and video (synchronized image and sound) recordings of grey gurnards during competitive feeding interactions. Experimental fish ranged from small juveniles to large adults and were grouped in four size classes: 10–15, 15–20, 25–30 and 30–40 cm in total length. We show that, in this species, both sound production and feeding behaviour change with fish size. Sound production rate decreased in larger fish. Sound duration, pulse duration and the number of pulses increased whereas the peak frequency decreased with fish size, in both sound types (knocks and grunts). Interaction rate and the frequency of agonistic behaviour decreased with increasing fish size during competitive feeding sessions. The proportion of feeding interactions accompanied by sound production was similar in all size classes. However, the proportion of interactions accompanied by knocks (less aggressive sounds) and by grunts (more aggressive) increased and decreased with fish size, respectively. Taken together, these results suggest that smaller grey gurnards compete for food by contest tactics whereas larger specimens predominantly scramble for food, probably because body size gives an advantage in locating, capturing and handling prey. We further suggest that sounds emitted during feeding may potentially give information on the motivation and ability of the individual to compete for food resources.     

Territorial interactions between larvae of the dragonfly Pyrrhosoma nymphula: outcome of encounters

The behaviour of final-instar larvae of the aquatic predator Pyrrhosoma nymphula (Odonata: Coenagrionidae) during laboratory-staged territorial interactions is described. Occupants, as distinct from intruders, won 72% of encounters. The behaviour of occupants during contests won by intruders was more like that of intruders during all contests than that of occupants during contests won by occupants. Contest outcome was little affected by either size differences between the contestants or the use of the Labial strike. Contest duration was not correlated with outcome, with size differences between contestants or with the use of the Labial strike. Winners and losers differed significantly in the number of acts used during encounters won by occupants (losers using more acts), but not during encounters won by intruders. Winners and losers also differed in their use of the behavioural acts Slow wave, Lateral display and Lamellae swipe during contests won by occupants, but not during contests won by intruders. The results are discussed in terms of the asymmetric war of attrition.     

Asymmetrical Resource Ownership Increases Owners’ and Reduces Non‐Owners’ Motivation to Fight in the Mangrove Rivulus,Kryptolebias marmoratus

Resource ownership often increases an individual's aggressiveness and its probability of defeating a competitor. Individuals contesting resource owners could therefore incur higher costs, making individuals reluctant to compete with owners. We tested the hypothesis that animals use asymmetry in resource ownership as a cue for contest costs and adjust contest decisions accordingly. Using a mangrove rivulus fish (Kryptolebias marmoratus), we staged (1) contests with a randomly assigned asymmetry in resource ownership (one fish was provided with a shelter) and (2) contests in which neither fish had a shelter. Owners that were in their shelters at the contest start showed a greater tendency to fight and won more contests than their intruder opponents; those outside the shelter at the start did not. Compared with fish in contests with no shelters at stake, shelter owners had a higher tendency to fight whether or not they were in their shelters at the start; intruders, however, had a lower tendency to fight only against owners that were inside the shelter at the start. These results demonstrate (1) that ownership status influences both owners’ and intruders’ contest decisions (and in opposite directions), producing a detectable ownership advantage and (2) that intruders required confirmation of their opponents’ ownership status before retreating without challenging them. Ownership status per se is therefore important to the fish's contest decisions.     

Sounds Modulate Males’ Aggressiveness in a Cichlid Fish

Acoustic signals are produced in many fish species during agonistic or courtship interactions. A way to test the biological role of these sounds is the use of acoustic playback experiments. However, sounds are usually associated with visual displays and playback experiments performed in fish so far, often failed to match acoustic and visual stimuli. To avoid this mismatch issue, we experimentally separated or coupled visual and acoustic channels to test the role of sounds produced during male–male aggressive interactions in a cichlid fish, Metriaclima zebra. Results show that aggressive behaviour is based on visual stimuli and that acoustic signals alone never trigger aggression. Furthermore, the association between visual and acoustic channels lowers the level of aggressiveness found when fish can only interact visually. This suggests that acoustic signals used during a dispute may complement visual displays to modulate males’ behaviour by reducing their aggressiveness and the risk of escalated fights.     

Sound production and reproductive behaviour of the armoured catfish Corydoras paleatus (Callichthyidae)

Sound production during reproductive behaviour, dyadic encounters and distress situations was investigated in the callichthyid catfish Corydoras paleatus. Sounds were broad-band, pulsed, acoustic signals produced during abduction of the pectoral spines. Only males emitted trains of sounds during courting and trains of sounds of shorter duration during dyadic encounters. Several males, which are usually smaller than females, courted one gravid female without obvious cooperation or competition between them. During mating, one previously vocalizing male clasped the female's barbels with one pectoral spine and inseminated the eggs. The number of successful spawnings, days until spawning, and number of eggs laid was not related to the number of males (one, two or three) combined with one female. Males did not behave aggressively towards each other during courting or in dyadic encounters. In distress situations, when fish were hand held, both sexes and juveniles produced single sounds. The dominant frequency was negatively correlated with body size and the sound duration was positively correlated with relative length of pectoral spines (standardized to body length). This acoustical behaviour in C. paleatus differs considerably from Hoplosternum thoracatum, a representative of the callichthyine subfamily, in which vocalization was observed during territorial behaviour in males and aggressive behaviour in both sexes. This is the first report of a major difference in vocalizing behaviour within one teleost family.     

Aspects of sound communication in the pearlfish Carapus boraborensis and Carapus homei (Carapidae)

Several species of Carapidae are known to have symbiotic relationships with marine invertebrates. The two most common species in Moorea (French Polynesia), Carapus boraborensis and Carapus homei, undergo conspecific and heterospecific encounters in the same holothurian host during which they produce sounds. Another characteristic of these fish lies in their abilities to produce sounds. The objective of this study was dual: (1) to seek if there was a sexual difference in the sounds produced by C. boraborensis; (2) to seek if there was a difference in the sound emissions between heterospecific and conspecific encounters. In each trial, sounds were only recorded when one individual entered the sea cucumber that was already occupied. In encounters, sounds were structured in regular pulse emissions whose pulse lengths and periods allowed to significantly distinguish each species, as well as both sexes in C. boraborensis. In the latter species, results show for the first time that temporal features of the emitted sounds can have a functional importance in sex identification. In heterospecific encounters, sounds were reduced 68% of the time to a single pulse emission and there was a modification in the pulse length of each species: it shortens in C. homei and it lengthens in C. boraborensis. It highlights that both carapids are able to adapt their sounds to the facing species. Because a modification of the sound appears to be done at the first emission, it is supposed that recognition precedes the sound emission.     

Acoustic threat displays and agonistic behaviour in the red-finned loach <Emphasis Type="Italic">Yasuhikotakia modesta</Emphasis>

Agonistic behaviour and the significance of acoustic threat displays were investigated in juvenile red-finned loaches, Yasuhikotakia modesta. This species produced two different vocalizations during agonistic encounters—clicks and butting sounds. Clicks were produced at some distance from the opponent whereas butting sounds were emitted when one fish touched the other with its mouth. This occurred primarily during circling. Both sound types were short broadband signals with the main energies concentrated at about 230 Hz, but clicks were longer in duration and lower in sound level. Agonistic behaviour usually started when one fish approached the other, spread its fins and produced clicks (threat displays), which was followed by parallel displaying, circling and chasing. All fish approached a mirror quickly and displayed aggressively in a parallel position. The number and duration of the threat displays in front of the mirror image were significantly elevated compared with control experiments (rear of the mirror). When playing back click trains in the presence of a mirror image, loaches vocalized significantly less often than during the silent periods, whereas the amount of lateral displaying remained similar. These data indicate that agonistic sounds reduced acoustic displays in red-finned loaches.     

Spawning Sounds of the Male Haddock, Melanogrammus aeglefinus

The codfish family, Gadidae, contains many vocal species. The sounds produced are species-characteristic and relatively simple. Unusually within this family, the haddock Melanogrammus aeglefinus, produces a range of sounds in different contexts. Both male and female haddock produce short sequences of repeated knocks during agonistic encounters. During the spawning season, however, male fish produce sounds which vary in their characteristics as courtship proceeds. The repertoire of the male fish consists of a graded series of sounds ranging from a short series of slowly repeated knocks to long sounds of rapidly repeated knocks. The fastest sounds are heard as a continuous humming. Different behavioural acts leading up to the mating embrace are associated with particular sounds, the sounds becoming longer and faster as the level of arousal of the male increases. It is suggested that the sounds serve to bring male and female fish together in the same part of the ocean, and that the sounds also play a role in synchronising the reproductive behaviour of the male and female.     

SOUND PRODUCTION IN THE BLUE-GREEN DAMSELFISH,CHROMIS VIRIDIS (CUVIER, 1830) (POMACENTRIDAE)

ABSTRACT

Sound production is widespread in coral reef fish of the family Pomacentridae. As commonly found in other teleosts, damselfish emit calls in agonistic and courtship contexts. In this paper, evidence of sound production by the blue-green damselfish Chromis viridis is presented for the first time. The recorded sounds consisted of clicks produced during agonistic interactions.