Sound Characteristics and Outcome of Contests in Male Croaking Gouramis (Teleostei)

A correlative study using similar-sized males of the croaking gourami Trichopsis vittata was carried out to investigate whether sound characteristics influenced winning and if relative fighting ability was assessed by acoustic signals. Pair-wise contests between males were decided using lateral displays (LD) and vocalization in 26 cases, whereas 66 fights escalated to the frontal display (FD) phase. Physical fighting (mouth wrestling) and injuries were rarely observed in this species. Winners were generally larger than their opponents, and this effect was more pronounced in non-escalated than in escalated contests. Sounds of fight winners had a higher sound pressure level and also a lower dominant frequency. Neither number of acoustic signals nor duration of lateral and frontal displays were predictors of contest outcome. Acoustic measures were highly correlated to body weight. These results indicate that traits correlated with RHP (such as sound pressure level and dominant frequency) were predictors of the outcome, while traits not correlated with size (such as number and duration of displays) did not influence winning. In accordance with the main prediction of assessment models, the contest duration (cost) increased with the decrease in asymmetry of body length as well as sound pressure level. No such relationships were found for weight and dominant frequencies in LD- and FD-contests. The present study indicates that morphological and sound characteristics influence winning in fish. Moreover, the results suggest that croaking gouramis settle conflicts without damaging combats by assessing asymmetries in different components of RHP such as body weight and length, which may reliably be signalled by acoustic and visual assessment signals.     

Acoustic signalling in female fish: factors influencing sound characteristics in croaking gouramis

The characteristics of sounds produced by fishes are influenced by several factors such as size. The current study analyses factors affecting structural properties of acoustic signals produced by female croaking gouramis Trichopsis vittata during agonistic interactions. Female sounds (although seldom analysed separately from male sounds) can equally be used to investigate factors affecting the sound characteristics in fish. Sound structure, dominant frequency and sound pressure levels (SPL) were determined and correlated to body size and the order in which sounds were emitted. Croaking sounds consisted of series of single-pulsed or double-pulsed bursts, each burst produced by one pectoral fin. Main energies were concentrated between 1.3 and 1.5 kHz. The dominant frequency decreased with size, as did the percentage of single-pulsed bursts within croaking sounds. The SPL and the number of bursts within a sound were independent of size but decreased significantly with the order of their production. Thus, acoustic signals produced at the beginning of agonistic interactions were louder and consisted of more bursts than subsequent ones. Our data indicate that body size affects the dominant frequency and structure of sounds. The increase in the percentage of double-pulsed bursts with size may be due to stronger pectoral muscles in larger fish. In contrast, ongoing fights apparently result in muscle fatigue and subsequently in a decline in the number of bursts and SPL. The factor ‘order of sound production’ points to an intra-individual variability of sounds and should be considered in future studies.     

Contests with deadly weapons: telson sparring in mantis shrimp (Stomatopoda)

Mantis shrimp strike with extreme impact forces that are deadly to prey. They also strike conspecifics during territorial contests, yet theoretical and empirical findings in aggressive behaviour research suggest competitors should resolve conflicts using signals before escalating to dangerous combat. We tested how Neogonodactylus bredini uses two ritualized behaviours to resolve size-matched contests: meral spread visual displays and telson (tailplate) strikes. We predicted that (i) most contests would be resolved by meral spreads, (ii) meral spreads would reliably signal strike force and (iii) strike force would predict contest success. The results were unexpected for each prediction. Contests were not resolved by meral spreads, instead escalating to striking in 33 of 34 experiments. The size of meral spread components did not strongly correlate with strike force. Strike force did not predict contest success; instead, winners delivered more strikes. Size-matched N. bredini avoid deadly combat not by visual displays, but by ritualistically and repeatedly striking each other''s telsons until the loser retreats. We term this behaviour ‘telson sparring'', analogous to sparring in other weapon systems. We present an alternative framework for mantis shrimp contests in which the fight itself is the signal, serving as a non-lethal indicator of aggressive persistence or endurance.     

Production of acoustic signals during aggression in Coosa bass, <Emphasis Type="Italic">Micropterus coosae</Emphasis>

Although sound production has been described for sunfishes, it is previously unknown for basses, both groups of fishes in the family Centrarchidae. We document production of acoustic signals during aggressive encounters in Coosa bass, Micropterus coosae. During dyadic encounters, presumptive winners of contests produced sounds associated with a variety of behaviors, including chases, lateral displays, circle swims, nudging, jerking and during post aggression, while fish were stationary. These sounds are low-frequency, non-harmonic and consist of one to 41 separate pulses. In most trials larger fish won contests, regardless of territory ownership (which fish was put into the test tank first) and size difference.     

Perception of alarm cues influences the outcome of shelter competition in crayfish20

The effects of predators on prey populations may significantly alter many aspects of prey biology, including spatial distribution, foraging activities, and social interactions. In aquatic habitats, chemosensation is an important mode of communication and has been shown for many taxa, including crayfish, to be used in detection of predator and/or conspecific alarm cues. Here, we report on an experiment to test the hypothesis that detection of alarm cues results in greater individual investment in contests over shelters. We tested this hypothesis through dyadic contests between sex- and size-matched, non-reproductive individuals of Faxonius virilis. We found that crayfish responded to exposure to alarm cues by spending more time inside a shelter. We also report that in contests between pairs in which one crayfish had been exposed to alarm cues and the other had not, exposed individuals were significantly more likely to win ownership of a single shelter. However, we did not detect any differences in the contest parameters we recorded between exposed and unexposed crayfish. These impacts on both individual and social behavior indicate that the presence of predators is likely to have large effects on the distribution and structure of crayfish populations.     

Post-contest behaviour in black-capped chickadees (<Emphasis Type="Italic">Poecile atricapillus</Emphasis>): loser displays,not victory displays,follow asymmetrical countersinging exchanges

Victory displays are behaviours that occur after the conclusion of a signaling contest, performed solely by the contest winner. Victory displays may reinforce the dominance of the winner either to the loser or to other conspecifics within signaling range. Victory displays are poorly studied despite the significant consequences that post-conflict behaviour may have on the individuals involved. We examined the period immediately following 50 territorial countersinging contests between males in 10 neighbourhoods of black-capped chickadees (Poecile atricapillus) of known dominance rank. We characterized the post-contest singing behaviour of chickadees and evaluated whether post-contest behaviour is consistent with victory displays. Using a 16-microphone acoustic location system to simultaneously record entire neighbourhoods of breeding chickadees, we isolated 50 dyadic countersinging contests and measured the vocal behaviour of the contestants in the minutes following each interaction. Eighty-six percent of contests were followed by a period of solo singing by one of the contestants, while 14% were followed by silence. The post-contest singer was most often the contestant who held a subordinate dominance position in the previous winter’s dominance hierarchy; dominant males performed post-contest song bouts significantly less often. Asymmetry in overlapping between contestants did not predict which bird sang a post-contest bout. However, in a significant majority of cases, the post-contest singer was pitch-matched by his opponent during the contest more than he pitch-matched his opponent. Our results indicate that male chickadees do not perform acoustic victory displays after countersinging contests. In contrast, the post-contest behaviour of territorial chickadees is more consistent with a “loser display”.     

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 Behavior in the Squid Loligo plei (Loliginidae,Teuthoidea): Fighting Tactics and the Effects of Size and Resource Value

Observations of small schools of squids in captivity suggested that dominance relationships among males were based upon major differences in the frequency or duration of their agonistic behavior, but staged contests showed few differences. During staged contests, squids exhibited up to 21 separate behaviors. Some contests included a complex array of visual signals and side-by-side posturing (Lateral Display) followed by physical contact during Fin beating. There was behavioral variability and step-wise escalation during the contests: squids performed either 1. long sequences of visual signaling followed by Chasing and Fleeing; or 2. short sequences of visual signaling followed by physical Fin beating and ending with Chasing and Fleeing. Size influenced outcome in all contests; larger males were more likely to win the contest. Size had no effect on contest duration, but contest duration was shorter when resource value was high, especially when a male established temporary ownership of a female. We speculate that when the perceived resource value is high, male squids are more likely to engage in a shorter yet riskier fighting tactic.     

条纹短攀鲈的雄性个体大小、雌性偏好以及雄性之间的竞争

本研究考察了条纹短攀鲈(Trichopsis vittata)雄性个体的身体大小对雌性个体性偏好的影响以及对雄性之间竞争的影响。本研究设立了两种处理来研究雌性个体的性偏好以及雄性之间的竞争。在一种处理中,放入同样大小的雄性个体,而在另一种处理中,放入大小不同的雄性个体。结果表明,雄性个体的大小不影响雌性条纹短攀鲈的性偏好。在对雄性之间竞争的研究中,发现个体较大的个体获胜的次数比较多。在个体大小相同的处理中,雄性之间打斗的持续时间比另一种处理中的打斗持续时间长。对这两种处理中不同对抗行为的比较表明,个体大小相同处理组中的发声、咬、以及总体对抗行为发生得更为频繁。对个体大小不同处理组中的大、小个体的进一步观察也揭示出体型大的个体比体型小的个体有更多的追逐行为和更少的逃脱行为。这些结果表明,在雄性个体比雌性个体大的物种中,体型的性两型可能与雄性之间的竞争有关,而不是与雌性偏好有关。     

Does size matter? Assessment and fighting in small and large size‐matched pairs of adult male convict cichlids

Contests between matched pairs of sexually mature convict cichlids Archocentrus nigrofasciatus were staged to determine if size alone affected the ways in which the males fought. Both small and large contests began with a period of visual displays. As fights progressed, displays diminished, and were replaced by more escalated behaviours. Small and large contests were also of similar duration. Despite these consistencies with sequential assessment, large and small contests were not entirely alike. For example, large males engaged in more lateral displays and were slower to escalate than small males. Small males displayed less and escalated to biting sooner than large males. Two possible explanations are suggested for these contrasts in contest structure: absolute opponent size and differences in the males' ages coupled with differences in experience.     

Sex-Specific Differences in Agonistic Behaviour,Sound Production and Auditory Sensitivity in the Callichthyid Armoured Catfish Megalechis thoracata

Background

Data on sex-specific differences in sound production, acoustic behaviour and hearing abilities in fishes are rare. Representatives of numerous catfish families are known to produce sounds in agonistic contexts (intraspecific aggression and interspecific disturbance situations) using their pectoral fins. The present study investigates differences in agonistic behaviour, sound production and hearing abilities in males and females of a callichthyid catfish.

Methodology/Principal Findings

Eight males and nine females of the armoured catfish Megalechis thoracata were investigated. Agonistic behaviour displayed during male-male and female-female dyadic contests and sounds emitted were recorded, sound characteristics analysed and hearing thresholds measured using the auditory evoked potential (AEP) recording technique. Male pectoral spines were on average 1.7-fold longer than those of same-sized females. Visual and acoustic threat displays differed between sexes. Males produced low-frequency harmonic barks at longer distances and thumps at close distances, whereas females emitted broad-band pulsed crackles when close to each other. Female aggressive sounds were significantly shorter than those of males (167 ms versus 219 to 240 ms) and of higher dominant frequency (562 Hz versus 132 to 403 Hz). Sound duration and sound level were positively correlated with body and pectoral spine length, but dominant frequency was inversely correlated only to spine length. Both sexes showed a similar U-shaped hearing curve with lowest thresholds between 0.2 and 1 kHz and a drop in sensitivity above 1 kHz. The main energies of sounds were located at the most sensitive frequencies.

Conclusions/Significance

Current data demonstrate that both male and female M. thoracata produce aggressive sounds, but the behavioural contexts and sound characteristics differ between sexes. Sexes do not differ in hearing, but it remains to be clarified if this is a general pattern among fish. This is the first study to describe sex-specific differences in agonistic behaviour in fishes.     

Development of agonistic behaviour and vocalization in croaking gouramis

The development of agonistic behaviour and vocalization in the croaking gourami Trichopsis vittata was studied from hatching to sexual maturity (4 months of age). Initial interactions started when fry were 11 days old and consisted of approach and flight in a feeding context. More complex threat patterns appeared during dyadic encounters as fish grew older. Lateral display (spreading of median fins in a lateral position) first occurred during the third week, circling shortly afterwards and pectoral fin beating when fish were 7 weeks old. Rapid pectoral fin beating was first accompanied by sound emission at 8 weeks. Initially, croaking sounds were built up mainly of a series of single pulses, each one produced by one pectoral fin. Later, single pulses gave way to double pulses. Furthermore, pulse period and number of pulses increased, while the dominant frequency of croaks decreased significantly with age. After vocalization was established, frontal display, mouth biting and retreat behaviour occurred at the age of 10 weeks. Initially, young exhibited vertical bars which gave way to dots and horizontal bars at 8 weeks when fish started to vocalize. The order of appearance of behavioural patterns during ontogeny corresponds to the order of appearance in fights between adults. This is the first study demonstrating that the ontogenetic development of social signalling comprises characteristic changes in behaviour, vocalization and coloration in a teleost fish.     

Acoustic and Visual Display Behavior of Gekkonid Lizards

Visual and acoustic mechanisms of communication are compared.Their properties are found to be similar except that acousticsystems function more efficiently when light levels are low.The ability of geckos to receive and produce visual and acousticmessages is discussed. Geckos are found to have excellent visionand good hearing. They also possess the visual attributes andsound producing mechanisms necessary for complex displays. Thedisplay behavior of geckos is reviewed. Display types are categorizedaccording to the display mechanism used. Visual displays arefound to utilize color, pattern, posture, and movement. Thesedisplays are used in predator threat as well as in intraspecificsocial contexts such as aggression and courtship. Combined visual-acousticdisplays involve color, pattern, postures, movement, and sound.Combined displays are used in predator threat and in intraspecificaggressive encounters. Acoustic displays have little or no visualcomponent and involve sounds that may be single chirps or temporallypatterned multiple chirps. The single chirps are associatedwith distress while the multiple chirp calls are heard in intraspecificsocial contexts. The displays of diurnal and nocturnal geckosare compared and it is found that differences are correlatedwith differences in their diel activity cycles. In conclusion,it is pointed out that many areas remain to be studied beforegecko display behavior is well understood.     

Effects of body size and resource value on fighting behaviour in a jumping spider

Fights between male Euophrys parvula, a New Zealand salticid spider, consist of a number of discrete ‘stages’, of increasing intensity. Two aspects of these contests were investigated: (1) relative body size of the two opponents, and (2) the presence of a ‘resource’ (a female model). In 92% of all contests where a size difference existed, the larger of the two opponents won. Contest intensity (measured as the highest intensity behaviour elicited during the contest) was inversely correlated with relative body size of the two opponents (measured as carapace width). Contests escalated further when the female model was present. No relationship was found between contest duration and either relative body size or the presence of the model. It is suggested that for contests in which a number of behaviours of different intensity are used, contest intensity may be a better estimate of contest cost than duration. The results are discussed in terms of theoretical models of contest behaviour.     

Visual information, resource value, and sequential assessment in convict cichlid (Cichlasoma nigrofasciatum) contests

We staged contests between convict cichlids (Cichlasoma nigrofasciatum)that were matched for size and gender to test the influenceof prior information and resource value on the duration andstructure of fights. The contestants were separated before thecontest by either clear or opaque dividers to allow or preventvisual assessment, respectively. Contests were shorter in the"clear" than in the "opaque" treatment, suggesting that visualassessment occurred. The duration of lateral display, a noncontactdisplay, was shorter in the clear than in the opaque treatment,but the treatments did not differ significantly in the durationof three contact displays (biting, mouth wrestling, and circling).These results are consistent with the hypothesis that lateraldisplay provides primarily visual information, probably aboutbody size, whereas the other behavior patterns provide primarilynonvisual information, probably about strength. Second contestsbetween the same pair of fish were shorter than first contests,suggesting that the information acquired during the first contestmade it easier to resolve the second. After the subordinatefish from the second contest was given access to a mate, itfought more persistently so that third contests were longerthan second contests. Our results support the predictions ofthe sequential assessment model.     

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.     

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.     

Correlation between auditory sensitivity and vocalization in anabantoid fishes

Several anabantoid species produce broad-band sounds with high-pitched dominant frequencies (0.8–2.5 kHz), which contrast with generally low-frequency hearing abilities in (perciform) fishes. Utilizing a recently developed auditory brainstem response recording-technique, auditory sensitivities of the gouramis Trichopsis vittata, T. pumila, Colisa lalia, Macropodus opercularis and Trichogaster trichopterus were investigated and compared with the sound characteristics of the respective species. All five species exhibited enhanced sound-detecting abilities and perceived tone bursts up to 5 kHz, which qualifies this group as hearing specialists. All fishes possessed a high-frequency sensitivity maximum between 800 Hz and 1500 Hz. Lowest hearing thresholds were found in T. trichopterus (76 dB re 1 μPa at 800 Hz). Dominant frequencies of sounds correspond with the best hearing bandwidth in T. vittata (1–2 kHz) and C. lalia (0.8–1 kHz). In the smallest species, T. pumila, dominant frequencies of acoustic signals (1.5–2.5 kHz) do not match lowest thresholds, which were below 1.5 kHz. However, of all species studied, T. pumila had best hearing sensitivity at frequencies above 2 kHz. The association between high-pitched sounds and hearing may be caused by the suprabranchial air-breathing chamber, which, lying close to the hearing and sonic organs, enhances both sound perception and emission at its resonant frequency. Accepted: 26 November 1997     

Singing above the chorus: cooperative Princess cichlid fish (<Emphasis Type="Italic">Neolamprologus pulcher</Emphasis>) has high pitch

Teleost fishes not only communicate with well-known visual cues, but also olfactory and acoustic signals. Communicating with sound has advantages, as acoustic signals propagate fast, omnidirectionally, around obstacles and over long distances. Heterogeneous environments might favour multimodal communication, especially in socially complex species, as the combination of modalities’ strengths helps overcome their individual limitations. Fishes of the ecologically and morphologically diverse family Cichlidae are known to be vocal. Here we investigated sound production in the socially complex Princess cichlid Neolamprologus pulcher from Lake Tanganyika in East Africa. We show that wild and captive N. pulcher produce only short-duration, broadband high-frequency sounds (mean: 12 kHz), when stimulated by mirror images. The evolutionary reasons for this “low frequency silencing” are still unclear. In laboratory experiments, N. pulcher produced distinct two-pulsed calls mostly, but not exclusively, associated with agonistic displays. Princess cichlids produce these high-frequency sounds both in combination with and independent from visual displays, suggesting that sounds are not a by-product of behavioural displays. Further studies on the hearing abilities of N. pulcher are needed to clarify whether the high-frequency sounds are used in intra- or inter-specific communication.     

Victory displays: a game-theoretic analysis

Two rationales have been proposed verbally for the functionof victory displays, which are performed by the winners of contestsbut not by the losers. The "advertising" rationale is that victorydisplays are attempts to communicate victory to other membersof a social group that do not pay attention to contests or cannototherwise identify the winner. The "browbeating" rationale isthat victory displays are attempts to decrease the probabilitythat the loser of a contest will initiate a future contest withthe same individual. We formally explore the logic of theserationales with game-theoretic models. The models show thatboth rationales are logically sound; however, all other thingsbeing equal, the intensity of victory displays will be highestthrough advertising in groups where the reproductive advantageof dominance is low and highest through browbeating in groupswhere the reproductive advantage of dominance is high.