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.     

Signaling without the risk of illegitimate receivers: do predators respond to the acoustic signals of <Emphasis Type="Italic">Cyprinella</Emphasis> (Cyprinidae)?

Acoustic and visual signals are commonly used by fishes for communication. A significant drawback to both types of signals is that both sounds and visual stimuli are easily detected by illegitimate receivers, such as predators. Although predator attraction to visual stimuli has been well-studied in other animals, predator response to acoustic stimuli has received virtually no research attention among fishes and snakes. This study assessed whether the calls of male tricolor shiner (Cyprinella trichroistia) made during the breeding season would attract potential predators. We also examined the effect of visual stimulus of tricolor shiners on predators. Predators used were red eye bass (Micropterus coosae) and midland water snakes (Nerodia sipedon pleuralis). Neither predator was attracted to tricolor sounds when presented alone. Micropterus coosae responded significantly more to a visual stimulus, and to a combination of visual and acoustic stimuli, but with no greater intensity in the latter. Nerodia sipedon pleuralis did not responded to visual stimulus presented alone, but did respond to visual and acoustic stimuli presented simultaneously, and with greater intensity to the latter, indicating that acoustic signals may play a role in prey detection by N. sipedon pleuralis.     

Direct mate choice for simultaneous acoustic and visual courtship displays in the damselfish, Dascyllus albisella (Pomacentridae)

Acoustic signals are well established as key components of mate selection in terrestrial species, but not in aquatic species. It has long been known that damselfish (Pomacentridae) use a combined visual and acoustic display in their courtship.. This study examined several male qualities including individual size, courtship vigor, territory size and complexity, as well as components of the acoustic call including dominant frequency, pulse characteristics and repetition rate. The objective was to determine which male traits were correlated with mating success. Observations made over ten reproductive cycles revealed that female mate choices were not random and that male mating success was correlated with courtship rate (a simultaneous visual and acoustic cue) and the number of neighboring females, but not with male morphological traits, territory quality, or acoustic call structure. These results suggest that females choose mates based on a condition-dependent trait (courtship rate) that advertises quality of paternal care, which supports good parent models of sexual selection, thereby demonstrating the importance of the combined acoustic/visual display for sexual selection in fishes     

Visual signals or displacement activities? The function of visual displays in agonistic interactions in nocturnal tree frogs

The efficiency of intraspecific communication directly affects male reproductive success. Acoustic signaling is the primary form of communication in nocturnal anurans. However, visual signaling can also be important in social interactions. We tested the hypothesis that open environments favor visual signals in a territorial defense context, in a nocturnal tree frog. We established three treatments each with eight males of Hypsiboas albomarginatus: (1) Clear Vision, with a mirror without visual obstacles; (2) Obstructed Vision, with half the mirror covered, and (3) Control, with mirror completely covered. We classified behavioral responses into orientation/locomotion, visual display, or acoustic signal. We calculated the mean emission rate per minute per behavior in each treatment and compared them among treatments using one-way ANOVA. Orientation and locomotion, visual display, and the advertisement call did not differ among treatments. However, the emission of aggressive calls in the Obstructed Vision treatment was significantly higher than in the Clear Vision treatment. The lowest rate of aggressive calls occurred in the Control. Thus, visual recognition of an intruder male was enough for resident males to adjust their rate of emission of acoustic aggressive signals, but not visual displays. Therefore, the recognition of the intruder male is not the only feature required for the evolution of visual signals in nocturnal tree frogs during agonistic interactions. This suggests that some visual displays may not be directly used for communication but rather constitute displacement activity.     

Phenotypic similarity in sympatric crow species: Evidence of social convergence?

Crows, rooks, and ravens (Corvus spp.) display marked morphological and voice similarities that have been hypothesized to stem from competitive interactions, as a case of nonaposematic mimicry. Here, I test predictions of the mimicry hypothesis at the macrovolutionary scale, examining whether species morphological and acoustic traits covary with those of coexisting congeners, and whether phenotypic similarity has facilitated the coexistence of related species after secondary contact. Body size and the temporal patterns of the commonest call display high levels of similarity among sympatric species, even after controlling for the effect of shared climate and habitat, and phylogenetic constraints in the production of variation. When sister species differed in these acoustic and morphological traits, their transition to secondary sympatry was delayed relative to those with more similar traits. No similarity was found in the sexual call of crows, suggesting that convergence occurs only when function does not favour maintenance of species‐specific traits. Crow similarities in morphological and acoustic features may therefore be associated with coevolving interactions with congeners, in line with a broad array of studies documenting convergence among species that interact aggressively or forage communally.     

Are Centrally Displaying Males Always the Centre of Female Attention? Acoustic Display Position and Female Choice in a Lek Mating Subterranean Insect

Several conceptual models seek to explain patterns of male display and factors that influence female mate choice in lek mating systems. The central advantage model predicts that males displaying at or near the lek centre should be more attractive to females than are males positioned along the lek periphery. Females may exhibit biases toward these centrally displaying males based on either spatial or display‐related cues. We tested the prediction of the central advantage model in investigating the importance of male display position in the subterranean and lek mating prairie mole cricket (Gryllotalpa major). Gryllotalpa major males form mating aggregations in the early spring and produce an acoustic advertisement signal from a constructed calling chamber at the soil surface. Pair formation occurs in the calling chamber, and males typically maintain these structures for the duration of the reproductive season. To assess whether G. major females exhibit a preference for males calling from centrally located acoustic burrows, we documented the spatial position and number of female attractions for all advertising males across the focal lek. Six spatial attributes related to display position were reduced using principal component analysis and examined for an association with male attractiveness. We found that in general, female attractions were distributed randomly across the lek; male attractiveness was not related to proximity to the lek centre nor to any factor associated with display position. The most highly attractive males, however, were located further from the lek centre and from nearest calling neighbours than other attractive males. Advertising males that segregate themselves within the aggregation and locate nearer the lek margin may gain a geometric advantage resulting in the increased probability of attracting a searching female.     

Atypical Song Reveals Spontaneously Developing Coordination between Multi-Modal Signals in Brown-Headed Cowbirds (Molothrus ater)

The courtship and dominance behavior of brown-headed cowbirds (Molothrus ater) consists of a multi-modal display, including song as well as postural and wing movements. The temporal sequences of the acoustic and the visual display are coordinated. In adult male cowbirds the largest wing movements of the display are synchronized with silent periods of song, but it is unknown how this coordination emerges during song development. Here we investigate how visual display features are coordinated with song by using atypical song sequence structure of isolation-reared male cowbirds. In birds with atypical song, all components of the visual display were highly similar to those of “normal” song displays, but their timing was slightly different. The number of maximal wing movement cycles of isolation-reared males was linked to the number of sound units in the song, and was therefore reduced during the abbreviated song types of isolates. These data indicate that young cowbirds do not need to be exposed to a model of the visual display during ontogeny and that there is synchronization with the temporal structure of song. A physiological link between respiratory and syringeal control of silent periods between sound units and wing movement cycles may be driving this synchronization.     

Multimodal Signaling in Male and Female Foot-Flagging Frogs Staurois guttatus (Ranidae): An Alerting Function of Calling

In multimodal communication, individuals use several sensory modalities for information transfer. We report on novel observations of foot‐flagging in the Bornean ranid frog Staurois guttatus that is temporally linked to advertisement calling. In addition, we document the first case of foot‐flagging in a female anuran as well as additional visual displays in both males and females including arm‐waving, vocal‐sac pumping and open‐mouth display. In males, advertisement calls and foot‐flags were given throughout most of the day, suggesting that acoustic and visual signals form a multicomponent and multimodal display. We tested the efficacy‐based alerting signal hypothesis of multimodal communication using acoustic playback experiments with males. This hypothesis predicts that an initial signal draws the receiver's attention to the location of a subsequent more informative signal. Several lines of evidence supported the alerting hypothesis. First, the latency between foot‐flags and advertisement calls was significantly higher than that between advertisement calls and foot‐flags, suggesting a functional linkage with calls drawing attention to foot‐flags. Secondly, advertisement calling had a signaling function with males responding significantly more often with both calls and foot‐flags compared with pre‐ and post‐playback control periods. Finally, and most notably, all males tested turned towards the playback stimulus, suggesting that the advertisement call serves to focus their attention on subsequent signals. We discuss the potential of multimodal signaling for conspecific and heterospecific communication and the circumstances under which such a multimodal communication system could evolve.     

From uni- to multimodality: towards an integrative view on anuran communication

Undeniably, acoustic signals are the predominant mode of communication in frogs and toads. Acoustically active species are found throughout the vast diversity of anuran families. However, additional or alternative signal modalities have gained increasing attention. In several anurans, seismic, visual and chemical communications have convergently evolved due to ecological constraints such as noisy environments. The production of a visual cue, like the inevitably moving vocal sac of acoustically advertising males, is emphasized by conspicuously coloured throats. Limb movements accompanied by dynamic displays of bright colours are additional examples of striking visual signals independent of vocalizations. In some multimodal anuran communication systems, the acoustic component acts as an alert signal, which alters the receiver attention to the following visual display. Recent findings of colourful glands on vocal sacs, producing volatile species-specific scent bouquets suggest the possibility of integration of acoustic, visual and chemical cues in species recognition and mate choice. The combination of signal components facilitates a broadened display repertoire in challenging environmental conditions. Thus, the complexity of the communication systems of frogs and toads may have been underestimated.     

Visual cues contribute to predator detection in anuran larvae

The ability of prey to detect predators directly affects their probability of survival. Chemical cues are known to be important for predator detection in aquatic environments, but the role of other potential cues is controversial. We tested for changes in behaviour of Rana temporaria tadpoles in response to chemical, visual, acoustic, and hydraulic cues originating from dragonfly larvae (Aeshna cyanea) and fish (Gasterosteus aculeatus). The greatest reduction in tadpole activity occurred when all cues were available, but activity was also significantly reduced by visual cues only. We did not find evidence for tadpoles lowering their activity in response to acoustic and hydraulic cues. There was no spatial avoidance of predators in our small experimental containers. The results show that anuran larvae indeed use vision for predator detection, while acoustic and hydraulic cues may be less important. Future studies of predator‐induced responses of tadpoles should not only concentrate on chemical cues but also consider visual stimuli. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.     

The effect of acoustic and visual priming stimuli on the reproductive behaviour of female zebra finches, <Emphasis Type="Italic">Taeniopygia guttata</Emphasis>

We investigated the influences of reproductive priming, using acoustic stimuli alone or a combination of acoustic and visual stimuli on egg-laying in female zebra finches (Taeniopygia guttata). One group of females was exposed during 6 days to both acoustic and visual stimuli from males while another was exposed only to acoustic stimuli; a control group was unable to see or hear males prior to the introduction of unfamiliar males for pairing. We also manipulated the amount of visual stimulation by presenting either: males with normal red bands, males with red bands without ultraviolet reflection or unadorned males. Females exposed to visual stimuli spent more time on perches near males than control females or those only hearing males. However, there were no statistically significant differences in subsequent total eggs produced, or the latency to egg-laying between females exposed to priming males with different visual characteristics; they did not significantly differ from the control females in these parameters either. Females that heard, but did not see, priming stimuli produced more eggs when paired with males than the controls. Thus, acoustic stimuli alone may have promoted reproductive condition while the acoustic and visual stimuli together did not. Our results contradict a previous report, and may reflect components of the experimental design we employed (i.e. by pairing females with unfamiliar males after their initial exposure to priming males, we may have suppressed their ability to advance their reproductive state). Females that only heard priming males may have been more willing to accept pairing males because of the absence of visual identifiers.     

Behavior of crested auklets (<Emphasis Type="Italic">Aethia cristatella</Emphasis>, Charadriiformes,Alcidae) in the breeding season: Visual and acoustic displays

The crested auklet, a highly social planktivorous bird species of the Northern Pacific, is an important component of marine ecosystems. Although visual and acoustic modalities play a major role in the communication of these birds, the available data on the repertoire of their vocal signals and postures are scarce and lack quantitative analysis. This study deals with visual and acoustic displays of crested auklets on their breeding grounds and the occurrence frequencies of certain forms of social behavior in male and female birds. The data were collected on Talan Island (the Sea of Okhotsk) in 1987–1991 and 2008. They show that the rate of contacts between birds is very high and sex-specific: on average, males initiate 1.13 contacts/min, compared to 0.65 contacts/min initiated by females. Directionality of ruff-sniff displays differs depending on the posture of the recipient bird. The duration of the trumpeting display in males depends on their social surroundings. However, the duration of either the trumpeting display or the mutual cackling display during courtship is independent of the behavioral context. Vocalization of crested auklets is characterized by two independent basic frequencies occurring either sequentially or simultaneously. The role of different communicative modalities in the behavior of the crested auklet is discussed.     

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.     

Interaction of influences from the auditory and somatosensory afferent systems on neurons of the primary auditory cortex

In experiments on anesthetized cats, 80 neurons of the primary auditory cortex (A1) were studied. Within the examined neuronal population, 66 cells (or 82.5%) were monosensory units, i.e., they responded only to acoustic stimulations (sound clicks and tones); 8 (10.1%) neurons responded to acoustic stimulation and electrocutaneous stimulation (ECS); the rest of the units (7.4%) were either trisensory (responded also to visual stimulation) or responded only to non-acoustic stimulations. In the A1 area, neurons responding to ECS with rather short latencies (15.6–17.0 msec) were found. ECS usually suppressed the impulse neuronal responses evoked by sound clicks. It is concluded that somatosensory afferent signals cause predominantly an inhibitory effect on transmission of an acoustic afferent volley to the auditory cortex at a subcortical level; however, rare cases of excitatory convergence of acoustic and somatosensory inputs toA1 neurons were observed.     

Responses of domestic chicks (Gallus gallus domesticus) to multimodal aposematic signals

Many aposematic prey combine their visual warning signals withadditional signals. Together, these signals constitute a multimodalor multicomponent warning display. The additional signals arethought to increase the effects of the visual signals on predators.Olfactory signals are much emphasized, but later studies haveshown that also auditory signals like the buzzing of certaininsects might have multimodal effects. The wasp displays typicalvisual aposematic signals, black and yellow stripes, but doesalso emit a characteristic buzzing. We wanted to test if, andin what way, the visual and acoustic display of the wasp hasan aversive function on the predators. We therefore conducteda 12-trial discrimination-learning task on inexperienced chicksto study whether there are innate biases toward these signalsand how they affect the speed of avoidance learning. We alsoperformed three extinction-learning trials to study how memorablethe signals were to the chicks. We show that the visual signalsin the display of the wasp contribute to the protection frompredators but in different ways; the yellow color had an aversiveeffect on inexperienced predators, while the striped patternimproved the aversion learning. The sound did not enhance theinnate aversions but increased the aversion learning of stripesin green prey.     

Distinguishing behavioral interactions from visual cues as causes of adult sex change in a coral reef fish

Two experiments tested the hypothesis that adult female-to-male sex reversal in protogynous fish is induced by the loss of close-contact behavioral interactions between males and females, and not by the loss of simple visual cues from the male. Twenty-six laboratory groups of Anthias squamipinnis were manipulated so that females within each group (1) retained chemical and acoustic access to a male, (2) were denied behavioral access to a male, and (3) were either allowed or denied visual access to a male alone or to a male interacting with another female. At least one female subsequently changed sex in each of 22 groups. While acoustic and chemical cues were not completely eliminated as possible causes, sex change is apparently induced by loss of male-female behavioral interaction in combination with continued interaction between females.     

Multimodal communication in a noisy environment: a case study of the Bornean rock frog Staurois parvus

High background noise is an impediment to signal detection and perception. We report the use of multiple solutions to improve signal perception in the acoustic and visual modality by the Bornean rock frog, Staurois parvus. We discovered that vocal communication was not impaired by continuous abiotic background noise characterised by fast-flowing water. Males modified amplitude, pitch, repetition rate and duration of notes within their advertisement call. The difference in sound pressure between advertisement calls and background noise at the call dominant frequency of 5578 Hz was 8 dB, a difference sufficient for receiver detection. In addition, males used several visual signals to communicate with conspecifics with foot flagging and foot flashing being the most common and conspicuous visual displays, followed by arm waving, upright posture, crouching, and an open-mouth display. We used acoustic playback experiments to test the efficacy-based alerting signal hypothesis of multimodal communication. In support of the alerting hypothesis, we found that acoustic signals and foot flagging are functionally linked with advertisement calling preceding foot flagging. We conclude that S. parvus has solved the problem of continuous broadband low-frequency noise by both modifying its advertisement call in multiple ways and by using numerous visual signals. This is the first example of a frog using multiple acoustic and visual solutions to communicate in an environment characterised by continuous noise.     

An evaluation of active acoustic methods for detection of marine mammals in the Canadian Beaufort Sea

A commercially available fisheries sonar was mounted on an icebreaker and evaluated during an environmental baseline study in the Canadian Beaufort Sea, to determine the applicability of active acoustic monitoring (AAM) for marine mammal detection by comparing marine mammal observer (MMO) visual sightings and active acoustic detections. During 170 h of simultaneous MMO and AAM, 115 bowhead whales (Balaena mysticetus) and four beluga whales (Delphinapterus leucas) were visually sighted by MMOs, while 59 sonar detections of bowhead whales occurred using AAM. The fisheries sonar detected 92% of the cetaceans observed within 2,000 m. Additional observations of ringed seals (Pusa hispida) and bearded seals (Erignathus barbatus) were recorded both by MMOs and AAM. Comparative results indicate that a commercially available active acoustic system can consistently detect marine mammals within varying ranges dictated by water column properties. Shallow environments and strong pycnoclines currently present challenges to AAM.     

Human visual and auditory analyzers under the conditions of acceleration: Comparative analysis of the development of disturbances

More than 500 pinpoint physiological experiments were performed to compare the state and development of visual and auditory disturbances during rotation on an 8-m armed centrifuge at 14 g. A high level instrumentation provided a broad variety of measurements within very short intervals, including the acuity and angle of vision, absolute light sensitivity, critical flicker frequency, thresholds of tone hearing, and speech intelligibility. The state of eyeground blood vessels under acceleration was estimated both remotely and by an ophthalmologist sitting by the subject during rotation. Experimental results showed the impairment of the visual function during an acceleration increase and an almost complete loss of vision at 12–14 g. As regards the hearing function, acoustic energy incurred some loss on the way to Corti’s organ and yet hearing remained good enough to support operator’s orientation in the whole range of accelerations not resulting in the loss of consciousness. The significance of hearing retention is confirmed by successful experience of using audio information in the study of effectiveness of manual spacecraft operation at 18 g at the same laboratory. Comparative analysis of these and other laboratory and literature data makes it possible to assess the functional state of different components of light and acoustic energy transportation and conversion on the way to the central representations and to reveal the weak points of both analyzers. The data favor the view of retina as a blocker of light energy transportation. Development of this phenomenon is associated primarily with blood circulation impairment in the a. centralis retinae.     

Multiple behavioral contexts of a melanized tail display in a desert lizard

Conspicuous color displays in animals are often studied in the context of how they communicate an individual's reproductive value, ability to escape capture, or overall health. The study of sexual dichromatism often focuses on the evolution of male display traits balanced between detectability and mate acquisition, representing constraints stemming from both natural and sexual selection. Melanistic coloration and melanin color patterns play important roles in both intraspecific and interspecific signaling in animals; as melanin serves multiple purposes in organismal biology, the evolution of melanin-based visual displays might not be restricted to a single behavioral or ecological context. Here, we examine the behavioral contexts of the conspicuous melanin-based tail display in the greater earless lizard (Cophosaurus texanus), asking if this melanized tail pattern is associated with (a) female association preference of males varying in the concentration of melanin, (b) individual locomotor performance capacity, and (c) thermal ecology. We found the amount of tail melanin is linked with both locomotor performance and female association preference, with greater concentrations of melanin predicting the evolution of faster performance capacities and females preferring males with more discrete melanin bars. We found limited support that differences in melanin are linked with thermoregulation or thermal ecology. Overall, we find that multiple behavioral contexts shape the evolution of this melanized display trait. We conclude that behavioral constraints stemming from both natural and sexual selection can interact synergistically to favor the evolution and expression of a melanistic visual display, even in potentially costly ecological contexts.