The Canestrini’s goby Pomatoschistus canestrinii (Ninni) is an endemic sand goby occurring in lagoons and estuaries of the northern Adriatic Sea. Likewise as in other sand gobies, reproduction implies nest acquisition and defence, mate attraction, and repulsion of other male intruders that may try to penetrate the nest and perform sneaking fertilisations of the eggs. Furthermore, sound production has been documented in this species by previous work, occurring both in reproductive and aggressive behavioural contexts. In this paper, sound production and associated behaviours were assessed and compared in pairs spawning in two different experimental situations: 1) Isolated resident males 2) Resident males paired with a smaller male, and therefore exposed to possible nest intrusions. The simultaneous video- and acoustical recording of the spawning behaviour allowed to quantify the intensity of sound production and associated behaviours, that were then compared between the groups of males. Results indicated that the spawning behaviour of the nest-holding male was affected by the presence of a male intruder, as the spawning sequence was repeatedly interrupted by the intrusion attempts. This was reflected in an intense aggression and associated sound production of the nestholding male towards the intruder male, but also in a significant increase of aggressive sounds and aggressive visual displays towards the female. Furthermore, the frequency of a female visual display increased significantly when the male was exposed to nest intruders. By contrast, the overall frequency of pre-spawning sounds did not change between the two situations, although the mean duration of the burst containing the highest number of sounds was higher in the group of males exposed to male intruders that in the isolated spawning males. On the whole, these results indicate that parasitic nest intrusions affect significantly the spawning patterns of the nest-holding males, even in terms of sound rate.
Voice breaking is a process associated with puberty of human males and attends adolescence also in some birds. This phenomenon is well studied in humans, but still is poor studied in birds including cranes. Unanswered are questions about when do cranes start and complete the process, what changes occur in time and frequency vocal parameters throughout it and how they are related to the sex, date of birth and overall body growth. Here we traced the vocal development in 31 cranes from hatching to 1.5 years old relating to increase of body mass and in comparison with voices of 13 conspecific adults. During voice breaking, calls of both sexes contained two independent fundamental frequencies: the high one, that was a retained juvenile frequency, and the low one, that was a newly appeared adult frequency. Before voice breaking, calls contained only the high frequency, while after voice breaking – only the low frequency. Values of both frequencies didn’t overlap and didn’t change during all ontogenesis. Cranes starts voice breaking in 7 month and complete it at 11.5 month on average. The onset of voice breaking coincided with achieving the adult weight, while factors influencing on its completion were not evident. We don’t find any effect of sex and date of birth on the onset and completion of voice breaking. We discuss that in nature the completion of voice breaking could be related to cessation of parental care after the break of a parent-chick bond closely before the beginning of a new breeding season.
The hypothesis that an alteration of synaptic functions could lead to autism spectrum disorders (ASD) was recently confirmed by the identification of mutations in synaptic proteins such as neuroligins, neurexins, Shank and contactins. Following these genetic studies, animal models were developed to better characterise the role of susceptibility genes in ASD. Knockout (KO) mice for the NLGN3 and NLGN4 genes showed a reduced interest in social interactions and a lower call rate than wild type mice. To further understand how mutations in the various genes implicated in ASD contributed to symptoms in the social, communicative or stereotyped behaviours, we compared the development of wild type mice and KO littermates for the NLGN4 and CNTN6 genes separately. We recorded pup isolation calls and examined developmental milestones every two days between P2 and P12. We expected deficits in acoustic communication to emerge in young pups, while their physical development should remain similar between KOs and wild types. Preliminary analyses of our data did not reveal any clear evidence of deficits in motor coordination and geotaxis perception. In contrast, NLGN4 KO mice tended to utter isolation calls at a lower rate than their wild type littermates. Further investigations will concentrate on the social and vocal behaviour of juvenile and adult littermates, and examine possible environmental effects on these phenotypes. Screening the behavioural phenotypes of further mutants should allow us to map the deficits related to each mutation over the long term.
Most birds are unlikely to be physically capable of producing low frequency sounds, because of their small size and lightweight. Few exceptions concern large species like capercaillies and capercaillies that have been shown to produce sounds with frequency components close to the infrasound domain. As very low frequencies propagate over long distances with little attenuation, they are optimal for long-range communication, such as occurring in species displaying in leks in the reproductive context. One example of such species is the Houbara Bustard (Gruiform, Otidae), a large size bird, in which males perform elaborated courtship displays including booming calls, in peculiar leks sites spaced by at least 500 m in semi-desert open areas. It is a polytypic species, separated on the basis of molecular, morphological, and behavioural criteria: Chlamydotis macqueenii and Chlamydotis undulata. The populations of these 2 species are now separated and were in the past likely to be sympatric in North Africa. In this context, the present study aims to: 1/ characterize the sounds produced by males booming and to quantify inter- and intra-individual variability in C. undulata and C. macqueenii, 2/ to estimate parameters potentially involved in the coding of species specificity and individuality. Our results of acoustic analysis in the temporal and the frequency domain of calls of different males (15 C. undulata and 12 C. macqueenii) show that the 2 species produce species-specific booming calls with components at very low frequency, using a modifying and enlarged trachea. The inter-individual and inter-species differences are discussed in the context of intra-sexual competition and inter-sexual attraction at long range.
Male Lusitanian toadfish, Halobatrachus didactylus, are territorial and have a wide acoustic repertoire. The sound production apparatus consists of a pair of intrinsic large sonic muscles on the two lobes of the swimbladder. Sonic muscle activity and the variability of the vocalizations were related using electromyograms (EMGs). EMG electrodes were surgically implanted on the sonic muscles of several territorial males. After recovery, the subjects were released into an experimental tank with an available nest. Sonic muscle activity was registered and the vocalizations were simultaneously recorded using a hydrophone. Social context was manipulated by releasing different kinds of intruders (male(s) or female(s)). This action elicited the production of boatwhistles, while grunts were generated during fish disturbance. Preliminary analysis shows that, unlike previously reported, the bilateral sonic muscles contract simultaneously during the generation of both signals. The muscle contraction period is halved during the production of the grunt relative to the boatwhistle. The EMG period matches the sound pulse period and determines the fundamental sound frequency.
As with other African great lakes, Lake Malawi exhibits an explosive radiation of several hundred cichlid species, most of which are endemics. Although visual communication is widely considered the predominant force driving species recognition and mate choice in this radiation, recent studies highlighted a potential role for acoustic signals. To corroborate this proposition, we are analyzing internal and external constraints on acoustic communication in several species from different tribes. Here we focus on the correlation between characteristics of species-specific vocalizations, auditory sensitivity, and eco-acoustical constraints shaping this communication system. Ambient noise in Lake Malawi is characterized by a steep increase to 800 Hz and a slow decline up to several kilohertz. This increase is particularly pronounced during windy conditions creating a low frequency sound window. Interestingly, hearing sensitivity in Melanochromis johanni and Metriaclima callainos revealed by auditory evoked potential measurements, is maximally sensitive at 150-200 Hz and lowest at 800-1000 Hz. Moreover, this is true whether sensitivity is measured in terms of acoustic pressure or particle acceleration. All genera investigated to date produce pulsed sounds during agonistic and reproductive interactions with energies concentrated between 200-300 Hz. Thus, the main frequencies for sound communication are concentrated both at the maximum auditory sensitivity, and within the ambient noise window of the lake. These results indicate that sound communication in Lake Malawi cichlids is facilitated by both internal sensory and eco-acoustical conditions in the lake, and could play a major role in speciation.
Hearing sensitivity and sound characteristics of poikilothermic animals are influenced by ambient temperature. The present study investigates the influence of temperature on the hearing ability and on sound characteristics in the neotropical Raphael catfish Platydoras costatus. Using the auditory evoked potential (AEP) recording technique, the hearing thresholds of eight specimens were tested at six different frequencies from 100 to 4000 Hz. The temporal resolution was determined by analyzing the minimum resolvable click period (0.3 - 5 ms). Hearing sensitivity and sound production were measured after acclimation to 22 °C followed by acclimation to 30 °C for at least three weeks each. Auditory sensitivity increased from 1 to 4 kHz with rising temperature, whereas the temporal resolution showed no change. Catfishes produce stridulation sound by rubbing the pectoral spines in the shoulder girdle during abduction and adduction of pectoral fins. Distress calls were recorded when fish were handheld. The stridulation sounds produced during pectoral fin spine abduction and adduction became shorter at the higher temperature. Maximum and minimum pulse period as well as pulse number did not change with temperature, whereas the dominant frequency of sounds was higher at the higher temperature. Our data indicate that constraints imposed on hearing sensitivity at different temperatures cannot be compensated even by longer acclimation. As sound characteristics also change with temperature, we suggest that the ambient temperature directly affects acoustic communication in the neotropical catfish P. costatus.
Current studies on the ontogenetic development of acoustic communication in the labyrinth fish Trichopsis vittata and the toadfish Halobatrachus didactylus show that the ability to detect conspecific sounds develops during growth. In order to investigate at which stage sound detection starts in an otophysine fish, we investigated the ontogenetic development of auditory sensitivity and vocalizations in the mochokid catfish Synodontis schoutedeni. Mochokids are also called squeakers because they produce broadband stridulation sounds during abduction and adduction of pectoral fin spines. Fish from five 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 (AEP) recording technique; stridulation sounds were recorded and their sound pressure levels determined. The smallest juveniles showed the poorest hearing abilities of all size groups between 50 Hz and 1000 Hz. At higher frequencies (5 and 6 kHz), hearing sensitivity was lowest in the largest groups. Duration of abduction and adduction sounds, sound pressure level and pulse period increased, while the dominant frequency of sounds decreased with size. Comparisons between audiograms and sound spectra revealed that the most sensitive frequencies correlate with the dominant frequencies of stridulation sounds in all Synodontis size groups and that all specimens are able to detect stridulation sounds. This study demonstrates that the hearing ability in the siluriform S. schoutedeni changes during ontogeny, whereas no changes were observed in two cypriniform species investigated earlier. Furthermore, S. schoutedeni is able to communicate acoustically at all stages of development, which contrasts to prior findings in teleosts.
The Hazel Grouse (Bonasa bonasia), a sedentary bird species belonging to the grouse family, breeds across northern Eurasia, central and eastern Europe in dense, mixed coniferous woodland. While the territorial call is a good indicator of the grouse's presence, the role of acoustic cues is not clear. This study aimed to assess acoustic characteristic of the Hazel Grouse call and differences between sexes. Recording and playback experiments were performed in Alpes-de-Haute-Provence (France). The territorial calls of males (n=8) and females (n=5) were recorded in the field. Analyses of signals show that the male has a high-pitched ti-ti-ti-ti-ti call, and the female a liquid tettettettettet call. The frequency of the peak of maximum amplitude of calls was very high for such a large bird: 6841Hz ±786 for the male and 6034Hz ±476 for the female. After careful analyses, it turns out that the whole spectrum of the call was within the audible domain. Moreover, within-individual variability, that allows encoding of the individual identity, is higher in males (Cvb/Cvi=2.28) than in females (Cvb/Cvi<0.01). The particularity of producing such high frequency calls may reflect the necessity to improve localization efficiency in dense woodland, as high frequencies are associated to a better directionality. Moreover our results suggest that acoustic characteristics of male calls have sufficient inter-individual variability to allow the coding of individual identity.
The oak platypodid beetle, Platypus quercivorus, produced sounds by stridulating their abdomen against the elytra. When a female was put onto the bark surface of a male-infested log, she began to walk and produced an “approaching chirp”, searching for a gallery entrance bored by a male. When finding one, she entered it, and the male pushed her back. While they pushed against each other, the female made a “pre-mating buzz” that lasted about 5-10 s. During this buzzing, the male backed out of the gallery in order to allow her in. Females that had been silenced via surgery did not evoke this male reaction; thus, males apparently identified females by their buzzing sound. The male then followed the female into the gallery, and produced an “in-gallery chirp” with his posterior abdomen visible. After a while, both sexes backed out of the hole and copulated at the entrance. Both sexes produced “stress chirps” when confined inside a cotton ball, and “spontaneous chirps” when walking alone on the surface of an oak bark piece. There are two local types in Japan and the inter-pulse-intervals in their buzzes were different.
