Correlation between acoustic divergence and phylogenetic distance in soniferous European gobiids (Gobiidae; Gobius lineage)

In fish, species identity can be encoded by sounds, which have been thoroughly investigated in European gobiids (Gobiidae, Gobius lineage). Recent evolutionary studies suggest that deterministic and/or stochastic forces could generate acoustic differences among related animal species, though this has not been investigated in any teleost group to date. In the present comparative study, we analysed the sounds from nine soniferous gobiids and quantitatively assessed their acoustic variability. Our interspecific acoustic study, incorporating for the first time the representative acoustic signals from the majority of soniferous gobiids, suggested that their sounds are truly species-specific (92% of sounds correctly classified into exact species) and each taxon possesses a unique set of spectro-temporal variables. In addition, we reconstructed phylogenetic relationships from a concatenated molecular dataset consisting of multiple molecular markers to track the evolution of acoustic signals in soniferous gobiids. The results of this study indicated that the genus Padogobius is polyphyletic, since P. nigricans was nested within the Ponto-Caspian clade, while the congeneric P. bonelli turned out to be a sister taxon to the remaining investigated soniferous species. Lastly, by extracting the acoustic and genetic distance matrices, sound variability and genetic distance were correlated for the first time to assess whether sound evolution follows a similar phylogenetic pattern. The positive correlation between the sound variability and genetic distance obtained here emphasizes that certain acoustic features from representative sounds could carry the phylogenetic signal in soniferous gobiids. Our study was the first attempt to evaluate the mutual relationship between acoustic variation and genetic divergence in any teleost fish.

Acoustic Variation of Syllable-Initial [ŋ] in Zhengding Chinese

The study explores the acoustic properties of syllable-initial [ŋ] in Zhengding dialect, to see whether the younger generation shows the same pattern with the senior group. 60 items with vowel realizations [ʌ, a, ɑ, ə, ɤ] and [ai, ɑo, ou] in ‘[ŋ]-V’ and ‘[g]-V’ structures are produced by 8 native speakers. Three experiments are conducted. Experiment I compares ‘[ŋ]-V’ and ‘[g]-V’ structures in senior speeches. Three acoustic effects due to the initial [ŋ] are established: vowels become less distinctive from each other by decreasing the first formant (F1), increasing the second formant (F2), and shrinking the gap between the second formant (F2) and the third formant (F3). Experiment II is conducted between ‘[ŋ]-V’ and ‘[g]-V’ in the younger speakers, investigating whether they have a similar pattern with the seniors. Experiment III is supplemented to compare the younger speeches in Zhengding dialect and Mandarin, to explore whether the generational variation in Zhengding dialect is relevant to dialect contact, i.e., whether the younger speakers are largely influenced by Mandarin. The result shows the younger generation does not produce the initial [ŋ] with the vowel realizations [ʌ, a, ɑ, ə, ai, ɑo, ou], which traditionally have an initial [ŋ], with an exception in [ɤ]. A fusion process is assumed in [ɤ] in the younger pattern, in which the initial nasal [ŋ] and the following vowel [ɤ] are combined into the single nasalized vowel [ɤ̃], with the nasal effects remained, but the initial nasal then deleted. From the sociovariationist perspective, the nasal-initial pronunciation is a partial variation in Zhengding dialect. Not all speakers pronounce with the velar-initial [ŋ]. The older generation largely remained the velar-initial variant, but the younger generation preferred the zero-onset, which might be due to the influence of dialect contact with Mandarin.

Noise-Related Song Variation Affects Communication: Bananaquits Adjust Vocally to Playback of Elaborate or Simple Songs

Birds communicate through acoustic variation in their songs for territorial defense and mate attraction. Noisy urban conditions often induce vocal changes that can alleviate masking problems, but that may also affect signal value. We investigated this potential for a functional compromise in a neotropical songbird: the bananaquit (Coereba flaveola). This species occurs in urban environments with variable traffic noise levels and was previously found to reduce song elaboration in concert with a noise-dependent reduction in song frequency bandwidth. Singing higher and in a narrower bandwidth may make their songs more audible in noisy conditions of low-frequency traffic. However, it was unknown whether the associated decrease in syllable diversity affected their communication. Here we show that bananaquits responded differently to experimental playback of elaborate vs. simple songs. The variation in syllable diversity did not affect general response strength, but the tested birds gave acoustically distinct song replies. Songs had fewer syllables and were lower in frequency and of wider bandwidth when individuals responded to elaborate songs compared to simple songs. This result suggests that noise-dependent vocal restrictions may change the signal value of songs and compromise their communicative function. It remains to be investigated whether there are consequences for individual fitness and how such effects may alter the diversity and density of the avian community in noisy cities.

Chimpanzee pant-hoots encode information about individual but not group differences

Vocal learning, the ability to voluntarily modify the acoustic structure of vocalizations based on social cues, is a fundamental feature of speech in humans (Homo sapiens). While vocal learning is common in taxa such as songbirds and whales, the vocal learning capacities of nonhuman primates appear more limited. Intriguingly, evidence for vocal learning has been reported in chimpanzees (Pan troglodytes), for example in the form of regional variation (‘dialects’) in the ‘pant-hoot’ calls. This suggests that some capacity for vocal learning may be an ancient feature of the Pan-Homo clade. Nonetheless, reported differences have been subtle, with inter-community variation representing only a small portion of the total acoustic variation. To gain further insights into the extent of regional variation in chimpanzee vocalizations, we performed an analysis of pant-hoots from chimpanzees in the neighboring Kasekela and Mitumba communities at Gombe National Park, Tanzania, and the geographically distant Kanyawara community at Kibale National Park, Uganda. We observed group differences only among the geographically isolated communities and did not find any differences between the neighboring communities at Gombe. Furthermore, we found differences among individuals in all communities. Hence, the variation in chimpanzee pant-hoots reflected individual differences, rather than group differences. The limited evidences for vocal learning in Pan suggest that extensive vocal learning emerged in the human lineage after the divergence from Pan.

The emotional canvas of human screams: patterns and acoustic cues in the perceptual categorization of a basic call type

Screams occur across taxonomically widespread species, typically in antipredator situations, and are strikingly similar acoustically, but in nonhuman primates, they have taken on acoustically varied forms in association with more contextually complex functions related to agonistic recruitment. Humans scream in an even broader range of contexts, but the extent to which acoustic variation allows listeners to perceive different emotional meanings remains unknown. We investigated how listeners responded to 30 contextually diverse human screams on six different emotion prompts as well as how selected acoustic cues predicted these responses. We found that acoustic variation in screams was associated with the perception of different emotions from these calls. Emotion ratings generally fell along two dimensions: one contrasting perceived anger, frustration, and pain with surprise and happiness, roughly associated with call duration and roughness, and one related to perceived fear, associated with call fundamental frequency. Listeners were more likely to rate screams highly in emotion prompts matching the source context, suggesting that some screams conveyed information about emotional context, but it is noteworthy that the analysis of screams from happiness contexts (n = 11 screams) revealed that they more often yielded higher ratings of fear. We discuss the implications of these findings for the role and evolution of nonlinguistic vocalizations in human communication, including consideration of how the expanded diversity in calls such as human screams might represent a derived function of language.

Individual-based acoustic variation of the alarm calls in the long-tailed ground squirrel

Based on their phylogenetic position, Nearctic ground squirrels are closest relatives to the long-tailed ground squirrel Urocitellus undulates even though it has Palaearctic distribution. We aimed to investigate the variability of alarm calls of the long-tailed ground squirrel to test the individual variation in alarm calls. This species is known to produce two types of alarm calls: whistle alarms and wideband calls. Although ground squirrels are a model group for the study of vocal individuality, this phenomenon has not yet been studied in a species producing two such completely different types of alarms. Most of ground squirrel species produce either whistle or wideband alarms and this species represents a unique model for testing the degree of individual variability depending on completely different acoustic structures. We analysed 269 whistle alarms produced by 13 individuals and 591 wideband alarms from 25 individuals at the western part of Lake Baikal. A discriminant function analysis (DFA) assigned 93.5% (88.9%, cross-validated result) of whistle alarms to the correct individual and 91.4% (84%) of wideband alarms. This is the first evidence of individual variation in wideband alarms compared with whistle alarms and occurrence of vocal individuality in two warning signals of a completely different acoustic structure produced by a ground squirrel.