Biology subjects

Briefer, E. F.

Publications and source records attributed to Briefer, E. F..

8 recordsLinked to original sources

bioRxiv2026

What is encoded in a marmoset phee call? Food context beyond arousal and valence

Animal vocalisations can convey information about external events, but whether this goes beyond reflecting the emotional state elicited by these events is debated. To explore this, we studied the acoustic structure of common marmoset (Callithrix jacchus) phee (long-distance contact) and ek (alert/mobbing) calls produced in five treatments varying in the emotional valence and arousal they elicit (internal state), as well as food and social context (external events). We measured changes in arousal via nasal temperature and analysed both basic acoustic parameters and Mel-frequency cepstral coefficients (MFCCs) of the calls. Support Vector Machines combined with Linear Mixed effect models revealed that phee calls encode both external events and internal states, while eks reflected predominantly arousal. Notably, an acoustic signature related to food context was present in phees both when provided (positive valence) and teased with highly preferred food items (negative valence), and even when food was not physically present (food call playback treatment). This suggests marmoset long-distant phee calls encode external information beyond emotional arousal and valence, and independently of the presence of an immediately triggering stimulus.

animal behavior and cognition↗

bioRxiv2025

Acoustic markers of negative arousal in lambs: evidence from behavioural and eye thermal profiles

Vocalizations are known indicators of emotional arousal in animals, but validation using simultaneously collected physiological and behavioural measures remains limited to a few species. This study investigated sheep vocal expression of negative emotional arousal using stress-related behaviours and eye temperature as non-invasive arousal indicators. To this aim, twenty lambs underwent a short-term isolation test with two phases aimed at eliciting different levels of arousal in response to separation from conspecifics: partial isolation, where lambs maintained visual, acoustic and tactile contact with conspecifics through a fence, and full isolation (complete separation). During full isolation, lambs expressed higher bodily activation--spending more time running, jumping, and changing state behaviours--and produced more open-mouthed bleats (321 vs 27) than in partial isolation, validating higher arousal. Eye temperature also increased from partial to full isolation (however only in small lambs and not large ones). Calls emitted in full isolation were characterised by higher frequencies, were less tonal (more chaos) and had shorter durations. When combining behavioural and physiological assessment of arousal and testing their impact on the spectro-temporal structure of vocalizations, we found that bodily activation, but not eye peak temperature, impacted on the frequency distribution and tonality of the calls. Call duration increased with eye temperature, but only in lambs expressing high bodily activation, while the mean of the second formant increased with eye temperature in smaller but not larger lambs. Overall, lamb vocalizations indicate arousal and are correlated with bodily activation, while co-variations with physiological measures depended on behaviour and individual traits. HighlightsO_LIAnimal calls indicate emotional arousal, but few species have validated measures C_LIO_LILamb calls became higher in frequency, less tonal and shorter with negative arousal C_LIO_LICalls indicated emotional arousal and were correlated with bodily activation C_LIO_LIChanges in calls with eye temperature depended on behaviour and individual traits C_LI

animal behavior and cognition↗

bioRxiv2025

Socio-acoustic co-selection? Vocal encoding of sociability prevails over emotions in sheep bleats

Vocalisations of animals are good indicators of their emotions. Temperament is known to influence the regulation and expression of emotions. However, how animal temperament affects their vocalisations and particularly their vocal expressions of emotions remains largely unexplored. Sociability is often measured as the behavioural reactivity to social separation and is a temperament trait intrinsically linked to emotional reactivity. Most social species respond to this challenging situation using contact calls. Here, we investigated whether the acoustic structure of these calls reflect sociability, emotions or both. Among 152 recorded female lambs, 42 belonged to two diverging sheep lines selected for high or low sociability. High bleats were recorded both in isolation (social challenge, all lambs) then before receiving a food treat (non-social challenge, selected lambs) to investigate the link between vocalisations, emotions and heritable sociability. The acoustic features of isolation bleats differed between lines, but it was not the case for pre-food treat bleats. Surprisingly, the genetic selection index and social behaviour explained better the structure of isolation bleats than the arousal. Last, encoding of individuality in isolation bleats was impaired by the genetic selection. Our findings show that selecting for sociable animals affects vocal signatures in calls produced during a social challenge, leading us to hypothesize a socio-acoustic co-selection.

animal behavior and cognition↗

bioRxiv2024

Emotional contexts influence vocal individuality in ungulates

To group-living animals, such as most ungulates, being able to recognise the members of ones social groups is crucial. While vocalisations often carry cues to identity, they are also impacted by the affective state of the caller, with signals often becoming more chaotic in contexts of negative valence or high arousal. How might this influence vocal individuality - and is there a pattern across taxa? To understand how the individual information content is maintained over emotionally charged contexts, we studied putatively negative and positive contact calls of seven ungulate species: cattle, goats, sheep, pigs, wild boars, horses, and Przewalskis horses. The information content of these calls was assessed using Beechers statistic and the Potential of Individuality Coding. Across the species, the information content was lower in calls of negative than positive valence. In each of the species, at least one acoustic parameter was a reliable indicator of individuality across contexts. Our results indicate that negative valence overrides individual information in ungulate vocalisations at least to some extent, and imply that individual vocal recognition may require acoustic stability of certain important parameters. These findings reveal a nuanced role of affective communication in maintaining social bonds among socially complex animals.

animal behavior and cognition↗

bioRxiv2024

Same data, different results? Evaluating machine learning approaches for individual identification in animal vocalisations

Automated acoustic analysis is increasingly used in behavioural ecology, and determining caller identity is a key element for many investigations. However, variability in feature extraction and classification methods limits the comparability of results across species and studies, constraining conclusions we can draw about the ecology and evolution of the groups under study. We investigated the impact of using different feature extraction (spectro-temporal measurements, linear and Mel-frequency cepstral coefficients, as well as highly comparative time-series analysis) and classification methods (discriminant function analysis, neural networks, random forests, and support vector machines) on the consistency of caller identity classification accuracy across 16 mammalian datasets. We found that Mel-frequency cepstral coefficients and random forests yield consistently reliable results across datasets, facilitating a standardised approach across species that generates directly comparable data. These findings remained consistent across vocalisation sample sizes and number of individuals considered. We offer guidelines for processing and analysing mammalian vocalisations, fostering greater comparability, and advancing our understanding of the evolutionary significance of acoustic communication in diverse mammalian species.

animal behavior and cognition↗

bioRxiv2024

Long distance calls: negligible information loss of seabird social vocalisations over propagation down to the hearing threshold

How well does the information contained in vocal signals travel through the environment? To assess the efficiency of information transfer in little auk (Alle alle, an Arctic seabird) calls over distance, we selected two of the social call types with the highest potential for individuality coding. Using available recordings of known individuals, we calculated the apparent source levels, with apparent maximum peak sound pressure level (ASPL) of 63 dB re 20 {micro}Pa at 1 m for both call types. Further, we created a sound propagation model using meteorological data collected in the vicinity of the little auk colony in Hornsund, Spitsbergen. Using this model, we simulated call propagation up to the putative hearing threshold of the species, calculated to equal ASPL of signals propagated to roughly one kilometre. Those propagated calls were then used in a permuted discriminant function analysis, support vector machine models, and linear models of Beechers information statistic, to investigate whether transmission loss will affect the retention of individual information of the signal. Calls could be correctly classified to individuals above chance level independently of the distance, down to and over the putative physiological hearing threshold. Interestingly, the information capacity of the signal did not decrease with propagation. While this study touches on signal properties purely and cannot provide evidence of the actual use by the animals, it shows that little auk signals can travel long distances with negligible information loss. For the animals, this could mean that they can recognize calls of the members of their social networks as far as those calls are actually audible, and support the hypothesis that vocalisations could facilitate long-distance communication in the species.

animal behavior and cognition↗

bioRxiv2022

Delayed benefits for fallow bucks: more fights decrease same day mating success, but may increase matings the next day

Dominance hierarchies help to reduce unnecessary fights and associated costs during the mating season. Fallow deer (Dama dama) typically have high levels of male-male competition and strong reproductive skew. Nevertheless, how male dominance and daily fight rates affect mating success remains unknown. We used a two-year dataset from a large population of tagged fallow deer (620-689 individuals), to calculate male dominance ranks based on their agonistic interactions prior to the mating season ( prerut), in order to then examine how rank is related to fight rates and mating success during the mating season ( rut). Overall, higher-ranked males fought at least twice a day on a higher proportion of days during the rut and secured more matings. Males engaging in more than 10 fights per day were less likely to secure a mating that same day, and those males exceeding 15 fights per day secured no matings at all. Nevertheless, males with the highest numbers of fights (i.e. 15-21 fights per day) on a given day had higher mating success on subsequent days. Although higher-ranked males secured most matings during the rut, their fight rates decreased towards the end. We propose that engaging in more fights negatively affects daily individual mating success, but may benefit mating success on subsequent days, and potentially increase long-term fitness benefits. Additionally, engaging in more fights as the rut progresses probably allows lower-ranked males to secure some matings before the availability of oestrous females ends for almost a year. SIGNIFICANCE STATEMENTFighting carries a risk of injury and high energetic costs. Male fallow deer establish dominance hierarchies, that help reduce unnecessary fights among individuals of different competitive abilities. However, whether high-ranked males fight more or less is yet unknown. By calculating social ranks of fallow bucks before the start of their mating period, we show that males of higher social status do fight and mate more during the mating season (rut). Furthermore, by investigating how investment in fights affects individual mating success that same day and the next day, we find that males that fight more cause a decrease in their immediate daily mating success, but can potentially increase their chances of mating in subsequent days. Thus, to fight more may allow males to climb the hierarchical social ladder, hence increasing longer-term fitness benefits associated to higher ranks.

animal behavior and cognition↗

bioRxiv2022

Goat kid recognition of their mothers' calls is not impacted by changes in source-filter parameters.

Features varying more between than within individuals are usually considered as potential cues for individual recognition. According to the source-filter theory of vocal production, the fundamental frequency of mammals vocalisations depends on the characteristics of the vocal folds, while formants are determined by the characteristics of the vocal tract. Goat mothers and their kids (Capra hircus) display mutual recognition, and both source-related parameters (F0) and filter-related ones (formants) have been shown to be individualised in their vocalisations. Here, we aimed to identify if these parameters (source-related parameters (F0) and/or filter vocal parameters) are used by goat kids to recognise their mothers vocalisations. To this aim, we used an algorithm to modify either F0 or formants of the calls of goat mothers to different degrees (within or exceeding the range of natural intra-individual variability), and we played back these modified calls to their kids. We did not observe any difference in the kid reactions to the modified maternal vocalisations and to the natural calls. We suggest that either: (i) fundamental frequency and formants are not involved in maternal recognition in goats; (ii) goat kids have a tolerance for variation when recognising their mothers calls that exceeds the shifts we performed; (iii) goat maternal recognition is based on other vocal features than those tested here, or (iv) goat kid maternal recognition is based on a combination of different features and might be more flexible than previously thought, such that when one main feature is modified, kids focus on other features.

animal behavior and cognition↗