Cross-taxa similarities in affect-induced changes of vocal behavior and voice in arboreal monkeys.

International audienceMeasuring the affective state of an individual across species with comparable non-invasive methods is a current challenge in animal communication research. This study aims to explore to which extent affect intensity is conveyed in the vocal behaviours of three nonhuman primate species (Campbell's monkeys, De Brazza's monkeys, red-capped mangabeys), which vary in body size, ecological niche and social system. Similarly in the three species, we experimentally induced a change in captive social groups' affect by locking all group members together in their outside enclosure. The two experimental conditions which varied in affect intensity consisted in imposing a pre-reunion 90 mn-separation by splitting up the respective group into two subgroups (High affect condition) or not (Low affect condition). We measured call rates as well as voice features at the time of reunion in both conditions. The three studied species reacted in a very similar way. Across species, call rates changed significantly between the behaviourally defined states. Furthermore, contact call duration and, to some extent, voice pitch increased. Our results suggest, for the first time in arboreal Old World monkeys, that affect intensity is conveyed reliably in vocal behaviour and specific acoustic characteristics of voice, irrespective of body size and ecological niche differences between species. Cross-taxa similarities in acoustic cues of affect intensity point to phylogenetic constraints and inheritance from a common ancestor, whereas variations in vocal behaviour and affect intensity-related acoustic cues between species may be an adaptation to specific social requirements and depend on social systems. Our findings as well as a comparison with published works on acoustic communication in other vertebrate groups support the hypothesis that affect intensity in human voice originates from precursors already found deep inside the vertebrate phylogeny

Tenseness relaxed by vocalizing, illustrated by horses (Equus caballus) whinnying

International audienceAnimal calls are commonly considered indicators of a sudden change in their arousal state. However, reports evidencing associated internal physiological changes are rare. By homology with human "emotional" vocal productions (e.g., laughter and crying), we predicted that animal vocal productions may result in relaxing tenseness or excitement. In this study, 15 stallions equipped with a heart rate monitor were presented a mare at some distance so as to prevent contact, thereby increasing the males' arousal. Stallions' heart rates increased just before whinnying but returned to baseline rates while vocalizing. We found that sudden changes of a caller's arousal state could be associated with vocalizing, and this opens new lines for noninvasive research concerning the self-regulation of emotional via vocal production in humans and animals. (PsycINFO Database Recor

Stallion’s voice: an indicator of fertility and a basis for female choice?

International audienceVocalisations of mammals, carrying information on caller’s familiarity, identity, age or size, play a key role in coordinating sexual partners. Some studies showed that females select partners based on vocal attributes. However, we still fail to understand why such capacities evolved and which consequences these choices can have on reproduction. Wild mares actively choose the family group into which they are going to migrate, spotting at a distance the potential stallion partners. Whinnies are vocalizations allowing long-distance communication and we thus investigated if and how they could guide the choice of females. At first, the voices of 15 reproductive stallions were recorded in three national Stud farms while they were held at a distance from a mare. Acoustic analysis then showed that there was a correlation between frequency parameters and the reproductive success of the caller, stallions with a higher-pitched voice presented more successful gestations. Interestingly, acoustic parameters appeared to be more reliable predictors of fertility than seminal and hormonal features. Secondly, 40 adult mares were individually exposed to the simultaneous loud-speaker playback of pairs of whinnies (high-and low-pitched). Mares showed a very clear preference of orientation towards low-pitched voices. These results open lines of basic and applied research on the relationship between vocal characteristics and reproduction in mammals

La voix de l’étalon : un indicateur de fertilité et une base de choix pour les femelles ?

National audienceCertaines vocalisations des mammifères, porteuses d'informations sur la familiarité, l'identité, l'âge ou la taille de l'émetteur, jouent un rôle dans la coordination des partenaires sexuels. Quelques études ont montré que les femelles prennent en compte les qualités vocales des mâles dans leurs choix de partenaires. Cependant, nous comprenons encore mal pourquoi de telles aptitudes ont évolué et quelles conséquences ces choix peuvent avoir sur la reproduction. Dans la nature, les juments choisissent activement le groupe familial dans lequel elles vont s'insérer, repérant à distance les étalons partenaires potentiels. Les hennissements sont des vocalisations permettant cette communication à distance et nous avons donc cherché à savoir si et comment ils pouvaient guider le choix des femelles. Dans un premier temps, les voix de 15 étalons reproducteurs ont été enregistrées dans trois Haras nationaux alors qu'ils étaient tenus en main à distance d'une jument. Des analyses acoustiques ont alors montré qu'il y avait une corrélation entre des paramètres de fréquence et le succès reproducteur de l'émetteur, les étalons avec la voix plus grave présentaient davantage de gestations réussies. De façon intéressante, les paramètres vocaux se sont révélés plus fiables dans la prédiction de la fertilité que les analyses séminales et hormonales. Dans un second temps, 40 juments adultes ont été individuellement confrontées à la diffusion simultanée par haut-parleurs de paires de hennissements (graves et aigus). Les juments ont montré une nette préférence d'orientation vers les voix graves. Ces résultats ouvrent des lignes de recherches fondamentales et appliquées sur le lien entre caractéristiques vocales et reproduction chez les mammifères

Mares Prefer the Voices of Highly Fertile Stallions

International audienceWe investigated the possibility that stallion whinnies, known to encode caller size, also encoded information about caller arousal and fertility, and the reactions of mares in relation to type of voice. Voice acoustic features are correlated with arousal and reproduction success, the lower-pitched the stallion's voice, the slower his heart beat and the higher his fertility. Females from three study groups preferred playbacks of low-pitched voices. Hence, females are attracted by frequencies encoding for large male size, calmness and high fertility. More work is needed to explore the relative importance of morpho-physiological features. Assor-tative mating may be involved as large females preferred voices of larger stallions. Our study contributes to basic and applied ongoing research on mammal reproduction, and questions the mechanisms used by females to detect males' fertility

Validation of an Auditory Sensory Reinforcement Paradigm: Campbell's Monkeys (Cercopithecus campbelli) Do Not Prefer Consonant Over Dissonant Sounds

International audienceThe central position and universality of music in human societies raises the question of its phylogenetic origin. One of the most important properties of music involves harmonic musical intervals, in response to which humans show a spontaneous preference for consonant over dissonant sounds starting from early human infancy. Comparative studies conducted with organisms at different levels of the primate lineage are needed to understand the evolutionary scenario under which this phenomenon emerged. Although previous research found no preference for consonance in a New World monkey species, the question remained opened for Old World monkeys. We used an experimental paradigm based on a sensory reinforcement procedure to test auditory preferences for consonant sounds in Campbell's monkeys (Cercopithecus campbelli campbelli), an Old World monkey species. Although a systematic preference for soft (70 dB) over loud (90 dB) control white noise was found, Campbell's monkeys showed no preference for either consonant or dissonant sounds. The preference for soft white noise validates our noninvasive experimental paradigm, which can be easily reused in any captive facility to test for auditory preferences. This would suggest that human preference for consonant sounds is not systematically shared with New and Old World monkeys. The sensitivity for harmonic musical intervals emerged probably very late in the primate lineage

A spectrogram of a whinny showing acoustic measures taken.

<p>A spectrogram of a whinny showing acoustic measures taken.</p

Acoustic stimuli spectrograms (a) low pitch and (b) high pitch.

<p>Acoustic stimuli spectrograms (a) low pitch and (b) high pitch.</p

Relationships among physiological features.

<p>Relationships among physiological features.</p

Mares’ responses to playbacks (Experiment 2).

<p>Mares’ responses to playbacks (Experiment 2).</p