Behavioural reactivity testing in sheep indicates the presence of multiple temperament traits

Temperament in sheep is commonly presented as unidimensional, with a 'nervous' temperament indicative of fear and reactivity towards humans and novel environments. However, temperament is multidimensional, with some traits expressed only under certain conditions (context-specific). There is evidence that a common temperament test in sheep, the isolation-box (IB), measures level of activity and not fearfulness as intended, and that behaviours measured in the IB test are indicative of different traits. To investigate this, 16 behavioural responses to a human, to being startled, and to confinement (IB test) were measured in 89 lambs, twice, three months apart. Our results agree with previous studies that vocalisations in all tests and locomotion in two, show high repeatability over time. A principal component analysis identified that vocalisations are domain-general, and are indicative of the trait 'sociability', however locomotion is context-specific' and captures the traits 'exploration-avoidance', 'boldness-shyness' and 'general activity'. A cluster analysis identified four behavioural profiles that indicate the trait 'boldness-shyness' captures reactivity towards humans. This suggests the IB test, which measures 'general activity', is unsuitable for measuring reactivity towards humans in sheep, and that when studying the impact of temperament on other factors, multiple conditions should be used when identify temperament traits.

The vocal repertoire of preterm infants: Characteristics and possible applications

We investigated infants' capacities to express themselves orally at very early developmental stages. Most reports focus on crying when in pain or hungry. We evaluated young preterm infants' spontaneous vocal production in non-painful contexts. We identified a vocal repertoire composed of nine types of vocalisations. High-pitched sounds were associated with relaxed postures, implying a positive valence, whereas long low-pitched vocalisations, associated more with grimaces and muscle tensions, appeared to have a more negative valence. Infants' vocalisations were useful indicators of their internal state in two situations (when exposed to clothing constraints and environmental noises).

Vocal Repertoire and Intraspecific Variation within Two Loud Calls of the Small-Eared Greater Galago (Otolemur garnettii) in Tanzania and Kenya

Vocal repertoires and call structure can provide insights into the behaviour and evolution of species, as well as aid in taxonomic classification. Nocturnal primates have large vocal repertoires. This suggests that acoustic communication plays an important role in their life histories. Little is known about the behavioural context or the intraspecific variation of their vocalisations. We used autonomous recording units and manual recorders to investigate the vocal behaviour and structure of loud calls of the small-eared greater galago (Otolemur garnettii)in Kenya and Tanzania. We describe the vocal repertoire, temporal calling patterns and structure of 2 loud calls of 2 subspecies: O. g. panganiensis and O. g. kikuyuensis. We found considerable intraspecific structural differences in both loud calls. These are congruent with the current subspecies classification. Differences in vocalisations among populations are not consistent with the "acoustic adaptation hypothesis," rather they are likely a result of geographic variation due to isolation caused by vegetational barriers in southern Kenya.

Low Geographic and Subspecific Variation in the Loud Call of the Widespread and Phenotypically Cryptic Northern Lesser Galago (Galago senegalensis) Suggests Taxonomic Uniformity

Like other nocturnal primates, many species of galago (Galagidae) are phenotypically cryptic, making their taxonomic status difficult to resolve. Recent taxonomic work has disentangled some of the confusion. This has resulted in an increase in the number of recognised galago species. The most widespread galago species, and indeed the most widespread nocturnal primate, is the northern lesser galago (Galago senegalensis) whose geographic range stretches >7,000 km across Africa. Based on morphology, 4 subspecies are currently recognised: G. s. senegalensis, G. s. braccatus, G. s. sotikae and G. s. dunni. We explore geographic and subspecific acoustic variation in G. senegalensis, testing three hypotheses: isolation by distance, genetic basis, and isolation by barrier. There is statistical support for isolation by distance for 2 of 4 call parameters (fundamental frequency and unit length). Geographic distance explains a moderate amount of the acoustic variation. Discriminant function analysis provides some degree of separation of geographic regions and subspecies, but the percentage of misdesignation is high. Despite having (putative) parapatric geographic ranges, the most pronounced acoustic differences are between G. s. senegalensis and G. s. dunni. The findings suggest that the Eastern Rift Valley and Niger River are significant barriers for G. senegalensis. The acoustic structures of the loud calls of 121 individuals from 28 widespread sites are not significantly different. Although this makes it unlikely that additional unrecognised species occur within G. senegalensis at the sites sampled, vast areas of the geographic range remain unsampled. We show that wide-ranging species do not necessarily exhibit large amounts of variation in their vocal repertoire. This pattern may also be present in nocturnal primates with smaller geographic ranges.

A Behavioural Case Study of Early Social Isolation of a Subadult White-Handed Gibbon (Hylobates lar)

Our aim in this study was to analyse the effects of early social isolation on the behaviour of a white-handed gibbon (Hylobates lar) and at the same time to improve his level of welfare. The subject was a 6-year-old male, isolated from conspecific as well as other non-human primates since he was 3 months old. We presented the gibbon with a series of species-specific vocalisations, and we then introduced a 23-year-old conspecific female into his cage. Our subject did not respond to playbacks, whereas he immediately interacted positively with the conspecific female. After 2 days of presentation, the pair started to spend time in proximity to each other and initiated grooming through the wire-mesh dividing the cages. Four days later we recorded vocal duets. No obvious ste-reotypic behaviours were observed, and the prolonged isolation did not seem to compromise the ability of the young gibbon to socialise with the female conspecific. It appears that prolonged isolation does not always compromise the possibility of recovering socially in a satisfactory manner.

Perception of emotional valence in horse whinnies

Background

Non-human animals often produce different types of vocalisations in negative and positive contexts (i.e. different valence), similar to humans, in which crying is associated with negative emotions and laughter is associated with positive ones. However, some types of vocalisations (e.g. contact calls, human speech) can be produced in both negative and positive contexts, and changes in valence are only accompanied by slight structural differences. Although such acoustically graded signals associated with opposite valence have been highlighted in some species, it is not known if conspecifics discriminate them, and if contagion of emotional valence occurs as a result. We tested whether domestic horses perceive, and are affected by, the emotional valence of whinnies produced by both familiar and unfamiliar conspecifics. We measured physiological and behavioural reactions to whinnies recorded during emotionally negative (social separation) and positive (social reunion) situations.

Results

We show that horses perceive acoustic cues to both valence and familiarity present in whinnies. They reacted differently (respiration rate, head movements, height of the head and latency to respond) to separation and reunion whinnies when produced by familiar, but not unfamiliar individuals. They were also more emotionally aroused (shorter inter-pulse intervals and higher locomotion) when hearing unfamiliar compared to familiar whinnies. In addition, the acoustic parameters of separation and reunion whinnies affected the physiology and behaviour of conspecifics in a continuous way. However, we did not find clear evidence for contagion of emotional valence.

Conclusions

Horses are thus able to perceive changes linked to emotional valence within a given vocalisation type, similar to perception of affective prosody in humans. Whinnies produced in either separation or reunion situations seem to constitute acoustically graded variants with distinct functions, enabling horses to increase their apparent vocal repertoire size.

Electronic supplementary material

The online version of this article (doi:10.1186/s12983-017-0193-1) contains supplementary material, which is available to authorized users.

Young, active and well-connected: adult-born neurons in the zebra finch are activated during singing

Neuronal replacement in the pallial song control nucleus HVC of adult zebra finches constitutes an interesting case of homeostatic plasticity; in spite of continuous addition and attrition of neurons in ensembles that code song elements, adult song remains remarkably invariant. New neurons migrate into HVC and later synapse with their target, arcopallial song nucleus RA (HVCRA). New HVCRA neurons respond to auditory stimuli (in anaesthetised animals), but whether and when they become functionally active during singing is unknown. We studied this, using 5-bromo-2'-deoxyuridine to birth-date neurons, combined with immunohistochemical detection of immediate-early gene (IEG) expression and retrograde tracer injections into RA to track connectivity. Interestingly, singing was followed by IEG expression in a substantial fraction of new neurons that were not retrogradely labelled from RA, suggesting a possible role in HVC-intrinsic network function. As new HVC neurons matured, the proportion of HVCRA neurons that expressed IEGs after singing increased significantly. Since it was previously shown that singing induces IEG expression in HVC also in deaf birds and that hearing song does not induce IEG expression in HVC, our data provide the first direct evidence that new HVC neurons are engaged in song motor behaviour.