Abstract The study of great ape cognition offers insights into the evolutionary origins of human intelligence, but is hindered by small sample sizes and restricted access to data. To address this, we present the EVApeCognition Dataset, a publicly available resource comprising 262 experimental datasets from 150 scientific publications from the Wolfgang Köhler Primate Research Center (2004–2021) in Leipzig, Germany. Eighty-one apes participated in 150 studies, with a majority (N = 78) participating in more than one study. Publication of the dataset aims to make these unique datasets accessible for future meta-analyses and correlational analyses, helping us better understand how our great ape relatives think, learn, and behave.

Large mammal species are declining globally, and zoo populations may help support or re-establish wild populations through reinforcement or reintroduction. However, zoo environments differ from natural habitats, which may alter behaviours, including vocalisations, potentially affecting social interactions in relocated animals. Here, we investigated whether the acoustic structure of southern white rhinoceros' (Ceratotherium simum simum) contact calls, 'pants', differs between individuals from zoo and wild populations, as well as between four separate wild and zoo populations for which we had sufficient data to investigate population effects further. Our data set included pants from 43 individuals recorded across five European zoos and four African wild populations. The results did not reveal any marked differences between the pants of zoo-housed and wild individuals or between individuals from different populations. We suggest that the lack of vocal divergence is likely due to the vocal repertoire being innate, potentially enhanced by the low genetic heterozygosity of contemporary southern white rhinoceroses. Our study contributes to the relatively limited body of the literature examining population-level variations in vocalisations among large ungulates and megaherbivores. The lack of acoustic structure in vocalisations across populations can potentially facilitate the translocation of individuals without risking disruption of social cohesion and reproduction success.

For broiler chicks, the entire hatching process and hatching itself take place in specialized hatcheries. After hatching, the chicks are transported to the broiler farm and raised there. Hatching in the barn is an alternative in which the incubated eggs are transported on the 18th day of incubation and the broiler chicks are hatched in the barn. The aim of the present field study consisted in comparing the behaviour, in particular the drinking and eating behaviour and vocalization of broiled chicks hatched conventionally in a hatchery (HH) with chicks hatched in the barn (OH) within the first days of life. For this, video-based behavioural analyses were conducted and individual calls were recorded based on continuous audio recordings and noise level measurements. The results showed that both hatching forms first consumed food (p < 0.001) and then water intake took place (p = 0.02), whereby the OH-chicks performed all types of behaviour comparatively earlier. The focal animal observation of the OH-chicks showed that they fed for the first time after hatching on average after 9:42:10 h (SD: 10:15:17 h) and drank from the nipple drinkers on average 16:04:40 h (SD: 13:01:19 h) after hatching. The HH-chicks fed for the first time 27:58:20 h (SD: 00:05:06 h) after hatching and drank at the nipple drinkers for an average of 29:37:30 h (SD: 03:53:47 h) after hatching. In addition, the HH-chicks, with a difference of 4.6 dB to the OH-chicks, showed a higher noise level (p < 0.001) and a higher maximum frequency of calls (p = 0.015), which was on average 61.8 Hz higher compared to the OH-chicks. Concerning the duration, the calls of the chicks of both hatching forms did not differ significantly on average. Based on the time until the first feed and water intake and the resulting duration of feed and water deprivation after hatching as well as the vocalization of the included broilers, it can be concluded that hatching in the barn promotes well-being and potentially reduces the stress level in the first phase of life.

In southern white rhinoceroses (Ceratotherium simum simum), pant calls are well-studied contact vocalisations, whereas the function of frequently emitted snorts remains unclear. We conducted playback experiments with 15 rhinoceroses at three European zoos. The first experiment tested responses to conspecific versus heterospecific snorts, comparing pulsed and non-pulsed acoustic structures. The second experiment contrasted conspecific snorts with conspecific pants from males differing in age and faecal testosterone metabolite (fTM) levels. Behavioural responses—including body orientation, approach toward loudspeaker, locomotion, and vocalisations—were analysed. Snorts, regardless of sender species or pulsation, elicited uniformly low-intensity responses, suggesting limited communicative function. In contrast, pants evoked significantly stronger responses depending on sex and group setting. While males showed increased locomotion, females vocalised more, reflecting the species’ social dynamics. Individuals tested alone displayed overall heightened vigilance and vocal activity compared to those tested in pairs, emphasising the role of social context. No evidence was found for discrimination between pant calls differing in fTM levels. Our findings reinforce the communicative relevance of pants in conveying social cues while indicating that snorts may either lack species-specific acoustic markers or not be socially salient. Playback experiments thus appear as valuable tools for assessing acoustic communication in zoo-housed mammals.

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 (MFCC), as well as highly comparative time‐series analysis) and classification methods (discriminant function analysis, neural networks, random forests (RF), and support vector machines) on the consistency of caller identity classification accuracy across 16 mammalian datasets. We found that MFCCs and RFs 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.

Chapter 36 The mouse lemurs Jennifer Wittkowski, Jennifer WittkowskiSearch for more papers by this authorAnnette Klein, Annette KleinSearch for more papers by this authorAnnika Kollikowski, Annika KollikowskiSearch for more papers by this authorMarina Scheumann, Marina ScheumannSearch for more papers by this authorDaniel Schmidtke, Daniel SchmidtkeSearch for more papers by this authorElke Zimmermann, Elke ZimmermannSearch for more papers by this authorUte Radespiel, Ute RadespielSearch for more papers by this author Jennifer Wittkowski, Jennifer WittkowskiSearch for more papers by this authorAnnette Klein, Annette KleinSearch for more papers by this authorAnnika Kollikowski, Annika KollikowskiSearch for more papers by this authorMarina Scheumann, Marina ScheumannSearch for more papers by this authorDaniel Schmidtke, Daniel SchmidtkeSearch for more papers by this authorElke Zimmermann, Elke ZimmermannSearch for more papers by this authorUte Radespiel, Ute RadespielSearch for more papers by this author Book Editor(s):Huw Golledge, Huw Golledge Universities Federation Animal Welfare, UKSearch for more papers by this authorClaire Richardson, Claire Richardson Universities Federation Animal Welfare, UKSearch for more papers by this author First published: 14 March 2024 https://doi.org/10.1002/9781119555278.ch36 AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onEmailFacebookTwitterLinkedInRedditWechat Summary Mouse lemurs form one genus within the family of the Cheirogaleidae that belongs to the 100% endemic lemurs of Madagascar and, thereby, to the primate suborder Strepsirrhini. Mouse lemurs are nocturnal and the smallest-bodied primates. The best studied mouse lemur species, both in nature and in captivity, is the grey mouse lemur. Mouse lemurs are seasonal breeders with an onset of reproduction that varies between different species, but mainly starts during the long-day period. Due to the nocturnal lifestyle of mouse lemurs, it is assumed that they mainly use their olfactory and auditory senses for communication and foraging. Mouse lemurs show a variety of olfactory behaviours to distribute scent marks and urine. The economic advantages of mouse lemurs over other nonhuman primates in laboratory research are obvious. Being the smallest primates in the world, they can be kept cost-effectively in large numbers. References Agnani , P. , Kauffmann , C. , Hayes , L.D. and Schradin , C. ( 2018 ) Intra-specific variation in social organization of strepsirrhines . 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Vocalizations coordinate social interactions between conspecifics by conveying information concerning the individual or group identity of the sender. Social accommodation is a form of vocal learning where social affinity is signalled by converging or diverging vocalizations with those of conspecifics. To investigate whether social accommodation is linked to the social lifestyle of the sender, we investigated sex-specific differences in social accommodation in a dispersed living primate, the grey mouse lemur ( Microcebus murinus ), where females form stable sleeping groups whereas males live solitarily. We used 482 trill calls of 36 individuals from our captive breeding colony to compare acoustic dissimilarity between individuals with genetic relatedness, social contact time and body weight. Our results showed that female trills become more similar the more time females spend with each other, independent of genetic relationship, suggesting vocal convergence. In contrast, male trills were affected more by genetic than social factors. However, focusing only on socialized males, increasing time as cage partners caused greater divergence in males’ trills. Thus, grey mouse lemurs show the capacity for social accommodation, with females converging their trills to signal social closeness to sleeping group partners, whereas males do not adapt or diverge their trills to signal individual distinctiveness. This article is part of the theme issue 'The power of sound: unravelling how acoustic communication shapes group dynamics'.

Global biodiversity is under accelerating threats, and species are succumbing to extinction before being described. Madagascar’s biota represents an extreme example of this scenario, with the added complication that much of its endemic biodiversity is cryptic. Here we illustrate best practices for clarifying cryptic diversification processes by presenting an integrative framework that leverages multiple lines of evidence and taxon-informed cut-offs for species delimitation, while placing special emphasis on identifying patterns of isolation by distance. We systematically apply this framework to an entire taxonomically controversial primate clade, the mouse lemurs (genus Microcebus, family Cheirogaleidae). We demonstrate that species diversity has been overestimated primarily due to the interpretation of geographic variation as speciation, potentially biasing inference of the underlying processes of evolutionary diversification. Following a revised classification, we find that crypsis within the genus is best explained by a model of morphological stasis imposed by stabilizing selection and a neutral process of niche diversification. Finally, by clarifying species limits and defining evolutionarily significant units, we provide new conservation priorities, bridging fundamental and applied objectives in a generalizable framework. A spatial taxonomic framework integrating genomic, morphological, ecological, life history and acoustic data is used to clarify the cryptic evolution of the taxonomically controversial mouse lemur complex, with a view to aiding future conservation of this and other similarly cryptic clades.

Graded call types predominate in species inhabiting open habitats with complex social systems, whereas discrete call types predominate in species with simple social systems living in closed habitats. This study aims to establish the vocal repertoire of Etruscan shrews, the smallest terrestrial mammal, which lives in pairs in closed habitats. Through various behavioral experiments, vocalizations were recorded and analyzed using unsupervised soft clustering, identifying four call types, one of which exhibited gradation. These calls were present in both pups and adults, showing age-related acoustic differences. One call type was observed during socio-positive behavior, with higher call rates during female-male interactions, while the others occurred during socio-negative contexts, with higher call rates for animals housed in pairs. Delivering the first detailed insight into Etruscan shrew vocal behavior, we demonstrated that the smallest terrestrial mammal possesses graded and discrete call types, regardless of its social system and habitat.

Drumming is a non-vocal auditory display producing airborne as well as seismic vibrations by tapping body extremities on a surface. It is mostly described as an alarm signal but is also discussed to signal dominance or mating quality. To clarify the function of drumming in Mongolian gerbils (Meriones unguiculatus), we compared the occurrence of drumming during predator, opposite-sex and same-sex encounters. We tested 48 captive Mongolian gerbils (Meriones unguiculatus) in three experiments. In predator experiments, subjects were exposed alone or with their cagemate to aerial and terrestrial predator dummies. In social encounter experiments, familiar and unfamiliar male–female dyads and same-sex dyads were confronted. For the same-sex encounters, a dominance index was calculated for each subject based on the number of won and lost conflicts. Drumming and drumming-call combinations were counted, and a multi-parametric sound analysis was performed. In all experiments drumming and drumming-call combinations occurred. In predator experiments, more subjects drummed when confronted with the predator stimulus than in the habituation phase. In social encounter experiments, more subjects drummed when facing an unfamiliar than a familiar conspecific. In addition, the accompanying call type and body posture of the sender differed between experiments. Thus, we suggest that whereas drumming signals an increased arousal state of the sender, the accompanying call type and the body posture signal context specific information.

Early identification of tail biting and intervention are necessary to reduce tail lesions and their impact on animal health and welfare. Removal of biters has become an effective intervention strategy, but finding them can be difficult and time-consuming. The aim of this study was to investigate whether tail biting and, in particular, individual biters could be identified by detecting pig screams in audio recordings. The study included 288 undocked weaner pigs housed in six pens in two batches. Once a tail biter (n = 7) was identified by visual inspection in the stable and removed by the farm staff, the previous days of video and audio recordings were analyzed for pig screams (sudden increase in loudness with frequencies above 1 kHz) and tail biting events until no biting before the removal was observed anymore. In total, 2893 screams were detected in four pens where tail biting occurred. Of these screams, 52.9% were caused by tail biting in the observed pen, 25.6% originated from other pens, 8.8% were not assignable, and 12.7% occurred due to other reasons. In case of a tail biting event, screams were assigned individually to biter and victim pigs. Based on the audio analysis, biters were identified between one and nine days prior to their removal from the pen after visual inspection. Screams were detected earlier than the increase in hanging tails and could therefore be favored as an early warning indicator. Analyzing animal vocalization has potential for monitoring and early detection of tail biting events. In combination with individual marks and automatic analysis algorithms, biters could be identified and tail biting efficiently reduced. In this way, biters can be removed earlier to increase animal health and welfare.

Tail biting is a major problem in pig husbandry and early intervention is essential to maintain animal health and welfare. To facilitate early identification of tail biters a detector software was created that can detect scream-linked biting events through analyzing video and audio recordings. Undocked weaner pigs housing in different pens and batches were recorded for a duration of 39 days. Screamlinked tail biting events were firstly identified manually and then automatically through the developed detector by analyzing the audio track of the video recordings. The detector's performance was evaluated by testing different sensitivity parameters (e.g., loudness threshold, call duration, frequency range). In four pens (748 h), a total of 2,898 screams were manually detected, with 52.8 % caused by tail biting. In the second step, 89.9 % of the detected screams were classified correctly as screams by the detector (precision 0.81-1.00). From the detected screams, 64.0 % were caused by tail biting. The detector automatically analyzes the latest videos in user-defined periods and sends warning messages if a threshold of screams per hour is exceeded. Then, biters can be identified manually using the detector extracted incidence video clips. In conclusion, automatic analysis of pig screams has high potential as an early intervention tool by detecting tail biting events followed by evaluation of time synchronized video clips for biter identification.

Automated acoustic analysis is increasingly used in animal communication studies, 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, Mel-frequency cepstral coefficients, and highly comparative time-series analysis) and classification methods (discriminant function analysis, support vector machines, Gaussian mixture models, neural networks, and random forests) on the consistency of 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. ### Competing Interest Statement The authors have declared no competing interest.

Dehorning is a conservation measure used to protect rhinoceroses ('rhinos') from being poached by removing most of the visible horn and thus reducing the monetary reward for the risk that a poacher takes. Rhinos use their horns in comfort and aggressive social behaviours. The loss of the horn might result in a decrease in aggressive and affiliative behaviours and an increase in avoidance behaviours after dehorning due to a reduced effectiveness and potential discomfort when using the nasal body part. The dehorning procedure, which includes chasing and immobilization, can lead to the separation of groups and might therefore result in fewer social interactions. To estimate whether the stress of the dehorning procedure and the loss of the horn affect the activity budget of the rhino, we compared general activities and horn-related behaviours before and after dehorning. We observed nine (six females and three males) wild white rhinos (Ceratotherium simum simum) in Botswana for 1 month before and 1 month after dehorning. The proportions of feeding, resting, comfort, aggressive, avoidance and affiliative behaviours did not change significantly within 1 month after dehorning. We observed sex-specific changes in proportions of locomotion and in vocalization rates, which we linked to the chasing during the procedure and to the social events of two births in the study population. Effects of the dehorning itself seemed to be weak and short-lived. Our results suggest that dehorning has no major impact on rhino behaviour. However, there is a key need to investigate the effectiveness of dehorning in reducing poaching events.

Raw data file for the publication "Assessing the potential of conspecific playbacks as a post-translocation management tool for white rhinoceros"

Translocations can be a useful management tool to support endangered species. Translocated white rhinoceroses sometimes disperse from their release sites and leave protected areas, requiring sedation and return transport by vehicles. To avoid stressful transportation, less invasive management tools are needed to get animals back to the release site. We tested whether playbacks of white rhinoceros calls can influence their movements and thereby offer a potential management tool. We performed 200 experiments with 26 free-roaming white rhinoceroses in two reserves in Botswana and recorded response intensity and duration, including body movement toward and away from the loudspeaker in response to a socio-positive and a socio-negative call. Rhinoceroses responded more to conspecific calls than to control sounds but did not show consistent behavioral responses across all experiments per call type. Males approached the loudspeaker more often than females. The intensity of responses was higher for calls recorded from unfamiliar than from familiar callers and behavioral responses differed between reserves. Further research is necessary to develop an applicable design for a combination of playbacks that would more reliably lead to directed body movement responses.

In human infants babbling is an important developmental stage of vocal plasticity to acquire maternal language. To investigate parallels in the vocal development of human infants and non-human mammals, seven key features of human babbling were defined, which are up to date only shown in bats and marmosets. This study will explore whether these features can also be found in gray mouse lemurs by investigating how infant vocal streams gradually resemble the structure of the adult trill call, which is not present at birth. Using unsupervised clustering, we distinguished six syllable types, whose sequential order gradually reflected the adult trill. A subset of adult syllable types was produced by several infants, with the syllable production being rhythmic, repetitive, and independent of the social context. The temporal structure of the calling bouts and the tempo-spectral features of syllable types became adult-like at the age of weaning. The age-dependent changes in the acoustic parameters differed between syllable types, suggesting that they cannot solely be explained by physical maturation of the vocal apparatus. Since gray mouse lemurs exhibit five features of animal babbling, they show parallels to the vocal development of human infants, bats, and marmosets.

In mammals, common rules for the encoding of arousal and physical characteristics of the sender are suggested based on a similar vocal production apparatus. In this study, we want to investigate to what extent vocalizations of developing Mongolian gerbil pups fulfill these rules. We recorded vocalizations of 28 Mongolian gerbil pups in four developmental stages using a separation paradigm, suggested to induce different arousal levels. For low arousal, a pup was placed in an arena isolated from its siblings and parents; for high arousal, the pup was additionally stressed through the simulation of a predator. An unsupervised cluster analysis revealed three call types: ultrasonic (USV), audible vocalizations (ADV), and transitions between both (USV-ADV). The USV and USV-ADV rate showed an age-dependent decrease, contrasting an age-dependent increase for ADVs. Vocal correlates for the encoding of arousal were found for USVs and of physical characteristics for USVs and ADVs. However, the pattern of encoding these cues differed between call types and only partly confirmed the common rules suggested for mammals. Our results show that divergent encoding patterns do not only differ between species but also between call types within a species, indicating that coding rules can be shaped by socio-ecological factors or call type specific production mechanisms.