Trace and rare earth elements in phytoplankton from the Tyrrhenian Sea (Italy).

Plankton plays a very crucial role in bioaccumulation and transfer of metals in the marine food web and represents a suitable bioindicator of the occurrence of trace and rare earth elements in the ecosystem. Trace elements and REEs were analyzed by ICP-MS in phytoplankton samples from the northwestern Mediterranean Sea. Metal concentrations in phytoplankton were found strongly influenced by seasons and depth of collection (- 30 m, - 50 m). Principal component analysis (PCA) has shown that Al, As, Cr, Cu, Ga, and Sn concentrations were related to summer and autumn in samples collected at 30 m depth, while Fe, Mn, Ni, V, and Zn levels related strongly with summer and spring at 50 m depth. Fe, Al, and Zn were the most represented elements in all samples (mean values respectively in the ranges 4.2-8.2, 9.6-13, and 1.0-4.4 mg kg-1) according to their widespread presence in the environment and in the earth crust. Principal component analysis (PCA) performed on REEs showed that mostly all lanthanides' concentrations strongly correlate with summer and autumn seasons (- 30 m depth); the highest ∑REE concentration (75 µg kg-1) was found in winter. Phytoplankton REE normalized profile was comparable to those of other marine biota collected in the same area according to the suitability of lanthanides as geological tracers.

Isochrony and rhythmic interaction in ape duetting.

How did rhythm originate in humans, and other species? One cross-cultural universal, frequently found in human music, is isochrony: when note onsets repeat regularly like the ticking of a clock. Another universal consists in synchrony (e.g. when individuals coordinate their notes so that they are sung at the same time). An approach to biomusicology focuses on similarities and differences across species, trying to build phylogenies of musical traits. Here we test for the presence of, and a link between, isochrony and synchrony in a non-human animal. We focus on the songs of one of the few singing primates, the lar gibbon (Hylobates lar), extracting temporal features from their solo songs and duets. We show that another ape exhibits one rhythmic feature at the core of human musicality: isochrony. We show that an enhanced call rate overall boosts isochrony, suggesting that respiratory physiological constraints play a role in determining the song's rhythmic structure. However, call rate alone cannot explain the flexible isochrony we witness. Isochrony is plastic and modulated depending on the context of emission: gibbons are more isochronous when duetting than singing solo. We present evidence for rhythmic interaction: we find statistical causality between one individual's note onsets and the co-singer's onsets, and a higher than chance degree of synchrony in the duets. Finally, we find a sex-specific trade-off between individual isochrony and synchrony. Gibbon's plasticity for isochrony and rhythmic overlap may suggest a potential shared selective pressure for interactive vocal displays in singing primates. This pressure may have convergently shaped human and gibbon musicality while acting on a common neural primate substrate. Beyond humans, singing primates are promising models to understand how music and, specifically, a sense of rhythm originated in the primate phylogeny.

Vocal tract shape variation contributes to individual vocal identity in African penguins.

Variation in formant frequencies has been shown to affect social interactions and sexual competition in a range of avian species. Yet, the anatomical bases of this variation are poorly understood. Here, we investigated the morphological correlates of formants production in the vocal apparatus of African penguins. We modelled the geometry of the supra-syringeal vocal tract of 20 specimens to generate a population of virtual vocal tracts with varying dimensions. We then estimated the acoustic response of these virtual vocal tracts and extracted the centre frequency of the first four predicted formants. We demonstrate that: (i) variation in length and cross-sectional area of vocal tracts strongly affects the formant pattern, (ii) the tracheal region determines most of this variation, and (iii) the skeletal size of penguins does not correlate with the trachea length and consequently has relatively little effect on formants. We conclude that in African penguins, while the variation in vocal tract geometry generates variation in resonant frequencies supporting the discrimination of conspecifics, such variation does not provide information on the emitter's body size. Overall, our findings advance our understanding of the role of formant frequencies in bird vocal communication.

Penguins perceive variations of source- and filter-related vocal parameters of species-specific vocalisations.

Animal vocalisations encode a wide range of biological information about the age, sex, body size, and social status of the emitter. Moreover, vocalisations play a significant role in signalling the identity of the emitter to conspecifics. Recent studies have shown that, in the African penguin (Spheniscus demersus), acoustic cues to individual identity are encoded in the fundamental frequency (F0) and resonance frequencies (formants) of the vocal tract. However, although penguins are known to produce vocalisations where F0 and formants vary among individuals, it remains to be tested whether the receivers can perceive and use such information in the individual recognition process. In this study, using the Habituation-Dishabituation (HD) paradigm, we tested the hypothesis that penguins perceive and respond to a shift of ± 20% (corresponding to the natural inter-individual variation observed in ex-situ colonies) of F0 and formant dispersion (ΔF) of species-specific calls. We found that penguins were more likely to look rapidly and for longer at the source of the sound when F0 and formants of the calls were manipulated, indicating that they could perceive variations of these parameters in the vocal signals. Our findings provide the first experimental evidence that, in the African penguin, listeners can perceive changes in F0 and formants, which can be used by the receiver as potential cues for the individual discrimination of the emitter.

Vocal accommodation in penguins (Spheniscus demersus) as a result of social environment.

The ability to vary the characteristics of one's voice is a critical feature of human communication. Understanding whether and how animals change their calls will provide insights into the evolution of language. We asked to what extent the vocalizations of penguins, a phylogenetically distant species from those capable of explicit vocal learning, are flexible and responsive to their social environment. Using a principal components (PCs) analysis, we reduced 14 vocal parameters of penguin's contact calls to four PCs, each comprising highly correlated parameters and which can be categorized as fundamental frequency, formant frequency, frequency modulation, and amplitude modulation rate and duration. We compared how these differed between individuals with varying degrees of social interactions: same-colony versus different-colony, same colony over 3 years and partners versus non-partners. Our analyses indicate that the more penguins experience each other's calls, the more similar their calls become over time, that vocal convergence requires a long time and relative stability in colony membership, and that partners' unique social bond may affect vocal convergence differently than non-partners. Our results suggest that this implicit form of vocal plasticity is perhaps more widespread across the animal kingdom than previously thought and may be a fundamental capacity of vertebrate vocalization.

Cross-modal individual recognition in the African penguin and the effect of partnership.

An animal's ability to recognize another individual by matching their image to their voice suggests they form internal representations of other individuals. To what extent this ability, termed cross-modal individual recognition, extends to birds other than corvids is unknown. Here, we used an expectancy violation paradigm to determine whether a monogamous territorial seabird (Spheniscus demersus) can cross-modally recognize familiar conspecifics (partners or colony-mates). After pairs of penguins spent time together in an isolated area, one of the penguins was released from the area leaving the focal penguin alone. Subsequently, we played contact calls of the released penguin (congruent condition) or a different penguin (incongruent condition). After being paired with a colony-mate, focal penguins' response latency to the auditory stimulus was faster in the incongruent compared to congruent condition, indicating the mismatch violated their expectations. This behavioural pattern was not observed in focal penguins after being paired with their partner. We discuss these different results in the light of penguins' natural behaviour and the evolution of social communication strategies. Our results suggest that cross-modal individual recognition extends to penguins and reveals, in contrast with previously thought, that social communication between members of this endangered species can also use visual cues.

Long-term stability of vocal individuality cues in a territorial and monogamous seabird.

The stability of individual acoustic features is fundamental in social species, and more importantly in monogamous and territorial species, showing long-term fidelity both to the partner and the breeding site. In this study, the stability over time of two discrete vocal types was investigated in the African penguin (Spheniscus demersus), a monogamous and territorial seabird. Contact calls and ecstatic display songs were recorded from an ex situ colony in 2017 and in 2020. For each vocalisation, we measured 14 spectral and temporal acoustic parameters related to both source and filter components. Two separate leave-one-out cross-validated Discriminant Function Analyses (DFA) were then performed, generating the discriminant functions from the vocalisations collected in 2017 to classify those recorded in 2020. The DFA correctly classified 62% of the contact calls (10 subjects) and 80.9% of the ecstatic display songs (seven subjects) according to the correct emitter, showing that acoustic cues to individuality encoded in both vocal types remained unchanged over four consecutive breeding seasons. We suggest that, in this monogamous and territorial bird species, individual acoustic stability could be selected for to identify groupmates and neighbours over the years and to help couples to reunite in consecutive breeding seasons, increasing individual fitness.

Linguistic laws of brevity: conformity in Indri indri.

Vocal and gestural sequences of several primates have been found to conform to two general principles of information compression: the compensation between the duration of a construct and that of its components (Menzerath-Altmann law) and an inverse relationship between signal duration and its occurrence (Zipf's law of abbreviation). Even though Zipf's law of brevity has been proposed as a universal in animal communication, evidence on non-human primate vocal behavior conformity to linguistic laws is still debated, and information on strepsirrhine primates is lacking. We analyzed the vocal behavior of the unique singing lemur species (Indri indri) to assess whether the song of the species shows evidence for compression. As roars have a chaotic structure that impedes the recognition of each individual utterance, and long notes are usually given by males, we focused on the core part of the song (i.e., the descending phrases, composed of two-six units). Our results indicate that indris' songs conform to Zipf's and Menzerath-Altmann linguistic laws. Indeed, shorter phrases are more likely to be included in the song, and units' duration decrease at the increase of the size of the phrases. We also found that, despite a sexual dimorphism in the duration of both units and phrases, these laws characterize sequences of both males and females. Overall, we provide the first evidence for a trade-off between signal duration and occurrence in the vocal behavior of a strepsirrhine species, suggesting that selective pressures for vocal compression are more ancestral than previously assumed within primates.

Vocal production in postpartum dairy cows: Temporal organization and association with maternal and stress behaviors.

Mammalian vocalizations can encode contextual information in both the spectrographic components of their individual vocal units and in their temporal organization. Here we observed 23 Holstein-Friesian dairy cows immediately after birth during interactions with their calf and when their calf was separated to the other side of a fence line. We investigated whether the vocalizations emitted in these postpartum contexts would vary temporally. We also described the maternal and stress behaviors preceding and following postpartum vocal production using kinematic diagrams and characterized call sequence structure. The kinematic diagrams highlight the disruption of maternal responses caused by calf separation and show that behavioral and vocal patterns varied according to the cows' emotional states and proximity to the calf in both contexts. During calf interactions, cows mainly produced closed-mouth calls simultaneous to licking their calf, whereas an escalation of stress responses was observed during calf separation, with the cows approaching the fence line, becoming alert to the calf, and emitting more mixed and open-mouth calls. Call sequences were similarly structured across contexts, mostly containing repetitions of a single call type, with a mean interval of 0.57 s between calls and a greater cumulative vocalization duration, attributed to an increased number of vocal units per sequence. Overall, calf separation was associated with a greater proportion of calls emitted as a sequence (inverse of single isolated calls), a shorter interval between separate call sequences, and a greater number of vocal units per sequence, compared with calf interactions. These temporal vocal features varied predictably with the high stress expression from cows during calf separation and may represent temporal modulations of emotional expression. Despite the noisy farm soundscape, empirical call type and temporal vocal features were easy to measure; thus, findings could be applied to future cattle studies wishing to analyze vocalizations for on-farm welfare assessments.

Do penguins' vocal sequences conform to linguistic laws?

Information compression is a general principle of human language: the most frequent words are shorter in length (Zipf's Law of Brevity) and the duration of constituents decreases as the size of the linguistic construct increases (Menzerath-Altmann Law). Vocal sequences of non-human primates have been shown to conform to both these laws, suggesting information compression might be a more general principle. Here, we investigated whether display songs of the African penguin, which mediate recognition, intersexual mate choice and territorial defence, conform with these laws. Display songs are long, loud sequences combining three types of syllables. We found that the shortest type of syllable was the most frequent (with the shortest syllable being repeated stereotypically, potentially favouring signal redundancy in crowded environments). We also found that the average duration of the song's constituents was negatively correlated with the size of the song (a consequence of increasing the relative number of the shortest syllable type, rather than reducing the duration across all syllable types, thus preserving the communication of size-related information in the duration of the longest syllable type). Our results provide the first evidence for conformity to Zipf's and Menzerath-Altmann Laws in the vocal sequences of a non-primate species, indicating that these laws can coexist with selection pressures specific to the species' ecology.

Goats distinguish between positive and negative emotion-linked vocalisations.

BACKGROUND: Evidence from humans suggests that the expression of emotions can regulate social interactions and promote coordination within a group. Despite its evolutionary importance, social communication of emotions in non-human animals is still not well understood. Here, we combine behavioural and physiological measures, to determine if animals can distinguish between vocalisations linked to different emotional valences (positive and negative). Using a playback paradigm, goats were habituated to listen to a conspecific call associated with positive or negative valence (habituation phase) and were subsequently exposed to a variant of the same call type (contact call) associated with the opposite valence (dishabituation phase), followed by a final call randomly selected from the habituation phase as control (rehabituation phase). The effects of the calls on the occurrence of looking and cardiac responses in these phases were recorded and compared. RESULTS: We found that when the valence of the call variant changed, goats were more likely to look at the source of the sound, indicating that they could distinguish calls based on their valence. Heart rate was not affected by the valence of the calls played, whereas heart-rate variability tended to be higher in the habituation and rehabituation phases, when positive calls were played compared to negative ones. Together, the behavioural and physiological measures provide evidence suggesting, first, that goats are able to distinguish call variants based on their valence, and second, that goat behaviour and cardiac responses are affected by call valence. CONCLUSION: This study indicates that auditory modalities are a potent means to communicate emotions in non-human animals. These findings can contribute to our understanding of the evolution of emotion perception in non-human animals.

Molecular Genetics Unveiled Unknown Family Relationships and Hybrids in an Ex-Situ Colony of African Penguins (Spheniscus demersus).

Genealogical relationships among colony members, inbreeding status, and presence of hybrids are crucial data that can assist zoo curators in captive colony management and decision-making on relocation for reproduction. This study employed molecular markers to study a large colony (n = 56) of African Penguin hosted in an Italian biopark. A panel of 15 STRs (single tandem repeats) was selected, and genotype data were analyzed using COLONY software to determine parentage relationships and compare the existing studbook information to a pedigree built from genetic analyses. The existence of extra-pair mating and the presence of hybrids were investigated: discrepancies in kinship relationships emerged following molecular parentage analysis and 10 unknown genetic relationships were revealed. Infidelity of one member of the pair was observed in 6 cases and extra-pair copulation was assessed by genetic analysis in 2 episodes. One member of the colony was found to be a hybrid (S. demersus × S. humboldti); his progeny, derived by extra-pair copulation, was traced. Three other hidden hybrids were discovered and assessed using the identified candidate private alleles. Overall, our results demonstrate that molecular methods to confirm parentage and analyze relatedness among colony members are a valuable tool to complement studbook-based genetic management of African penguin captive populations. Because a variety of behavioral dynamics (e.g., extra-pair mating) can make observations ineffective in some species and because molecular markers outperform studbook in identifying the presence of hybrids, reliance on studbook information alone is not recommended.

Evidence suggests vocal production learning in a cross-fostered Risso's dolphin (Grampus griseus).

Vocal learning is a rare skill in mammals, and we have limited information about the contexts in which they use it. Previous studies suggested that cetaceans in general are skilled at imitating sounds, but only few species have been studied to date. To expand this investigation to another species and to investigate the possible influence of the social environment on vocal learning, we studied the whistle repertoire of a female Risso's dolphin (Grampus griseus) that was stranded at an early age and was subsequently raised in a group of bottlenose dolphins (Tursiops truncatus). We show that this cross-fostered animal produced vocal signals more akin to those of its Tursiops poolmates than those of Risso's dolphins in the wild. This is one of very few systematic cross-fostering studies in cetaceans and the first to suggest vocal production learning in the Risso's dolphin. Our findings also suggest that social experience is a major factor in the development of the vocal repertoire in this species.

Sex- and age-related variation in metal content of penguin feathers.

The presence of xenobiotics, such as metals, in ecosystems is concerning due to their durability and they pose a threat to the health and life of organisms. Moreover, mercury can biomagnify in many marine food chains and, therefore, organisms at higher trophic levels can be adversely impacted. Although feathers have been used extensively as a bio-monitoring tool, only a few studies have addressed the effect of both age and sex on metal accumulation. In this study, the concentrations of trace elements were determined in the feathers of all members of a captive colony of African Penguins (Spheniscus demersus) housed in a zoological facility in Italy. Tests were performed by inductively coupled plasma-mass spectrometry to detect aluminum, arsenic, cadmium, cobalt, chromium, copper, iron, manganese, nickel, lead, selenium, tin, vanadium, and zinc. Mercury was detected by a direct mercury analyzer. Sexing was performed by a molecular approach based on analyzing the chromo-helicase-DNA-binding1 gene, located on the sex chromosomes. Sex- and age-related differences were studied in order to investigate the different patterns of metal bioaccumulation between male and female individuals and between adults and juveniles. Juvenile females had significantly higher arsenic levels than males, while selenium levels increased significantly with age in both sexes. Penguins kept in controlled environments-given that diet and habitat are under strict control-represent a unique opportunity to determine if and how metal bioaccumulation is related to sex and age.

Polycyclic aromatic hydrocarbon levels in European catfish from the upper Po River basin.

Polycyclic aromatic hydrocarbons (PAHs) are a major concern in environmental studies as many of them have been labeled as probable carcinogens by the International Agency for Research on Cancer (IARC 1983). Due to their lipophilic properties and resistance to degradation, PAHs can accumulate in organic tissue. As a consequence, alarming concentrations of these compounds have been found in many aquatic species. The European catfish (Silurus glanis) is a top food chain predator that is considered to be a reliable bio-indicator of environmental pollution. From 2009 to 2011, 54 specimens of S. glanis were captured from four different sites covering the area of the Po River basin (Northern Italy). Fish muscles were analyzed in the laboratory to determine the levels of nine PAHs, namely naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, pyrene, benz[a]anthracene, chrysene, and benz[a]pyrene (BaP), which were detected by high-performance liquid chromatography (HPLC). The total average concentration of PAHs was 26.90 ± 49.50 ng g(-1) (min 0.60, max 275.75 ng g(-1)). Analysis showed that 9.20% of the fish muscles exceeded the maximum levels of 2 ng g(-1) set for BaP by European regulations (Commission Regulation (EC), 2006). Values measured for benz[a]pyrene ranged from 0.05 to 8.20 ng g(-1) (mean 1.07 ± 1.58 ng g(-1)). Chrysene and benz[a]anthracene, both considered potential human carcinogens (PAH2), were found at levels of 4.40 and 0.05 ng g(-1) (mean values), respectively. The highest mean concentration was recorded for anthracene (12.92 ng g(-1)), which has been recently included in the list of substances of very high concern (SVHC) as reported by the European Chemicals Agency (ECHA 1-9, 2009).

Bottlenose dolphins (Tursiops truncatus) display gaze alternation and referential communication in an impossible task.

Gaze cues play a vital role in conveying critical information about objects and locations necessary for survival, such as food sources, predators, and the attentional states of conspecific and heterospecific individuals. During referential intentional communication, the continuous alternation of gaze between a communicative partner and a specific object or point of interest attracts the partner's attention towards the target. This behaviour is considered by many as essential for understanding intentions and is thought to involve mental planning. Here, we investigated the behavioural responses of seven bottlenose dolphins (Tursiops truncatus) that were given an impossible task in the presence of two experimenters (a 'commanding experimenter' and a 'non-commanding experimenter'), whose attentional state towards the dolphins varied. We found that the dolphins spontaneously displayed gaze alternation, specifically triadic referential pointing, only when the human commanding experimenter was facing them. However, they ceased to alternate their gaze between the impossible object and the commanding experimenter when the experimenter had their back turned. Notably, the dolphins' behaviour differed from general pointing and gaze, as their triadic sequence occurred within a narrow time window. These findings suggest that the dolphins were sensitive to human attentional cues and utilized their own gaze cue (pointing) as a salient signal to attract the attention of the commanding experimenter towards a specific location.

Windy events detection in big bioacoustics datasets using a pre-trained Convolutional Neural Network.

Passive Acoustic Monitoring (PAM), which involves using autonomous record units for studying wildlife behaviour and distribution, often requires handling big acoustic datasets collected over extended periods. While these data offer invaluable insights about wildlife, their analysis can present challenges in dealing with geophonic sources. A major issue in the process of detection of target sounds is represented by wind-induced noise. This can lead to false positive detections, i.e., energy peaks due to wind gusts misclassified as biological sounds, or false negative, i.e., the wind noise masks the presence of biological sounds. Acoustic data dominated by wind noise makes the analysis of vocal activity unreliable, thus compromising the detection of target sounds and, subsequently, the interpretation of the results. Our work introduces a straightforward approach for detecting recordings affected by windy events using a pre-trained convolutional neural network. This process facilitates identifying wind-compromised data. We consider this dataset pre-processing crucial for ensuring the reliable use of PAM data. We implemented this preprocessing by leveraging YAMNet, a deep learning model for sound classification tasks. We evaluated YAMNet as-is ability to detect wind-induced noise and tested its performance in a Transfer Learning scenario by using our annotated data from the Stony Point Penguin Colony in South Africa. While the classification of YAMNet as-is achieved a precision of 0.71, and recall of 0.66, those metrics strongly improved after the training on our annotated dataset, reaching a precision of 0.91, and recall of 0.92, corresponding to a relative increment of >28 %. Our study demonstrates the promising application of YAMNet in the bioacoustics and ecoacoustics fields, addressing the need for wind-noise-free acoustic data. We released an open-access code that, combined with the efficiency and peak performance of YAMNet, can be used on standard laptops for a broad user base.

Isochronous singing in 3 crested gibbon species (Nomascus spp.).

The search for common characteristics between the musical abilities of humans and other animal species is still taking its first steps. One of the most promising aspects from a comparative point of view is the analysis of rhythmic components, which are crucial features of human communicative performance but also well-identifiable patterns in the vocal displays of other species. Therefore, the study of rhythm is becoming essential to understand the mechanisms of singing behavior and the evolution of human communication. Recent findings provided evidence that particular rhythmic structures occur in human music and some singing animal species, such as birds and rock hyraxes, but only 2 species of nonhuman primates have been investigated so far (Indri indri and Hylobates lar). Therefore, our study aims to consistently broaden the list of species studied regarding the presence of rhythmic categories. We investigated the temporal organization in the singing of 3 species of crested gibbons (Nomascus gabriellae, Nomascus leucogenys, and Nomascus siki) and found that the most prominent rhythmic category was isochrony. Moreover, we found slight variation in songs' tempo among species, with N. gabriellae and N. siki singing with a temporal pattern involving a gradually increasing tempo (a musical accelerando), and N. leucogenys with a more regular pattern. Here, we show how the prominence of a peak at the isochrony establishes itself as a shared characteristic in the small apes considered so far.

Postnatal development of echolocation abilities in a bottlenose dolphin (Tursiops truncatus): temporal organization.

In spite of all the information available on adult bottlenose dolphin (Tursiops truncatus) biosonar, the ontogeny of its echolocation abilities has been investigated very little. Earlier studies have reported that neonatal dolphins can produce both whistles and burst-pulsed sounds just after birth and that early-pulsed sounds are probably a precursor of echolocation click trains. The aim of this research is to investigate the development of echolocation signals in a captive calf, born in the facilities of the Acquario di Genova. A set of 81 impulsive sounds were collected from birth to the seventh postnatal week and six additional echolocation click trains were recorded when the dolphin was 1 year old. Moreover, behavioral observations, concurring with sound production, were carried out by means of a video camera. For each sound we measured five acoustic parameters: click train duration (CTD), number of clicks per train, minimum, maximum, and mean click repetition rate (CRR). CTD and number of clicks per train were found to increase with age. Maximum and mean CRR followed a decreasing trend with dolphin growth starting from the second postnatal week. The calf's first head scanning movement was recorded 21 days after birth. Our data suggest that in the bottlenose dolphin the early postnatal weeks are essential for the development of echolocation abilities and that the temporal features of the echolocation click trains remain relatively stable from the seventh postnatal week up to the first year of life.

Phthalate diester occurrence in marine feed and food (Mediterranean Sea).

Organic contaminants such as diesters of phthalic acid (PAEs) can be conveyed by microplastics in aquatic environment and constitute a relevant risk to marine organisms and humans that consume them. A method was developed for the identification and quantitative detection of 6 dimethyl phthalate (DMP), di-ethyl phthalate (DEP), di-n-butyl phthalate (DNBP), butyl benzyl phthalate (BBP), di-2-ethylesyl phthalate (DHEP), and di-n-octyl phthalate (DnOP). PAEs were then quantified in mesozooplankton, mollusk bivalves, and fish from the north-western Mediterranean Sea. Among all PAEs, DEHP was found in all zooplankton samples, in 30% of fish samples, and in 10% of bivalve samples. DBP was instead recovered in only 4% of samples (plankton and fish).