Individual Identity Information Research Articles

Vocal repertoire and individuality in the plains zebra (Equus quagga).

Acoustic signals are vital in animal communication, and quantifying them is fundamental for understanding animal behaviour and ecology. Vocalizations can be classified into acoustically and functionally or contextually distinct categories, but establishing these categories can be challenging. Newly developed methods, such as machine learning, can provide solutions for classification tasks. The plains zebra is known for its loud and specific vocalizations, yet limited knowledge exists on the structure and information content of its vocalzations. In this study, we employed both feature-based and spectrogram-based algorithms, incorporating supervised and unsupervised machine learning methods to enhance robustness in categorizing zebra vocalization types. Additionally, we implemented a permuted discriminant function analysis to examine the individual identity information contained in the identified vocalization types. The findings revealed at least four distinct vocalization types-the 'snort', the 'soft snort', the 'squeal' and the 'quagga quagga'-with individual differences observed mostly in snorts, and to a lesser extent in squeals. Analyses based on acoustic features outperformed those based on spectrograms, but each excelled in characterizing different vocalization types. We thus recommend the combined use of these two approaches. This study offers valuable insights into plains zebra vocalization, with implications for future comprehensive explorations in animal communication.

Individual identity information persists in learned calls of introduced parrot populations.

Animals can actively encode different types of identity information in learned communication signals, such as group membership or individual identity. The social environments in which animals interact may favor different types of information, but whether identity information conveyed in learned signals is robust or responsive to social disruption over short evolutionary timescales is not well understood. We inferred the type of identity information that was most salient in vocal signals by combining computational tools, including supervised machine learning, with a conceptual framework of "hierarchical mapping", or patterns of relative acoustic convergence across social scales. We used populations of a vocal learning species as a natural experiment to test whether the type of identity information emphasized in learned vocalizations changed in populations that experienced the social disruption of introduction into new parts of the world. We compared the social scales with the most salient identity information among native and introduced range monk parakeet (Myiopsitta monachus) calls recorded in Uruguay and the United States, respectively. We also evaluated whether the identity information emphasized in introduced range calls changed over time. To place our findings in an evolutionary context, we compared our results with another parrot species that exhibits well-established and distinctive regional vocal dialects that are consistent with signaling group identity. We found that both native and introduced range monk parakeet calls displayed the strongest convergence at the individual scale and minimal convergence within sites. We did not identify changes in the strength of acoustic convergence within sites over time in the introduced range calls. These results indicate that the individual identity information in learned vocalizations did not change over short evolutionary timescales in populations that experienced the social disruption of introduction. Our findings point to exciting new research directions about the robustness or responsiveness of communication systems over different evolutionary timescales.

QR code technology in individual identification training provides an introduction in hands-on forensic DNA genotyping to medical students

BackgroundForensic biology is a subject in the field of forensic science that stresses practical teaching and training in laboratory skills. Visualization of deoxyribonucleic acid (DNA) profiles is important in individual identification and is easily performed by well-trained examiners. Therefore, developing a novel training project for obtaining individual DNA profiles can improve the quality of teaching for medical students or trainees. DNA profiles based on quick response (QR) codes can also be applied to practical teaching and operation training for individual identification.MethodsA novel training project was developed through an experimental course in forensic biology. Blood samples and buccal swabs with oral epithelial cells, as used in the forensic DNA laboratory, were obtained from medical students at Fujian Medical University. DNA was isolated, and a number of short tandem repeat (STR) loci were used as genetic markers to generate DNA profiles. The students converted DNA profiles and individual information into a QR code. The QR code could then be scanned by a mobile phone for consulting and retrieval. Gene identity cards with QR codes were produced and provided to every student. The participation rate and passing rate of students who participated in the novel training project were calculated and compared with those of students in the traditional experimental course, and a chi-square test was carried out by SPSS 23.0 software to evaluate the teaching effectiveness. p < 0.05 indicated significant differences. In addition, a survey was conducted to investigate the likelihood of using of gene identity cards with QR codes in the future.ResultsA total of 54 of 91 medical students who studied forensic biology participated in the novel training project in 2021. Only 31 of 78 students who studied forensic biology participated in the traditional experimental course in 2020. The participation rate in the novel training project was 24% higher than that of the traditional experimental course. The participants in the novel training project showed better performance in forensic biological handling techniques. The passing rate of the students in the forensic biology course with the novel training project was approximately 17% higher than that of the students in the former course. The participation rates and passing rates of the two groups were significantly different (χ = 6.452, p = 0.008 and χ = 11.043, p = 0.001). In the novel training project, all participants made 54 gene identity cards with QR codes. Furthermore, in the DNA profiles of four African students who participated, we found two rare alleles that were not discovered in Asians. The survey showed that the use of gene identity cards with QR codes was accepted by most participants, and the likelihood of future utilization was 78%.ConclusionWe established a novel training project to promote the learning activities of medical students in experimental forensic biology courses. The participants showed great interest in using gene identity cards with QR codes to store general individual identity information and DNA profiles. They also examined the genetic population differences between different races based on DNA profiles. Hence, the novel training project could be useful for training workshops, forensic experimental courses, and medical big data research.

Chapter 17 - Proper names and personal identity

The present chapter reviews the body of knowledge acquired so far about the role of the temporal lobe in representing and processing proper names and individual identity information. This body of knowledge has been collected with the contribution of several methodologies, including neuroimaging, electrophysiological techniques, and, critically, clinical observations. All this evidence converges in showing that proper names and related information are processed in at least partially independent neural networks mainly placed in the anterior areas of the left temporal lobe. A description of the properties distinguishing proper names from common names is provided. These properties, it will be claimed, made a different anatomical organization necessary and, possibly, determined the evolution of the brain to support this advantageous distinction in meeting environmental demands.

Non-stereotyped amplitude modulation across signature whistle contours

Bottlenose dolphin signature whistles are characterized by distinctive frequency modulation over time. The stable frequency contours of these whistles broadcast individual identity information. Little is known however, about whether or not the amplitude contour is also stereotyped. Here, we examined the relative amplitude-time contour of signature whistle emissions from eight bottlenose dolphins (Tursiops truncatus) in the U.S. Navy Marine Mammal Program (MMP) in San Diego, CA. The results suggested that unlike the stable frequency-time contour, the amplitude-time contour of signature whistles were largely non-stereotyped, characterized by large variability across multiple whistle emissions. Relative amplitude was negatively related to log peak frequency, with more energy focused in the lower frequency bands. This trend was consistent over all eight dolphins despite having quite different signature whistle contours. This relationship led to the amplitude contours being slightly more stereotyped within than between dolphins. We propose that amplitude across signature whistle emissions may serve as an avenue for encoding additional communicative information. We encourage future studies to incorporate analyses of amplitude contours in addition to frequency contours of signature whistles in order to begin to understand what role it may play in the dolphin communication system.

Research on emitter individual identification technology based on Automatic Dependent Surveillance–Broadcast signal

Aiming at the shortcomings of the research on individual identification technology of emitters, which is primarily based on theoretical simulation and lack of verification equipment to conduct external field measurements, an emitter individual identification system based on Automatic Dependent Surveillance–Broadcast is designed. On one hand, the system completes the individual feature extraction of the signal preamble. On the other hand, it realizes decoding of the transmitter’s individual identity information and generates an individual recognition training data set, on which we can train the recognition network to achieve individual signal recognition. For the collected signals, six parameters were extracted as individual features. To reduce the feature dimensions, a Bessel curve fitting method is used for four of the features. The spatial distribution of the Bezier curve control points after fitting is taken as an individual feature. The processed features are classified with multiple classifiers, and the classification results are fused using the improved Dempster–Shafer evidence theory. Field measurements show that the average individual recognition accuracy of the system reaches 88.3%, which essentially meets the requirements.

Spatial capture-recapture with random thinning for unidentified encounters.

Spatial capture–recapture (SCR) models have increasingly been used as a basis for combining capture–recapture data types with variable levels of individual identity information to estimate population density and other demographic parameters. Recent examples are the unmarked SCR (or spatial count model), where no individual identities are available and spatial mark–resight (SMR) where individual identities are available for only a marked subset of the population. Currently lacking, though, is a model that allows unidentified samples to be combined with identified samples when there are no separate classes of “marked” and “unmarked” individuals and when the two sample types cannot be considered as arising from two independent observation models. This is a common scenario when using noninvasive sampling methods, for example, when analyzing data on identified and unidentified photographs or scats from the same sites.Here we describe a “random thinning” SCR model that utilizes encounters of both known and unknown identity samples using a natural mechanistic dependence between samples arising from a single observation model. Our model was fitted in a Bayesian framework using NIMBLE.We investigate the improvement in parameter estimates by including the unknown identity samples, which was notable (up to 79% more precise) in low‐density populations with a low rate of identified encounters. We then applied the random thinning SCR model to a noninvasive genetic sampling study of brown bear (Ursus arctos) density in Oriental Cantabrian Mountains (North Spain).Our model can improve density estimation for noninvasive sampling studies for low‐density populations with low rates of individual identification, by making use of available data that might otherwise be discarded.

Degrees of compositional shift in tree communities vary along a gradient of temperature change rates over one decade: Application of an individual-based temporal beta-diversity concept.

Temporal patterns in communities have gained widespread attention recently, to the extent that temporal changes in community composition are now termed “temporal beta‐diversity.” Previous studies of beta‐diversity have made use of two classes of dissimilarity indices: incidence‐based (e.g., Sørensen and Jaccard dissimilarity) and abundance‐based (e.g., Bray–Curtis and Ružička dissimilarity). However, in the context of temporal beta‐diversity, the persistence of identical individuals and turnover among other individuals within the same species over time have not been considered, despite the fact that both will affect compositional changes in communities. To address this issue, I propose new index concepts for beta‐diversity and the relative speed of compositional shifts in relation to individual turnover based on individual identity information. Individual‐based beta‐diversity indices are novel dissimilarity indices that consider individual identity information to quantitatively evaluate temporal change in individual turnover and community composition. I applied these new indices to individually tracked tree monitoring data in deciduous and evergreen broad‐leaved forests across the Japanese archipelago with the objective of quantifying the effect of climate change trends (i.e., rates of change in both annual mean temperature and annual precipitation) on individual turnover and compositional shifts at each site. A new index explored the relative contributions of mortality and recruitment processes to temporal changes in community composition. Clear patterns emerged showing that an increase in the temperature change rate facilitated the relative contribution of mortality components. The relative speed of compositional shift increased with increasing temperature change rates in deciduous forests but decreased with increasing warming rates in evergreen forests. These new concepts provide a way to identify novel and high‐resolution temporal patterns in communities.

Measuring individual identity information in animal signals: Overview and performance of available identity metrics

Abstract Identity signals have been studied for over 50 years but, and somewhat remarkably, there is no consensus as to how to quantify individuality in animal signals. While there is a variety of different metrics to quantify individuality, these methods remain un‐validated and the relationships between them unclear. We contrasted three univariate and four multivariate identity metrics (and their different computational variants) and evaluated their performance on simulated and empirical datasets. Of the metrics examined, Beecher's information statistic (HS) performed closest to theoretical expectations and requirements for an ideal identity metric. It could be also easily and reliably converted into the commonly used discrimination score (and vice versa). Although Beecher's information statistic is not entirely independent of study sampling, this problem can be considerably lessened by reducing the number of parameters or by increasing the number of individuals in the analysis. Because it is easily calculated, has superior performance, can be used to quantify identity information in single variable or in a complete signal and because it indicates the number of individuals who can be discriminated given a set of measurements, we recommend that individuality should be quantified using Beecher's information statistic in future studies. Consistent use of Beecher's information statistic could enable meaningful comparisons and integration of results across different studies of individual identity signals.

Identification of potential signature whistles from free-ranging common dolphins (Delphinus delphis) in South Africa

Conveying identity is important for social animals to maintain individually based relationships. Communication of identity information relies on both signal encoding and perception. Several delphinid species use individually distinctive signature whistles to transmit identity information, best described for the common bottlenose dolphin (Tursiops truncatus). In this study, we investigate signature whistle use in wild common dolphins (Delphinus delphis). Acoustic recordings were analysed from 11 encounters from three locations in South Africa (Hout Bay, False Bay, and Plettenberg Bay) during 2009, 2016 and 2017. The frequency contours of whistles were visually categorised, with 29 signature whistle types (SWTs) identified through contour categorisation and a bout analysis approach developed specifically to identify signature whistles in bottlenose dolphins (SIGID). Categorisation verification was conducted using an unsupervised neural network (ARTwarp) at both a 91% and 96% vigilance parameter. For this, individual SWTs were analysed type by type and then in a 'global' analysis whereby all 497 whistle contours were categorised simultaneously. Overall the analysis demonstrated high stereotypy in the structure and temporal production of whistles, consistent with signature whistle use. We suggest that individual identity information may be encoded in these whistle contours. However, the large group sizes and high degree of vocal activity characteristic of this dolphin species generate a cluttered acoustic environment with high potential for masking from conspecific vocalisations. Therefore, further investigation into the mechanisms of identity perception in such acoustically cluttered environments is required to demonstrate the function of these stereotyped whistle types in common dolphins.

Multimodal mother–offspring recognition: the relative importance of sensory cues in a colonial mammal

Animals often employ multiple sensory modalities for communication and recognition; however, the combination of sensory cues used by individuals in given contexts will vary. Although mother–offspring recognition has been widely investigated and is known to be a multimodal process in gregarious mammal species, there is a dearth of information about the interactions between various sensory cues. Here we show how acoustic, olfactory and visual cues are used in a synergistic way in Australian sea lion, Neophoca cinerea, mother–offspring recognition. We interpret the results using a cost–benefit perspective to disentangle the evolutionary pressures on each component of this communication system. Although olfactory cues can convey individual identity information it was their presence, not their congruency, that prompted female sniffs. We found that calls needed to be from the female's own pup for the identification process to be successful, with the information encoded in acoustic cues overriding that of olfactory cues. Despite each sensory cue accurately conveying identity information when presented in isolation, in a multimodal setting their importance, function or role may change and seems to be driven by the costs and benefits of obtaining information resulting from the constraints imposed by the active space of cues.

Vocal individuality and species divergence in the contact calls of banded penguins

Penguins produce contact calls to maintain social relationships and group cohesion. Such vocalisations have recently been demonstrated to encode individual identity information in the African penguin. Using a source-filter theory approach, we investigated whether acoustic cues of individuality can also be found in other Spheniscus penguins and the acoustic features of contact calls have diverged within this genus. We recorded vocalisations from two ex-situ colonies of Humboldt penguin and Magellanic penguin (sympatric and potentially interbreeding in the wild) and one ex-situ group of African penguins (allopatric although capable of interbreeding with the other two species in captivity). We measured 14 acoustic parameters from each vocalisation. These included temporal (duration), source-related (fundamental frequency, f0), and filter-related (formants) parameters. They were then used to carry out a series of stepwise discriminant function analyses (with cross-validation) and General Linear Model comparisons. We showed that contact calls allow individual discrimination in two additional species of the genus Spheniscus. We also found that calls can be classified according to species in a manner far greater than that attributable by chance, even though there is limited genetic distance among African, Humboldt, and Magellanic penguins. Our results provide further evidence that the source-filter theory is a valuable framework for investigating the biologically meaningful information contained in bird vocalisations. Our findings also provide novel insights into penguin vocal communication and suggest that contact calls of the penguin family are affected by selection for individuality.

Vocal individuality cues in the African penguin (Spheniscus demersus): a source-filter theory approach.

The African penguin is a nesting seabird endemic to southern Africa. In penguins of the genus Spheniscus vocalisations are important for social recognition. However, it is not clear which acoustic features of calls can encode individual identity information. We recorded contact calls and ecstatic display songs of 12 adult birds from a captive colony. For each vocalisation, we measured 31 spectral and temporal acoustic parameters related to both source and filter components of calls. For each parameter, we calculated the Potential of Individual Coding (PIC). The acoustic parameters showing PIC ≥ 1.1 were used to perform a stepwise cross-validated discriminant function analysis (DFA). The DFA correctly classified 66.1% of the contact calls and 62.5% of display songs to the correct individual. The DFA also resulted in the further selection of 10 acoustic features for contact calls and 9 for display songs that were important for vocal individuality. Our results suggest that studying the anatomical constraints that influence nesting penguin vocalisations from a source-filter perspective, can lead to a much better understanding of the acoustic cues of individuality contained in their calls. This approach could be further extended to study and understand vocal communication in other bird species.

Specialized visual learning of facial signals of quality in the paper wasp,Polistes dominula

Some primates and one species of paper wasp recognize faces using specific processing strategies to extract individual identity information from conspecific faces. Explanations for the evolution of face specialization typically focus on the complexity associated with individual recognition because all currently identified species with face specialization use faces for individual recognition. In the present study, we show an independent evolution of face specialization in a paper wasp species with facial patterns that signal quality rather than individual identity. Quality signals are simpler to process than individual identity signals because quality signals do not require simultaneous integration across multiple stimuli or learning and memory. Therefore, the results of the present study suggest that the complexity of processing may not be the key factor favouring the evolution of specialization. Instead, the predictable location of socially important signals relative to other anatomical features may allow easy categorization of features, thereby favouring specialized visual processing. Given that visual quality signals are found in many taxa, specific-processing mechanisms for social signals may be widespread.

The Encoding of Individual Identity in Dolphin Signature Whistles: How Much Information Is Needed?

Bottlenose dolphins (Tursiops truncatus) produce many vocalisations, including whistles that are unique to the individual producing them. Such “signature whistles” play a role in individual recognition and maintaining group integrity. Previous work has shown that humans can successfully group the spectrographic representations of signature whistles according to the individual dolphins that produced them. However, attempts at using mathematical algorithms to perform a similar task have been less successful. A greater understanding of the encoding of identity information in signature whistles is important for assessing similarity of whistles and thus social influences on the development of these learned calls. We re-examined 400 signature whistles from 20 individual dolphins used in a previous study, and tested the performance of new mathematical algorithms. We compared the measure used in the original study (correlation matrix of evenly sampled frequency measurements) to one used in several previous studies (similarity matrix of time-warped whistles), and to a new algorithm based on the Parsons code, used in music retrieval databases. The Parsons code records the direction of frequency change at each time step, and is effective at capturing human perception of music. We analysed similarity matrices from each of these three techniques, as well as a random control, by unsupervised clustering using three separate techniques: k-means clustering, hierarchical clustering, and an adaptive resonance theory neural network. For each of the three clustering techniques, a seven-level Parsons algorithm provided better clustering than the correlation and dynamic time warping algorithms, and was closer to the near-perfect visual categorisations of human judges. Thus, the Parsons code captures much of the individual identity information present in signature whistles, and may prove useful in studies requiring quantification of whistle similarity.

Female song in black-capped chickadees (Poecile atricapillus): Acoustic song features that contain individual identity information and sex differences

In temperate songbirds, song has traditionally been considered a vocalization mainly produced by males. However, in many temperate species, it is now recognized that both males and females produce song. The function and structure of male black-capped chickadee (Poecile atricapillus) fee-bee song have been well-studied, but female song, although briefly described in some field reports, has not often been quantitatively examined. We recorded spontaneous fee-bee songs produced by wild-caught male and female adult black-capped chickadees housed in captivity and used bioacoustic analyses to examine seven acoustic features in the songs. Using potential for individual coding and discriminant function analyses, we found that songs were individually distinctive. Using additional discriminant function analyses, we found that songs could be correctly classified based on sex of the producer. Specifically, our results indicate that the frequency decrease within the fee note (i.e., fee glissando) varies between the songs produced by males and females and this suggests that the fee glissando may be used as a sex identifier. While this study provides a quantitative description of the acoustic structure of female song, the development, perception and function of female song in this species requires further examination.

Sound transmission at ground level in a short-grass prairie habitat and its implications for long-range communication in the swift fox Vulpes velox

The acoustic environment of swift foxes Vulpes velox vocalizing close to the ground and the effect of propagation on individual identity information in vocalizations were quantified in a transmission experiment in prairie habitat. Sounds were propagated (0.45 m above the ground) at distances up to 400 m. Effects of transmission were measured on three sound types: synthesized sweeps with 1.3 kHz bandwidths spanning in the range of 0.3-8.0 kHz; single elements of swift fox barking sequences (frequency range of 0.3-4.0 kHz) and complete barking sequences. Synthesized sweeps spanning 0.3-1.6 and 1.2-2.5 kHz propagated the furthest and the latter sweeps exhibited the best transmission properties for long-range propagation. Swift fox barking sequence elements are centered toward the lower end of this frequency range. Nevertheless, measurable individual spectral characteristics of the barking sequence seem to persist to at least 400 m. Individual temporal features were very consistent to at least 400 m. The communication range of the barking sequences is likely to be farther than 400 m and it should be considered a long-ranging vocalization. However, relative to the large home ranges of swift foxes (up to 16 km(2) in the experimental area) the barking sequence probably functions at intermediate distances.

The information in scent over-marks of golden hamsters

Abstract. Although scent over-marking is a commonly observed behaviour among mammals, it has received little experimental attention. With regard to individual signatures, there are three types of information that might be obtained from such marks: (1) the scents might blend, thus creating a new odour quality but sacrificing individually distinctive information, (2) the scents might remain distinct, preserving individual identity information, or (3) the scent on top could mask the individual identity information in the bottom scent. These three possibilities were tested in golden hamsters for two scents (flank gland and vaginal secretions) that are deposited by hamsters using two distinct patterns of scent-marking behaviour. In an habituation paradigm, test animals were exposed on five successive trials to a simulated over-mark in which the scent from one individual was placed on top of scent from another individual. On the sixth (test) trial, males were exposed to two separate scents, one from a novel individual and the other from the individual that provided either the top or the bottom scent during the habituation trials. Results on the test trial were similar for both vaginal secretions (experiment 1) and flank gland scent (experiment 2). The novel scent was investigated more than the top scent, indicating that the top scent was familiar to the males, but the bottom scent and the novel scent were investigated equally, indicating that the bottom scent was not familiar. These results suggest that the distinctive information in the bottom scent was masked by that of the top scent; furthermore, they show that the other two possible phenomena (scents blending or remaining distinct) did not occur. This demonstration of scent masking may well be the first reported to date. The possible significance of over-marking in hamsters and other species is discussed, and it is suggested that the precision and thoroughness of covering one scent with another may relate to species differences in the information available in over-marks and therefore in the functions that such marks serve.