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

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.Grant NCN 2015/19/P/NZ8/0250

Acoustic communication of selected mammals and birds: identification of vocal categories and individuals

2 Summary Identification of vocal categories (e.g. call types, individuals, species) is a key task when we want to classify animal sounds. Same calls, especially broadband acoustic signals with varying frequency and amplitude modulation present problem for classification, because their energy is spread over a wide range of frequencies. In these sounds is difficult to decide which acoustical parameter to measure. To analyse complex vocalizations I applied a multiparametric method with using both temporal and spectral parameters. The most useful variables were variables describing distribution of the spectral energy. Frequency parameters were also useful in the case of tonal calls. I described vocal repertoire of Northern white rhinoceros and Bactrian camel. Both animals have low-frequency calls in their repertoire close to infrasound range, but it is evident that these signals are not used for long-distance communication. It seems that low-frequency components of their sounds are by product of their large body size. Growling sounds of camels are also interesting by their cohesive function, in contrast to growling sounds of rhinos and other mammals where such as calls are produced during aggressive interactions. I examined whether individual identity might be also encoded in very simple song types in...12 Souhrn Identifikace hlasových kategorií ať již se jedná o různé typy hlasu, individua, druhy, či jiné kategorie, je základním úkolem majícím za cíl jakoukoli klasifikaci hlasů živočichů. Některé hlasy, zvláště frekvenčně širokospektré signály obsahující variabilní frekvevenční i amplitudní modulace pak představují při klasifikaci problém. Akustická energie je v jejich případě rozprostřena napříč široké spektrum frekvencí, v důsledku čehož jsou signály nejasně ohraničeny. V těchto případech je pak obtížné rozhodnout, které parametry měřit. Pro analýzu takto komplexních vokalizací jsem použil mnohorozměrné metody zahrnující časové i spektrální parametry. Nejpřínosnější proměnné byly parametry popisující distribuci spektrální energie. Frekvenční parametry byly však také užitečné v případě tónických hlasů. Popsal jsem hlasový repertoár severního poddruhu nosorožce širokohubého a velblouda dvouhrbého. Jmenovaní savci měli ve svém repertoáru nízkofrekvenční hlasy zasahující do infrazvukové hladiny. Je ale zřejmé, že tyto nejsou využívány pro komunikaci na dlouhou vzdálenost. Zdá se že se v tomto případě jedná o vedlejší efekt velikosti těla. Zajímavé je, že vrčivé hlasy velbloudů jsou využívány v kohezivním kontextu. Tento typ hlasů většinou totiž doprovází agresivní interakce ať již se jedná o nosorožce nebo...Department of ZoologyKatedra zoologieFaculty of SciencePřírodovědecká fakult

Acoustic communication of selected mammals and birds: identification of vocal categories and individuals

2 Summary Identification of vocal categories (e.g. call types, individuals, species) is a key task when we want to classify animal sounds. Same calls, especially broadband acoustic signals with varying frequency and amplitude modulation present problem for classification, because their energy is spread over a wide range of frequencies. In these sounds is difficult to decide which acoustical parameter to measure. To analyse complex vocalizations I applied a multiparametric method with using both temporal and spectral parameters. The most useful variables were variables describing distribution of the spectral energy. Frequency parameters were also useful in the case of tonal calls. I described vocal repertoire of Northern white rhinoceros and Bactrian camel. Both animals have low-frequency calls in their repertoire close to infrasound range, but it is evident that these signals are not used for long-distance communication. It seems that low-frequency components of their sounds are by product of their large body size. Growling sounds of camels are also interesting by their cohesive function, in contrast to growling sounds of rhinos and other mammals where such as calls are produced during aggressive interactions. I examined whether individual identity might be also encoded in very simple song types in..

Individual and Geographic Variation in Non-Harmonic Phases of Male Capercaillie (<i>Tetrao urogallus</i>) Song

Individually distinct acoustic signals, produced mainly as tonal and harmonic sounds, have been recorded in many species; however, non-tonal ‘noisy’ signals have received little attention or have not been studied in detail. The capercaillies (Tetrao urogallus) produce complex courtship songs composed of non-tonal noisy signals in four discrete phases. We analyzed recordings from 24 captive male capercaillies in breeding centres in the Czech Republic, Poland, and Germany, and songs from wild males in Sweden, Norway, Finland, and Estonia to test whether a non-harmonic song can encode individual-specific information. We also analyzed the intra-population variation of the male song from three separate areas: Carpathian (Polish and Czech Beskid), Sumava, and Boreal (boreal range of species distribution). Temporal and frequency characteristics can reliably distinguish capercaillies at the individual level (91.7%). DFA model testing geographic variation assigned 91% of songs to the correct area (Carpathian, Sumava, Boreal). The cluster analysis revealed that males from the Boreal area formed a distinct cluster. Our analysis shows clear geographical patterns among our study males and may provide a valuable marker for identifying inter-population dynamics and could help to characterize the evolutionary histories of wood grouse. We discuss the potential use of this marker as a non-invasive monitoring tool for captive and free-roaming capercaillies

Comparative analysis of long-range calls in equid stallions (Equidae): Are acoustic parameters related to social organization?

Evolution of long-distance communication in equids may correspond with species-specific types of social organization. To compare harem-forming species (type I) with those that do not establish permanent social units (type II), we conducted a comparative analysis of stallion long-range calls in seven species/breeds of equids: two breeds of domestic horses (archaic and modern breeds) and five wild species: Przewalski’s horse, kiang, Somalian ass, Grevy’s zebra, Grant’s zebra). Acoustic features allowed assigning calls of stallions with 92% average classification  success to the correct species. The duration of the call clearly separated horses (type I) from type II species: kiang, Somalian ass and Grevy’s zebra. Accordingly to its harem social system (type I), the pattern of long-range call in Grant’s zebra deviates from that of its relatives in the direction of horses. Frequency of the first dominant band that was associated with body size separated modern horses from the archaic breed and Przewalski’s horse. Playback experiments confirmed that equids, especially the type II species, respond strongly to conspecific calls but also to calls of other equids.Key words: Equus, equids, calls, acoustic communication, social system

Vocal individuality in pant calls of northern white rhinos recorded in various social contexts.

<p>The plot shows the first two canonical discriminant functions with the centroid values of pant calls for each animal. 1 = Fatu, 2 = Nabiré, 3 = Nájin, 4 = Nesárí, 5 = Súdán, 6 = Suni.</p

Acoustic Repertoire of the Philippine Tarsier ( Tarsius syrichta fraterculus

We present the spectrographic description of the vocal repertoire of the Philippine tarsier (Tarsius syrichta fraterculus), a solitary living nocturnal primate for which a very limited information about acoustic communication exists to date. The majority of vocalizations were performed around sunset and, less frequently, at sunrise. We identified eight call types. Five calls recorded during communication between adults included three long-distance calls—loud call, smack-whistle, and whistle—then a soft locust-like chirp and a bird-like trill. Two other calls—cheep and twitter—were recorded during mother-infant communication. One distress call was emitted by adults during handling. All calls were performed in the 9752 Hz to more than 22 kHz frequency range. This study provides the first evidence of individual variation in the long-distance calls performed by tarsiers. Moreover, our study provides a basis for future comparison within as well as between tarsier species taxonomy. Bioacoustic methods can be used in monitoring of these cryptic species and determining their distribution range. Thus, bioacoustic studies can help to improve conservation strategies of different population/species

Contact Calls of the Northern and Southern White Rhinoceros Allow for Individual and Species Identification

<div><p>Inter-individual relationships particularly in socially living mammals often require a well-developed communication system. Vocal and olfactory signals are the most important for the communication of rhinos, however, their vocal communication has been investigated to a very limited extent so far. White rhinos have the most developed social system out of all the rhinoceros species and vocal signals might therefore play an important role in their social interactions. We recorded repetitive contact pant calls from six captive northern white rhinos (<i>Ceratotherium cottoni</i>) and 14 captive and free-ranging southern white rhinos (<i>Ceratotherium simum</i>) and examined if they transmit information about individual identity, species, social context and age class. Discriminant analyses revealed that a high percentage of the pant calls of both species could be classified to a correct individual. We calculated signature information capacity of pant calls recorded from adult animals in isolation at 3.19 bits for the northern white rhinos and at 3.15 bits for the southern white rhinos, which can potentially allow for a vocal discrimination of nine individuals of both species. We found that pant calls varied by species. Northern white rhinos had longer calls and also differed from the southern white rhinos in several frequency parameters of their calls. We also analysed the pant calls of southern white rhinos for the differences between the age classes and between social contexts in which they were recorded. Our results show that pant calls carry information about individual, species, age class and context. The ability to recognize this information would allow rhinos, in addition to olfactory cues, to communicate with highly increased accuracy. A better understanding of communication of white rhinos has potential practical use in their management and conservation particularly because of the low breeding success of white rhinos in captivity.</p></div

DFA structure matrices for northern and southern white rhinos showing pooled within group correlations between discriminating variables and standardized canonical discriminant functions with Eigenvalues>1.

<p>Only correlations≥0.35 are shown. Eigenvalue and percentage of variance explained by each discriminant function are also shown. The DFA 1 included calls of all the northern white rhinos recorded in various contexts, DFA 3 included calls of all the southern white rhinos recorded in various contexts. I = variable measured in inhalation, E = variable measured in exhalation.</p