Article

Individual acoustic identification as a non-invasive conservation tool: An approach to the conservation of the African wild dog Lycaon pictus (Temminck, 1820)

Authors:
To read the full-text of this research, you can request a copy directly from the author.

Abstract

Individual variation in acoustic signals can be used for discrimination or identification purposes as a valuable supplement to radio-tagging and visual recognition. In this study, 721 hoo-calls from captive and free-ranging African wild dogs Lycaon pictus (n=9) were investigated for individual acoustic cues. The investigation applied a computer-aided sound analysis that allowed measurement of 93 parameters for each hoo-call. Discriminant function analyses demonstrated that the individuals differed in their call parameters primarily measured on the fundamental frequency. Additional discriminant analyses were run in order to find out if individuals can be re-identified once their hoo-calls are recorded and catalogued into a voice library. This procedure yielded an overall 67% correct assignment for the test data (ranging from 37% to 98% per individual), suggesting an above chance level re-recognition of individuals. The results establish the capability of re-identifying wild dogs using specific acoustic characteristics of their hoo-call, and suggest that this technique can be a useful tool in conserving this highly endangered species.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the author.

... Such methods are commonly applied to vocal studies (e.g. Fischer et al. 2001;Darden et al. 2003;Range & Fischer 2004;Hartwig 2005;Terry et al. 2005;Mitchell et al. 2006) including perrisodactyls (Przewalski's horse: Karadños et al. 2009;white rhino: Policht et al. 2008). ...
... Resulting spectrograms were consequently analysed with LMA 2008 software package (developed by K. Hammerschmidt). We used a set of 19 frequency and temporal parameters that measure the statistical distribution of the frequency amplitudes in the spectrum (see Schrader & Hammerschmidt 1997;Fischer et al. 2001;Hartwig 2005). Such parameters are useful for categorization of complex noisy sounds and some of them have previously been shown to reflect body size, sex, context (including type of predator) and individual identity of the caller (e.g. ...
... Such parameters are useful for categorization of complex noisy sounds and some of them have previously been shown to reflect body size, sex, context (including type of predator) and individual identity of the caller (e.g. chacma baboon, Fischer et al. 2001; sooty mangabey, Range & Fischer 2004; African wild dog, Hartwig 2005). These parameters were: Q1END (end frequency 1st DFA-distribution of frequency amplitude), Q1MAX (location of the maximum frequency 1st DFA), Q1MED (median frequency 1st DFA), Q2END (end frequency 2nd DFA), Q2MALOC (location of the maximum frequency 2nd DFA), Q3MAX (maximum frequency 3rd DFA), Q3MED (median frequency 3rd DFA), DF1MAX (maximum frequency 1st DFA), DF1MED (median frequency 1st DFA), DF1-CHFRE (number of changes between original and floating average curve local modulation-LM1st DF), DF1CHMEA (mean deviation LM1st DF), DF1CHMAX (maximum deviation LM1st DF), DF1PR (% of time segments where a 1st DF could be found), DF1MALOC (location of the maximum frequency 1st DFA), DF1MTR (maximum deviation between 1st DF and linear trend), DF2MAX (maximum frequency 2nd DFA), RANMIN (minimum frequency range), PFST (start peak frequency) and PFMALOC (location of the maximum peak frequency). ...
Article
Full-text available
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.
... Individual identification is valuable in direct monitoring and particularly important for calibrating indirect monitoring methods (such as counting tracks or nests,). Artificial markings such as numbered leg bands or fin tags are widely used for individual identification; however, artificial tagging is laborious, often expensive, and may disrupt the animals' behaviour, physiology, and habitat (Pennycuick & Rudnai 1970; Hare 1994; Baptista & Gaunt 1997; McGregor, Peake & Gilbert 2000 2005; Cattet et al. 2008 ), so the use of naturally-occurring signatures is often desirable. Noninvasive individual identification , using natural signatures, can circumvent some costs associated with artificial tagging (Baptista & Gaunt 1997; Lubow & Ransom 2009). ...
... The most popular method is discriminant function analysis (DFA, McGregor, Peake & Gilbert 2000). (For examples of use, see Gilbert, McGregor & Tyler 1994; Jones & Smith 1997; Peake et al. 1998; Galeotti & Sacchi 2001; Hartwig 2005; Holschuh & Otter 2005; Tripp & Otter 2006;.) The DFA techniques determine the success of classifying samples within a known set and allow assessment of whether a signature trait is individually distinctive (McGregor, Peake & Gilbert 2000 ). ...
Article
Full-text available
1. Common ecological tasks, such as wildlife monitoring, adaptive management, and behavioural study, often make use of natural signatures (e.g. animal calls or visual markings) to identify individual animals noninvasively. However, there is no accepted method for pre-screening candidate natural signatures to select which signatures are the best-suited for this purpose. In this paper, we suggest a pre-screening checklist and focus on the challenge of assessing a candidate signature’s individuality.
... For example, in the context of territoriality, identifying a call from a neighbouring animal in their usual location will likely elicit a different response to that of an unfamiliar animal (McGregor 1993). Several studies on terrestrial mammals such as elephants (Loxodonta africana; Clemins et al. 2005), orangutans (Pongo pygmaeua wurmbii; Spillmann et al. 2017), tigers (Panthera tigris; Ji et al. 2013) wild dogs (Lycaon pictus; Hartwig 2005) and wolves (Canis lupus lycaon; Root-Gutteridge et al. 2013) have shown that certain elements of vocal signals are unique to individuals and may convey information relating to caller identity. The production of these unique call features is likely related to small variations in the morphology of the vocal apparatus between individuals (Fitch et al. 1997;Ey et al. 2007). ...
... Automation would facilitate longer term or even continuous surveys and significantly reduce the number of man-hours required for data management; a challenge that is inherent to camera trapping when individuals need to be manually identified. Hartwig (2005) highlighted the value of individual vocal identification of African wild dogs as a supplement to radio telemetry and visual recognition. Similarly, one of the primary benefits of acoustic monitoring of lions would be its facilitation of collar-free tracking which is likely to provide movement information for a greater number of individuals at lower cost compared to animal-borne systems. ...
Article
Previous research has shown that African lions (Panthera leo) have the ability to discriminate between conspecific vocalisations, but little is known about how individual identity is conveyed in the spectral structure of roars. Using acoustic – accelerometer biologgers that allow vocalisations to be reliably associated with individual identity, we test for vocal individuality in the fundamental frequency (f0) of roars from 5 male lions, firstly by comparing simple f0 summary features and secondly by modelling the temporal pattern of the f0 contour. We then assess the application of this method for discriminating between individuals using passive acoustic monitoring. Results indicate that f0 summary features only allow for vocal discrimination with 70.7% accuracy. By comparison, vocal discrimination can be achieved with an accuracy of 91.5% based on individual differences in the temporal pattern of the f0 sequence. We further demonstrate that passively recorded lion roars can be localised and differentiated with similar accuracy. The existence of individually unique f0 contours in lion roars and their relatively lower attenuation indicates a likely mechanism enabling individual lions to identify conspecifics over long distances. These differences can be exploited by researchers to track individuals across the landscape and thereby supplement conventional lion monitoring approaches.
... Calls that are highly stereotyped within individuals, but highly variable among individuals at the same time, have been reported for many mammalian taxa, including insectivores (Schneiderová and Zouhar, 2014), bats (Gillam and Chaverri, 2012), rodents (Matrosova et al., 2011), lagomorphs (Conner, 1985), carnivores (Frommolt et al., 2003;Volodina et al., 2006;Palacios et al., 2007;Smirnova et al., 2016), pinnipeds (Phillips and Stirling, 2000;Charrier et al., 2002Charrier et al., , 2010, ungulates (Vannoni and McElligott, 2007;Volodin et al., 2011;Sibiryakova et al., 2015), cetaceans (Janik et al., 2006), primates (Zimmermann and Lerch, 1993;Mitani et al., 1996;Ceugniet and Izumi, 2004), hyraxes (Koren and Geffen, 2011) and manatees (Sousa-Lima et al., 2002). Individual signatures may promote reliable vocal recognition between mother and offspring (Terrazas et al., 2003;Torriani et al., 2006;Charrier et al., 2010;Briefer and McElligott, 2011;Knörnschild et al., 2013;Sibiryakova et al., 2015), breeding mates (Zimmermann and Lerch, 1993;Reby et al., 2006;Russ and Racey, 2007), members of social groups (Mitani et al., 1996;Hartwig, 2005;Janik et al., 2006;Volodina et al., 2006;Gillam and Chaverri, 2012) and neighbours (Conner, 1985;Frommolt et al., 2003). In colonially living grounddwelling sciurids, individually distinctive alarm calls allow colony members to estimate the degree of danger by associating individual identity with the caller's past reliability as an alarm signaler (Hare and Atkins, 2001;Sloan and Hare, 2008;Matrosova et al., 2009;Thompson and Hare, 2010). ...
... Individual signatures may also have important applications in management and conservation since they allow the non-invasive discrimination and http://dx.doi.org/10.1016/j.beproc.2017.02.014 0376-6357/© 2017 Elsevier B.V. All rights reserved. monitoring of individuals (Butynski et al., 1992;Darden et al., 2003;Hartwig, 2005;Terry et al., 2005). ...
... ). Calls can be recorded from a distance, obviating the need for physical or visual contact. Call recordings have been used to individually monitor or census a wide variety of birds and mammals (e.g., African wild dogs(Hartwig 2005), titi monkeys, kingfishers(Saunders & Wooller 1988), owls(Galeotti & Sacchi 2001;Holschuh & Otter 2005;Tripp & Otter 2006), and corncrakes(Terry et al. 2001)). While it is important to assess the usefulness of any natural marker (visual, acoustic, genetic, etc.) before employing it in noninvasive individual monitoring, it is especially vital with acoustic signatures, which may have substantial within-individual variability(Gilbert et al. 1994;Jones & Smith 1997;Holschuh & Otter 2005). ...
... The most popular method is discriminant function analysis(DFA, McGregor et al. 2000). (For examples of use, seeGilbert et al. 1994;Jones & Smith 1997;Peake et al. 1998;Galeotti & Sacchi 2001;Hartwig 2005;Holschuh & Otter 2005;Tripp & Otter 2006.) The DFA techniques determine the success of classifying samples within a known set and allow assessment of whether a signature trait is individually distinctive. ...
Thesis
Full-text available
Animals vary dramatically in their sociality; social groups differ in size, cohesiveness, and complexity. Why this is so is one of the greatest mysteries in behavioral biology. Researchers have proposed a variety of ecological and life history factors that lead to, or arise from, these differences in sociality. In my dissertation, I focus on two comparatively under-explored factors: time allocation and individuality. How animals allocate their limited daily time to different activities is influenced by sociality in complex ways. Time budgeting requirements can thus permit or constrain evolutionary changes in social group size. Similarly, social behavior is influenced by animals’ ability to discriminate other individuals; levels of individuality may thus permit or constrain changes in social group size. I address these questions in a comparative context, looking for broad patterns across multiple species. Using 50 species of diurnal primates, I tested eight hypotheses relating time allocation to social group size. I found that resting time was negatively related to group size. This suggests daily time is an important resource whose use is affected by sociality and that resting time restrictions may constrain social group size. For individuality, I used acoustic analysis and information theoretic measures to quantify vocal individuality in alarm calls. I used computer models to uncover benefits of individuality and found that receivers increase their fitness by attending to the reliability of individual signallers. I furthermore described how individuality metrics can aid ecological research and conservation. Testing across 8 species of ground-dwelling sciurid rodents, I found a strong positive relationship between individuality and social group size, suggesting that large groups generate selective pressure for increased individuality and that increased individuality may permit the formation of larger social groups. Results indicate that two previously understudied factors, time allocation and individuality, are important in the evolution of sociality. These factors warrant inclusion in sociality models and are key to our understanding of how and why sociality evolves.
... In fact, the absence of within-family similarity in the acoustic structure of alarm calls has been demonstrated in the Yellow Ground Squirrel Spermophilus fulvus (Matrosova et al. 2008). Second, the application of individually distinct vocalizations in subsequent research requires that these individual differences persist over time and thus allow the identification of individuals after some period has passed (Hartwig 2005). Matrosova et al. (2009) published the first study about the temporal stability of alarm calls in ground squirrels, specifically the Speckled Ground Squirrel. ...
... Moreover, the species shows low genetic variability, and we can thus expect interest in ensuring its conservation to increase 40 ( Gündüz et al. 2007). An alternative and non-invasive bioacoustic method could occasionally replace methods based on the capturing of animals, which might be especially desirable when focusing on highly endangered species (Hartwig 2005). ...
Article
Full-text available
Vocalizations of many mammalian species have been reported to encode information about caller identity. In this study, we analyzed 300 alarm calls from 10 free-living European Ground Squirrels Spermophilus citellus (30 per individual) and 300 alarm calls from 10 free-living Taurus Ground Squirrels S. taurensis (30 per individual), and tested the potential of these calls to encode information about the callers' identities. Discriminant analysis including all 10 European Ground Squirrel individuals correctly classified 98% of calls, and cross-validation reached a classification success of 97%. Correct classification of 98% and cross-validation of 98% was assigned when the analysis included only those individuals producing calls consisting of both elements (eight individuals). For the Taurus Ground Squirrel, correct classification was 95% and cross-validation 94% for all 10 animals. When only those individuals producing calls consisting of both elements were included (eight individuals), discriminant analysis led to 94% correct classification and cross-validation produced a classification success of 93%. These analyses demonstrate that the structure of alarm calls in these two closely related species is highly variable and that it has significant potential to encode information about caller identity.
... In captivity, individual wolves can be recognized by the characteristics of their howling (TOOZE et al. 1990;PALACIOS et al. 2007) and the fundamental frequency was found to be the most effective variable to distinguish individuals (TOOZE et al. 1990). Individual vocal features have been recognized in a large variety of taxa, from birds (PEAKE et al. 1999) to several mammalian species, including canids (DURBIN 1998;DARDEN et al. 2003;FROMMOLT et al. 2003;HARTWIG 2005). It was recently shown that it was possible to distinguish individuals within a group of conspecifics by virtue of their vocalizations both in birds (BAKER 2004;RADFORD 2005) and in mammals (BOUGHMAN 1997;CROCKFORD et al. 2004;TOWNSEND et al. 2010). ...
... Individual recognition by vocal print has been proposed as a possible species conservation tool (DARDEN et al. 2003;HARTWIG 2005), even if it was noted that there are cases in which a species may alter its vocalizations in relation to the territory in which it is located (WALCOTT et al. 2006). However, there are only a few reports of acoustic identification used as a monitoring tool for mammals in the wild (O'FARRELL & GANNON 1999;OSWALD et al. 2007). ...
Article
Full-text available
Acoustic communication conveys a variety of information that is a helpful tool for animal conservation. The wolf is an elusive species, which can be detected through the howls that individuals emit. In this study we investigated the acoustic features of wild wolf pack howls from five locations in the province of Arezzo, Italy. We tested the hypothesis that each group had a distinctive vocal signature. Our results showed that these wolf packs emitted howls with significantly distinctive acoustic structures. We hypothesized that group-specific vocal signatures require temporal stability to be functional. Indeed, we did not find any statistical differences in howls collected from the same location during the same season or for 2 consecutive years. We suggest that the acoustic features of howls can be used to distinguish wolf packs in the wild.
... Another intriguing problem is which acoustic parameters could be responsible for the finer details of the information content of dog barks. Based on the vast literature of vocalization-based sex and individual recognition in other species, e.g., African wild dog, Lycaon pictus (Hartwig 2005); white-faced whistling duck, Dendrocygna viduata (Volodin et al 2005); or Wied's black-tufted-ear marmosets, Callithrix kuhlii (Smith et al 2009), one might expect dog barks to also carry specific cues of the caller's individual features, such as sex and age, for example. There are, however, considerable obstacles in testing such subtle pieces of information using classical techniques (i.e. ...
... Moreover, other work has focused on identifying calls from different animals such as bears, eagles, elephants, gorillas, lions and wolves, with k-nearest neighbor classifiers, artificial neural networks and hybrid methods (Gunasekaran and Revathy 2011). (Frommolt et al 2003), and African wild dogs (Hartwig 2005). Domestic dog barks have been analyzed again using discriminant analysis (Yin and McCowan 2004) for classification into context-based subtypes (three different contexts) and in order to identify individual dogs. ...
Article
Full-text available
Barking is perhaps the most characteristic form of vocalization in dogs; however, very little is known about its role in the intraspecific communication of this species. Besides the obvious need for ethological research, both in the field and in the laboratory, the possible information content of barks can also be explored by computerized acoustic analyses. This study compares four different supervised learning methods (naive Bayes, classification trees, [Formula: see text]-nearest neighbors and logistic regression) combined with three strategies for selecting variables (all variables, filter and wrapper feature subset selections) to classify Mudi dogs by sex, age, context and individual from their barks. The classification accuracy of the models obtained was estimated by means of [Formula: see text]-fold cross-validation. Percentages of correct classifications were 85.13 % for determining sex, 80.25 % for predicting age (recodified as young, adult and old), 55.50 % for classifying contexts (seven situations) and 67.63 % for recognizing individuals (8 dogs), so the results are encouraging. The best-performing method was [Formula: see text]-nearest neighbors following a wrapper feature selection approach. The results for classifying contexts and recognizing individual dogs were better with this method than they were for other approaches reported in the specialized literature. This is the first time that the sex and age of domestic dogs have been predicted with the help of sound analysis. This study shows that dog barks carry ample information regarding the caller's indexical features. Our computerized analysis provides indirect proof that barks may serve as an important source of information for dogs as well.
... Для многих псовых основанные на дискриминантном анализе исследования также показали высокий потенциал дальнедистантных вокализаций для индивидуального различения особей. Такие данные были получены для воя волка (Tooze et al., 1990), сериального лая песца, Alopex lagopus (Frommolt et al., 2003) и американского корсака, Vulpes velox (Darden et al., 2003), для "hoo''-криков гиеновых собак, Lycaon pictus (Hartwig, 2005) и аналогичных вокализации растянутого вяканья красного волка, Cuon alpinus (Durbin, 1998). Наличие индивидуальных вокальных признаков в дальнедистантных вокализациях имеет важное адаптивное значение, поскольку по таким крикам конспецифики могут распознавать социальных партнеров на расстоянии, в отсутствие визуальных и ольфакторных ключей, и соответственно видоизменять свое поведение в зависимости от того, кому принадлежат звуки (Никольский, 1984;Frommolt et al., 2003;McComb et al, 2003). ...
... Сопоставление индивидуальных, половых и межпородных различий в лае В целом, полученные нами результаты показали, что индивидуальные различия в лае домашних собак значительно превосходят половые и межпородные, что свидетельствует о первостепенной важности информации об индивидуальной принадлежности в дальнедистантных вокализациях домашних собак. Это хорошо согласуется с данными по другим видам псовых (Tooze et al., 1990;Durbin, 1998;Darden et al, 2003;Frommolt et al., 2003;Hartwig, 2005). По-видимому, это связано с тем, что для акустической коммуникации собак более важна информация об индивидуальной принадлежности, чем о принадлежности к полу или породе. ...
Article
Full-text available
Dog barks are complex in their structures and may vary from purely tonal to noisy even within individual barking bouts. The possibility to recognize individuality, sex, and breed in Borsoi and Hortaj Windhound breeds based on their acoustical cues was studied. Throughout 2002-2004, barks of 18 Hortaj and 9 Borsoi dogs (kept in a kennel) were recorded in the standard situation, when the same known person approached them. Discriminant analysis of the data on 1329 barks from 11 Hortaj and 9 Borsoi dogs showed 63.5% of their correct assignment to the dogs that exceeded the random value (9.3%). The average value of the correct assignment to sex (358 barks from 12 females and 375 barks from males) was as low as 67.9% (with a random of 58.7%). The value of correct assignment to breed (630 barks from 16 Hortaj and 630 from 8 Borsoi dogs) was only 71.6% (random 54.3%). These results suggest that barks provide for the information concerning individuality of a dog, and to a lesser extent, its sex or breed. The greater breed-dependent than sex-dependent differences in barks arise from greater differences in sizes between the breeds than between sexes. Barks of 3 females and 2 males of Hortaj dogs were tested in order to estimate stability of acoustic features responsible for the recognition of individuality. They were recorded twice with an interval of more than 11 months. The cross-validation analysis of barks recorded during 2003-2004 using discriminant functions of 2002 showed only 38.9% of correct assignment to dog. One can propose that a directional shift in bark characteristics took place due to replacement of a cagemate.
... Coyotes are the most vocal of all North American wild mammals and vocalizations are the primary means of communication (Lehner, 1978). Other Canids that use vocalizations are wolves Canis lupus, Artic foxes Alopex lagopus, dholes Cuon alpinus, and swift foxes Vulpes velox (Hartwig, 2005). ...
... Sirens, bugles, broadcasting recorded coyote howls, human imitations of coyote howls and other stimuli have all been used to elicit responses from wild coyotes (Henke and Knowlton, 1995). Howl surveys allow a researcher to collect data about the location and movements of individuals that are out of sight and not wearing radio-collars (Hartwig, 2005). However, only territorial coyote groups respond to howl surveys because transient coyotes do not have territory to advertise (Henke and Knowlton, 1995;Gese and Ruff, 1998). ...
... For many canids, discriminant analysis-based research has suggested a potential for individual recognition by long-distance calls. Such data were reported for howling of timber wolves (Tooze et al. 1990), for bark series of arctic foxes Alopex lagopus (Frommolt et al. 1997(Frommolt et al. , 2003 and swift foxes Vulpes velox (Darden et al. 2003), for hoo-calls of African wild dogs (Hartwig 2005) and corresponding to hoocall vocalization of dholes (Durbin 1998). Probably, the cues to individuality in distant calls of canids compensate for the absence of visual and olfactory stimuli that provide cues to individuality in close proximity. ...
Article
Full-text available
Biphonation (two independent fundamental frequencies in a call spectrum) represents one of the most widespread nonlinear phenomena in mammalian vocalizations. Recently, the structure of biphonations was described in detail; however, their functions are poorly understood. For the dhole (Cuon alpinus), biphonic calls represent a prominent feature of vocal activity. In this species, the biphonic call is composed of two frequency components – the high-frequency squeak and the low-frequency yap, which also occur alone as separate calls. In this study, we test the hypothesis that the complication of call structure, resulting from the joining of these calls into the biphonic yap–squeak may enhance the potential for individual recognition in the dhole. We randomly selected for analysis 30 high-frequency squeaks, 30 low-frequency yaps and 30 biphonic yap–squeaks per animal from five subadult captive dholes (450 calls in total). Discriminant analysis, based on 10 squeak parameter values, showed 80.7% correct assignment to a predicted individual. For 10 yap parameters, the correct assignment was only 44.7%. However, the analysis based on 10 parameters of the biphonic yap–squeak, selected as best contributing to discrimination, showed 96.7% correct assignment to a predicted individual. The results provide strong support for the hypothesis tested showing that the joining of two independent calls into a common vocalization may function to enhance individual recognition in the dhole.
... По издаваемым животными звукам возможно даже индивидуальное узнавание особей*. Это дает возможность проведения неинвазивных исследований -можно наблюдать конкретных зверей или птиц без какого-либо вмешательства в их жизнь, поскольку отпадает необходимость в отлове и мечении (Galeotti, Pavan, 1991;McGregor, Byle, 1992;Delpot et al., 2002;Hartwig, 2005;Dragonetti, 2007;Fox et al., 2008 и др.). Появился термин «биоакустический мониторинг». ...
Article
Full-text available
Bioacoustic data can be used as an important evidence of registration of a bird species but they are not often applied by our ornithologists. The aim of this paper is to describe these tools for faunistic studies. Main aspects of working with sounds were outlined: devices, technique of sound recording, computer analysis, reading of sonograms, etc. Solutions of difficult faunistic problems with the help of sound records were showed on several samples. [Russian].
... Acoustic identification of individual birds is widely used on animal monitors in such applications as evaluation of territorial boundaries, map home ranges (Mi�utani and Jewell, 1998;Betts et al., 2005), population censuses, monitoring population dynamics (Kemp and Kemp, 1989;Gilbert et al., 1994;Hartwig, 2005) and the detection of dispersal patterns (Laiolo and Tella, 2006;Laiolo et al., 2007), especially in situations where other markers would be difficult to detect (Rogers and Paton 2005;Terry et al., 2005;Grava et al., 2008). The Asian Stubtail is quite difficult to detect by vision and this may be the reason why so little research has been carried out on this secret species. ...
... Indeed, the monitoring of wild animals almost systematically presupposes their catching first. This invasive stage is not necessary when animals are acoustically monitored (Gilbert et al., 1994; Hartwig, 2005). Almost all vocal species possess unique acoustic patterns that differ significantly from one to another individual, while following a common structure typical of the species. ...
Article
Full-text available
1. Needs for non-invasive methods to identify and locate animals Population assessment and a proper understanding of behavioural strate-gies are central and urgent tasks in conservation biology. Nevertheless, up to now, field-based biological researches are held back by the difficulty, cost and intrusiveness of marking and tagging animals, and the relative ineffectiveness of manual data collection and analysis thereafter. Indeed, the monitoring of wild animals almost systematically presupposes their catching first. This invasive stage is not necessary when animals are acous-tically monitored (Gilbert et al., 1994; Hartwig, 2005). Almost all vocal species possess unique acoustic patterns that differ significantly from one to another individual, while following a common structure typical of the species. By using acoustic analysis methods, it is then possible to iden-tify individuals or species emitting vocalisations (insects, frogs, birds and mammals). Sound sources have also the property to be localisable. Until recently, localisation of wild animals by acoustic methods was not widely used. This was mainly due to technical limitations, as the monitoring of simultaneous acoustic sources is problematic in the field. Indeed, among several requirements, simultaneous field recordings devices have to share features such as being wireless, waterproof, easily transportable, and with large memory capacities. Now that technologies exist to overcome these limitations, it has become possible to localise and track the movements of animals that generate sounds. Such systems have been first called acoustic sensors-001-344.indd 83 sensors-001-344.indd 83 20/03/12 13:10 20/03/12 13:10 84 Ecophysiology and animal behaviour location systems (ALS) by McGregor et al. (1997), but are now currently named automatic acoustic survey systems (AASS). An accurate AASS must fulfil two conditions: it must allow to localise the sound source with precision and identify the emitter. Until now, AASS have been used mostly to detect marine mammals (e.g. Stafford et al., 1998; Mellinger and Clark, 2003; Clark and Clapham, 2004; see chapter I, 3). In contrast, AASS dedicated to the monitoring of terrestrial species are rather uncommon (even though Mennill et al. 2006 used it for a case study with birds). For cetaceans, sensors are hydrophones and AASS spa-tial precision for animal localisation is in the kilometre range. Animals can also be tagged with localisation systems such as Argos for more accu-rate localisation, but even these systems cannot provide an accuracy below the metre range. For terrestrial species, more accurate locations are often required, for example, to determine the relative positions of neighbouring birds. In addition, tagging small terrestrial animals is often impossible due to several technical reasons (small size, difficulty of catching animals, see chapter I, 2). Moreover, marine and terrestrial environments differ from an acoustic point of view, the latter being often less homogeneous, with more obstacles. Here we review and discuss the accuracy of AASS for monitoring the position of animals vocalising in different terrestrial environments. We first introduce the principles and purposes of acoustic location systems. Then, we propose a non-exhaustive review of the different methods that can be implemented in an AASS in order to automatically locate ani-mals from the sounds they produce. We also present several existing methods used to extract from a vocalisation the individual and the spe-cies signatures. Finally, we illustrate the use of these technologies with some recent field applications concerning the location of birds in forest habitats.
... If a method of identifying individual Screech-Owls via vocalization analysis could be developed, then current call surveys could yield markrecapture data as well as site occupancy information. Attempts at developing a method to discriminate individuals based on vocalizations has been successful in numerous species of birds (Corncrakes Crex crex: Peake et al., 1998; Barred Owls Strix varia: Freeman 2000; Wood Owls Strix woodfordii: Delport et al. 2002; Great Bitterns Botaurus stellaris: Gilbert et al. 2002; Western Screech-Owls Megascops kennicottii: Tripp and Otter 2006; Woodcock Scolopax rusticola: Hoodless et al. 2008; Willow Flycatcher Empidonax trailii extimus: Fernandez-Juricic et al. 2009; summarized by Terry and MacGregor 2002) as well as a few mammals (male Fallow Deer Dama dama: Reby et al. 1998; Swift Fox Vulpes velox: Darden et al. 2003; Wild Dog Lycaon pictus: Hartig 2005). If a reliable method of discerning individuals based on their vocalizations can be found, researchers can non-invasively monitor otherwise cryptic or difficult-to-sample species, often for a fraction of the cost, effort, and negative effects associated with other methods (Terry et al. 2005; Hoodless et al. 2008; Fernandez-Juricic et al. 2009). ...
Article
Full-text available
To more easily and non-invasively monitor urban Eastern Screech-Owl populations, we developed a method of distinguishing individual owls using their calls. A set of seven variables derived from recordings of ‘bounce’ calls taken from 10 known (either free-ranging birds recorded at a single site on a single night or identifiable captive owls) owls was tested using a model-based clustering analysis (Mclust) as a method of discriminating individual owls. The cluster analysis correctly classified these calls with 98% accuracy. A second set of calls from nine owls was used to further test the method and correctly classified 84% of the calls using the same variables. Four owls were recorded repeatedly from 2008 to 2010 to determine the extent to which calls changed over time; the cluster analysis correctly assigned 89% of the calls to the correct owl regardless of the year the recordings were made. Based on these results, we are confident that the Mclust analysis can be used to reliably and safely estimate abundance and survival of Eastern Screech-Owls within the time frame of a few years and of population sizes
... The study of vocalizations may also provide us with information for aiding the conservation of endangered species (e.g. bioacoustics as a conservation tool: Peake et al. 1998;Hartwig 2005), and/or to assist in the welfare assessment of captive animals (e.g. Burman et al. 2007). ...
Article
Although ultrasonic vocalizations (USVs) have been recorded in many species of rodent and in various contexts, e.g. sexual behaviour and aggression, it has not been demonstrated for the endangered Turkish Spiny Mouse Acomys cilicius Spitzenberger. This study investigated whether A. cilicius emits USVs and, if so, how these USVs associated with non-vocalization behaviour. Ultrasonic recording equipment was set up for 12 days in an off-exhibit enclosure of A. cilicius at Bristol Zoo. At least seven different types of USV were recorded. For eight of the 12 study days, ultrasonic and video recording equipment were run concurrently. From these observations it was found that emission of USVs were associated with sexual behaviour, aggression and social investigation. The results of this study show for the first time that captive A. cilicius produce USVs that resemble those produced by other rodent species, including its close relative the Egyptian Spiny Mouse A. cahirinus Desmarest. As these findings apply only to a captive Turkish Spiny Mouse population, additional work should be carried out to investigate the behaviour and USV production in the wild in addition to further research on captive populations investigating the apparent communicative function of these vocalizations.
... However, there have been few studies that have focused on captive and wild recordings of mammal species. Extending these results to other species, in particular canids known to carry individual identity information in their long-distance vocalizations such as coyotes (Mitchell et al. 2006) and African wild dogs (Lycaon pictus) (Hartwig 2005), could be possible. By improving the accuracy of individual identity, further insights into species' behavioural ecology may be made, similar to those reported for social learning in birds (Brumm and Slater 2006). ...
Article
Full-text available
Many bioacoustic studies have been able to identify individual mammals from variations in the fundamental frequency (F 0) of their vocalizations. Other characteristics of vocalization which encode individuality, such as amplitude, are less frequently used because of problems with background noise and recording fidelity over distance. In this paper, we investigate whether the inclusion of amplitude variables improves the accuracy of individual howl identification in captive Eastern grey wolves (Canis lupus lycaon). We also explore whether the use of a bespoke code to extract the howl features, combined with histogram-derived principal component analysis (PCA) values, can improve current individual wolf howl identification accuracies. From a total of 89 solo howls from six captive individuals, where distances between wolf and observer were short, we achieved 95.5% (+9.0% improvement) individual identification accuracy of captive wolves using discriminant function analysis (DFA) to classify simple scalar variables of F 0 and normalized amplitudes. Moreover, this accuracy was increased by 100% when using histogram-derived PCA values of F 0 and amplitudes of the first harmonic. We suggest that individual identification accuracy can be improved by including amplitude changes for species where F 0 has only been included so far. Using DFA on PCA values of both F 0 and amplitude could optimize vocal identification in a range of mammal bioacoustic studies.
... Individually distinctive acoustic features have been demonstrated for a large number of birds, mammals, cetacean, and amphibians. Various studies have been performed to identify individuals based on these voiceprints (whooping cranes [72], African wild dogs [73], eagle owls [74] and ant-thrushes [75]). ...
Article
Full-text available
Movement ecology is a field which places movement as a basis for understanding animal behavior. To realize this concept, ecologists rely on data collection technologies providing spatio-temporal data in order to analyze movement. Recently, wireless sensor networks have offered new opportunities for data collection from remote places through multi-hop communication and collaborative capability of the nodes. Several technologies can be used in such networks for sensing purposes and for collecting spatio-temporal data from animals. In this paper, we investigate and review technological solutions which can be used for collecting data for wildlife monitoring. Our aim is to provide an overview of different sensing technologies used for wildlife monitoring and to review their capabilities in terms of data they provide for modeling movement behavior of animals.
... There is, therefore, potential that such structurally complex calls may help to coordinate pack movements in areas of poor visibility, for example, high levels of vegetation, and aid the reliability of individual identification in dense crowds (Volodin et al. 2006b). Indeed, dhole are reported to use vocalisations to coordinate hunts (Barnett 1978) and when searching for prey in dense undergrowth, the vocal activity of painted dogs increases and they emit individually identifiable biphonic hoo calls (Wilden et al. 1998; Robbins 2000; Hartwig 2005). Individualistic, directional calls may also allow hunters to concentrate visual attention more on the prey and less on each other (E. ...
Article
Full-text available
Cooperative hunting is believed to have important implications for the evolution of sociality and advanced cogni- tive abilities. Variation in the level of hunt organisation amongst species and how their cognitive, behavioural and athletic adaptations may contribute to observed patterns of cooperative hunting behaviour, however, are poorly under- stood. We, therefore, reviewed the literature for evidence of different levels of hunt organisation and cooperation in carni- vorans and examined their social and physical adaptations for hunting. Descriptions of group hunting were scarce for many species and often of insufficient detail for us to be able to classify the level of hunt organisation involved. However, despite this, reports of behaviour fitting the description of collaboration, the most advanced level of hunt organisation, were found in over half the carnivorans reported to hunt coop- eratively. There was no evidence that this behaviour would require advanced cognitive abilities. However, there was some evidence that both social mechanisms reducing aggression between group members and information transfer amongst individuals may aid cooperative hunting. In general, the coop- erative strategies used seemed to depend partly on the species’ locomotor abilities and habitat. There was some evidence that individuals take on consistent roles during cooperative hunts in some species, but it was not clear if this reflects individuals’ physical differences, social factors or life experiences. Better understanding of the social, cognitive and physical mecha- nisms underlying cooperative hunting, and indeed establishing to what degree it exists in the first instance, will require more data for multiple individuals and species over many hunts.
... However, this method could be suitable for monitoring birds at their nesting place. A 'voice archive' (see Seymour and Titze 1989) of calls from known individuals would help to re-identify such individuals that were not identified visually (Hartwig 2005). ...
Article
Full-text available
This study presents the first multivariate analysis of hornbill vocalizations and the first bioacoustic study of any Philippine hornbill species. We analyzed loud calls of two Philippine hornbill species, the Rufous-headed Hornbill Aceros waldeni and the Visayan Hornbill Penelopides panini panini , to assess the possibility for their use in individual identification. Our study showed that individuals of the two studied hornbill species can be identified on the basis of their loud calls, which means that these calls potentially contain information about the caller. Discriminant analysis classified 89% of individual Rufous-headed Hornbills and 90% of individual Visayan Hornbills correctly. The acoustic variables describing the most variation among individual Visayan Hornbills were spectral variables (second amplitude peak) and temporal variables (location of the maximum amplitude and call duration). The calls of individual Rufous-headed Hornbill were differentiated mainly by spectral variables (the fundamental and the first harmonic frequency, and additionally the upper quartile of the frequency range). Frequency parameters in Rufous-headed Hornbill calls were significantly lower than those in Visayan Hornbills. The use of acoustic monitoring of individuals as a non-invasive marking technique could help to monitor hornbill individual life history and to improve census data using capture-mark-recapture technique.
... Examples of animals using individual vocal cues can be found in birds (Jouventin et al. 1999), primates (Cheney & Seyfarth 1980; Weiss et al. 2001), elephants (McComb et al. 2003), whales (Sayigh et al. 1999), and seals (Charrier et al. 2002). Within the wild canids, individual differences have been documented in swift foxes (Darden et al. 2003), African wild dogs (Hartwig 2005), wolves (Theberge & Falls 1967; Tooze et al. 1990), and dholes (Durbin 1998). Frommolt et al. (2003) documented individuality in barks of a territorial population of arctic foxes and also showed that foxes respond differently to barks from members of their own social group than they do to other foxes. ...
Article
Full-text available
The information content of coyote (Canis latrans)vocalizations is poorly understood, but has important implications for understanding coyote behaviour. Coyotes probably use information present in barks or howls to recognize individuals, but the presence of individually-specific information has not been demonstrated. We found that coyote barks and howls contained individually specific characteristics: discriminant analysis correctly classified barks of five coyotes 69% of the time and howls of six coyotes 83% of the time. We also investigated the stability of vocalization characteristics at multiple distances from the source. Recordings were played back and re-recorded at 10 m, 500 m, and 1,000 m. Vocalization features were measured at each distance and analyzed to determine whether characteristics were stable. Most howl characteristics did not change with distance, and regardless of the distance discriminant analysis was 81% accurate at assigning howls among six individuals. Bark characteristics, however, were less stable and it is unlikely that barks could be used for individual recognition over long distances. The disparate results for the two vocalization types suggest that howls and barks serve separate functions. Howls appear optimized to convey information (i.e. data), while barks seem more suitable for attracting attention and acoustic ranging.
... Several methods have been used to identify animals individually, usually by adding markers or by using naturally occurring markers. For vocalizing species, like most birds and some mammals, a promising technique is acoustic monitoring (Gilbert et al. 1994, Hartwig 2005). The great advantage of acoustic monitoring of individuals is that it is a non-invasive technique that can be used in poorly lit environments where visual markers may be difficult to detect and on human-sensitive species, as recordings may be taken from a distance without disturbing the animals. ...
Article
Full-text available
The Eagle Owl Bubo bubo is cited in Annex I of the Birds Directive of the European Union. Europe's biggest owl is extremely sensitive to human presence and needs special conservation measures. The present paper aims to show that monitoring of individuals by bioacoustic methods can be relevant to understanding population dynamics. Our study investigates the possibility of identifying a vocal signature in the wild-recorded calls of male and female Eagle Owls, and assesses the potential use of these signatures for long-term monitoring of individuals in the field. We show that both males and females of a given population can be identified individually on the basis of their calls. Our results also show that, regardless of the sex, most of the individuals recorded in the first year of the investigation may be identical to those recorded in the same places the year after. This bioacoustic approach could thus be used in studies of site fidelity.
... 2 Related work 2.1 Animal re-identification Animal re-identification is a broad term referring to the process of identifying an individual animal based on its features. The features are based on biological traits, and they can be captured in a number of ways, for example, acoustically (Hartwig, 2005;Pruchova, Jaška, & Linhart, 2017) or visually in the form of images (Vidal, Wolf, Rosenberg, Harris, & Mathis, 2021) or videos (Freytag et al., 2016). Currently, imagebased approaches are the most widely utilized approach due to the relative ease of data acquisition and manual analysis (Schneider, Taylor, Linquist, & Kremer, 2019). ...
Preprint
Full-text available
We propose a method for Saimaa ringed seal (Pusa hispida saimensis) re-identification. Access to large image volumes through camera trapping and crowdsourcing provides novel possibilities for animal monitoring and conservation and calls for automatic methods for analysis, in particular, when re-identifying individual animals from the images. The proposed method NOvel Ringed seal re-identification by Pelage Pattern Aggregation (NORPPA) utilizes the permanent and unique pelage pattern of Saimaa ringed seals and content-based image retrieval techniques. First, the query image is preprocessed, and each seal instance is segmented. Next, the seal's pelage pattern is extracted using a U-net encoder-decoder based method. Then, CNN-based affine invariant features are embedded and aggregated into Fisher Vectors. Finally, the cosine distance between the Fisher Vectors is used to find the best match from a database of known individuals. We perform extensive experiments of various modifications of the method on a new challenging Saimaa ringed seals re-identification dataset. The proposed method is shown to produce the best re-identification accuracy on our dataset in comparisons with alternative approaches.
... It is generally accepted that larger vocal folds in larger species or individuals can produce lower fundamental frequencies [Fitch and Hauser, 2002]. Therefore, larger adults should be able to produce lower fundamental frequencies than smaller juveniles, and this has been observed in some mammalian species [Elowson et al., 1992;Blumstein and Munos, 2005;Hartwig, 2005;Nikol'skii, 2007]. However, this is not true for several small mammals [Volodin et al., 2014], including the speckled ground squirrel (Spermophilus suslicus) and the yellow ground squirrel (S. fulvus) [Matrosova et al., 2007;Volodina et al., 2010]. ...
Article
The European ground squirrel (Spermophilus citellus) emits alarm calls that warn conspecifics of potential danger. Although it has been observed that inexperienced juveniles of this species emit alarm calls that sound similar to those of adults, studies focusing on juvenile alarm calls are lacking. We analyzed the acoustic structure of alarm calls emitted by six permanently marked European ground squirrels living in a semi-natural enclosure when they were juveniles and after 1 year as adults. We found that the acoustic structure of the juvenile alarm calls was significantly different from those of adults and that the alarm calls underwent nearly the same changes in all studied individuals. All juveniles emitted alarm calls consisting of one element with almost constant frequency, but their alarm calls included a second frequency-modulated element after their first hibernation as adults. Our data show that the duration of the first element is significantly shorter in adults than in juveniles. Additionally, the frequency of the first element is significantly higher in adults than in juveniles. Similar to previous findings in other Palearctic ground squirrel species, our data are inconsistent with the assumption that juvenile mammals emit vocalizations with higher fundamental frequencies than adults. However, our results do not support the previously suggested hypothesis that juvenile ground squirrels conceal information regarding their age in their alarm calls because we found significant differences in alarm calls of juveniles and adults. Zoo Biol. XX:XX-XX, 2015. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
... The use of vocalizations as a non-invasive census method for secretive or threatened birds is of great relevance when physically marking individuals is impractical for logistical or welfare reasons (Mcgregor & Byle 1992;Gilbert et al. 1994;Peake et al. 1997). Acoustic monitoring also offers advantages in complex environmentslike cloud forest -where visual markers are difficult to detect, and call recordings may be obtained from far away without having to disturb the animals (Gilbert et al. 1994;Hartwig 2005;Grava et al. 2008). Furthermore, if calls provide information about individuals, it is possible to estimate important population parameters such as abundance (Terry et al. 2005). ...
Article
The Horned Guan (Oreophasis derbianus) is a cracid restricted to cloud forests in the Sierra Madre of Chiapas in Mexico and the westerncentral Mountains in Guatemala. It is an endangered species and urgent conservation measures are required, such as non-invasive monitoring techniques. Here, we study individual features in the boom calls of Horned Guans. Boom calls are acoustic signals used by males during courtship and territorial displays. This call is made of seven notes, divided into two parts: an introductory section characterized by low-amplitude notes and a body section characterized by highamplitude notes. We recorded 10 males during the breeding seasons of 2010 and 2011 in two captive populations and measured 22 acoustic variables of the calls. We used a combination of statistical analyses to test individuality in Horned Guan vocalizations. Our results showed that time-related variables – but not frequency-related traits – varied between individuals, and that individual calls showed no variation between years. Our results suggest that Horned Guan individuals can be distinguished using fine structural characteristics of their calls and that calls remain stable across years. We argue that such vocal signature could be used to track wild populations as a non-invasive technique in order to improve census data in the short and long term.
... While previous works have explored the technical feasibility of acoustic monitoring based on vocal individual signature (Terry and McGregor, 2002;Hartwig, 2005;Grava et al., 2008;Policht et al., 2009;Adi et al., 2010;Feng et al., 2014;Budka et al., 2015Budka et al., , 2018Peri, 2018a) most field applications were based on sounds recorded from already known individuals (O'Farrell and Gannon, 1999;Peake and McGregor, 2001;Vögeli et al., 2008;Digby et al., 2013;Peri, 2018b). To the best of our knowledge, there is no published study investigating the generalization and reliability of an acoustic monitoring approach based on individual vocal signatures aimed at estimating the number of individuals in real field conditions. ...
... Identification and discrimination of acoustic signals is an established and non-invasive way of detecting and identifying loud-calling animals (Vaug han et al., 1997b;Horne, 2000;Jones et al., 2000;Hartwig, 2005;Oswald et al., 2007). This acoustic approach is often the most effective way for the species-specific identification of animals that are difficult to visually observe and detect (e.g., marine mammals - Oswald et al., 2003Oswald et al., , 2007 and difficult to capture and physically examine (O'Farrell and Miller, 1999), in addition to cryptic species that are morphologically similar but genetically distinct (Russo and Jones, 2000;Thabah et al., 2006;Bickford et al., 2007;Ramasindrazana et al., 2011). ...
Article
Bioacoustics can be a non-invasive, cost-effective way of studying echolocating bats, and is especially useful for detecting and identifying rare or cryptic species. The insectivorous bats of Madagascar are understudied in comparison to the rest of the island’s fauna, and very little is known about their habitat use. Here, we used a remote bioacoustic surveying technique in a bat survey of the Sahamalaza-Îles Radama National Park, northwest Madagascar, to study constant frequency echolocating bats (Hipposideridae and Rhinonycteridae). We used two passive acoustic monitoring units to automatically record bat activity from dusk until dawn in a range of habitat types that are characteristic of the region. Analysis of call acoustic parameters revealed three distinct constant frequency phonic types within the national park, which we identified as Commerson’s leaf-nosed bat (Macronycteris commersoni), the red trident bat (Triaenops menamena) and an unknown phonic type of ca. 78 kHz. We found significant differences in the habitat usage of these three species, suggesting species-specific habitat preferences among Madagascar’s bats. Our statistical analyses revealed significant differences between the acoustic echolocation calls of these three phonic types. The 78 kHz calls do not match any of the other constant frequency-calling bat species currently described for Madagascar, indicating either acoustic divergence among bat sub-populations or the possible existence of a new undescribed species. These results highlight the need for increased survey efforts to gain an understanding of species-specific geographic distributions and habitat usage among Malagasy bats and to disentangle their cryptic species complexes.
... For these species, variation in call rate can provide insight into, for example, foraging and reproduction in taxa from raptors to anurans (Townsend & Stewart 1994;Wood et al. 2019d). Individual identity is likely communicated through vocal cues (Terry et al. 2005;Prior et al. 2018) and has been assessed for owls, small passerines, and wild dogs in small-scale studies (Hartwig 2005;Kirschel et al. 2011;Odom et al. 2013). Discriminating between putative individuals at adjacent sites within years and putative individuals at the same site between years could substantially improve occupancy-based monitoring programs by reducing bias in population estimates and identifying turnover events. ...
Article
Recent bioacoustic advances have facilitated large-scale population monitoring for acoustically active species. Animal sounds, however, can of information that is underutilized in typical approaches to passive acoustic monitoring (PAM) that treat sounds simply as detections. We developed 3 methods of extracting additional ecological detail from acoustic data that are applicable to a broad range of acoustically active species. We conducted landscape-scale passive acoustic surveys of a declining owl species and an invasive congeneric competitor in California. We then used sex-specific vocalization frequency to inform multistate occupancy models; call rates at occupied sites to characterize interactions with interspecific competitors and assess habitat quality; and a flexible multivariate approach to differentiate individuals based on vocal characteristics. The multistate occupancy models yielded novel estimates of breeding status occupancy rates that were more robust to false detections and captured known habitat associations more consistently than single-state occupancy models agnostic to sex. Call rate was related to the presence of a competitor but not habitat quality and thus could constitute a useful behavioral metric for interactions that are challenging to detect in an occupancy framework. Quantifying multivariate distance between groups of vocalizations provided a novel quantitative means of discriminating individuals with ≥20 vocalizations and a flexible tool for balancing type I and II errors. Therefore, it appears possible to estimate site turnover and demographic rates, rather than just occupancy metrics, in PAM programs. Our methods can be applied individually or in concert and are likely generalizable to many acoustically active species. As such, they are opportunities to improve inferences from PAM data and thus benefit conservation.
... Furthermore, it is non-invasive, thereby minimizing the influence on A B S T R A C T bird's behavior or movements (Mennill, 2011). Individual identification based on vocalisations has been used to estimate territory and home-range size (Betts et al., 2005), explore dispersal patterns (Laiolo et al., 2007) and forecast population size and dynamics (Hartwig, 2005). ...
... To estimate absolute population numbers, we need to conduct future research on the maximum distance, probabilities, and other factors influencing the emission of maned wolves' vocal responses and approaches, as Cozzi et al. (2013) did for their target species. Another possibility is using playback-elicited vocal responses to create a vocal identity catalogue to then count and recognise/'recapture' individuals on recordings, as for African wild dogs (Hartwig 2005). Roar-barks have been demonstrated to be individually distinct (Sábato 2011), however, to date, our efforts have been insufficient to identify individuals on recordings in their natural habitat. ...
Article
Full-text available
Maned wolves are difficult to observe in the wild because of their low densities and their cryptic and crepuscular-nocturnal habits. Exploring their long-range acoustic communication may offer an efficient alternative to study the species. Here we evaluated the applicability of playbacks to study maned wolves in the wild and compare the results with 20 nights of passive recordings on the same area and month during the previous year. We obtained vocal responses on 3 of 6 nights tested, including responses involving two animals and an approach after an interactive playback. Although we conducted 3–6 playback sessions each day at different times, we only obtained vocal responses during sessions between 17:00 and 19:40. During our passive recordings we detected on average 0.86 roar-bark sequences per recorder per night, mostly during the first half of the night. Vocal activity – responses and spontaneous roar-bark sequences – during playback nights was nearly 4 times greater than during the passive recordings. We conclude that playbacks stimulate maned wolves to emit roar-barks and that this method is applicable to test hypotheses about maned wolf behaviour and aid in their monitoring.
... To discriminate between individuals, we apply a PCA-based method that relies on redundancy and requires the number of microphones to be equal to the number of sources (which is a common requirement in blind source separation algorithms) (Cao & Liu 1996;Naik & Wang 2014), yet this method still needs to be refined for noisy and uncontrolled environments. There are only a few previously proposed approaches for discriminating among calls of individuals in other taxa, such as canids and birds (Hartwig 2005;Fox 2008;Cheng et al. 2012;Ptacek et al. 2016) and, to the best of our knowledge, the present study is the first time that the acoustic identification of the stridulatory sounds of simultaneously-stridulating conspecifics (i.e. telling apart calls of individuals of the same species that are stridulating at the same time) has been addressed in insects. ...
Article
Full-text available
Bark beetles (Coleoptera: Curculionidae: Scolytinae) are a speciose subfamily of weevils that primarily live in bark and consequently largely communicate using sound. Having colonized multiple countries outside its native range, Hylurgus ligniperda (Fabricius) is considered to be a successful invader, yet little is known about its acoustic communication. In the present study, we investigate individual sound production and dyadic interactions among males and females of H. ligniperda. Two temporal parameters (duration and inter‐note interval) and three spectral parameters (minimum, maximum and centroid frequencies) are used as descriptors to quantify call variations depending on behavioural context. We also present a method for automatically extracting and analyzing these calls, which allows acoustic discrimination amongst individuals. Hylurgus ligniperda exhibits sexual dimorphism in its stridulatory organ. Females do not produce stridulatory sounds, whereas males produce single‐noted calls and modify their spectro‐temporal parameters in accordance with context. Acoustic stimulation from nearby males does not appear to be a causative factor in such modification. Instead, hierarchical clustering analysis shows that physical interactions play a more important role in affecting call parameters than acoustic signals. Centroid and maximum frequencies are the largest contributors to the variability of the data, suggesting that call variations in H. ligniperda mainly occur in the spectral domain. Males of Hylurgus ligniperda produce single‐noted calls for which the spectro‐temporal parameters vary under stimulation by external sources or direct contact with other individuals. Direct interactions between individuals are better modifiers of the parameters of the calls than acoustic stimuli. A method for automatically extracting bark beetle calls is presented and discussed.
... The use of vocalizations as a non-invasive census method for secretive or threatened birds is of great relevance when physically marking individuals is impractical for logistical or welfare reasons (Mcgregor & Byle 1992;Gilbert et al. 1994;Peake et al. 1997). Acoustic monitoring also offers advantages in complex environmentslike cloud forest -where visual markers are difficult to detect, and call recordings may be obtained from far away without having to disturb the animals (Gilbert et al. 1994;Hartwig 2005;Grava et al. 2008). Furthermore, if calls provide information about individuals, it is possible to estimate important population parameters such as abundance (Terry et al. 2005). ...
Article
The Horned Guan (Oreophasis derbianus) is a cracid restricted to cloud forests in the Sierra Madre of Chiapas in Mexico and the westerncentral Mountains in Guatemala. It is an endangered species and urgent conservation measures are required, such as non-invasive monitoring techniques. Here, we study individual features in the boom calls of Horned Guans. Boom calls are acoustic signals used by males during courtship and territorial displays. This call is made of seven notes, divided into two parts: an introductory section characterized by low-amplitude notes and a body section characterized by highamplitude notes. We recorded 10 males during the breeding seasons of 2010 and 2011 in two captive populations and measured 22 acoustic variables of the calls. We used a combination of statistical analyses to test individuality in Horned Guan vocalizations. Our results showed that time-related variables – but not frequency-related traits – varied between individuals, and that individual calls showed no variation between years. Our results suggest that Horned Guan individuals can be distinguished using fine structural characteristics of their calls and that calls remain stable across years. We argue that such vocal signature could be used to track wild populations as a non-invasive technique in order to improve census data in the short and long term.
... Vocal individuality has been used as a monitoring tool to investigate the distribution and abundance of bird populations over both time and space (Terry et al. 2005). This monitoring tool provides the benefits of saving a lot of time and effort in capturing, marking, and handling individuals while reducing disturbance, stress, and injury (Hartwig 2005). The invasive approaches of traditional marking techniques or radiotelemetry are capable of producing detrimental effects on reproductive success and survivorship by multiple captures or the transmitters imposed on the birds (Sockman and Schwabl 2001). ...
Article
Full-text available
Vocal individuality has been used as a monitoring tool, and two criteria are a prerequisite: high variation among individuals and low variation within individuals, and vocal consistency within and across seasons. We examined individual variation in the territorial hoot calls of the tawny owl (Strix aluco) to discriminate between males and to assess a possible conservation technique that would allow for monitoring individuals within a study area. The territorial calls were recorded from five males in the Naejang Mountain National Park in South Korea during the breeding season in 2015 and 2016 and analyzed both quantitatively and qualitatively to determine the amount of variation within and between individuals. Our results showed that the territorial calls were specific to individuals within a population and that the acoustic distances between males living in the same territory during the two years were the smallest for the four nesting sites. Our results suggest that territorial calls of the tawny owls are individually identifiable over two years and that this acoustic technique can be useful for monitoring individual site fidelity.
... Vocal individuality has been reported in a wide range of taxa including birds (Gilbert et al. 1994, Fitzsimmons et al. 2008, Hoodless et al. 2008, Fernández-Juricic et al. 2009, Policht et al. 2009, Xia et al. 2012, primates (Oyakawa et al. 2007, Sun et al. 2011, Feng et al. 2014, canids (Darden et al. 2003, Hartwig 2005, pinnipeds (Charrier andHarcourt 2006, Opzeeland et al. 2012), cetaceans (Janik et al. 1994, Mishima et al. 2015, and amphibians (Bee et al. 2001). For birds, vocal individuality has been documented extensively in passerines and seabirds over the last four decades (Beer 1970, Falls 1982, Freeman 2000, Favaro et al. 2015. ...
Article
Full-text available
Like many owl species, Sunda Scops-Owls (Otus lempiji) are difficult to monitor using traditional survey techniques, because of their nocturnal habits, secretive nature, and cryptic coloration. Individual variation in vocalizations could potentially be used to distinguish individuals of this owl species, as has been demonstrated for many bird species. The objectives of this study were to describe the territorial call of Sunda Scops-Owls, to determine whether the calls can be distinguished individually, and to examine whether the calls from the same individuals were stable over time. We analyzed 75 recordings collected from 12 owls from December 2014 to June 2015 in a lowland forest and oil palm smallholdings in Selangor State, Peninsular Malaysia. Using two temporal parameters and six frequency parameters derived from spectrogram, we employed ANOVA tests and found significant differences for all parameters among individual owls. Discriminant function analysis correctly classified 97.1% of the owl calls to the correct individuals. Based on the Wilcoxon signed-rank test, all vocal parameters did not vary significantly for the six birds that were vocally active over two predetermined survey sessions within the breeding period. Our results demonstrated that Sunda Scops-Owls can be identified individually by their vocalizations. This implies that assessing vocal individuality can be useful as a noninvasive method for surveying the Sunda Scops-Owls and the method should be further tested for other little-known owl species in the tropics.
... ARUs reduce the need for trained observers and potentially persurvey costs, which could allow for more frequent and spatially extensive surveys than traditional observer-based approaches (Borker et al., 2015;Shonfield et al., 2018;Hill et al., 2018). As a result, ARUs have been used to survey a broad range of marine and terrestrial species (Delport et al., 2002;Hartwig, 2005;Walters et al., 2012;Penone et al., 2013;Helble et al., 2013). Furthermore, the performance of ARUs compared to trained human observers in avian studies has been evaluated in a wide range of habitats and although the two approaches have different advantages and disadvantages, inferences regarding parameters of interest are generally comparable (Zwart et al., 2014). ...
... direct capture or the intrusive presence of observers in the field) [2,11]. Passive acoustics may also help to reduce the time and human resources required in the field [12,13]. These main features of passive acoustics suggest that this interesting approach could be employed for monitoring elusive species that require conservation or management plans, such as the grey wolf (Canis lupus). ...
Article
Full-text available
Background: The grey wolf (Canis lupus) is naturally recolonizing its former habitats in Europe where it was extirpated during the previous two centuries. The management of this protected species is often controversial and its monitoring is a challenge for conservation purposes. However, this elusive carnivore can disperse over long distances in various natural contexts, making its monitoring difficult. Moreover, methods used for collecting signs of presence are usually time-consuming and/or costly. Currently, new acoustic recording tools are contributing to the development of passive acoustic methods as alternative approaches for detecting, monitoring, or identifying species that produce sounds in nature, such as the grey wolf. In the present study, we conducted field experiments to investigate the possibility of using a low-density microphone array to localize wolves at a large scale in two contrasting natural environments in north-eastern France. For scientific and social reasons, the experiments were based on a synthetic sound with similar acoustic properties to howls. This sound was broadcast at several sites. Then, localization estimates and the accuracy were calculated. Finally, linear mixed-effects models were used to identify the factors that influenced the localization accuracy. Results: Among 354 nocturnal broadcasts in total, 269 were recorded by at least one autonomous recorder, thereby demonstrating the potential of this tool. Besides, 59 broadcasts were recorded by at least four microphones and used for acoustic localization. The broadcast sites were localized with an overall mean accuracy of 315 ± 617 (standard deviation) m. After setting a threshold for the temporal error value associated with the estimated coordinates, some unreliable values were excluded and the mean accuracy decreased to 167 ± 308 m. The number of broadcasts recorded was higher in the lowland environment, but the localization accuracy was similar in both environments, although it varied significantly among different nights in each study area. Conclusions: Our results confirm the potential of using acoustic methods to localize wolves with high accuracy, in different natural environments and at large spatial scales. Passive acoustic methods are suitable for monitoring the dynamics of grey wolf recolonization and so, will contribute to enhance conservation and management plans.
... northern elephant seals Mirounga angustirostris, Casey et al. 2015;primates, Symmes et al. 1979; hyenas Crocuta crocuta, East & Hofer 1991) and have been used successfully in the monitoring and size estimation of wildlife populations (e.g. wild dogs Lycaon pictus, Hartwig 2005). In the particular case of monitoring Mediterranean monk seals in Greece, the assignment of a unique acoustic tag to a newborn pup would enable estimation of the annual pupping rate, which is considered the most important monitoring parameter for the conservation of the species in the country. ...
Article
Full-text available
The Mediterranean monk seal Monachus monachus is considered Endangered by the IUCN, and is the most endangered pinniped in the world. Increasing our knowledge of this species is crucial in order to further our understanding of its social behaviour, but also to develop new methods to monitor and protect it. In many species, acoustic communication plays a major role in social interactions, and vocal signals convey important information about the emitter understanding the diverse information encoded in vocalizations is helpful in wildlife monitoring. In the present study, we used passive, audio-video surveys to describe the aerial vocal repertoire of the Mediterranean monk seal during the pupping season. An exhaustive analysis was performed on the different call types, and individual vocal signatures were investigated. A total of 5 call types were identified: bark, chirp, grunt, short scream and scream, with bark and scream being the 2 main call types. A discriminant function analysis based on 10 acoustic variables revealed that all call types except grunts can be correctly classified, with an average rate of 86.7%. Furthermore, the individual vocal signature investigated in barks and screams revealed that both call types are individually specific, showing average correct classification rates of 54.2 and 66.1% respectively. Based on these findings, future research should focus on collecting new recordings from wellidentified seals to develop a new passive acoustic monitoring system based on individual identification. This system will enable the evaluation of annual pup production and thus provide essential information on the conservation status of the Mediterranean monk seal in Greece.
Article
Full-text available
We analyzed the structure and variation of the songs of the Brownish-flanked Bush Warbler (Cettia fortipes), a species common in southeastern Asia, including southwestern China, site of our study. During the breeding season of 2009, we investigated the possibility of distinguishing individuals by song. Most Brownish-flanked Bush Warblers we studied had a unique song repertoire composed predominantly of two song types. Whether singing spontaneously or in response to playback, the birds deliver the two types alternately. We defined type alpha as a song consisting of two notes, type beta as a song consisting of three notes. Both song types varied from individual to individual. Discriminant analysis revealed that the songs of individual Brownish-flanked Bush Warbler songs were distinct; rates of correct classification were 98% for the alpha song and 99% for the beta song. Analizamos la estructura y la variación del canto de Cettia fortipes, una especie común en el sudeste de Asia, incluyendo el sudoeste de China, lugar de nuestro estudio. Durante la estación reproductiva de 2009, investigamos la posibilidad de distinguir individuos por medio del canto. La mayoría de los individuos de C. fortipes que estudiamos tuvo un reportorio único de cantos compuesto predominantemente por dos tipos de cantos. Ya fuera cantando de modo espontáneo o respondiendo a grabaciones, las aves emitieron los dos tipos alternativamente. Definimos el tipo alfa como un canto consistente en dos notas y el tipo beta como un canto consistente de tres notas. Ambos tipos de cantos variaron de individuo a individuo. Los análisis discriminantes revelaron que los cantos de los individuos de C. fortipes fueron diferentes; las tasas de clasificación correcta fueron del 98% para el canto alfa y del 99% para el canto beta.
Thesis
Full-text available
Population censuses of male rock ptarmigans (Lagopus muta) are conducted by point count protocol in spring (late May - early June). Several observers are placed at given points within the area and spend an hour listening to singing males trying to deduce an estimate of their number. The counting conditions are diffcult and cast doubt on the good representativeness of this protocol. The first objective of this thesis was to quantify the counting biases. The thesis then focused on finding ways to develop new counting methods to compensate for the biases of traditional counting. The acoustic signals emitted by animals carry several levels of information, such as the identity of the transmitter. The second part of my thesis showed that bioacoustic techniques based on acoustic differences in vocalizations were suitable to ptarmigan and that it was possible to determine the number of males in an area using the sounds they produce. The third part of the thesis is a generalization of the method on long-term recordings under real field conditions. It was not only possible to obtain the number of males but also the time of presence of each male and to assess his reproductive status. In conclusion, I showed the interest of the bioacoustic tool to monitor ptarmigan’s populations. My thesis opens up perspectives for futur large scale monitoring of ptarmigan’s populations.
Chapter
Full-text available
Ecological sciences deal with the way organisms interact with one another and their environment. Using sensors to measure various physical and biological characteristics has been a common activity since long ago. However the advent of more accurate technologies and increasing computing capacities demand a better combination of information collected by sensors on multiple spatial, temporal and biological scales. This book provides an overview of current sensors for ecology and makes a strong case for deploying integrated sensor platforms. By covering technological challenges as well as the variety of practical ecological applications, this text is meant to be an invaluable resource for students, researchers and engineers in ecological sciences. This book benefited from the Centre National de la Recherche Scientifique (CNRS) funds, and includes 16 contributions by leading experts in french laboratories.
Article
Full-text available
Invasive trapping and radio-collaring techniques are currently used by conservation biologists to study the population dynamics of gray wolves (Canis lupus). Previous research has found wolf howls can be used to determine individual identity on high quality recordings from captive animals, offering an opportunity for non-invasive monitoring of packs.We recorded wild wolves in Central Wisconsin to determine the effectiveness of these features in determining individuality in low quality recordings. The wolf howls analyzed were from two adult individuals from separate packs. Using a principle component analysis, maximum frequency and end frequency of the calls were determined to be most individualistic. Using these features in a discriminant function analysis, howls were able to be identified from individuals with 100% accuracy. Gray wolves play an important role in ecosystem maintenance, however, the current monitoring techniques are costly and invasive. The creation of an easily accessible, non-invasive technique that can be used by individuals with a variety of technical backgrounds is necessary to address concerns faced by conservation efforts. To address these issues, all analyses performed usedfree or low-cost software, making this method of individual identification a useful alternative for conservation biologists. KEYWORDS: Canis lupus lycaon; Gray Wolf; Acoustic Signatures; Howls; Tracking Method; Conservation; Vocal Individuality
Article
This paper investigates the extent of tiger (Panthera tigris) vocal individuality through both qualitative and quantitative approaches using long distance roars from six individual tigers at Omaha's Henry Doorly Zoo in Omaha, NE. The framework for comparison across individuals includes statistical and discriminant function analysis across whole vocalization measures and statistical pattern classification using a hidden Markov model (HMM) with frame-based spectral features comprised of Greenwood frequency cepstral coefficients. Individual discrimination accuracy is evaluated as a function of spectral model complexity, represented by the number of mixtures in the underlying Gaussian mixture model (GMM), and temporal model complexity, represented by the number of sequential states in the HMM. Results indicate that the temporal pattern of the vocalization is the most significant factor in accurate discrimination. Overall baseline discrimination accuracy for this data set is about 70% using high level features without complex spectral or temporal models. Accuracy increases to about 80% when more complex spectral models (multiple mixture GMMs) are incorporated, and increases to a final accuracy of 90% when more detailed temporal models (10-state HMMs) are used. Classification accuracy is stable across a relatively wide range of configurations in terms of spectral and temporal model resolution.
Article
Censusing nocturnal species such as the Tawny Owl (Strix aluco) living in a dense population can lead to an overestimate if individual signatures are not available. A technique that separates the individualistic call of the Tawny Owl could be a useful tool for an exhaustive census. Six Tawny Owl males were followed for nine months; 654 vocalizations were analysed. Three methods – Spectrographic Cross Correlation (SPCC), Acoustic Space (AS) and Visual Spectrogram Comparison (VSC) – were tested to assess their ability to classify the typical male call. For SPCC, 10 randomly selected hoots for each male were compared: the distributions of correlation coefficients differed in only 26.7% of the cases when intra and inter individual variability are compared. For AS, all the spectrograms were measured through 13 parameters and intra and inter individual distances were compared: the interval containing 95.4% of intra-individual measures also contained 95.9% of inter-individual comparisons. Both SPCC and AS are considered not to be able to adequately separate subjects. For VSC, 31 randomly selected hoots were visually compared by 5 helpers; their classifications were compared pairwise and with the real situation; operators correctly identified a male in 70% of cases (mean = 70.4 SD = 5.4). If we integrate VSC with information coming from field notes, we have a more powerful tool than the mapping method. It is plausible that this technique can be useful for an exhaustive census of Tawny Owl populations living at high densities.
Thesis
Full-text available
The growing number of studies carried out in recent years has shown that bioacoustics is particularly interesting for the monitoring of secretive species. The emergence of autonomous recording devices, combined with new methods of analysis, have recently contributed to the increase of studies in this field. Over the last 30 years, many bioacoustic studies have been developed for the Grey wolf (Canis lupus), a secretive large carnivore known for its howls spreading over distances up to several kilometers. These researches notably aimed to improve its monitoring, which is complex because of the strong wolf dispersal capacities over long distances, the large extent of their territories and the various natural contexts in which they live. In this context, this PhD thesis was organized around three research axes. The first two axes focused on the contribution of passive bioacoustics for the Grey wolf monitoring in the field. By combining acoustic, statistical and cartographic analysis, the first objective was to develop a spatial sampling method adapted to large study areas for the detection of wolf howls by using autonomous recorders. Then, the same protocol was used to investigate the possibility to localize wolves thanks to their howls. Field experimentations, conducted in mid-mountain (Massif des Vosges) and lowland (Côtes de Meuse) environments, in two study areas of 30 km² and with an array of 20 autonomous recorders, demonstrated the high potential of passive bioacoustics for the Grey wolf monitoring. Indeed, nearly 70% of broadcasts (synthetic sound with similar acoustic properties to howls) were detected by at least one autonomous recorder in mid-mountain environment and more than 80% in lowland environment, for sound source-recorders distances of up to 2.7 km and 3.5 km respectively. By using statistical model and Geographic Information System, the detection probability of wolf howls was modeled in both study areas. In the mid-mountain environment, this detection probability was high or very high (greater than 0.5) in 5.72 km² of the study area, compared with 21.43 km² in lowland environment. The broadcast sites were localized with an overall mean accuracy of 315 ± 617 (SD) m, reducing until 167 ± 308 (SD) m after setting a temporal error threshold defined from the data distribution. The third axe focused on the application of acoustic diversity indices to estimate the number of howling wolves in choruses and thus to contribute to pack size monitoring. Index values of the six indices (H, Ht, Hf, AR, M, and ACI) were positively correlated with the number of howling wolves in the artificial tested choruses. Interesting size predictions based on real choruses were obtained with one of the indices (ACI). The effects of several biases on the reference values for the acoustic indices were then explored, showing that three of them were relatively insensitive (Hf, AR and, ACI). Finally, results obtained with autonomous recorders confirm the real potential of passive acoustic methods for detecting the presence of wolves but also for localizing individuals with high precision, in contrasting natural environments, at large spatial and temporal scales. The use of acoustic diversity indices also opens new perspectives for estimating pack sizes. All of the promising methods emerging from this thesis require now further investigations before considering a concrete application for monitoring the Grey wolf in its natural environment.
Chapter
From these histories, capture frequency statistics and estimates of capture probabilities can be derived.
Thesis
Le nombre croissant de travaux réalisés ces dernières années a montré que la bioacoustique est particulièrement intéressante pour le suivi d’espèces discrètes. L’émergence de dispositifs d’enregistrement autonomes, associée à de nouvelles méthodes d’analyse, ont récemment participé à l’accroissement des études dans ce domaine. Au cours des 30 dernières années, le Loup gris (Canis lupus), mammifère carnivore aux mœurs discrètes connu pour ses hurlements de longue portée, a fait l’objet de nombreuses études acoustiques. Ces dernières visaient notamment à améliorer son suivi, qui s’avère complexe du fait des grandes capacités de déplacement des loups, de l’étendue de leurs territoires et de la diversité des milieux dans lesquels ils vivent. Cependant, la bioacoustique passive a jusqu’alors très peu été exploitée pour le suivi du Loup. C’est dans ce contexte que la présente thèse s’est organisée autour de trois axes de recherche. Les deux premiers axes portent sur l’apport de la bioacoustique passive pour le suivi du Loup gris en milieu naturel. En combinant des analyses acoustiques, statistiques et cartographiques, le premier objectif a été d’élaborer une méthode pour l’échantillonnage spatial de vastes zones d’étude, afin d’y détecter des hurlements de loups à l’aide de réseaux d’enregistreurs autonomes. Ce même dispositif a ensuite permis, dans un second temps, de tester la possibilité de localiser les loups grâce à leurs hurlements. Les expérimentations conduites en milieu de moyenne montagne (Massif des Vosges) et de plaine (Côtes de Meuse), sur deux zones d’étude de 30 km² et avec un réseau de 20 enregistreurs autonomes, ont permis de démontrer l’intérêt de la bioacoustique passive pour le suivi du Loup gris. En effet, près de 70% des émissions sonores (son synthétique aux propriétés similaires à celles de hurlements de loups) ont été détectés par au moins un enregistreur autonome en milieu de moyenne montagne et plus de 80% en milieu de plaine, pour des distances enregistreurs– source sonore atteignant respectivement plus de 2.7 km et plus de 3.5 km. Grâce à un modèle statistique et à un Système d’Information Géographique, la probabilité de détection des hurlements a pu être cartographiée sur les deux zones. En moyenne montagne, elle était forte à très forte (>0.5) sur 5.72 km² de la zone d’étude, contre 21.43 km² en milieu de plaine. Les sites d’émission ont été localisés avec une précision moyenne de 315 ± 617 (SD) m, réduite à 167 ± 308 (SD) m après l’application d’un seuil d’erreur temporelle défini d’après la distribution des données. Le troisième axe de travail porte quant à lui sur l’application d’indices de diversité acoustique pour estimer le nombre d’individus participant à un chorus et ainsi contribuer au suivi de l’effectif des meutes. Les valeurs obtenues pour les six indices (H, Ht, Hf, AR, M et ACI) étaient corrélées avec le nombre de loups hurlant dans les chorus artificiels testés. De bonnes prédictions de l’effectif ont été obtenues sur des chorus réels avec l’un de ces indices (ACI). L’influence de plusieurs biais sur la précision des prédictions de chacun des six indices a ensuite pu être étudiée, montrant que trois d’entre eux y étaient relativement peu sensibles (Hf, AR et ACI). Finalement, les résultats obtenus avec les enregistreurs autonomes montrent le potentiel des méthodes acoustiques passives pour la détection de la présence de loups mais aussi pour les localiser avec une bonne précision, dans des milieux contrastés et à de larges échelles spatiale et temporelle. L’utilisation des indices de diversité acoustique ouvre également de nouvelles perspectives pour l’estimation de l’effectif des meutes. Prometteuses, l’ensemble des méthodes émergeant de ce travail nécessite à présent quelques investigations complémentaires avant d’envisager une application concrète pour le suivi du Loup gris dans son milieu naturel.
Article
Full-text available
Ecological sciences deal with the way organisms interact with one another and their environment. Using sensors to measure various physical and biological characteristics has been a common activity since long ago. However the advent of more accurate technologies and increasing computing capacities demand a better combination of information collected by sensors on multiple spatial, temporal and biological scales. This book provides an overview of current sensors for ecology and makes a strong case for deploying integrated sensor platforms. By covering technological challenges as well as the variety of practical ecological applications, this text is meant to be an invaluable resource for students, researchers and engineers in ecological sciences. This book benefited from the Centre National de la Recherche Scientifique (CNRS) funds, and includes 16 contributions by leading experts in french laboratories.
Article
Lycaon pictus (Temminck, 1820), the African wild dog, is a moderately sized carnivore with dog-like appearance and irregularly mottled black, yellow-brown, and white pelage. It has a head–body length of 76–112 cm, tail length of 30–41 cm, shoulder height of 61–78 cm, and body weight of 17–36 kg. Lycaon pictus has four toes on each foot, differentiating it from other canids; is the only extant species within the genus with no subspecies; and is unlikely to be confused with any other canid. Lycaon pictus was once widespread throughout sub-Saharan Africa inhabiting nearly all environments and now inhabits grasslands, montane savanna, and open woodlands. Lycaon pictus is recognized as “Endangered” (EN) by the U.S. Fish and Wildlife Service and the International Union for Conservation of Nature.
Article
Full-text available
Recordings were made of contact-location vocalizations and behaviors of six troop-living juvenile stumptail macaques. Quantitative analysis of 354 spectrograms distinguished thirteen of the fifteen pairs of animals and led to construction of a "profile" of distinctive acoustic features for the vocalizations of each animal. Individual variation was also found in vocalization occurrence rates in five contextual categories. Acoustic distinctions found between two behavioral contexts were the same found to differentiate similar social settings in Japanese macaques (GREEN, 1975). Individual differences in acoustic features and rates of vocalization are correlated with stages of social development, serve as contextual cues, and are an important source of variability in primate communication.
Article
Full-text available
Individual primates typically produce acoustically distinct calls. To investigate the factors that facilitate the evolution of individual vocal signatures, we examined two components of the call repertoire of chimpanzees: the pant hoot and pant grunt. Pant hoots are long-distance signals whose recipients can be several hundred meters away, while pant grunts are short-range calls given to conspecifics within close visual range. Given their markedly different contexts of emission, we predicted that natural selection would favor the elaboration of individually distinctive acoustic features in pant hoots compared with pant grunts. Analyses of nine acoustic features revealed that pant hoots are more stereotyped within-individuals and variable between-individuals than pant grunts. These data are consistent with the hypothesis that selection may act to encode varying degrees of individuality in different components of the vocal repertoire of a single species.
Article
Full-text available
Vocal individuality has been found in a number canid species. This natural variation can have applications in several aspects of species conservation, from behavioral studies to estimating population density or abundance. The swift fox (Vulpes velox) is a North American canid listed as endangered in Canada and extirpated, endangered, or threatened in parts of the United States. The barking sequence is a long-range vocalization in the species' vocal repertoire. It consists of a series of barks and is most common during the mating season. We analyzed barking sequences recorded in a standardized context from 20 captive individuals (3 females and 17 males) housed in large, single-pair enclosures at a swift fox breeding facility. Using a discriminant function analysis with 7 temporal and spectral variables measured on barking sequences, we were able to correctly classify 99% of sequences to the correct individual. The most important discriminating variable was the mean spacing of barks in a barking sequence. Potential applications of such vocal individuality are discussed.
Article
Full-text available
Recently it was suggested that the handling of wild dogs (Lycaon pictus) by researchers in the Serengeti ecosystem created stress, resulting in the reactivation of latent rabies viruses in carrier animals. We present data from ongoing studies on free-ranging and captive wild dogs elsewhere in Africa which do not support this hypothesis. Cortisol profiles suggest that immobilization of wild dogs does not cause the chronic stress required for stress-reactivation of latent viruses. Furthermore, there is no evidence of handling-related mortalities in wild dogs: the survivorship of unhandled and handled free-ranging wild dogs did not differ and no captive animals died within a year of handling (immobilization and/or vaccination against rabies). We suggest that the mortalities observed in Tanzania were due to an outbreak of a disease which rabies vaccination was unable to prevent. Intensive monitoring and active management research programmes on wild dogs are essential as without these, critically endangered wild dog populations have little hope of survival.
Article
Archives of voice recordings could provide a source of information for voice scientists and clinicians interested in voice analysis and in cultural and historical changes of vocal styles and qualities. Large collections of sound recordings exist that could be used as databases for such inquiries, although no comprehensive list of such collections currently exists. A preliminary survey of major collections is presented. Voice scientists and voice archivists have many common areas of interest in the recording, reproduction, copying, and analysis of sound. The Recording and Research Center, as part of its ongoing research in establishment of standards for voice analysis, has begun an archive of laboratory recordings. A protocol for recording trained, normal, abnormal, and neurologically impaired voices is in development. This survey of sound archives will continue as well.
Article
It had been shown that Barbary macaque (Macaca sylvanus) mothers are able to individually recognise their offspring by its vocal signals, but it remained unclear which acoustical cues may account for such an ability. In order to address this issue from a basic perspective, about 1800 calls of infants and yearlings (N = 10) were investigated. The investigation applied a method of signal analysis which allowed to determine a large number of parameters (N = 84) for each vocal signal. The application of discriminant and cluster analyses provided the following results: (1) Animals differed in almost all call parameters. However, individuals were best identified by specific parameters which formed an individually characteristic parameter set. (2) Those parameters that facilitated the assignment of vocal patterns to a given individual usually were different among individuals. (3) Infants and yearlings achieved the same maximum value of correct assignment. However, infants achieved a reasonable assignment at a much small er number of call parameters. (4) Cluster analysis of vocalisations revealed that Barbary macaques uttered individual versions of common call types. (5) When the discriminant analysis was rerun on the call clusters, the correct assignment could be improved from 81% to 94% for infants and from 80.5% to 96% for yearlings. Our findings suggest that Barbary macaque mothers can recognise their offspring by more than one signal cue, and such a strategy may improve the recognition system's robustness against possible distortions caused by the environment. The pronounced differences in vocal patterns of young Barbary macaques may help mothers or other group members to readily learn and recognise the individually specific signal features. The methodological procedures described in this paper provide a powerful tool for an assessment of signal parameters also in other areas of vocal interactions.
Article
This study describes selection derived from habitat acoustics on the physical structure of avian sounds. Sound propagation tests were made in forest, edge, and grassland habitats in Panama to quantify pure tone and random noise band sound transmission levels. The sounds of bird species in each habitat were analyzed to determine the emphasized frequency, frequency range, and sound type (whether pure tonelike or highly modulated). Forest habitats differ from grass and edge in that a narrow range of frequencies (1,585-2,500 Hz) has lower sound attenuation than lower or higher frequencies. Attenuation increases rapidly above 2,500 Hz. Bird sounds from species occurring at the lower forest levels were found to be predominantly pure tonelike with a frequency emphasized averaging 2,200 Hz, conforming to the predictions based on sound propagation tests. The edge habitat is characterized by a wide range of frequencies having a generally similar attenuation rate. Pure tone and random noise band sounds did not diffe...
Article
From 1992-1998, a study of up to six radio-collared packs of free-ranging African wild dogs (Lycaon pictus) was conducted in Hwange National Park, Zimbabwe. Wild dogs were primarily observed during the day and data were collected across seasons on vocalizations and social context. An analysis of spectral properties, along with an examination of context and function, is presented. A vocal repertoire consisting of 11 vocal classes and 18 subclasses was identified. The sound system of this socially obligate carnivore is among the most complex in Canidae. Several vocal classes, i.e. twitters, begging cries, and rumbles, appear to be unique. Heavy investment in high frequency sounds relative to other social canids is offset by a greater variety of low frequency sounds. More kinds of barks are found in its reportoire than have been reported for other canids. Sound mixing is an integral component of wild dog vocal communication and occurs via succession or superimposition of noisy and harmonic sounds. Mixing by succession occurs for all classes, while mixing by superimposition occurs for yelp/squeals, whines, moans, growls, and barks. The Lycaon vocal repertoire is highlighted by comparison with other social canids (i.e. wolves, bush dogs, dholes, and domestic dogs). Finally, attention is drawn to features in the wild dog sound system that are both consistent and inconsistent with the motivation-structural rules of Morton's model. While most sounds conform to the model, there appear to be anomalies between the expected design features of certain vocalizations (i.e. twitters, barks, and rumbles) and the contexts in which they are given. Some of these anomalies appear to reflect the highly cohesive social system of the wild dog.
Article
In this paper we assess the applicability to the extraction of conservation information of three commonly used methods of examining the individuality of acoustic signals: qualitative assessment, spectrographic cross-correlation and discriminant function analysis. We tested the ability of human observers, with different levels of training, to sort and match spectrograms of bittern and fantail warbler vocalisations. This simulated a census and monitoring situation. We found that training had little effect on accuracy and high inter-individual variation made generalisations difficult. Cross- correlation provides an objective measure of similarity but was shown to be sensitive to background noise and the signal structure being compared. Discriminant function analysis is a powerful descriptor of individuality and functions well when developing predictive tools. However it should not be used to count a population and its use is constrained to re-identification in populations of known size.
Article
The computer-aided analysis of acoustic signals of mammals is still a problem, as ofte (a) sound structures are complex, (b) vocal repertoires often comprise an enormou variety of vocalisations, (c) recordings are influenced by the acoustic conditions of th environment, and (d) the distance and spatial orientation of the sender to th microphone changes. In recent software packages for the analysis of acoustic signal procedures are integrated which allow the calculation of a variety of signal feature: However, these algorithms are often problematic under the conditions mentioned abovi In this paper, we present a multi-parametric approach which reduces these problem and which allows a quantitative and reproducible analysis of complex animi vocalisations. Our approach comprises the following aspects: (1) reduction of influence of recording conditions, (2) determination of different sound features and (3) calculatio of parameters to characterise these sound features. All calculations are done on the bas: of the digitised spectrograms. Special attention is given to the use of smoothin algorithms and dynamic thresholds in order to estimate sound features and to reduc influences resulting from recording conditions. The suitability of our approach has bee demonstrated successfully for vocalisations of different species.
Article
The Asiatic wild dog or dhole Cuon alpinus is a threatened social canid that uses a repetitive whistle call to maintain group contact in dense habitats. Recordings were made over 12 days of dholes kept in 2 adjacent enclosures at a wild animal park. Spectrographic analysis of digitized recordings revealed significant differences between the whistles of captive dholes, allowing callers to be reliably identified. The most important discriminatory characteristics were the period from the start of one syllable to the next, the fundamental frequency, and the maximum frequency. The individual distinctiveness of the whistle is discussed in terms of its functional significance and possible survey applications. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
Whistle vocalizations of five odontocete cetaceans, the false killer whale P. crassidens, short-finned pilot whale G. macrorhynchus, long-finned pilot whale G. melas, white-beaked dolphin L. albirostris and Risso's dolphin G. griseus, were analysed and summarized quantitatively. Recordings were acquired from a number of locations and encounters. Significant differences were found between species and, to a lesser extent, between locations. The calls of the two pilot whale species are distinct despite their close relatedness, and similar size and morphology. This may be due to selection pressures to maintain distinctiveness. The variance was partitioned into between-species, between-location (within species) and within-location factors. For the frequency variables, variation between-species is high relative to variation between locations. Thus geographic variation is a relatively minor effect, compared to the many processes which cause interspecific differences. The within-location component includes such factors as social context, behaviour and group composition. This component is of a similar magnitude to the between-species component, indicating that whistles vary considerably with these factors. Significant between-location differences may be attributable to these confounding factors. For whistle duration, most of the variation occurred within location. There is less significant variation in duration across species compared with the frequency measures. This study highlights the need to collect samples across all potential strata whenever possible, and provides a framework for future, more comprehensive work.
Article
Isolation peeps (IP's) made by captive squirrel monkeys (Saimiri sciureus) of both the Gothic and Roman type have been analysed by spectrographic and statistical methods designed to quantify the degree of individuality found in utterances from single individuals. Clustering analysis confirmed that in both groups of monkeys individually distinct combinations of acoustic features characterize the IP and that such unique combinations persist over periods of several years. Differences between the Gothic and Roman form of the IP were found in more aspects of acoustic structure than had previously been known. The evidence suggests that information about the identity of the vocalizer is contained in the the IP.
Article
In East Africa, spotted hyaenas live in highly structured, female-dominated social groups. They use a loud call, the whoop, for medium-and long-distance communication. Whoops are produced in bouts as a sequence of a variable number of discrete calls. Bouts may be composed of any combination of three structurally distinct types of whoops. Cubs, adult males and adult females differed in the composition of whooping bouts. Cubs also produced fewer calls per bout than adults, and adult males produced fewer calls per bout than adult females. Spotted hyaenas can probably recognize callers individually, since the structure of whoops of the same individual over a period of several years was stable, while variation between individuals could be impressive.
Article
Approximately 5,000 photographs of African wild dogs Lycaon pictus taken in the Kruger National Park and some neighbouring reserves, in combination with direct observations, were used to assess the number of dogs, their pack sizes, sex ratio and breeding success during 1988 and 1989. A total of 357 dogs were identified in 26 packs, giving a minimum density of 16·7 dogs/1000 km2. Comparisons with earlier observations suggest that this population has remained stable over the last 25 years. Mean pack size was 13·7 ± SD 7·1 and the sex ratio of 1 male: 0·9 female close to parity. At least 69% of packs raised pups in 1988. Litter size at three months was 11·9 ± SD 3·0 and pup mortality between four and 10 months was 44%. Pup survival was positively correlated with the number of females in a pack. This large conservation area with stable prey populations, and a low incidence of disease and poaching, provides an environment conductive to wild dog survival.
Article
Howls were recorded from seven captive wolves temporarily individually isolated from their pack-mates. Sound spectrograms of these recordings were then digitized and 14 variables were measured and subjected to multivariate statistical analyses. Both principal components analysis and discriminant analysis indicated that individuals could be reliably discriminated primarily on the basis of the fundamental frequency of howls and the variability of frequency within howls. The significance of the presence of vocal signatures in this long distance vocalization is discussed in the context of wolf social organization.
Article
During field studies on a wild population of Arctic foxes, Alopex lagopus, on the Commander Island Mednyi (Northern Pacific) we examined whether acoustic long-distance signals were used for individual recognition. Barks of 10 individually known animals from five neighbouring groups were tape recorded. The spectral characteristics of the barks were described in terms of averaged 1/12 octave spectra.With a discriminant function analysis, more than 90% of the calls could be assigned to the correct individual on the basis of the spectral parameters. Discrimination was only slightly improved when we added temporal parameters to the analysis. We carried out playback experiments with eight foxes near the territory boundary of their family groups. The foxes were significantly more likely to respond with territorial behaviour and longer barking bouts to playbacks of neighbours or strangers than to playbacks of group members. We conclude that individuals can distinguish between barks of members of their own social group and those of other foxes. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.
Article
Thesis (Ph. D.)--University of California, Berkeley, 1980. Includes bibliographical references (leaves 167-178). Photocopy. Ann Arbor, Mich. : University Microfilms International, 1981. -- viii, 178 p. ; 22 cm.
Article
Analysed sound-spectrographically 129 field tape-recordings of the pant-hooting vocalization of seven chimpanzees at the Gombe Stream National Park, Tanzania. Quantitative statistical comparisons revealed that each animal had distinctive differences, sufficient to permit observers and probably chimpanzees to identify individuals. A consistent sexual difference was found, as well as a possible ageclass difference.
Article
The demography of Serengeti wild dog study packs and their extinction in 1991 was documented by Burrows et al. (1994). One explanation for pack loss compatible with demographic evidence was viral disease induced by stress caused by intervention (vaccination, immobilization and radio-collaring). Several studies claim to reject this hypothesis. However, cortisol levels measured in immobilized Lycaon, whose pathogen exposure is unknown, do not demonstrate that interventions in the Serengeti were benign. The analysis of survivorship in Lycaon in other ecosystems minimized the chance of demonstrating any effect of intervention and failed to consider vaccinations as intervention. There is now evidence that intervention significantly decreased survivorship of Masai Mara Lycaon. Further simulations of the likelihood of population extinction in Serengeti Lycaon, evidence of limited population variability and a small scaling factor in Serengeti Lycaon strengthen Burrows et al.'s conclusion that the extinction was unlikely to be due to chance alone. Although some studies claim that Lycaon conservation is doomed without intervention, to date vaccinations, blood sampling and radio-telemetry have contributed little to Lycaon conservation. All studies fail to disprove the Burrows hypothesis or provide convincing alternatives.
Individual differences in vocalization of Japanese macaque infants Macaca fuscata
  • T Riede
Riede, T. (1997). Individual differences in vocalization of Japanese macaque infants Macaca fuscata. Primate Report, 47, 31-47.
Communication behaviour and conservation
  • P K Mcgregor
  • T M Peake
  • G Gilbert
McGregor, P. K., Peake, T. M. & Gilbert, G. (2000). Communication behaviour and conservation. In Behaviour and Conservation (Ed. by L.M. Gosling & W.J. Sutherland), pp. 261-282. Cambridge: Cambridge University Press.
A potential tool for the swift fox Vulpes velox conservation: individuality of long range barking sequences Handling-induced stress and mortalities in African wild dogs (Lycaon pictus)
  • S K Darden
  • T Dabelsteen
  • S B Pedersen
  • M S De Villiers
  • D G A Meltzer
  • J Van Heerden
  • M G L Mills
  • P R K Richardson
  • A S Jaarsveld
Darden, S. K. Dabelsteen, T. & Pedersen, S. B. (2003). A potential tool for the swift fox Vulpes velox conservation: individuality of long range barking sequences. Journal of Mammology, 84, 1417-1427. de Villiers, M.S., Meltzer, D.G.A., van Heerden, J., Mills, M.G.L., Richardson, P.R.K. & van Jaarsveld, A.S. (1995). Handling-induced stress and mortalities in African wild dogs (Lycaon pictus). Proceedings of the Royal Society of London B262, 215-220.
Phonetische Variabilitii.t in der Lautgebung Mrikanischer Wildhunde Lycaon pictus und deren friihe Ontogenese
  • I Wilden
Wilden, I. (1997). Phonetische Variabilitii.t in der Lautgebung Mrikanischer Wildhunde Lycaon pictus und deren friihe Ontogenese. Ph.D. dissertation. Humboldt-Universitii.t zu Berlin; Berlin.
Beobachtungen zur Integration eines Afrikanischen Wildhundes Lycaon pictus aus Zoohaltung in eine Wildfang-Gruppe und deren gemeinsame Auswilderung
  • S Hartwig
  • G S A Rasmussen
Hartwig, S. & Rasmussen, G. S. A. (1999). Beobachtungen zur Integration eines Afrikanischen Wildhundes Lycaon pictus aus Zoohaltung in eine Wildfang-Gruppe und deren gemeinsame Auswilderung. Der Zoologische Garten, 69, 324-334.
Multivariate Analysemethoden Bioacoustics as a tool in conservation studies
  • K Backhaus
  • B Erichson
  • W Plinke
  • R Weiher
  • L F Baptista
  • S L L Gaunt
Backhaus, K., Erichson, B., Plinke, W. & Weiher, R. (1993). Multivariate Analysemethoden. Berlin: Springer Verlag. Baptista, L. F. & Gaunt, S. L. L. (1997). Bioacoustics as a tool in conservation studies. In Behavioural approaches to conservation in the wild (Ed. by J. R. Clemmons & R. Buchholz), pp. 212-242. Cambridge: Cambridge University Press.
Akustische Kommunikation bei Sii.ugetieren. Wissenschaftliche Buchgesellschaf Darmstadt
  • G Tembrock
Tembrock, G. (1996). Akustische Kommunikation bei Sii.ugetieren. Wissenschaftliche Buchgesellschaf Darmstadt.
The role of individual identification in conservation biology
  • P K Mcgregor
  • T M Peake
McGregor, P. K. & Peake, T. M. (1998). The role of individual identification in conservation biology. In Behavioural Ecology and Conservation Biology (Ed. by T.M. Caro), pp. 261-284. Oxford: Oxford University Press.
Population and habitat viability assessment for the Mrican wild dog (Lycaon pictus) in Southern Mrica. IUCN I SSC Conservation Breeding Specialist Group: Apple Valley, Selection for acoustic individuality within the vocal repertoire of wild chimpanzees
  • Mn Mitani
  • J C Gros-Louis
  • J Macedonia
Population and habitat viability assessment for the Mrican wild dog (Lycaon pictus) in Southern Mrica. IUCN I SSC Conservation Breeding Specialist Group: Apple Valley, MN. Mitani, J. C., Gros-Louis, J. & Macedonia, J. M. (1996). Selection for acoustic individuality within the vocal repertoire of wild chimpanzees. International Journal of Primatology, 17, 569-583.
Bioacoustics as a tool in conservation studies
  • L F Baptista
  • S L L Gaunt
Baptista, L. F. & Gaunt, S. L. L. (1997). Bioacoustics as a tool in conservation studies. In Behavioural approaches to conservation in the wild (Ed. by J. R. Clemmons & R. Buchholz), pp. 212-242. Cambridge: Cambridge University Press.
Population and habitat viability assessment for the African wild dog (Lycaon pictus) in Southern Africa
  • M G L Mills
  • S Ellis
  • R Woodroffe
  • A Maddock
  • P Stander
  • R Rasmussen
  • A Pole
  • P Fletcher
  • M Bruford
Mills, M. G. L., Ellis, S., Woodroffe, R., Maddock, A., Stander, P., Rasmussen, R., Pole, A., Fletcher, P., Bruford, M., Macdonald, D. & Seal, U. (eds.) (1998). Population and habitat viability assessment for the African wild dog (Lycaon pictus) in Southern Africa. IUCN/SSC Conservation Breeding Specialist Group: Apple Valley, MN.
  • Rendell L. E.