L'un des plus grands défis posés par la communication est que l'information codée par l'émetteur est toujours modifiée avant d'atteindre le récepteur, et que celui-ci doit traiter cette information altérée afin de recouvrer le message. Ceci est particulièrement vrai pour la communication acoustique, où la transmission du son dans l'environnement est une source majeure de dégradation du signal, ce qui diminue l'intensité du signal relatif au bruit. La question de savoir comment les animaux transmettent l'information malgré ces conditions contraignantes a été l'objet de nombreuses études, portant soit sur l'émetteur soit sur le récepteur. Cependant, une recherche plus intégrée sur l'analyse de scènes auditives est nécessaire pour aborder cette tâche dans toute sa complexité. Le but de ma recherche était d'utiliser une approche transversale afin d'étudier comment les oiseaux s'adaptent aux contraintes de la communication à longue distance, en examinant le codage de l'information au niveau de l'émetteur, les dégradations du signal acoustiques dues à la propagation, et la discrimination de cette information dégradée par le récepteur, au niveau comportemental comme au niveau neuronal. J'ai basé mon travail sur l'idée de prendre en compte les problèmes réellement rencontrés par les animaux dans leur environnement naturel, et d'utiliser des stimuli reflétant la pertinence biologique des problèmes posés à ces animaux. J'ai choisi de me focaliser sur l'information d'identité individuelle contenue dans le cri de distance des diamants mandarins (Taeniopygia guttata) et d'examiner comment la signature vocale individuelle est codée, dégradée, puis discriminée et décodée, depuis l'émetteur jusqu'au récepteur. Cette étude montre que la signature individuelle des diamants mandarins est très résistante à la propagation, et que les paramètres acoustiques les plus individualisés varient selon la distance considérée. En testant des femelles dans les expériences de conditionnement opérant, j'ai pu montrer que celles-ci sont expertes pour discriminer entre les signature vocales dégradées de deux mâles, et qu'elles peuvent s'améliorer en s'entraînant. Enfin, j'ai montré que cette capacité de discrimination impressionnante existe aussi au niveau neuronal : nous avons montré l'existence d'une population de neurones pouvant discriminer des voix individuelles à différent degrés de dégradation, sans entrainement préalable. Ce niveau de traitement évolué, dans le cortex auditif primaire, ouvre la voie à de nouvelles recherches, à l'interface entre le traitement neuronal de l'information et le comportement / In communication systems, one of the biggest challenges is that the information encoded by the emitter is always modified before reaching the receiver, who has to process this altered information in order to recover the intended message. In acoustic communication particularly, the transmission of sound through the environment is a major source of signal degradation, caused by attenuation, absorption and reflections, all of which lead to decreases in the signal relative to the background noise. How animals deal with the need for exchanging information in spite of constraining conditions has been the subject of many studies either at the emitter or at the receiver's levels. However, a more integrated research about auditory scene analysis has seldom been used, and is needed to address the complexity of this process. The goal of my research was to use a transversal approach to study how birds adapt to the constraints of long distance communication by investigating the information coding at the emitter's level, the propagation-induced degradation of the acoustic signal, and the discrimination of this degraded information by the receiver at both the behavioral and neural levels. Taking into account the everyday issues faced by animals in their natural environment, and using stimuli and paradigms that reflected the behavioral relevance of these challenges, has been the cornerstone of my approach. Focusing on the information about individual identity in the distance calls of zebra finches Taeniopygia guttata, I investigated how the individual vocal signature is encoded, degraded, and finally discriminated, from the emitter to the receiver. This study shows that the individual signature of zebra finches is very resistant to propagation-induced degradation, and that the most individualized acoustic parameters vary depending on distance. Testing female birds in operant conditioning experiments, I showed that they are experts at discriminating between the degraded vocal signatures of two males, and that they can improve their ability substantially when they can train over increasing distances. Finally, I showed that this impressive discrimination ability also occurs at the neural level: we found a population of neurons in the avian auditory forebrain that discriminate individual voices with various degrees of propagation-induced degradation without prior familiarization or training. The finding of such a high-level auditory processing, in the primary auditory cortex, opens a new range of investigations, at the interface of neural processing and behavior

O canal acústico é um sistema de sinalização de longo alcance eficiente que pode ser especialmente efetivo para animais com hábitos crepusculares/noturnos. O lobo-guará é um canídeo ameaçado com hábitos crepusculares/noturnos que, no senso comum, é visto como uma espécie solitária. De fato, seria melhor definida como uma espécie gregária, uma vez que macho e fêmea dividem o mesmo território e a distância espacial entre eles varia de acordo com o período reprodutivo da fêmea. O aulido do lobo-guará é uma vocalização de longa distância que funciona como um mecanismo para aumentar a distância espacial entre coespecíficos, bem como para permitir casais de encontrarem um ao outro. Variações individuais nesta vocalização foram relatadas, mas a possibilidade de que elas possam ser percebidas e usadas pela espécie nunca foi testada. Deve-se esperar que essas variações individuais possam ser percebida, pois somente neste cenário seria plausível para o aulido ter a dupla função mencionada acima. Se esta variabilidade individual não é percebida pelos coespecíficos, a eficiência desta vocalização a longas distâncias seria comprometida, já que o ouvinte não seria capaz de identificar se o remetente é o seu parceiro reprodutivo ou um possível rival. Em nosso estudo usamos playbacks para testar se essas variações individuais podem ser percebidas por lobos em cativeiro e concluimos que eles podem. Pelo que conhecemos, esta é a primeira vez se demonstra que o lobo-guará é capaz de discriminar entre aulidos emitidos por diferentes indivíduos / The acoustic channel is an efficient long-distance signaling system that may be especially effective for animals with crepuscular/nocturnal habits. The maned wolf is a threatened canid with crepuscular/nocturnal habits that is thought to be a solitary species in common sense. As a matter of fact, it would be better defined as a gregarious species, since male and female share the same wide territory and the spatial distance between them varies according to the females reproductive period. The maned wolfs extended-bark is a long-distance vocalization that functions as a mechanism to increase spatial distance among conspecifics as well as to enable pair-mates to find each other. Individual variations in this vocalization have been reported, but the possibility that they can be perceived and used by the species has never been tested. One should expect these individual variations to be perceived by the species, since only in this scenario it would be plausible for the extended-bark to have the dual function stated above. If this individual variability is not perceived by conspecifics, the efficiency of this vocalization at long distances, at least for the hypothesized functions, would be compromised, as the hearer would not be able to identify if the sender is its reproductive partner or a possible rival. In our study we used playbacks to test if these individual variations can be perceived by captive wolves and have concluded that they can. To our knowledge, this is the first time it has been demonstrated that the maned wolf is capable of discriminating among extended-barks of different individuals

O canal acústico é um sistema de sinalização de longo alcance eficiente que pode ser especialmente efetivo para animais com hábitos crepusculares/noturnos. O lobo-guará é um canídeo ameaçado com hábitos crepusculares/noturnos que, no senso comum, é visto como uma espécie solitária. De fato, seria melhor definida como uma espécie gregária, uma vez que macho e fêmea dividem o mesmo território e a distância espacial entre eles varia de acordo com o período reprodutivo da fêmea. O aulido do lobo-guará é uma vocalização de longa distância que funciona como um mecanismo para aumentar a distância espacial entre coespecíficos, bem como para permitir casais de encontrarem um ao outro. Variações individuais nesta vocalização foram relatadas, mas a possibilidade de que elas possam ser percebidas e usadas pela espécie nunca foi testada. Deve-se esperar que essas variações individuais possam ser percebida, pois somente neste cenário seria plausível para o aulido ter a dupla função mencionada acima. Se esta variabilidade individual não é percebida pelos coespecíficos, a eficiência desta vocalização a longas distâncias seria comprometida, já que o ouvinte não seria capaz de identificar se o remetente é o seu parceiro reprodutivo ou um possível rival. Em nosso estudo usamos playbacks para testar se essas variações individuais podem ser percebidas por lobos em cativeiro e concluimos que eles podem. Pelo que conhecemos, esta é a primeira vez se demonstra que o lobo-guará é capaz de discriminar entre aulidos emitidos por diferentes indivíduos / The acoustic channel is an efficient long-distance signaling system that may be especially effective for animals with crepuscular/nocturnal habits. The maned wolf is a threatened canid with crepuscular/nocturnal habits that is thought to be a solitary species in common sense. As a matter of fact, it would be better defined as a gregarious species, since male and female share the same wide territory and the spatial distance between them varies according to the females reproductive period. The maned wolfs extended-bark is a long-distance vocalization that functions as a mechanism to increase spatial distance among conspecifics as well as to enable pair-mates to find each other. Individual variations in this vocalization have been reported, but the possibility that they can be perceived and used by the species has never been tested. One should expect these individual variations to be perceived by the species, since only in this scenario it would be plausible for the extended-bark to have the dual function stated above. If this individual variability is not perceived by conspecifics, the efficiency of this vocalization at long distances, at least for the hypothesized functions, would be compromised, as the hearer would not be able to identify if the sender is its reproductive partner or a possible rival. In our study we used playbacks to test if these individual variations can be perceived by captive wolves and have concluded that they can. To our knowledge, this is the first time it has been demonstrated that the maned wolf is capable of discriminating among extended-barks of different individuals