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  • Author or Editor: Thierry Lengagne x
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Abstract

Most studies dealing with individual pattern in acoustic signals are based on recordings made within a few hours or a few days. However, in long-lived animals, individual signatures are likely to be involved in social contact and pairing over several years. Variability of calls and more particularly of individual specific pattern over years has been poorly investigated. This study examines calls produced by a nocturnal long-lived raptor, eagle owls (Bubo bubo) in order (1) to determine which call structures are individually specific and (2) to examine variability of these individual structures over 2 years. A computerised sound analysis and subsequent data were submitted to univariate and multivariate statistics to determine individual specific cues of the call. A first analysis conducted on 116 calls emitted by 9 wild males recorded on a short time period enables to identify each emitter without any mistake. Analysis conducted on 70 calls emitted by 5 captive birds recorded during two different years emphasised a weak variation of all call parameters. Discriminant analysis correctly classified 100% of the individual eagle owls and thus, it is possible to reliably assign a call to the individual caller based on the acoustic properties of the vocalisation. We therefore conclude that territorial calls emitted by eagle owls may constitute an individual pattern over several years. The possible biological role of individual signatures and their use for monitoring population purpose are discussed.

In: Behaviour

Abstract

In the king penguin, during the three months of incubation and the brooding stage, members of a pair alternate care duties on land with foraging trips. Contrary to most of the species of birds that nest at a fixed location, the king penguin carries its egg on its feet during incubation. This allows the incubating parents to move in the colony. Brooding or incubating parents moved on average 4.4 meters between egg-laying and the end of the brooding stage. This movement in a group of thousands of other birds reduced the reliability of visual cues for recovering the pair mate during the change-over. We showed that the difficulty in relocating the mate was more important during the brooding stage than during incubating. We confirmed earlier findings that acoustic communication was the main mode of communication during a change-over, and showed that the omnidirectional properties of sound allowed birds to reach more than five hundred other birds with each emitted call. Our experiments proved that the communication system is performed at short or medium range. On average, the birds identified their mate at a distance of 8.8 m. Seventy percent of the birds started the acoustic search of their mate when the distance was shorter or equal to this discrimination range, and so acoustic communication is a particularly efficient strategy in the king penguin. Chez le manchot royal (Aptenodytes patagonicus) le male et la femelle participent tous deux a l'incubation et a l'elevage du poussin. Si en general les oiseaux possedent un nid dont la position fixe aide les deux partenaires a se retrouver lors des releves, le manchot royal est une des rares especes sans nid. En effet, l'adulte incube et protege son oeuf ou son poussin sur ses pattes ce qui lui permet de se deplacer dans la colonie. Nous avons mesure un deplacement moyen de 4.4 metres entre le moment de la ponte et la fin de l'elevage individuel. Ce deplacement parmis des milliers d'autres oiseaux morphologiquement semblables rend tous reperes visuels inutilisables lors des releves entre male et femelle. Pour se reconnaitre individuellement, les manchots utilisent une signature acoustique. Nous avons montre que les proprietes omnidirectionelles du son permettent au manchot qui cherche son partenaire de communiquer potentiellement avec plus de 500 oiseaux pour chaque chant emis. La degradation rapide de la signature lors de la propagation du signal dans la colonie ne permet pas une communication a longue distance: les oiseaux identifient le chant de leur partenaires a une distance moyenne de 8.8 metres. La majorite des manchots royaux (70%) commencent a chanter a une distance inferieure ou egale a la portee du signal ce qui revele une strategie de communication particulierement efficace.

In: Behaviour

Abstract

In nocturnal chorusing anurans, mate choice has long been considered to be based exclusively on the highly conspicuous male calls. However an additional visual cue, the pulsing male vocal sac, has recently been shown to increase male attractiveness. In several species, including the European treefrog Hyla arborea, this organ is characterized by a bright orange colouration. In the present study, analysis of the pigments extracted from the vocal sacs of European treefrogs revealed the colouration of these organs to be based on several pigments, including three carotenoids, which are highly costly immune function enhancing molecules. This result raises the important question as to whether the carotenoid-based colouration of the vocal sac in H. arborea could constitute an additional visual cue used by females to discriminate male quality.

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In: Amphibia-Reptilia

In terrestrial habitats, traffic noise is responsible for chronic noise exposure and impacts both signal detection and acoustic signal structure. Several species are known to adapt their call structures to cope with noise. However, compromised hearing affects more than acoustic communication, and noise should be consider as a stress factor that can also alter visual communication in the case of carotenoid-based signals. Here, we experimentally investigated the impact of traffic noise on the expression of secondary sexual signals in the European treefrog, Hyla arborea. Treefrogs use multimodal communication in the sexual selection process (mating calls and vocal sac colouration). We found that treefrogs seem unable to adjust their call structure. Nonetheless, males showed a significant decrease in colouration intensity. Our findings highlight for the first time the negative effect of traffic noise on colour signals. This suggests that anthropogenic noise could affect a wider range of species than previously thought.

In: Behaviour

Immune responsiveness, one measure of individual quality, can be used as a sensitive, non-lethal variable that may be negatively affected in animals exposed to degraded, contaminated or otherwise disturbed areas. One frequently used technique to measure immune responsiveness is the phytohaemagglutinin (PHA) challenge test. Swelling occurring at the injection sites are measured before and 24 h after PHA injection. The immune response is considered to be the difference between the two measures. Although this method is easily performed with wild animals, it has been rarely used on small amphibians. Here, we test the possibility of using a PHA test with the European tree frog, Hyla arborea, and we identify the optimal procedure for measuring immune responsiveness in this species. The results allowed us to simplify the procedure in eliminating phosphate-buffered saline (PBS) injection and reducing the duration of the experiment. Injection of PHA into the leg of H. arborea triggered an immune response with a peak of swelling 14 h after injection. A second injection of PHA into the same animal induced more intense leg swelling. In addition, haematological responses showed that the total number of leucocytes increased after PHA injection. A link between the leg swelling and the total leucocytes count recorded in blood has been found. Consequently, this method may provide a useful tool for predicting the pro-inflammatory capacity of field populations of small amphibians.

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In: Amphibia-Reptilia