1,720,987 research outputs found
Identification and characteristics of signature whistles in wild bottlenose dolphins (Tursiops truncatus) from Namibia.
Full text linkA signature whistle type is a learned, individually distinctive whistle type in a dolphin's acoustic repertoire that broadcasts the identity of the whistle owner. The acquisition and use of signature whistles indicates complex cognitive functioning that requires wider investigation in wild dolphin populations. Here we identify signature whistle types from a population of approximately 100 wild common bottlenose dolphins (Tursiops truncatus) inhabiting Walvis Bay, and describe signature whistle occurrence, acoustic parameters and temporal production. A catalogue of 43 repeatedly emitted whistle types (REWTs) was generated by analysing 79 hrs of acoustic recordings. From this, 28 signature whistle types were identified using a method based on the temporal patterns in whistle sequences. A visual classification task conducted by 5 naïve judges showed high levels of agreement in classification of whistles (Fleiss-Kappa statistic, κ = 0.848, Z = 55.3, P<0.001) and supported our categorisation. Signature whistle structure remained stable over time and location, with most types (82%) recorded in 2 or more years, and 4 identified at Walvis Bay and a second field site approximately 450 km away. Whistle acoustic parameters were consistent with those of signature whistles documented in Sarasota Bay (Florida, USA). We provide evidence of possible two-voice signature whistle production by a common bottlenose dolphin. Although signature whistle types have potential use as a marker for studying individual habitat use, we only identified approximately 28% of those from the Walvis Bay population, despite considerable recording effort. We found that signature whistle type diversity was higher in larger dolphin groups and groups with calves present. This is the first study describing signature whistles in a wild free-ranging T. truncatus population inhabiting African waters and it provides a baseline on which more in depth behavioural studies can be based
Entanglement of Cape Fur Seals (Arctocephalus pusillus pusillus) in South Africa
Full text linkGlobal pollution is increasing, and marine mammals are commonly affected by the waste in the ocean. Endemic to the African continent, the pinniped species, Cape fur seal (Arctocephalus pusillus pusillus), are vulnerable to entanglement due to their curious nature and thick fur. Entanglement data were available from systematic photographic surveys of six colonies in South Africa (2019-2022) as well as opportunistic and citizen science records, photographs, aerial images and historical records from 1997 onwards. Overall, 314 cases of entangled seals were identified. As calculated from the systematic surveys, Baboon Point in Elands Bay (0.24% ± 0.78%, n = 7, with a 95% confidence interval) had the highest entanglement incidence. Seal Island in False Bay had the highest overall number of entanglements (50) and the highest mean number per survey (5.10 ± 0.46 number of entangled seals, n = 10), but this was also the largest colony assessed. Entanglement was observed the most in adults (61%, n = 189), with fishing materials being the primary cause of entanglements (40%, n = 59), specifically monofilament fishing lines (33%, n = 103). Although most entanglements were deemed ‘sight' (67%, n = 100), 28 cases (19%) were considered ‘severe,' likely impacting the health and welfare of affected individuals. Random Forest classification analysis identified the item of entangling material as an important predictor variable in terms of the severity level of the entanglement. The most common entangling material color was white (35%, n=82) followed by green (13%, n=30) and clear (7%, n=17) which may reflect the proportion of materials seals are exposed to, how they perceive them underwater, or their attraction to such colors. Aerial photographs showed higher efficiency in detecting entanglement cases than boat-based data where comparisons were possible. This is the first study to investigate entanglements of Cape fur seals in South Africa and highlights the need for correct disposal of waste, particularly that derived from the fishing industry, to mitigate its impacts on the welfare and conservation of marine fauna
Réseau de communication acoustique chez l’otarie à fourrure du Cap (Arctocephalus pusillus pusillus) : décrypter les différentes informations codées dans les signaux vocaux
No full textPendant la saison de reproduction, l'otarie à fourrure du Cap forme des colonies extrêmement denses dans lesquelles l'utilisation de signaux vocaux pour communiquer est contrainte par un bruit de fond élevé et un important risque de confusion. Pourtant, toutes les interactions sociales telles que la défense du territoire, les soins maternels et les relations intersexuelles nécessitent la production de vocalisations. Cette thèse a pour but de décoder la structure et le fonctionnement du réseau de communication acoustique de cette espèce en étudiant les cris, les informations qu'ils contiennent et les mécanismes de reconnaissance entre individus.Dans la première partie, je me suis intéressée à son répertoire vocal et j'ai décrit les vocalisations produites par les femelles, les mâles et les jeunes (structure, caractéristiques acoustiques et contextes de production). De plus, j'ai étudié les variations géographiques en comparant plusieurs types de cris enregistrés à différents sites en Namibie et Afrique du Sud. La deuxième partie traite de l'information codée dans les cris. J'ai d'abord estimé le degré de stéréotypie vocale dans les types de cris puis fait des comparaisons intra- et inter-espèces parmi les pinnipèdes. Ensuite, j'ai dédié une large partie à l'étude du système de reconnaissance vocale individuelle entre la mère et son jeune. Des expériences ont permis de tester leur capacité à se reconnaître par la voix, l'ontogénèse de cette reconnaissance après la mise-bas ainsi que les paramètres acoustiques impliqués dans le décodage de leur signature vocale. D'autres études ont concerné les mâles et ont répondu à des questions sur l'utilisation de leurs cris dans la modulation des interactions entre mâles territoriaux voisins et entre mâles territoriaux et subadultes. Enfin, j'ai utilisé des expériences de diffusion de bruit à plusieurs localités pour évaluer l'impact du bruit anthropique sur le comportement des otaries pendant la reproduction, et les facteurs à l'origine de variations intra-espèces dans leur réponse.During the breeding season, the Cape fur seal form extremely dense colonies in which the use of vocal signals to communicate is highly constrained by a loud background noise and a high risk of confusion. However, all social interactions such as territorial defence, maternal care or inter-sexual interactions involve the production of vocalisations. This thesis aims to unravel the structure and functioning of the Cape fur seal's acoustic communication network by studying their calls, the information they contain, and the mechanisms of vocal recognition among individuals. In the first part, I focussed on the species' vocal repertoire and described the in-air calls produced by females, males and pups during the breeding season (structure, acoustic features and contexts of production). Additionally, I investigated both micro- and macro-geographical variations by comparing several call types recorded at different study sites in Namibia and South-Africa.The second part concerns the information encoded in Cape fur seals' calls. I first assessed the degree of vocal stereotypy in different call types and made intra- and inter-species comparisons with other Pinnipeds. Then, I dedicated an important part to the study of the mother-pup individual vocal recognition system. Experiments were performed to test their ability to recognise each other's calls, the timing of the onset of the recognition after birth and the acoustic features involved in the decoding of their vocal signature. Further investigations were made at the level of males and answered questions on whether territorial males use vocal signals to modulate their interactions with neighbouring males or subadult ones. Finally, I used noise playback experiments at multiple study sites to assess the impact of anthropogenic noise on Cape fur seals' on-land behaviour during the breeding season and factors driving intra-species variation in their reaction
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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