1,720,985 research outputs found
Breeding success of the endemic mara Dolichotis patagonum in relation to habitat selection: Conservation implications
Full text linkAlthough maras (Dolichotis patagonum) are among the most representative mammals of South America, knowledge on the ecological processes affecting their conservation is scarce. In particular, the study of habitat requirements and its relationship with breeding success is necessary to identify possible threats and develop conservation action for this endemic mammal. I investigated hábitat selection patterns by maras and their relationship with breeding success in Penı´nsula Valde´ s, Argentine Patagonia. Maras bred from mid-August to late December, and they tended to build the breeding warrens in open, grass-dominated habitats more than expected while avoided closed habitats dominated by taller shrubs. Mean number of breeding adults per warren was 4.26, while mean number of pups born per warren was 4.46. Overall, 30 (45%) of 67 pups survived until the 6th week of life, but pups born in warrens located in open habitats survived significantly better than pups born in warrens located in closed habitats (50% vs. 30% of the pups born). As grass-dominated áreas uphold the highest densities of domestic sheep and habitat modification due to overgrazing is a widespread process across arid Patagonia, effects on the availability of suitable breeding sites for maras are likely to occur and require further investigation.Fil: Baldi, Ricardo. Wildlife Conservation Society; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin
Feeding habits of the puma (Puma concolor) and the incidence of predation on guanaco (Lama guanicoe) mortality in northeastern Patagonia
Full text linkEn la Patagonia, las relaciones funcionales entre el puma y sus presas nativas se han modificado como consecuencia de la introducción de especies exóticas. Estudiamos los hábitos alimentarios de Puma concolor en el nordeste del Chubut durante un período de 3 años y encontramos que: (1) el guanaco, Lama guanicoe, fue la presa más importante en su dieta; (2) ante una reducción sustancial en la abundancia de ovinos, el puma respondió con una ampliación de su nicho trófico mediante la incorporación de presas de menor tamaño; y (3) la depredación por pumas fue la principal causa de muerte de guanacos.In Patagonia, the functional relationships between pumas and their native prey species have been modified as a result of the introduction of exotics. We studied the feeding habits of Puma concolor in northeastern Chubut province during 3 years and found that (1) the native guanaco, Lama guanicoe, was the most important prey in the diet of pumas; (2) pumas expanded their trophic niche by incorporating smaller prey species to their diets after a substantial reduction in the abundance of the introduced sheep; and (3) puma predation was the main cause of guanaco mortalityFil: Fernández, Cynthia. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro; ArgentinaFil: Baldi, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Wildlife Conservation Society. Patagonian and Andean Steppe Program; Argentin
Location of breeding warrens as indicators of habitat use by maras (Dolichotis patagonum) in Península Valdés, Argentina
Full text linkWe characterized the habitat use by maras (Dolichotis patagonum) on a microhabitat scale in the area surrounding the warren, assessing the conditioning effect of the warren over space use and exploitation of other resources. We evaluated the relationships between the probability and intensity of use, habitat configuration and distance to the warren, counting feces along transects departing from each warren. Our results showed that the location of breeding warrens was positively associated with the habitat use by maras on a microhabitat scale. The core area of the annual activity of maras was concentrated around the warren and there was no evidence of alternative areas of activity. According to the fitted models, maras used microhabitats with a high proportion of bare soil and close to infrastructure elements. The spatial autocorrelation components indicated that intensively used patches are small and disperse. The patterns of habitat use observed in this study suggest that maras use multipurpose areas including the breeding site and resources needed throughout the year. These patterns suggest that warrens are good all year-round indicators of mara habitat use and spatial ecology.Fil: Alonso Roldán, Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; ArgentinaFil: Baldi, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; Argentina. Wildlife Conservation Society; Estados Unido
Vigilance patterns of territorial guanacos (Lama guanicoe): The role of reproductive interests and predation risk
Full text linkWe conducted focal observations of territorial guanacos, a highly polygynous and social mammal, to compare time budgets between sexes and test the hypothesis that the differences in reproductive interests are associated with differential group size effects on male and female time allocation patterns. In addition, we used group instantaneous sampling to test the hypothesis that grouping improves detection capacity through increased collective vigilance. We fit GLM to assess how group size and group composition (i.e., presence or absence of calves) affected individual time allocation of males and females, and collective vigilance. As expected from differences in reproductive interests, males in family groups devoted more time to scan the surroundings and less to feeding activities compared to females. Both sexes benefited from grouping by reducing the time invested in vigilance and increased foraging effort, according to predation risk theory, but the factors affecting time allocation differed between males and females. Group size effects were significant when females were at less than five body-lengths from their nearest neighbour, suggesting that grouping benefits arise when females are close to each other. Female time budgets were also affected by season, topography and vegetation structure. In contrast to our expectation, males reduced the time invested in vigilance as the number of females in the group increased, supporting the predation risk theory rather the intrasexual competition hypothesis. The presence of calves was associated with an increase in male individual vigilance; and vegetation type also affected the intensity of the group size effect over male time allocation. In closed habitats, collective vigilance increased with the number of adults but decreased with the number of calves present. Although male and female guanacos differed in their time allocation patterns, our results support the hypothesis that both sexes perceive significant antipredator benefits of group living.Fil: Marino, Andrea Ivana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Baldi, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Wildlife Conservation Society; Estados Unido
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
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