1,720,988 research outputs found
Reproductive strategies and body shape in the European pond turtle (Emys orbicularis) from contrasting habitats in Italy
No full textComparisons within and among populations offer important insights into variation
in life-history traits and possible adaptive patterns to environmental conditions.
We present the results of observed differences in body size, body shape and
patterns of reproduction in four separate populations of the European pond turtle
Emys orbicularis in central and southern Italy – coastal (n=3) and mountainous
(n=1) sites and pond (n=2) and canal (n=2) habitats – to determine whether
phenotypic plasticity affects reproductive output. Although we did not find any
significant latitudinal variation in body size, we observed significant differences in
body shape between canal (rounded body shape) and pond (elongated body shape)
systems and smaller size with rounded shape in the mountainous population.
Reproductive output is similar among populations (median=5 eggs per clutch),
whereas reproductive investment (relative clutch mass to maternal body mass) is
higher in the mountain population (one clutch per year) than in coastal populations
(two clutches per year), suggesting differential trade-offs between geographic
locality, elevation and habitat type. Turtle shell shape and geographic location
together affect reproductive output in E. orbicularis in Italy
Curiosity or aggressivity? Surface predatory behavior of the great white shark
Full text linkThe Great White Shark (Carcharodon carcharias) is an important top predator; however a little is known about its behaviour. During five study expeditions surface behaviour of Great White Sharks living in Dyer Island (South Africa) was observed. Aims of the research were to give more data in order to confirm the hypothesis that this area could be considered as a “training place”, where young sharks can learn new predator techniques, and to understand what is shark approach to a unnatural, floating and
passive prey. By comparing behaviours performed by young and mature specimens, our data showed that latters exhibited more complex ethograms. Sharks showed also a curiosity approach to passive preys employed for this studies, with a strong predominance of the parading
Preliminary observations about white shark's (Carcharodon carcharias) discriminatory patterns during surface predatory activity and type of approach
Full text linkThe aim of the present study was to gather information on the behaviour of great white shark Carcharodon carcharias during surface predatory activities. According to the present results, vision plays an important role in feeding patterns and appears correlated to weather conditions
Visual approach tactics by white sharks (Carcharodon carcharias) under baited conditions and effects of cloud cover
No full textUnderstanding white shark feeding habits and the influence of environmental factors on feeding is an important step for modelling its behaviour and making decisions about the management of aquatic habitats. To better understand what factors drive variation in shark feeding habits and decisions, we studied feeding and attack behaviour in Dyer Island Nature Reserve (South Africa) in two consecutive years. Specifically, we examined variation in approach patterns and preference using two types of bait (seal decoy and raw tuna) and asked whether these approach patterns and preferences were affected by changes in cloud cover. We found a significant association between approach type and sharks’ length such that large animals mainly performed vertical approaches, while smaller sharks preferred horizontal approaches. Horizontally-oriented approaches were the most often performed approaches. In addition, for the first approach, white sharks significantly preferred the seal-shaped decoy to the bait, but this preference disappeared with subsequent approaches. We observed effects of variation in cloud cover on both approach frequency and approach patterns. Approaches were more frequent as cloud cover increased, and we observed a transition from horizontally oriented approaches to vertically oriented approaches when cloud cover increased. As demonstrated for other environmental factors, cloud cover may affect the white shark’s ability to detect and approach a target, especially during the earliest stages of predation cycle. Keywords: behaviour, Carcharodon carcharias, cloud cover, Dyer Islan
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
Spatiotemporal distribution of great white shark (Carcharodon carcharias, Linnaeus 1758) along Italian coasts: Records from international Medlem program and other contributions
No full textThe Great white shark (Carcharodon carcharias Linnaeus 1758), is an apex predator living in almost all the seas of the world, preferring cold-temperate and temperate waters among the 8 and the 25° C (Compagno et al., 2005). It is nevertheless present with important populations in only 8 areas of the globe: California and Baja California, Mexico, central Chile, New England, Mediterranean Sea, Western South Africa, southern Australia, New Zealand and Japan (Compagno et al., 2005). Recently it was added to IUCN redlist as vulnerable species (IUCN 2001). It is one of the 72 species that have been observed in Italian waters (Vacchi & Serena, 2010), the biology and ecology of this shark is still quite misunderstood. Despite being aware of the importance of this species in the marine ecosystem (Carey et al., 1982; Casey & Pratt, 1985; Klimley et al., 1992) and in spite attention paid to it by the public, much remains to be discovered about the Mediterranean Great White Shark. The aim of the present work was to organize and analyze data concerning the spatiotemporal pattern of distribution of white sharks along Italian coasts, collected by international LEM programme database and by other contributions
Spatiotemporal patterns of distribution of large predatory sharks in Calabria (central Mediterranean, southern Italy)
Full text linkDuring the 2000-2009, a survey study on the spatiotemporal patterns of distribution of large predatory sharks was carried out in the Calabria region. A total of 12 species were recorded and among them the blue shark Prionace glauca and the bluntnose sixgill shark Hexanchus griseus were the most common ones. Also of interest was the frequency of species such as Carcharodon carcharias, Sphyrna zygaena and Cetorhinus maximus. 57% of all reported records derived from the Tyrrhenian side of the region and 43% on the Ionian side. A significant relationship between season of the year versus number of records was found, but this could be related to the small number of observers that were active during the winter months. The presence of Sphyrna lewini is reported for the study area; this species was previously recorded only in the western part of the Mediterranean Sea. This paper also provides evidence of the second and first documented accounts of white shark predation upon Tursiops truncatus and Stenella coeruleoalba, respectively, in the Mediterranean Sea. The recover ing of Ionian Sphyrna zygaena populations and the declining of Lamna nasus populations were also noted
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
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