1,721,166 research outputs found
Canid livestock predation research has become more robust, but gaps remain
Full text linkLivestock have been and continue to be an important part of the agricultural landscape in North America. Research on how to mitigate livestock predation by North American carnivores developed quickly during the 20th century. We collected information on 75 field-based experiments published since 1970 that evaluated strategies to mitigate livestock predation by wolves and coyotes. Collected research came from journal articles and grey literature, and we identified 22 mitigation strategies. We developed a ‘robustness index’ to compare each experiment based on its empirical design, temporal/spatial coverage, and sample size. We found the robustness index values increased over time, particularly for lethal mitigation strategies. Overall robustness of research on lethal mitigation strategies was similar to the robustness of research on non-lethal mitigation strategies. Some strategies were not well evaluated as 12 of the 22 mitigation strategies were evaluated only once or twice; some common lethal mitigation strategies (e.g., shooting) were not formally evaluated until the 1990s. We identified some robust assessments of mitigation strategies that reported positive effects (e.g., predator sterilization, protection llamas). In some cases, these were the only evaluation or the only robust evaluation of a strategy. In the few cases where there were multiple robust assessments for a single strategy, the outcomes were inconsistent. No strategies evaluated more than once had consistently high robustness index values and positive outcomes. Importantly, older practices based on less robust research should be re-evaluated or discarded
Density and genetic diversity of grizzly bears at the northern edge of their distribution
Full text linkSpecies at the periphery of their range are typically limited in density by poor habitat quality. As a result, the central–marginal hypothesis (CMH) predicts a decline in genetic diversity of populations toward the periphery of a species’ range. Grizzly bears (Ursus arctos) once ranged throughout most of North America but have been extirpated from nearly half of their former range, mainly in the south. They are considered a species at risk even in Canada’s remote North, where they occupy the northernmost edge of the species’ continental distribution in a low-productivity tundra environment. With climate change, one of their main prey species in the tundra (caribou), which has always shown yearly fluctuations, is declining, but simultaneously, grizzlies
appear to be expanding their range northward in the same tundra environment. Yet, a lack of population density estimates across the North is hindering
effective conservation action. The CMH has implications for the viability of peripheral populations, and the links between population fluctuations, potential bottlenecks, and genetic diversity need to be determined to contribute to species’ conservation. Using noninvasive genetic sampling from 2012 to 2014 and autosomal DNA genotyping (via microsatellites), we estimated bear density using a spatial capture–recapture framework and analyzed genetic diversity using observed heterozygosity (Ho), allelic richness (AR), and expected heterozygosity (He). We compared our findings to other studies that used comparable methodologies on grizzly bears and a related species (black bears; Ursus americanus). We found densities of grizzly bears that were low for the species but characteristic for the region (5.9 ± 0.4 bears/1000 km2 ), but with high Ho (0.81 ± 0.05), AR (7 ± 0.78), and He (0.71 ± 0.03), despite a signal of recent bottlenecks. In both species, peripherality was not correlated with Ho but was negatively correlated with density. We suggest that the apparent growth of this expanding population of grizzlies offsets the negative impacts of recent bottlenecks on Ho. Indigenous knowledge provides historical context (on the order of centuries, e.g., arctic large mammal fluctuations, grizzly bear bottlenecks) for the current bear population dynamics (on the order of decades, e.g., climate change, northern grizzly bear expansion)
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
Space–time clusters for early detection of grizzly bear predation
Full text linkAccurate detection and classification of predation events is important to determine
predation and consumption rates by predators. However, obtaining this information
for large predators is constrained by the speed at which carcasses disappear and the
cost of field data collection. To accurately detect predation events, researchers have
used GPS collar technology combined with targeted site visits. However, kill sites are
often investigated well after the predation event due to limited data retrieval options
on GPS collars (VHF or UHF downloading) and to ensure crew safety when working
with large predators. This can lead to missing information from small-prey
(including
young ungulates) kill sites due to scavenging and general site deterioration (e.g., vegetation
growth). We used a space–time permutation scan statistic (STPSS) clustering
method (SaTScan) to detect predation events of grizzly bears (Ursus arctos) fitted with
satellite transmitting GPS collars. We used generalized linear mixed models to verify
predation events and the size of carcasses using spatiotemporal characteristics as predictors.
STPSS uses a probability model to compare expected cluster size (space and
time) with the observed size. We applied this method retrospectively to data from
2006 to 2007 to compare our method to random GPS site selection. In 2013–2014,
we applied our detection method to visit sites one week after their occupation. Both
datasets were collected in the same study area. Our approach detected 23 of 27 predation
sites verified by visiting 464 random grizzly bear locations in 2006–2007, 187
of which were within space–time clusters and 277 outside. Predation site detection
increased by 2.75 times (54 predation events of 335 visited clusters) using 2013–2014
data. Our GLMMs showed that cluster size and duration predicted predation events
and carcass size with high sensitivity (0.72 and 0.94, respectively). Coupling GPS satellite
technology with clusters using a program based on space–time probability models
allows for prompt visits to predation sites. This enables accurate identification of the
carcass size and increases fieldwork efficiency in predation studies
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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