1,721,016 research outputs found
Denning ecology of Scandinavian brown bears (Ursus Arctos) in a dynamic landscape
Full text linkHuman encroachment, habitat fragmentation, resource exploitation, and hunting can affect the presence, habitat use, behavior, life history, and population dynamics of wildlife species. Wide-ranging large mammals with low reproductive rates are especially susceptible to negative fragmentation effects at the population level. In Scandinavia, brown bears (Ursus arctos) were persecuted for centuries, almost leading to extinction. However, they recovered after being protected in the early 20th century. As an adaptation to survive the winter in environments with strong seasonality and when food is scarce, the brown bear hibernates. Therefore, they spend about 5-7 months in a den every winter. Den disturbance by humans leads to arousal from hibernation and den abandonment, which is extremely costly in terms of energy loss and offspring survival. This makes the choice of den site and den type important, and is a reason why the brown bear avoids human activity. Especially pregnant females are more selective in choice of den type as they give birth to multiple altricial young in their winter den. Because reproduction is costly in terms of energy use, pregnant females may show a preference for anthill dens, as these seem to result in the best reproductive success. However, there is an indication of a decline in the use of anthill dens by brown bears in our study area, which might indicate a decline in the availability of suitable, i.e., large, inactive, anthills. This could partially be because anthills probably take a long time to reach dimensions suitable for denning and therefor are most likely found in old forest. Also, clearcuts are probably destroying anthills directly, and therefore potential dens. Intensive forestry could therefore be a cause to the decline in anthill use for denning. To sum up, good quality denning sites are probably far away from anthropogenic activity and in older growth forests containing big anthills. I hypothesize (H1) that there has, in fact, been a decrease in the probability of female bears denning in an anthill den in the study area over the years 1986-2014. Secondly, I hypothesize (H2) that the probability of denning in an anthill den is positively related to (H2a) old growth forests and to (H2b) areas far from human disturbance (e.g., settlements and roads). I also predict (H2c) that anthill dens occur less frequently in clearcuts than random. Thirdly, I hypothesize (H3) that habitat loss and fragmentation has negatively affected the availability of good-quality denning sites during the study period (1986-2014). I used a logistic mixed effect regression model to predict the probability for a bear (all bears) to use an excavated anthill as a den. I also did this separately for adult pregnant females (< 3 years) and adult females (< 3 years) that entered the den with cubs (1 year and older). Results showed a temporal decline (1986-2014), and a positive correlation with age of the bear. I used the resource selection function (RSF) modeling approach to evaluate spatial patterns in den site selection by comparing resource ‘use’ with resource ‘availability’ with a logistic regression model. Results showed avoidance of anthropogenic structures, and clearcuts and bogs. I also mapped the model output of the most parsimonious model of the RSF models to assess den site selection for all dens, and for anthill dens alone (used by females of all age classes). With this I visualized general denning and anthill den habitat suitability in the study area (2000-2014). The results showed a degradation in quality of habitat over the study period
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
Niche differentiation among boreal mammals and birds regarding their roles as endozoochorical seed dispersers
Full text linkPlant seed dispersal by endozoochory (seed dispersal via the digestive system of animals) is an important process affecting plant species composition in ecosystems. Recent studies in temperate regions have shown that a wide range of animal species disperse plant seeds via endozoochory, and that plant species from many taxa and with different dispersal adaptations are dispersed through endozoochory. The seed dispersal niche of an animal implies its role as seed disperser, where the assemblage of plant species dispersed is an important component. The endozoochorical seed dispersal niches of the animals in the boreal forest are poorly studied, and this study seeks to assess the seed dispersal niches of an assemblage of medium-sized and large boreal forest mammals and birds by quantifying the assemblage of plant species germinating from their scats
Selection of trees marked by rubbing by Andean bears in the Peruvian dry forest
Full text linkThe Andean bear (Tremarctus ornatus) is one of the least known species of Ursidae. One area about which very little is known is the bear’s marking behavior. This is a key aspect of bear ecology and marks can give information on the behavior and relative abundance of the species in an area. Mammalian selection of marking sites is associated with location, often in areas frequently used by conspecifics, and the physical characteristics of the tree or substrate used for marking. In this study I tested the hypothesis that Andean bears in the Peruvian dry forest leave more rub marks on trees close to water and on certain species based on the size and characteristics of the tree. Analysis of 117 mark locations, 94 rub trees and 243 available trees within a 5-m radius of rub trees, hereafter called unmarked trees showed that the bears preferred to rub trees with a smaller height and closer to water holes. Water is rare in the dry forest and waterholes act as a central point for bear activity. The highest selection ratio for rub trees was found for chilco (Baccharis sp), chaquiroz (Pithecellobium excellsum), vichayo (Beautempsia avicenniifolia), and vichayo falso (Capparicordis crotonoides). These species may have been chosen because of the resin and sap properties of the bark and the trees’ aroma, which could help the persistence and detection of bear signal by conspecifics. This study presents the first insight into how bears of the Peruvian dry forest rub trees for communication and could assist in future study and conservation of this species.M-ECO
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
Unravelling the role of wild boar carcasses in African swine fever transmission and control
No full textIn recent years, the emergence of infectious wildlife diseases has posed significant health risks to wildlife populations, domestic animals, and, in the case of zoonotic pathogens, to humans. One of these diseases is African swine fever (ASF), which has spread rapidly across numerous countries and affects both the wild boar (Sus scrofa) and domestic pigs (Sus scrofa domesticus). The disease causes severe symptoms and leads to high mortality rates, resulting in substantial economic losses in the pork industry and reductions in wild boar populations. ASF virus (ASFV) transmission in both domestic pigs and wild boar can occur through various pathways, including contact with infected group members. In wild boar populations, transmission is primarily associated with contact with carcasses of conspecifics that died from ASF.This thesis explores the multifaceted role of wild boar carcasses in ASF outbreaks, providing comprehensive insights into the transmission dynamics based on the behavior of wild boar and other scavenger species, and offers strategies for effective disease management.Chapter I focuses on understanding wild boar behavior towards conspecific carcasses. Using 64 carcasses placed systematically throughout a temperate mountainous region in southeast Germany and monitored via camera traps, we recorded 446 wild boar events over 9,625 camera-trapping days. Of these, 195 events involved direct contact with carcasses, which were detected on average 65 days after placement, with shorter detection times correlated with warmer temperatures. No direct cannibalism was observed; however, frequent behaviors such as chewing on bones and touching carcasses raise concerns about the potential for ASFV transmission. These findings highlight the critical need for timely search and removal of carcasses to prevent disease spread, particularly in the early stages of decomposition, as wild boar approached and touched carcasses increasingly during later stages of decomposition.Chapter II examines the role of vertebrate scavengers in the dispersion of infectious material, which can complicate efforts to locate and remove carcasses. The study utilized 41 wild boar carcasses (Chapter III delves into the decomposition process of wild boar carcasses and explores whether natural decomposition can inactivate pathogens like ASFV. This investigation monitored internal temperatures and pH levels in 64 decomposing carcasses, pH levels in 12 carcasses, and the soil pH surrounding 74 carcasses. Findings revealed significant temperature increases during aerobic decomposition, with maximum internal temperatures reaching 58°C and pH levels rising above 9 in the soil. However, the pH levels in both carcass and soil did not fall below 4, a critical threshold for inactivating ASFV. Although these findings suggest some potential for pathogen inactivation, the study concluded that the dynamics of temperature and pH alone are insufficient to effectively inactivate ASFV. This highlights the need for complementary strategies to manage the risk of ASF spread from decomposing carcasses and calls for future research exploring pathogen survival during the decomposition process.Chapter IV evaluates the effectiveness of drone-based thermal imaging in detecting wild boar carcasses under various environmental and carcass conditions. With 379 flyovers of 42 carcasses, the study determined that detection probability was influenced by factors such as habitat type, air temperature, forest canopy cover, and the presence of maggots. Specifically, open habitats and warmer air temperatures, resulting in the accumulation of maggot-masses, facilitated higher detection rates (up to 80%), while dense forests and low air temperature (below 3°C) reduced the detection probability. The study's findings underscore the potential of thermal imaging as a tool to support ground searches by highlighting its possibilities and limitations.Overall, the findings of this thesis provide a comprehensive investigation of potential disease transmission dynamics and prevention methods and offer crucial insights for wildlife disease management. The work in this thesis underscores the necessity for continued research in disease transmission, and highlights the importance of refining strategies for controlling ASF and other infectious wildlife diseases
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