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Aspects of the Feeding Ecology of the Antillean Manatee (<italic>Trichechus manatus manatus</italic>) in the Wetlands of Tabasco, Mexico
No full textManatees (Mammalia: Sirenia), along with the closely related dugongs, are the only herbivorous marine mammals. Manatees consume a wide variety of vascular plants and algae in both marine and freshwater habitats. However, little is known about what characteristics influence diet and food selectivity, especially in freshwater habitats, which represent a large portion of the available habitat for the endangered Antillean manatee, Trichechus manatus manatus, in Central and South America. Understanding foraging ecology is an important element of effective conservation strategies.This dissertation investigated various aspects of the foraging ecology of the Antillean manatee in a freshwater habitat, specifically: 1) how plant availability (i.e. species richness, diversity, and abundance) varied seasonally with changes in water depths, 2) manatee food selectivity from a representative set of plant species from that freshwater habitat, and 3) the relationship of plant nutritive compounds and availability with manatee food selectivity. In addition, this dissertation describes the multiple uses of sonar technology for studying manatees and habitat characteristics in freshwater.Plant availability to manatees was evaluated by conducting monthly plant surveys from July 2010-July 2011 in four contact lakes in the wetlands of Tabasco, Mexico. Manatee food selectivity was examined by conducting food selection experiments on a wild adult manatee during the low water season with 54 plant species representing 25+ genera. The nutritive components (i.e. crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose (HC), and ash) and plant availability values for selected and non-selected plants species were evaluated to determine their relationship with manatee food selectivity. The applicability of using side-scan sonar for manatee research was tested in various freshwater and estuarine habitats in Honduras, Costa Rica, Panama, and the wetlands of Tabasco, Mexico between 2006-2011.The major findings of this dissertation are as follows. Plant species richness, diversity, and abundance were greatest during the rising water season (July-August) and lowest during the low water season (March-June). No plants were available in April-June, which represented the majority of the low water season. The wild manateeselected 27 (11+ genera) of the 54 species examined during the feeding experiments. Of the plant characteristics tested (i.e. nutritive components and plant availability), only digestible fiber (HC) was significantly related to manatee food selection, with manateesselecting plants with higher HC content. Four unique applications were identified for the use of side-scan sonar to facilitate manatee research in freshwater habitats: 1) confirmation of visual sightings and determination of group size, 2) determination of mother-calf pairs, 3) habitat characterization, and 4) assisting manatee captures.Results from this study reveal that manatees living in the freshwater wetlands of Tabasco, Mexico have to cope with a highly seasonal availability of plants and that while manatees consume plants from a wide variety of genera, they are highly selective. Unlike other herbivorous mammals, manatee food selectivity was not influenced by CP, NDF, or ADF, but rather by digestible fiber. A unique suit of anatomical and physiological characteristics suggests that manatees may be fiber digestion specialists. Both seasonal plant availability and the manatee's large dietary breadth must be considered when developing 1) conservation strategies for wild manatees in freshwater habitats and 2) protocols for captive rehabilitation of orphaned and stranded manatees that will be reintroduced into the wild.</p
The Foraging Ecology of the Delacour's langur (Trachypithecus delacouri) in Van Long Nature Reserve, Vietnam
No full textDelacour's langurs (Trachypithecus delacouri), one of the six limestone langur taxa of Southeast Asia, inhabit isolated, rugged limestone karst mountains in Northern Vietnam, although the reason for their current restriction to this habitat is unclear. The occupation of karst habitats by limestone langurs has been attributed to the refuge these rocky outcrops provide in a dramatically anthropogenically-altered landscape. Conversely, several ecological explanations have been proposed to account for their distribution, though the ecology of wild Delacour's langurs had yet to be studied. In this dissertation, I quantified the foraging ecology of Delacour's langurs living on Dong Quyen Mountain in Van Long Nature Reserve, Vietnam to address if these langurs show special adaptations to limestone karst or if they are exploiting a refuge habitat into which they have been pushed. I quantified their foraging ecology by systematically investigating their diet and feeding ecology, the chemisty of their eaten leaves, and the locomotions and substrates they utilized.
From August 2007 through July 2008, I used instantaneous focal-animal sampling during all-day follows of Delacour's langurs on Dong Quyen Mountain. I collected data on activity budget, diet, and positional behavior. I also collected samples of soils and eaten and uneaten leaves which were tested for phytochemical content.
With nearly 79% leaves in the diet, 60% of which were young leaves, Delacour's langurs are among the most folivorous of studied colobines, and- along with the closely related T. leucocephalus of southern China- the most folivorous of the Asian langurs. None of the plants that were important in the Delacour's langur diet were endemic limestone plants, and therefore feeding dependence alone cannot explain the current distribution of limestone langurs on karst habitat. Langurs ate leaves with high protein:fiber ratios, and despite a high percentage of carbon in the soil, young leaves were available throughout the year and plant defenses did not seem to have a large impact on eaten leaves. Delacour's langurs spent nearly 80% of their time on rocks. Quadrupedalism was their dominant locomotor style, more than double that of climbing. Terrestrialism, however, does not adequately describe the dangerous locomotion of these langurs; they are cliff-climbers. Delacour's langurs leapt only 6% of the time, much less than other African and Asian colobines, but their morphology (intermembral index) does not suggest terrestrialism or an evolutionary adaptation for limestone karst. Delacour's langurs appear to be a flexible taxon occupying a refuge habitat into which they have pushed. However, this restricted limestone habitat does not appear limiting in resources. The population at Van Long Nature Reserve is increasing which means that- if protected- this local population can rebound. Persistent hunting for traditional medicine and the more recent emergence of quarrying limestone for cement, however, threatens their survival.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Social and reproductive strategies of male mantled howlers (Alouatta palliata) at La Pacifica, Costa Rica
No full textThe author has granted permission for their work to be available to the general public.This dissertation examines the competitive and cooperative strategies of male mantled howlers <italic>(Alouatta palliata)</italic> living within a fragmented habitat at La Pacifica (LP), Costa Rica. Mantled howlers exhibit considerable intraspecific variation in their social behavior, and there remains much to learn regarding the nature of their sociality and the proximate mechanisms that underlie it, particularly among males living in multimale groups. In contrast to males at other mantled howler study sites, males at LP had higher rates of within-group agonism, and exhibited clear dominance hierarchies. Both groups inhabited a fragmented forest, which may exert greater pressure to compete for both food and reproductive resources than mantled howler males living in more intact forests. However, data from this dissertation also suggest that males may adjust competitive relationships as forest fragment characteristics within the same population vary. The group inhabiting the larger forest fragment experienced higher intergroup competition but lower intragroup competition than the group inhabiting the smaller fragment, allowing higher-ranking males to be more tolerant of subordinates accessing key resources, including females, in order to cooperate in group defense. Despite clear hierarchies, males at LP nevertheless form both preferred and avoided associations with specific males, which suggest that cooperative relationships among males have adaptive value. Neither rank nor age emerged as clear drivers shaping competitive and cooperative relationships. Collectively, these results suggest that male mantled howlers show considerable flexibility in their social relationships that are likely dependent on a complexity of ecological, social, and demographic factors.Anthropolog
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Average Body Weight for Mantled Howling Monkeys (Alouatta palliata): An Assessment of Average Values and Variability
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