12,055 research outputs found

    Home Is Where the Food Is: Causes and Consequences of Partial Migration in Elk

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    Migratory and non-migratory ungulates often coexist in partially migratory populations, but the mechanisms that drive and maintain different migratory behaviors within the same herd are poorly understood. In western North America, increasing numbers of elk (Cervus canadensis) reside on low-elevation winter range year-round. These residents can cause issues associated with crop damage, potential for disease transmission to livestock, and reduced effectiveness of harvest management strategies. Because migrants transfer nutrients, alter carnivore distributions, and structure vegetative communities across seasonal ranges, reductions in migratory behavior raise ecological as well as management-related concerns. This work investigated the factors affecting migratory behavior of female elk and assessed the nutritional consequences of different behaviors. In our study of a partially migratory elk population in west-central Montana, we found that migrants had access to lower-quality forage during summer than their non-migratory counterparts. In our broader-scale study of 16 elk herds across western Montana, we found that migratory behavior of individuals was best-explained by a combination of native forage, irrigated agriculture, and conspecific density. Together, these results reveal a strong influence of irrigated agriculture on migratory behavior of elk. Migration is commonly considered a strategy to increase assess to high-quality forage; our results reveal that irrigated agriculture can alter the traditional nutritional benefits of migration by providing high-quality forage at low elevations throughout the year. Although elk were less likely to migrate if they overwintered in irrigated agricultural areas, predictable availability of better forage elsewhere mitigated that effect. Thus, maintaining or improving the quality of forage available on migratory summer ranges should encourage migratory behavior, as should excluding elk from irrigated agricultural areas. Given the importance of nutritional intake during late summer and fall to elk fecundity and calf survival, improving the forage available to migrants could go beyond preserving current behaviors to effectively increase prevalence of migration where irrigated agriculture has subsidized increasing numbers of resident ungulates

    Nipah shell disorder, modes of infection, and virulence

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    The Nipah Virus (NiV) was first isolated during a 1998–9 outbreak in Malaysia. The outbreak initially infected farm pigs and then moved to humans from pigs with a case-fatality rate (CFR) of about 40%. After 2001, regular outbreaks occurred with higher CFRs (~71%, 2001–5, ~93%, 2008–12). The spread arose from drinking virus-laden palm date sap and human-to-human transmission. Intrinsic disorder analysis revealed strong correlation between the percentage of disorder in the N protein and CFR (Regression: r2 = 0.93, p < 0.01, ANOVA: p < 0.01). Distinct disorder and, therefore, genetic differences can be found in all three group of strains. The fact that the transmission modes of the Malaysia strain are different from those of the Bangladesh strains suggests that the correlations may also be linked to the modes of viral transmission. Analysis of the NiV and related viruses suggests links between modes of transmission and disorder of not just the N protein but, also, of M shell protein. The links among shell disorder, transmission modes, and virulence suggest mechanisms by which viruses are attenuated as they passed through different cell hosts from different animal species. These have implications for development of vaccines and epidemiological molecular analytical tools to contain outbreaks

    Emerging Bacterial Zoonoses in Migratory Birds

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    The seasonal variance, global warming, and extraordinary climate conditions around the world change the physiology and behaviors of different animal species. Free ranging birds and mammals harbor some species of potentially pathogenic bacteria; however, these diseases do not result in spontaneous deaths. Being significant individuals of the ecosystem, free living immigrant birds are prone to bacterial diseases. Migratory birds are accommodated in areas located on migration routes to provide rest, food, and water. During this stay, they spread the diseases they bring with them to the poultry in the region and to the poultry farms that do not take adequate biosecurity measures—especially to the free range poultry farms. The migratory birds confront numerous health risks brought on by bacterial species that affect other livestock populace and public health. This chapter provides brief reference on bird-to-bird transmission and general aspects of emerging bacterial zoonoses of migratory birds for wildlife professionals, veterinary practitioners, and students

    Migration to the US among rural Puerto Ricans who inject drugs: influential factors, sources of support, and challenges for harm reduction interventions

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    Background: While PWID of Puerto Rican origin have been migrating to the US for decades, the range of factors influencing their migration to the US and the resources they draw on to do so are not well understood. This is particularly true for rural Puerto Rican PWID, and the present study is the first empirical research to document migration patterns among this population. The specificities of their migration raise important challenges that need to be documented in order to implement more effective harm reduction policies at home (Puerto Rico) and abroad (US). Methods: This paper draws from data obtained employing a modified NHBS survey which was administered to (N =296) PWID in four rural municipalities of Puerto Rico with participants 18 years or older. The primary dependent variables for this paper are the number of times a person has lived in the continental US, and if they are planning on moving to the continental US in the future. Results: Findings suggest that 65% of the sample reported ever lived in the US and that 49% are planning on moving in the future. The number of times living in the US is associated with higher education and older age, but not with self-reported positive HIV or HCV statuses. Planning to move to the US is associated with knowing PWID who have moved or plan to move, negatively associated with age, and is not associated with HIV or HCV status. Around one-third of those that lived in the US reported having some sort of support, with the majority receiving support from family sources. No participant received help to enter HIV/HCV treatment. Conclusions: A multi-region approach to prevention is required to make a dent in curbing HIV/HCV transmission in this population. Understanding PWID migration patterns, risk behaviors, and health care needs in the US is now more important than ever as natural disasters prompted by human-made climate change will only increase in the future, raising demands not only for service providers but also harm reduction policies to cope with an increasing influx of “climate refugees” as PWID move across national borders

    Seasonal movements and habitat use of African buffalo in Ruaha National Park, Tanzania.

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    BACKGROUND:Assessing wildlife movements and habitat use is important for species conservation and management and can be informative for understanding population dynamics. The African buffalo (Syncerus caffer) population of Ruaha National Park, Tanzania has been declining, and little was known about the movement, habitat selection, and space use of the population, which is important for understanding possible reasons behind the decline. A total of 12 African buffalo cows from four different herds were collared with satellite transmitters. Movements were assessed over 2 years from 11 animals. RESULTS:The space use of the individual collared buffaloes as an approximation of the 95% home range size estimated using Brownian bridge models, ranged from 73 to 601 km2. The estimated home ranges were larger in the wet season than in the dry season. With the exception of one buffalo all collared animals completed a wet season migration of varying distances. A consistent pattern of seasonal movement was observed with one herd, whereas the other herds did not behave the same way in the two wet seasons that they were tracked. Herd splitting and herd switching occurred on multiple occasions. Buffaloes strongly associated with habitats near the Great Ruaha River in the dry season and had little association to permanent water sources in the wet season. Daily movements averaged 4.6 km (standard deviation, SD = 2.6 km), with the longest distances traveled during November (mean 6.9 km, SD = 3.6 km) at the end of the dry season and beginning of the wet season. The shortest daily distances traveled occurred in the wet season in April-June (mean 3.6 km, SD = 1.6-1.8 km). CONCLUSION:The Great Ruaha River has experienced significant drying in the last decades due to water diversions upstream, which likely has reduced the suitable range for buffaloes. The loss of dry season habitat due to water scarcity has likely contributed to the population decline of the Ruaha buffaloes

    Behavioral responses of sub-adult Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) to electromagnetic and magnetic fields under laboratory conditions

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    Electromagnetic fields (EMF) produced by high voltage (HV), submarine transmission cables leading from offshore wind energy generation facilities could affect foraging or migratory behaviors of electro-receptive fishes, including endangered Atlantic Sturgeon. However, no published studies have quantitatively evaluated the possible behavioral effects of EMF exposure on sturgeon during residence in coastal waters. This study evaluated behavioral responses by sub-adult Atlantic Sturgeon to electromagnetic and magnetic fields under controlled laboratory conditions. Fabricated EMF generators were used to emulate a range of field EMF conditions that migratory fishes could encounter in proximity to submarine HV sources. Sensor arrays and digital video recorders synoptically quantified EMF conditions and fish behaviors during experimental trials. This thesis will describe the unique, experimental EMF generator/sensor array, present results of the behavior study, and suggest implications of the findings for Atlantic Sturgeon management and conservation. 45 trials were conducted over the course of the study. Study fish were subjected to 3 different field strengths (5µT, 100 µT, 1000 µT), generated using both AC and DC current. Time spent in generated field area, number of passes through the field area, and swimming speed were used to quantify behavioral changes in test subjects. From the data collected and analyzed there was no evidence indicating a change in fish behavior due to the influence of field strengths, field orientations, or field types used during the study

    The physiology of movement

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    Movement, from foraging to migration, is known to be under the influence of the environment. The translation of environmental cues to individual movement decision making is determined by an individual's internal state and anticipated to balance costs and benefits. General body condition, metabolic and hormonal physiology mechanistically underpin this internal state. These physiological determinants are tightly, and often genetically linked with each other and hence central to a mechanistic understanding of movement. We here synthesise the available evidence of the physiological drivers and signatures of movement and review (1) how physiological state as measured in its most coarse way by body condition correlates with movement decisions during foraging, migration and dispersal, (2) how hormonal changes underlie changes in these movement strategies and (3) how these can be linked to molecular pathways. We reveale that a high body condition facilitates the efficiency of routine foraging, dispersal and migration. Dispersal decision making is, however, in some cases stimulated by a decreased individual condition. Many of the biotic and abiotic stressors that induce movement initiate a physiological cascade in vertebrates through the production of stress hormones. Movement is therefore associated with hormone levels in vertebrates but also insects, often in interaction with factors related to body or social condition. The underlying molecular and physiological mechanisms are currently studied in few model species, and show -in congruence with our insights on the role of body condition- a central role of energy metabolism during glycolysis, and the coupling with timing processes during migration. Molecular insights into the physiological basis of movement remain, however, highly refractory. We finalise this review with a critical reflection on the importance of these physiological feedbacks for a better mechanistic understanding of movement and its effects on ecological dynamics at all levels of biological organization
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