6,767 research outputs found

    Saigas on the brink: Multidisciplinary analysis of the factors influencing mass mortality events

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    In 2015, more than 200,000 saiga antelopes died in 3 weeks in central Kazakhstan. The proximate cause of death is confirmed as hemorrhagic septicemia caused by the bacterium Pasteurella multocida type B, based on multiple strands of evidence. Statistical modeling suggests that there was unusually high relative humidity and temperature in the days leading up to the mortality event; temperature and humidity anomalies were also observed in two previous similar events in the same region. The modeled influence of environmental covariates is consistent with known drivers of hemorrhagic septicemia. Given the saiga population’s vulnerability to mass mortality and the likely exacerbation of climate-related and environmental stressors in the future, management of risks to population viability such as poaching and viral livestock disease is urgently needed, as well as robust ongoing veterinary surveillance. A multidisciplinary approach is needed to research mass mortality events under rapid environmental change

    Radiocarbon Dates on Saiga Antelope (Saiga Tatarica) Fossils from Yukon and the Northwest Territories

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    Saiga antelopes (Saiga tatarica), presently confined to Central Asia, spread westward to England and eastward to the Northwest Territories of Canada during the late Pleistocene. Two saiga cranial fragments from the Yukon Territory and the Northwest Territories have yielded radiocarbon dates of 13 390 ±180 and 14 920 ±160 B.P. respectively. Thus, saigas occupied the easternmost part of their known Pleistocene range toward the close of the Wisconsinan glaciation. Saigas probably died out between 13 000 and 10 000 years ago in North America because of rapid changes in climate and plantscapes occurring about that time, as former steppe-like terrain was replaced by spruce forest and tundra.Key words: saiga antelope, Saiga tatarica, Yukon Territory, Northwest Territories, late Pleistocene, vertebrate fossilsLa saïga, ou antilope des steppes,(Saiga tatarica) qu'on ne trouve actuellement qu'en Asie centrale, couvrait pendant le pléistocène tardif un territoire s'étendant vers l'ouest jusqu'à l'Angleterre et vers l'est jusqu'aux Territoires du Nord-Ouest du Canada. Deux fragments de crâne de saïga venant du Territoire du Yukon et des Territoires du Nord-Ouest ont donné par radiodatation un âge de 13 390 ± 180 et de 14 920 ± 160 BP respectivement. La saïga occupait donc la région la plus orientale de son territoire connu au pléistocène, vers la fin de la glaciation du Wisconsin. La saïga a probablement disparu il y a environ 13 000 à 10 000 ans en Amérique du Nord en raison des changements rapides dans le climat et les paysages végétaux qui se produisirent à cette époque, alors que la pessière et la toundra remplacèrent le terrain steppique.Mots clés: saïga, Saiga tatarica, Territoire du Yukon, Territoires du Nord-Ouest, pléistocène tardif, fossiles de vertébré

    Dynamical Properties of the 1/r^2-Type Supersymmetric t-J Model in a Magnetic Field: Manifestation of Spin-Charge Separation

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    Quasi-particle picture in a magnetic field is pursued for dynamical spin and charge correlation functions of the one-dimensional supersymmetric t-J model with inverse-square interaction. With use of exact diagonalization and the asymptotic Bethe-ansatz equations for finite systems, excitation contents of relevant excited states are identified which are valid in the thermodynamic limit. The excitation contents are composed of spinons, antispinons, holons and antiholons obeying fractional statistics. Both longitudinal and transverse components of the dynamical spin structure factor are independent of the electron density in the region where only quasi-particles with spin degrees of freedom (spinons and antispinons) contribute. The dynamical charge structure factor does not depend on the spin-polarization density in the region where only quasi-particles with charge (holons and antiholons) are excited. These features indicate the strong spin-charge separation in dynamics, reflecting the high symmetry of the model.Comment: 10 pages, 1 table (PS file), 15 figures (JPEG file). Submitted to J. Phys. Soc. Jp

    Coastal State\u27s Jurisdiction over Foreign Vessels

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    Capture of Ungulates in Central Asia Using Drive Nets: Advantages and Pitfalls Illustrated by the Endangered Mongolian Saiga Saiga Tatarica Mongolica

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    The study of mammals suffering intense poaching in remote areas poses an increasingly difficult conservation challenge, in part because the extreme flightiness of such species complicates safe capture. The benefits of handling (an opportunity to obtain biological information and attach radio collars) must be weighed against stress to the animals and potential capture-related mortality. In parts of Central Asia this problem is not trivial, as populations have been heavily harvested and opportunities for restraint are often limited. Mongolian saiga Saiga tatarica mongolica, being both Endangered and poached, typifies these issues. Here we describe capture protocols for adult females handled quickly and without anaesthesia. Using multiple vehicles driven at high speed, individual saiga were isolated from groups and herded into nets. Chase time was linearly associated with rectal temperature (P \u3c 0.03), with maximum pursuits and temperatures of 9 minutes and 43.1 degrees C, respectively; time to release averaged \u3c7 minutes. Given that rural residents often chase saiga and other desert and steppe-dwelling ungulates, for photography or for amusement, our results offer conservationists and government officials an empirical basis for recommending prudence on chase times and/or for recommending that the practice be prevented

    Saturated Ferromagnetism from Statistical Transmutation in Two Dimensions

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    The total spin of the ground state is calculated in the U -> infinity Hubbard model with uniform magnetic flux perpendicular to a square lattice, in the absence of Zeeman coupling. It is found that the saturated ferromagnetism emerges in a rather wide region in the space of the flux density \phi and the electron density n_e. In particular, the saturated ferromagnetism at \phi = n_e is induced by the formation of a spin-1/2 boson, which is a composite of an electron and the unit flux quantum.Comment: 4 pages, 3 figures; final versio

    Capture of ungulates in Central Asia using drive nets: advantages and pitfalls illustrated by the Endangered Mongolian saiga \u3ci\u3eSaiga tatarica mongolica\u3c/i\u3e

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    The study of mammals suffering intense poaching in remote areas poses an increasingly difficult conservation challenge, in part because the extreme flightiness of such species complicates safe capture. The benefits of handling (an opportunity to obtain biological information and attach radio collars) must be weighed against stress to the animals and potential capture-related mortality. In parts of Central Asia this problem is not trivial, as populations have been heavily harvested and opportunities for restraint are often limited. Mongolian saiga Saiga tatarica mongolica, being both Endangered and poached, typifies these issues. Here we describe capture protocols for adult females handled quickly and without anaesthesia. Using multiple vehicles driven at high speed, individual saiga were isolated from groups and herded into nets. Chase time was linearly associated with rectal temperature (P,0.03), with maximum pursuits and temperatures of 9 minutes and 43.1 degrees C, respectively; time to release averaged \u3c7 minutes. Given that rural residents often chase saiga and other desert and steppe-dwelling ungulates, for photography or for amusement, our results offer conservationists and government officials an empirical basis for recommending prudence on chase times and/or for recommending that the practice be prevented
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