1,097 research outputs found
Bears Remain Top Summer Predators
In the ten years since wolves (Canis lupus) were restored to Yellowstone National Park (YNP), elk (Cervus elaphus) numbers have substantially decreased. The northern range elk herd is the largest elk herd in Yellowstone, and constitutes the majority of the park’s elk population. During 1994–2005, early winter counts of northern Yellowstone elk decreased from 19,045 to 9,545. Also, during winters 2000–2004, calf:cow ratios declined from 29:100 to 12:100, and were among the lowest recorded during the past several decades. Though many factors (e.g., predation, hunting, and drought) likely contributed to this decreasing abundance and low recruitment, several state and federal legislators continue to speculate that wolves are the primary reason for the recent decrease in elk recruitment rates, and have called for the immediate delisting and liberal control of the abundance and distribution of wolves. Because both wolves and elk are culturally, economically, and ecologically important in the Yellowstone area, it is vital to determine the basis for the decline in the elk population. To help this effort, we initiated a three-year study of northern Yellowstone elk calf mortality in May 2003. Our study was designed to follow up on Dr. Francis Singer et al.’s baseline pre–wolf restoration elk calf mortality study (1987–1990)
Elk Calf Survival and Mortality Following Wolf Restoration to Yellowstone National Park
We conducted a 3-year study (May 2003–Apr 2006) of mortality of northern Yellowstone elk (Cervus elaphus) calves to determine the cause for the recruitment decline (i.e., 33 calves to 13 calves/100 adult F) following the restoration of wolves (Canis lupus). We captured, fit with radiotransmitters, and evaluated blood characteristics and disease antibody seroprevalence in 151 calves ≤6 days old (68M:83F). Concentrations (x, SE) of potential condition indicators were as follows: thyroxine (T4; 13.8 μg/dL, 0.43), serum urea nitrogen (SUN; 17.4 mg/dL, 0.57), γ-glutamyltransferase (GGT; 66.4 IU/L, 4.36), gamma globulins (GG; 1.5 g/dL, 0.07), and insulin-like growth factor-1 (IGF-1; 253.6 ng/mL, 9.59). Seroprevalences were as follows: brucellosis (Brucella abortus; 3%), bovine-respiratory syncytial virus (3%), bovine-viral-diarrhea virus type 1 (25%), infectious-bovine rhinotracheitis (58%), and bovine parainfluenza-3 (32%). Serum urea nitrogen, GGT, GG, and IGF-1 varied with year; T4, SUN, and GG varied with age (P ≤ 0.01); and SUN varied by capture area (P=0.02). Annual survival was 0.22 (SE=0.035, n=149) and varied by calving area but not year. Neonates captured in the Stephens Creek/Mammoth area of Yellowstone National Park, USA, had annual survival rates \u3e3x higher (0.54) than those captured in the Lamar Valley area (0.17), likely due to the higher predator density in Lamar Valley. Summer survival (20 weeks after radiotagging) was 0.29 (SE=0.05, n=116), and calving area, absolute deviation from median birth date, and GG were important predictors of summer survival. Survival during winter (Nov–Apr) was 0.90 (SE=0.05, n=42), and it did not vary by calving area or year. Sixty-nine percent (n=104) of calves died within the first year of life, 24% (n=36) survived their first year, and 7% (n=11) had unknown fates. Grizzly bears (Ursus arctos) and black bears (Ursus americanus) accounted for 58–60% (n = 60–62) of deaths, and wolves accounted for 14–17% (n = 15–18). Summer predation (95% of summer deaths) increased, and winter malnutrition (0% of winter deaths) decreased, compared with a similar study during 1987–1990 (72% and 58%, respectively). Physiological factors (e.g., low levels of GG) may predispose calves to predation. Also, the increase in bear numbers since wolf restoration and spatial components finer than the northern range should be considered when trying to determine the causes of the northern Yellowstone elk decline. This is the first study to document the predation impacts from reintroduced wolves on elk calf mortality in an ecosystem already containing established populations of 4 other major predators (i.e., grizzly and black bears, cougars [Puma concolor], and coyotes [Canis latrans]). The results are relevant to resource managers of the Yellowstone ecosystem in understanding the dynamics of the elk population, in providing harvest quota recommendations for local elk hunts to the Montana Department of Fish, Wildlife and Parks, the United States Fish and Wildlife Service regarding wolf and grizzly bear recovery, and to all areas worldwide where predators are increasing, by providing managers with information about potential carnivore impacts on elk populations
Mitochondrial reactivity following acute exposure to experimental pain testing in people with HIV and chronic pain
Magnetic Phase Diagram of Spin-1/2 Two-Leg Ladder with Four-Spin Ring Exchange
We study the spin-1/2 two-leg Heisenberg ladder with four-spin ring exchanges
under a magnetic field. We introduce an exact duality transformation which is
an extension of the spin-chirality duality developed previously and yields a
new self-dual surface in the parameter space. We then determine the magnetic
phase diagram using the numerical approaches of the density-matrix
renormalization-group and exact diagonalization methods. We demonstrate the
appearance of a magnetization plateau and the Tomonaga-Luttinger liquid with
dominant vector-chirality quasi-long-range order for a wide parameter regime of
strong ring exchange. A "nematic" phase, in which magnons form bound pairs and
the magnon-pairing correlation functions dominate, is also identified.Comment: 18pages, 7 figure
Oxidation of Thiols to Disulfides using an Environmentally “Green” Organocatalyst and New Mechanistic Insights
The selective oxidation of thiols to disulfides is an area of great importance in the areas of materials and medicinal chemistry research. The production of polymers, rubber, pharmaceuticals, and the folding of proteins in biological systems all rely on the formation of disulfide bonds. Herein, we introduce a stoichiometric and electrocatalytic method for the oxidation of various pharmaceutically and biologically relevant thiols into their respective disulfides in more environmentally benign solvents such as water and alcohol solvents. The scope of the transformation was evaluated and a detailed mechanistic study involving control experiments, experimental kinetic studies, and computational investigations led to new insights into how the oxidation takes place via an unusual anionic process
Orthogonality catastrophe in a one-dimensional system of correlated electrons
We present a detailed numerical study of the orthogonality catastrophe
exponent for a one-dimensional lattice model of spinless fermions with nearest
neighbor interaction using the density matrix remormalization group algorithm.
Keeping up to 1200 states per block we achieve a very great accuracy for the
overlap which is needed to extract the orthogonality exponent reliably. We
discuss the behavior of the exponent for three different kinds of a localized
impurity. For comparison we also discuss the non-interacting case. In the weak
impurity limit our results for the overlap confirm scaling behavior expected
from perturbation theory and renormalization group calculations. In particular
we find that a weak backward scattering component of the orthogonality exponent
scales to zero for attractive interaction. In the strong impurity limit and for
repulsive interaction we demonstrate that the orthogonality exponent cannot be
extracted from the overlap for systems with up to 100 sites, due to finite size
effects. This is in contradiction to an earlier interpretation given by Qin et
al. based on numerical data for much smaller system sizes. Neverthless we find
indirect evidence that the backward scattering contribution to the exponent
scales to 1/16 based on predictions of boundary conformal field theory.Comment: 16 pages, Latex, 8 eps figures, submitted to Phys. Rev.
Effects of Different Exercise Modalities on Executive Cognitive Function
Please download pdf version here
Effects of Different Exercise Modalities on Executive Cognitive Function
Please download pdf version here
Methods for Managing Human–Deer Conflicts in Urban, Suburban, and Exurban Areas
This monograph identifies challenges and benefits associated with many human–deer conflict mitigation actions as well as methods to monitor the response of deer populations to management actions. Deer exploit urban, suburban, and exurban areas where human populations provide anthropogenic attractants, either intentionally or inadvertently, which often leads to human–deer conflicts. Mitigating actions have varying degrees of efficacy and may not be effective or accepted in every situation. Wildlife and municipal managers must work together to seek methods to reduce attractants, mitigate conflicts, and perpetuate the conservation of wildlife species that adds to the appreciation of nature in our lives.https://digitalcommons.usu.edu/hwi_monographs/1001/thumbnail.jp
- …