Behavioural changes in African elephants in response to wildlife tourism

Eco-tourism and human-wildlife interaction can lead to increases in stress, vigilance and aggression in many species, however, studies investigating wildlife viewing are scarce. We present the first study investigating the impact of wildlife tourism on African elephant, Loxodonta africana, behaviour. Over 15 months, we studied the effect of monthly tourist pressure (tourist numbers) on the occurrence of stress-related, vigilance and conspecific-directed aggressive behaviour in 27 individually identified elephants and the effect of up to 3 vehicles on the direction of travel of non-identified herds using five-minute continuous focal observations. We analysed the effect of tourist pressure and vehicle presence using generalised linear mixed models, including habitat type, herd type and size, and season, as well as sex and age for behaviour models, as additional factors. We found no effect of factors on stress-related behaviour, but elephants were more likely to perform vigilance behaviours at waterholes compared to other habitat types. As tourist pressure increased, conspecific-directed aggression in elephants increased and male elephants were more likely to perform conspecific directed aggression compared to female elephants. . Further, we found that elephant herds became increasingly likely to move away with increasing numbers of vehicles present. Results suggest that reserves should monitor elephant behaviour to identify when tourist pressure has potential effects on elephant welfare and train guides to monitor behaviour and adjust minimum distances flexibly to ensure high welfare standards and tourist safety. This study further contributes to a small but growing body of literature on non-consumptive wildlife tourism impacts on wild animals

The incidence and nature of injuries in South African rugby players in the rugby Super 12 competition

Background: There are sparse scientific data concerning the aetiology and incidence of injuries in the Super 12 rugby competition. Aim: The aim of the study was to document the incidence, nature and risk factors associated with injuries during a Super 12 rugby competition. Methods: Injuries, defined as injuries preventing playing or training, or requiring medical treatment, were recorded in a cohort of 75 South African Super 12 players over one season. Injury severity was graded according to sessions missed: minor (1 - 3 missed), intermediate (4 - 9) and severe (> 9). Results: During the tournament, a total of 740 player game hours and 4 900 player training hours were recorded. The overall incidence of injuries was 55.4 injuries / 1 000 player game hours, and 4.3 injuries / 1 000 player training hours. The most common injury types were: ligament sprains (25.8%), musculotendinous strains / tears (24.2%). The most common injured sites were: pelvis, hip (19.3%), head and knee (12.9% each). The tackle caused 40.3%, and rucks and mauls 11.3% of injuries. Injuries sustained during training accounted for 34%, and chronic overuse injuries 9.7% of injuries. Conclusions: There is a high injury rate during a Super 12 rugby competition. However, the majority of injuries were minor injuries. The most dangerous phase of play was the tackle. Training in tackling and rucking techniques, and rule enforcement are therefore recommended to reduce risk of injury. Injuries tended to occur late in games and early in the season, suggesting lack of physical conditioning and fatigue as possible causes of injury.South African Medical Journal Vol. 96 (12) 2006: pp. 1260-126

Constraining the evolutionary history of Newton's constant with gravitational wave observations

Space-borne gravitational wave detectors, such as the proposed Laser Interferometer Space Antenna, are expected to observe black hole coalescences to high redshift and with large signal-to-noise ratios, rendering their gravitational waves ideal probes of fundamental physics. The promotion of Newton's constant to a time-function introduces modifications to the binary's binding energy and the gravitational wave luminosity, leading to corrections in the chirping frequency. Such corrections propagate into the response function and, given a gravitational wave observation, they allow for constraints on the first time-derivative of Newton's constant at the time of merger. We find that space-borne detectors could indeed place interesting constraints on this quantity as a function of sky position and redshift, providing a {\emph{constraint map}} over the entire range of redshifts where binary black hole mergers are expected to occur. A LISA observation of an equal-mass inspiral event with total redshifted mass of 10^5 solar masses for three years should be able to measure $\dot{G}/G$ at the time of merger to better than 10^(-11)/yr.Comment: 11 pages, 2 figures, replaced with version accepted for publication in Phys. Rev. D

Normalized Difference Vegetation Index, temperature, and age affect faecal thyroid hormone concentrations in free-ranging African elephants.

Conservation biologists can use hormone measurements to assess animals’ welfare, reproductive state, susceptibility to stressors, as well as energy expenditure. Quantifying hormone concentrations from faecal samples is particularly advantageous as samples can be collected without disturbing animals’ behaviour. In order for an endocrine marker to be useful for wildlife managers, we need to understand how extrinsic and intrinsic factors affect hormone concentrations in free-ranging animal populations. Thyroid hormones are linked to basal metabolic rate and energy expenditure. Previous research demonstrated that triiodothyronine (T3) can be measured successfully in faecal matter of African elephants, Loxodonta africana. However, to our knowledge, research into factors affecting changes in elephant T3 levels has only been carried out in captive elephants so far. Thus, we present the first study of faecal T3 metabolite (mT3) concentrations of a large population of free-ranging African elephants. Over 15 months, we collected faecal samples from identified (n=43 samples) and unidentified (n=145 samples) individuals in Madikwe Game Reserve, South Africa. We investigated whether vegetative productivity (NDVI) in interaction with mean monthly temperature, age, and sex affected mT3 concentrations. We found a significant negative interaction effect of NDVI and temperature. Increasing NDVI was related to higher concentrations of mT3, but increasing temperature was related to a decrease in mT3 concentrations in individually identified and unidentified elephants. In unidentified individuals, juvenile elephants had significantly higher mT3 concentrations compared to adult elephants. Faecal T3 can successfully be quantified in samples from free-ranging elephant populations and thus provides insight into energy expenditure in large herbivores

A Long-term synoptic-scale climate study over Mariepskop, Mpumalanga, South Africa

Mariepskop forms part of the northernmost edge of the Drakensberg Mountain range and is known for its complex topography associated with meso-scale atmospheric circulation, and therefore its numerous climatic zones. The mountain hosts a high biodiversity. The peak of Mariepskop lies at approximately 1900m Above Mean Sea Level (AMSL), which is higher than the surrounding escarpment to the east. Its foothills also extend well into the Lowveld at about 700 m AMSL. Mariepskop is therefore ideal for studying airflow exchange between the industrial Highveld and the Lowveld with its diversity of natural resources. It is also ideal for detecting global warming signals on altitudinal gradients extending from the Lowveld to altitudes above the Highveld escarpment. In this study long-term National Centre for Atmospheric Research / National Centre for Environmental Prediction (NCAR/NCEP) wind data at two atmospheric pressure levels (850 and 700 hPa), as well as near-surface temperature data, were obtained for the Mariepskop region for the summer (December-January-February: DJF (1981-2011 )) and winter (June-July-August: JJA (1980-2012)) seasons. The data was used to study synoptic wind flow across the mountain in the upper (700 hPa) and lower (800 hPa) atmosphere, as well as near-surface temperature gradients. During the summer season, east-south-easterly and south-easterly winds were found to be the most prominent. These winds are commonly associated with both continental and ridging anticyclonic conditions. During winter, the predominant wind direction at 850 hPa is south-easterly, which is also due to the influence of ridging anticyclones, while at 700 hPa the dominant winter wind direction becomes west-south-west, which is due to the more frequent eastward passing of cyclonic frontal systems across the Highveld towards the Lowveld. Long-term near-surface temperatures exhibit a weak increasing linear temperature trend for both seasons, which might be due to global warming

Aperiodic optical variability of intermediate polars - cataclysmic variables with truncated accretion disks

We study the power spectra of the variability of seven intermediate polars containing magnetized asynchronous accreting white dwarfs, XSS J00564+4548,IGR J00234+6141, DO Dra, V1223 Sgr, IGR J15094-6649, IGR J16500-3307 and IGR J17195-4100, in the optical band and demonstrate that their variability can be well described by a model based on fluctuations propagating in a truncated accretion disk. The power spectra have breaks at Fourier frequencies, which we associate with the Keplerian frequency of the disk at the boundary of the white dwarfs' magnetospheres. We propose that the properties of the optical power spectra can be used to deduce the geometry of the inner parts of the accretion disk, in particular: 1) truncation radii of the magnetically disrupted accretion disks in intermediate polars, 2) the truncation radii of the accretion disk in quiescent states of dwarf novaeComment: Accepted for publication in A&

Simulation of Asymptotically AdS5 Spacetimes with a Generalized Harmonic Evolution Scheme

Motivated by the gauge/gravity duality, we introduce a numerical scheme based on generalized harmonic evolution to solve the Einstein field equations on asymptotically anti-de Sitter (AdS) spacetimes. We work in global AdS5, which can be described by the (t,r,\chi,\theta,\phi) spherical coordinates adapted to the R{\times}S3 boundary. We focus on solutions that preserve an SO(3) symmetry that acts to rotate the 2-spheres parametrized by \theta,\phi. In the boundary conformal field theory (CFT), the way in which this symmetry manifests itself hinges on the way we choose to embed Minkowski space in R{\times}S3. We present results from an ongoing study of prompt black hole formation via scalar field collapse, and explore the subsequent quasi-normal ringdown. Beginning with initial data characterized by highly distorted apparent horizon geometries, the metrics quickly evolve, via quasi-normal ringdown, to equilibrium static black hole solutions at late times. The lowest angular number quasi-normal modes are consistent with the linear modes previously found in perturbative studies, whereas the higher angular modes are a combination of linear modes and of harmonics arising from non-linear mode-coupling. We extract the stress energy tensor of the dual CFT on the boundary, and find that despite being highly inhomogeneous initially, it nevertheless evolves from the outset in a manner that is consistent with a thermalized N=4 SYM fluid. As a first step towards closer contact with relativistic heavy ion collision physics, we map this solution to a Minkowski piece of the R{\times}S3 boundary, and obtain a corresponding fluid flow in Minkowski space

The Relationship Between X-ray Luminosity and Duty Cycle for Dwarf Novae and their Specific Frequency in the Inner Galaxy

We measure the duty cycles for an existing sample of well observed, nearby dwarf novae using data from AAVSO, and present a quantitative empirical relation between the duty cycle of dwarf novae outbursts and the X-ray luminosity of the system in quiescence. We have found that $\log DC=0.63(\pm0.21)\times(\log L_{X}({\rm erg\,s^{-1}})-31.3)-0.95(\pm0.1)$, where DC stands for duty cycle. We note that there is intrinsic scatter in this relation greater than what is expected from purely statistical errors. Using the dwarf nova X-ray luminosity functions from \citet{Pretorius12} and \citet{Byckling10}, we compare this relation to the number of dwarf novae in the Galactic Bulge Survey which were identified through optical outbursts during an 8-day long monitoring campaign. We find a specific frequency of X-ray bright ($L_{X}>10^{31}\,{\rm erg\,s^{-1}}$) Cataclysmic Variables undergoing Dwarf Novae outbursts in the direction of the Galactic Bulge of $6.6\pm4.7\times10^{-5}\,M_{\odot}^{-1}$. Such a specific frequency would give a Solar neighborhood space density of long period CVs of $\rho=5.6\pm3.9\times10^{-6}\,$pc$^{-3}$. We advocate the use of specific frequency in future work, given that projects like LSST will detect DNe well outside the distance range over which $\rho\approx{\textrm const}$.Comment: 9 pagers, 4 figures Accepted for publication in MNRA

Semianalytical estimates of scattering thresholds and gravitational radiation in ultrarelativistic black hole encounters

Ultrarelativistic collisions of black holes are ideal gedanken experiments to study the nonlinearities of general relativity. In this paper we use semianalytical tools to better understand the nature of these collisions and the emitted gravitational radiation. We explain many features of the energy spectra extracted from numerical relativity simulations using two complementary semianalytical calculations. In the first calculation we estimate the radiation by a "zero-frequency limit" analysis of the collision of two point particles with finite impact parameter. In the second calculation we replace one of the black holes by a point particle plunging with arbitrary energy and impact parameter into a Schwarzschild black hole, and we explore the multipolar structure of the radiation paying particular attention to the near-critical regime. We also use a geodesic analogy to provide qualitative estimates of the dependence of the scattering threshold on the black hole spin and on the dimensionality of the spacetime.Comment: 29 pages, 19 figure, 6 tables, minor changes to match version in press in Phys.Rev.