1. Some animals migrate huge distances in search of resources with locomotory mode (flying/swimming/walking) thought to drive the upper ceilings on migration distance. Yet in cross-taxa comparisons, ...upper ceilings on migration distance have been ignored for one important group, sea turtles. 2. Using migration distances recorded for 407 adult and 4715 juvenile sea turtles across five species, we show that for adult cheloniid turtles, the upper ceiling on species migration distances between breeding and foraging habitats (1050—2850 km across species) is similar to that predicted for equivalent-sized marine mammals and fish. 3. In contrast, by feeding in the open ocean, adult leatherback turtles (Dermochelys coriacea) and juveniles of all turtle species can travel around 12000 km from their natal regions, travelling across the widest ocean basins. For juvenile turtles, this puts their maximum migration distances well beyond those expected for equivalent-sized marine mammals and fish, but not those found in some similar sized birds. 4. Post-hatchling turtles perform these long-distance migrations to juvenile foraging sites only once in their lifetime, while adult turtles return to their breeding sites every few (generally ≥2) years. Our results highlight the important roles migration periodicity and foraging mode can play in driving the longest migrations, and the implications for Marine Protected Area planning are considered in terms of sea turtle conservation.
We have measured the 3d→2p transition x rays of kaonic ^{3}He and ^{4}He atoms using superconducting transition-edge-sensor microcalorimeters with an energy resolution better than 6 eV (FWHM). We ...determined the energies to be 6224.5±0.4(stat)±0.2(syst) eV and 6463.7±0.3(stat)±0.1(syst) eV, and widths to be 2.5±1.0(stat)±0.4(syst) eV and 1.0±0.6(stat)±0.3(stat) eV, for kaonic ^{3}He and ^{4}He, respectively. These values are nearly 10 times more precise than in previous measurements. Our results exclude the large strong-interaction shifts and widths that are suggested by a coupled-channel approach and agree with calculations based on optical-potential models.
A prominent line of research on electoral systems and income redistribution argues that proportional representation (PR) leads to tax-and-transfer policies that benefit the poor at the expense of the ...rich. This is because PR produces encompassing center-left coalitions that protect the poor and middle classes. Yet countries with PR electoral systems tend to rely heavily on consumption taxes and tax profits lightly, both of which are inconsistent with this expectation. Both policies are regressive and seem to benefit the rich at the expense of the poor. This article argues that PR electoral institutions, when combined with trichotomous multipartism, are not as hostile to the rich as commonly believed, and that it is important to understand how electoral and party systems interact with labor market institutions in order to explain the puzzling pattern of taxation that is observed. The author develops a theoretical model and evaluates its empirical implications for a world in which production has become multinational.
For organisms that fly or swim, movement results from the combined effects of the moving medium — air or water — and the organism's own locomotion. For larger organisms, propulsion contributes ...significantly to progress but the flow usually still provides significant opposition or assistance, or produces lateral displacement (‘drift’). Animals show a range of responses to flows, depending on the direction of the flow relative to their preferred direction, the speed of the flow relative to their own self-propelled speed, the incidence of flows in different directions and the proportion of the journey remaining. We here present a classification of responses based on the direction of the resulting movement relative to flow and preferred direction, which is applicable to a range of taxa and environments. The responses adopted in particular circumstances are related to the organisms' locomotory and sensory capacities and the environmental cues available. Advances in biologging technologies and particle tracking models are now providing a wealth of data, which often demonstrate a striking level of convergence in the strategies that very different animals living in very different environments employ when moving in a flow.
Identifying the reasons for the loss of signals in satellite tracking studies is important for directing future improvements in transmitter technology and attachment systems, as well as defining the ...status of the tracked animals (alive or dead) at the end of the tracking period, which is integral to assessing survival rates through established methods. We highlight the importance of transmitted diagnostic data that reveal the status of a tag. We show in marine wildlife satellite tracking that the reasons behind transmitter signal loss can often be identified. Exhaustion of batteries, salt-water switch failure, antenna breakage, animal mortality and premature detachment of tags were all identified as causes of signal loss from transmitters routinely attached to turtles, fish and marine mammals. In principle, battery management systems should allow tracking of individuals for several years, even with existing transmitter technology, although in such long-term deployments in a marine setting, failure of the salt-water switch may persist as the Achilles heel of existing tags.
Estimating the absolute number of individuals in populations and their fecundity is central to understanding the ecosystem role of species and their population dynamics as well as allowing informed ...conservation management for endangered species. Estimates of abundance and fecundity are often difficult to obtain for rare or cryptic species. Yet, in addition, here we show for a charismatic group, sea turtles, that are neither cryptic nor rare and whose nesting is easy to observe, that the traditional approach of direct observations of nesting has likely led to a gross overestimation of the number of individuals in populations and underestimation of their fecundity. We use high-resolution GPS satellite tags to track female green turtles throughout their nesting season in the Chagos Archipelago (Indian Ocean) and assess when and where they nested. For individual turtles, nest locations were often spread over several tens of kilometres of coastline. Assessed by satellite observations, a mean of 6.0 clutches (range 2–9, s.d. = 2.2) was laid by individuals, about twice as many as previously assumed, a finding also reported in other species and ocean basins. Taken together, these findings suggest that the actual number of nesting turtles may be almost 50% less than previously assumed.
Mutualisms often define ecosystems, but they are susceptible to human activities. Combining experiments, animal tracking, and mortality investigations, we show that the invasive big-headed ant (
) ...makes lions (
) less effective at killing their primary prey, plains zebra (
). Big-headed ants disrupted the mutualism between native ants (
spp.) and the dominant whistling-thorn tree (
), rendering trees vulnerable to elephant (
) browsing and resulting in landscapes with higher visibility. Although zebra kills were significantly less likely to occur in higher-visibility, invaded areas, lion numbers did not decline since the onset of the invasion, likely because of prey-switching to African buffalo (
). We show that by controlling biophysical structure across landscapes, a tiny invader reconfigured predator-prey dynamics among iconic species.
The proposed Mitchell Institute Neutrino Experiment at Reactor (MINER) experiment at the Nuclear Science Center at Texas A&M University will search for coherent elastic neutrino-nucleus scattering ...within close proximity (about 2m) of a 1MW TRIGA nuclear reactor core using low threshold, cryogenic germanium and silicon detectors. Given the Standard Model cross section of the scattering process and the proposed experimental proximity to the reactor, as many as 5–20events/kg/day are expected. We discuss the status of preliminary measurements to characterize the main backgrounds for the proposed experiment. Both in situ measurements at the experimental site and simulations using the MCNP and GEANT4 codes are described. A strategy for monitoring backgrounds during data taking is briefly discussed.
Over 25 years ago the first satellite tracking studies of sea turtles were published. The technology and attachment methods have now come of age with long-term tracks over a year being commonplace ...and the ability to relay high resolution GPS locations via the Argos satellite system along with behavioural (e.g. diving and activity) and environmental (e.g. temperature) data. Early studies focused on breeding females because they come ashore to nest, allowing individuals to be restrained relatively easily for tag attachment. However, today the development of methods for the capture of turtles at sea are increasingly allowing studies on both adult male turtles as well as immature turtles as small as 11cm carapace length. Here we review the extent of work after many thousands of individual turtles have been tracked. We consider the state-of-the-art equipment for satellite tracking turtles and how this technology is being used to tackle key questions. We highlight some of the emerging opportunities arising from improved spatial resolution of tracking, increased robustness and miniaturisation of tags as well as increasing availability of environmental data. We highlight the huge potential for big-data studies to make use of the thousands of tracks that exist, although we discuss the long-standing challenges surrounding data accessibility.
The new Horizontal Wind Model (HWM07) provides a statistical representation of the horizontal wind fields of the Earth's atmosphere from the ground to the exosphere (0–500 km). It represents over 50 ...years of satellite, rocket, and ground‐based wind measurements via a compact Fortran 90 subroutine. The computer model is a function of geographic location, altitude, day of the year, solar local time, and geomagnetic activity. It includes representations of the zonal mean circulation, stationary planetary waves, migrating tides, and the seasonal modulation thereof. HWM07 is composed of two components, a quiet time component for the background state described in this paper and a geomagnetic storm time component (DWM07) described in a companion paper.
PDF
