10 research outputs found
Decomposing risk: landscape structure and wolf behavior generate different predation patterns in two sympatric ungulates
Recolonizing carnivores can have a large impact on the status of wild ungulates,
which have often modified their behavior in the absence of predation. Therefore,
understanding the dynamics of reestablished predator–prey systems is crucial to predict their
potential ecosystem effects. We decomposed the spatial structure of predation by recolonizing
wolves (Canis lupus) on two sympatric ungulates, moose (Alces alces) and roe deer (Capreolus
capreolus), in Scandinavia during a 10-year study. We monitored 18 wolves with GPS collars,
distributed over 12 territories, and collected records from predation events. By using
conditional logistic regression, we assessed the contributions of three main factors, the
utilization patterns of each wolf territory, the spatial distribution of both prey species, and
fine-scale landscape structure, in determining the spatial structure of moose and roe deer
predation risk. The reestablished predator–prey system showed a remarkable spatial variation
in kill occurrence at the intra-territorial level, with kill probabilities varying by several orders
of magnitude inside the same territory. Variation in predation risk was evident also when a
spatially homogeneous probability for a wolf to encounter a prey was simulated. Even inside
the same territory, with the same landscape structure, and when exposed to predation by the
same wolves, the two prey species experienced an opposite spatial distribution of predation
risk. In particular, increased predation risk for moose was associated with open areas,
especially clearcuts and young forest stands, whereas risk was lowered for roe deer in the same
habitat types. Thus, fine-scale landscape structure can generate contrasting predation risk
patterns in sympatric ungulates, so that they can experience large differences in the spatial
distribution of risk and refuge areas when exposed to predation by a recolonizing predator.
Territories with an earlier recolonization were not associated with a lower hunting success for
wolves. Such constant efficiency in wolf predation during the recolonization process is in line
with previous findings about the naı¨ve nature of Scandinavian moose to wolf predation. This,
together with the human-dominated nature of the Scandinavian ecosystem, seems to limit the
possibility for wolves to have large ecosystem effects and to establish a behaviorally mediated
trophic cascade in Scandinavia
Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station
A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.</p
Decomposing risk: landscape structure and wolf behavior generate different predation patterns in two sympatric ungulates
Recolonizing carnivores can have a large impact on the status of wild ungulates,
which have often modified their behavior in the absence of predation. Therefore,
understanding the dynamics of reestablished predator–prey systems is crucial to predict their
potential ecosystem effects. We decomposed the spatial structure of predation by recolonizing
wolves (Canis lupus) on two sympatric ungulates, moose (Alces alces) and roe deer (Capreolus
capreolus), in Scandinavia during a 10-year study. We monitored 18 wolves with GPS collars,
distributed over 12 territories, and collected records from predation events. By using
conditional logistic regression, we assessed the contributions of three main factors, the
utilization patterns of each wolf territory, the spatial distribution of both prey species, and
fine-scale landscape structure, in determining the spatial structure of moose and roe deer
predation risk. The reestablished predator–prey system showed a remarkable spatial variation
in kill occurrence at the intra-territorial level, with kill probabilities varying by several orders
of magnitude inside the same territory. Variation in predation risk was evident also when a
spatially homogeneous probability for a wolf to encounter a prey was simulated. Even inside
the same territory, with the same landscape structure, and when exposed to predation by the
same wolves, the two prey species experienced an opposite spatial distribution of predation
risk. In particular, increased predation risk for moose was associated with open areas,
especially clearcuts and young forest stands, whereas risk was lowered for roe deer in the same
habitat types. Thus, fine-scale landscape structure can generate contrasting predation risk
patterns in sympatric ungulates, so that they can experience large differences in the spatial
distribution of risk and refuge areas when exposed to predation by a recolonizing predator.
Territories with an earlier recolonization were not associated with a lower hunting success for
wolves. Such constant efficiency in wolf predation during the recolonization process is in line
with previous findings about the naı¨ve nature of Scandinavian moose to wolf predation. This,
together with the human-dominated nature of the Scandinavian ecosystem, seems to limit the
possibility for wolves to have large ecosystem effects and to establish a behaviorally mediated
trophic cascade in Scandinavia
Informal description and analysis of geographic requirements: an approach based on problems
Properties of Cosmic Helium Isotopes Measured by the Alpha Magnetic Spectrometer
Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of He3 and He4 fluxes are presented. The measurements are based on 100 million He4 nuclei in the rigidity range from 2.1 to 21 GV and 18 million He3 from 1.9 to 15 GV collected from May 2011 to November 2017. We observed that the He3 and He4 fluxes exhibit nearly identical variations with time. The relative magnitude of the variations decreases with increasing rigidity. The rigidity dependence of the He3/He4 flux ratio is measured for the first time. Below 4 GV, the He3/He4 flux ratio was found to have a significant long-term time dependence. Above 4 GV, the He3/He4 flux ratio was found to be time independent, and its rigidity dependence is well described by a single power law 08R\u394 with \u394=-0.294\ub10.004. Unexpectedly, this value is in agreement with the B/O and B/C spectral indices at high energies
Towards Understanding the Origin of Cosmic-Ray Electrons
Precision results on cosmic-ray electrons are presented in the energy range from 0.5 GeV to 1.4 TeV based on 28.1
7106 electrons collected by the Alpha Magnetic Spectrometer on the International Space Station. In the entire energy range the electron and positron spectra have distinctly different magnitudes and energy dependences. The electron flux exhibits a significant excess starting from 42.1-5.2+5.4 GeV compared to the lower energy trends, but the nature of this excess is different from the positron flux excess above 25.2\ub11.8 GeV. Contrary to the positron flux, which has an exponential energy cutoff of 810-180+310 GeV, at the 5\u3c3 level the electron flux does not have an energy cutoff below 1.9 TeV. In the entire energy range the electron flux is well described by the sum of two power law components. The different behavior of the cosmic-ray electrons and positrons measured by the Alpha Magnetic Spectrometer is clear evidence that most high energy electrons originate from different sources than high energy positrons