scholarly journals Ungulates rely less on visual cues, but more on adapting movement behaviour, when searching for forage

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3178 ◽  
Author(s):  
Jan A. Venter ◽  
Herbert H.T. Prins ◽  
Alla Mashanova ◽  
Rob Slotow
Keyword(s):  
Visual Cues ◽  
A Priori ◽  
Step Length ◽  
Habitat Patch ◽  
Movement Behaviour ◽  
Large Herbivores ◽  
Heterogeneous Landscape ◽  
Equus Burchelli ◽  
Scale Step ◽  
Patch Scale

Finding suitable forage patches in a heterogeneous landscape, where patches change dynamically both spatially and temporally could be challenging to large herbivores, especially if they have noa prioriknowledge of the location of the patches. We tested whether three large grazing herbivores with a variety of different traits improve their efficiency when foraging at a heterogeneous habitat patch scale by using visual cues to gaina prioriknowledge about potential higher value foraging patches. For each species (zebra (Equus burchelli), red hartebeest (Alcelaphus buselaphussubspeciescamaa) and eland (Tragelaphus oryx)), we used step lengths and directionality of movement to infer whether they were using visual cues to find suitable forage patches at a habitat patch scale. Step lengths were significantly longer for all species when moving to non-visible patches than to visible patches, but all movements showed little directionality. Of the three species, zebra movements were the most directional. Red hartebeest had the shortest step lengths and zebra the longest. We conclude that these large grazing herbivores may not exclusively use visual cues when foraging at a habitat patch scale, but would rather adapt their movement behaviour, mainly step length, to the heterogeneity of the specific landscape.

scholarly journals Ungulates rely less on visual cues, but more on adapting movement behaviour, when searching for forage

2017 ◽  
Author(s):  
Jan A Venter ◽  
Herbert H. T. Prins ◽  
Alla Mashanova ◽  
Rob Slotow
Keyword(s):  
Visual Cues ◽  
A Priori ◽  
Step Length ◽  
A Priori Knowledge ◽  
Habitat Patch ◽  
Movement Behaviour ◽  
Large Herbivores ◽  
Scale Step ◽  
Patch Scale ◽  
Priori Knowledge

Finding suitable forage patches in a heterogeneous landscape, where patches change dynamically both spatially and temporally could be challenging to large herbivores, especially if they have no a priori knowledge of the location of the patches. We tested whether three large grazing herbivores with a variety of different traits, improve their efficiency when foraging at a heterogeneous habitat patch scale, by using visual cues to gain a priori knowledge about potential higher value foraging patches. For each species (zebra (Equus burchelli ), red hartebeest (Alcelaphus buselaphus subspecies camaa ) and eland ( Tragelaphus oryx )), we used step lengths and directionality of movement to infer whether they were using visual cues to find suitable forage patches at a habitat patch scale. Step lengths were significantly longer for all species when moving to non-visible patches than to visible patches, but all movements showed little directionality. Of the three species, zebra movements were the most directional. Red hartebeest had the shortest step lengths and zebra the longest. We conclude that these large grazing herbivores may not exclusively use visual cues when foraging at a habitat patch scale, but would rather adapt their movement behaviour, mainly step length, to the heterogeneity of the specific landscape.

scholarly journals Ungulates rely less on visual cues, but more on adapting movement behaviour, when searching for forage

2017 ◽  
Author(s):  
Jan A Venter ◽  
Herbert H. T. Prins ◽  
Alla Mashanova ◽  
Rob Slotow
Keyword(s):  
Visual Cues ◽  
A Priori ◽  
Step Length ◽  
A Priori Knowledge ◽  
Habitat Patch ◽  
Movement Behaviour ◽  
Large Herbivores ◽  
Scale Step ◽  
Patch Scale ◽  
Priori Knowledge

Finding suitable forage patches in a heterogeneous landscape, where patches change dynamically both spatially and temporally could be challenging to large herbivores, especially if they have no a priori knowledge of the location of the patches. We tested whether three large grazing herbivores with a variety of different traits, improve their efficiency when foraging at a heterogeneous habitat patch scale, by using visual cues to gain a priori knowledge about potential higher value foraging patches. For each species (zebra (Equus burchelli ), red hartebeest (Alcelaphus buselaphus subspecies camaa ) and eland ( Tragelaphus oryx )), we used step lengths and directionality of movement to infer whether they were using visual cues to find suitable forage patches at a habitat patch scale. Step lengths were significantly longer for all species when moving to non-visible patches than to visible patches, but all movements showed little directionality. Of the three species, zebra movements were the most directional. Red hartebeest had the shortest step lengths and zebra the longest. We conclude that these large grazing herbivores may not exclusively use visual cues when foraging at a habitat patch scale, but would rather adapt their movement behaviour, mainly step length, to the heterogeneity of the specific landscape.

The mechanics of locating earthquakes

1976 ◽  
Vol 66 (1) ◽  
pp. 173-187
Author(s):  
Ray Buland
Keyword(s):  
Degrees Of Freedom ◽  
A Priori Estimates ◽  
A Priori ◽  
Joint Probability ◽  
Step Length ◽  
Earth Model ◽  
Random Errors ◽  
Qr Algorithm ◽  
Location Parameters ◽  
Chi Squared

abstract A complete reexamination of Geiger's method in the light of modern numerical analysis indicates that numerical stability can be insured by use of the QR algorithm and the convergence domain considerably enlarged by the introduction of step-length damping. In order to make the maximum use of all data, the method is developed assuming a priori estimates of the statistics of the random errors at each station. Numerical experiments indicate that the bulk of the joint probability density of the location parameters is in the linear region allowing simple estimates of the standard errors of the parameters. The location parameters are found to be distributed as one minus chi squared with m degrees of freedom, where m is the number of parameters, allowing the simple construction of confidence levels. The use of the chi-squared test with n-m degrees of freedom, where n is the number of data, is introduced as a means of qualitatively evaluating the correctness of the earth model.

scholarly journals Risk assessment and the use of novel shortcuts in spatial detouring tasks in jumping spiders

2019 ◽  
Vol 30 (5) ◽  
pp. 1488-1498 ◽  
Author(s):  
Samuel Aguilar-Argüello ◽  
Daniel Gerhard ◽  
Ximena J Nelson
Keyword(s):  
Spatial Ability ◽  
Visual Cues ◽  
Prey Capture ◽  
Dimensional Space ◽  
A Priori ◽  
Complex Environments ◽  
Environmental Complexity ◽  
3 Dimensional ◽  
Jumping Spiders ◽  
Efficient Route

AbstractSelection on individuals that incorporate risk to quickly and accurately make a priori navigational assessments may lead to increased spatial ability. Jumping spiders (Araneae: Salticidae) are characterized by their highly acute vision, which mediates many behaviors, including prey capture and navigation. When moving to a specific goal (prey, nest, a potential mate, etc.), salticids rely on visual cues and spatial memory to orient in 3-dimensional space. Salticid spatial ability has been studied in homing and detour tasks, with Portia being considered one of the most skillful genera in terms of spatial ability in the family. Commonly living in complex environments, salticids are likely to encounter a wide variety of routes that could lead to a goal, and, as selection favors individuals that can accurately make assessments, they may be able to assess alternative route distances to select the most efficient route. Here, we tested whether 2 salticid species (Portia fimbriata and Trite planiceps) can discriminate and assess between different available routes by their length, and riskiness to escape from a stressful scenario. Results suggest that while Portia is more likely to choose the easiest and shortest escape routes, Trite is faster in both decision making about which route to take, and to escape. However, some individuals were able to use novel shortcuts instead of the routes expected, with Portia containing a higher proportion of shortcut-takers than Trite. These differences in spatial ability seem to correspond with the environmental complexity inhabited by each species.

scholarly journals Risks and opportunities of trophic rewilding for arthropod communities

2018 ◽  
Vol 373 (1761) ◽  
pp. 20170441 ◽  
Author(s):  
Roel van Klink ◽  
Michiel F. WallisDeVries
Keyword(s):  
Biodiversity Conservation ◽  
A Priori ◽  
Grey Literature ◽  
Control Treatment ◽  
Arthropod Communities ◽  
Large Herbivore ◽  
Large Herbivores ◽  
Natural Processes ◽  
Published Evidence ◽  
Eukaryotic Organisms

Trophic rewilding is a restoration strategy focusing on the restoration of trophic interactions to promote self-regulating, biodiverse ecosystems. It has been proposed as an alternative to traditional conservation management in abandoned or defaunated areas. Arthropods constitute the most species-rich group of eukaryotic organisms, but are rarely considered in rewilding. Here, we first present an overview of direct and indirect pathways by which large herbivores and predators affect arthropod communities. We then review the published evidence of the impacts of rewilding with large herbivores on arthropods, including grey literature. We find that systematic monitoring is rare and that a comparison with a relevant control treatment is usually lacking. Nevertheless, the available data suggest that when the important process of top-down control of large-herbivore populations is missing, arthropod diversity tends to decrease. To ensure that rewilding is supportive of biodiversity conservation, we propose that if natural processes can only partially be restored, substitutes for missing processes are applied. We also propose that boundaries of acceptable outcomes of rewilding actions should be defined a priori , particularly concerning biodiversity conservation, and that action is taken when these boundaries are transgressed. To evaluate the success of rewilding for biodiversity, monitoring of arthropod communities should be a key instrument. This article is part of the theme issue ‘Trophic rewilding: consequences for ecosystems under global change’.

scholarly journals A Cooperative Machine Learning Approach for Pedestrian Navigation in Indoor IoT

Sensors ◽  
2019 ◽  
Vol 19 (21) ◽  
pp. 4609 ◽  
Author(s):  
Marzieh Jalal Abadi ◽  
Luca Luceri ◽  
Mahbub Hassan ◽  
Chun Tung Chou ◽  
Monica Nicoli
Keyword(s):  
Machine Learning ◽  
A Priori ◽  
Dead Reckoning ◽  
Step Length ◽  
Consensus Algorithm ◽  
Learning Approach ◽  
Indoor Environments ◽  
Machine Learning Approach ◽  
Multiple Devices ◽  
Priori Information

This paper presents a system based on pedestrian dead reckoning (PDR) for localization of networked mobile users, which relies only on sensors embedded in the devices and device- to-device connectivity. The user trajectory is reconstructed by measuring step by step the user displacements. Though step length can be estimated rather accurately, heading evaluation is extremely problematic in indoor environments. Magnetometer is typically used, however measurements are strongly perturbed. To improve the location accuracy, this paper proposes a novel cooperative system to estimate the direction of motion based on a machine learning approach for perturbation detection and filtering, combined with a consensus algorithm for performance augmentation by cooperative data fusion at multiple devices. A first algorithm filters out perturbed magnetometer measurements based on a-priori information on the Earth’s magnetic field. A second algorithm aggregates groups of users walking in the same direction, while a third one combines the measurements of the aggregated users in a distributed way to extract a more accurate heading estimate. To the best of our knowledge, this is the first approach that combines machine learning with consensus algorithms for cooperative PDR. Compared to other methods in the literature, the method has the advantage of being infrastructure-free, fully distributed and robust to sensor failures thanks to the pre-filtering of perturbed measurements. Extensive indoor experiments show that the heading error is highly reduced by the proposed approach thus leading to noticeable enhancements in localization performance.

scholarly journals Mathematical models and soil fertility management software

2020 ◽  
Vol 210 ◽  
pp. 04008
Author(s):  
Sergey Mitrofanov ◽  
Nikolay Novikov ◽  
Vasily Nikitin ◽  
Sergey Belykh
Keyword(s):  
A Priori ◽  
Three Dimensional ◽  
Estimation Algorithm ◽  
Step Length ◽  
Descent Method ◽  
Soil Fertility Management ◽  
Problem Statement ◽  
Functions Of Two Variables ◽  
Microsoft Windows ◽  
Parametric Approximation

The article presents the results of studies on parametric approximation in spaces R2 (functions of one variable), R3 (functions of two variables) and Rn(n>3) (functions of three or more variables). Various classes of functions satisfying a priori conditions were studied: f(0, 0, 0)=0, $\mathop {\lim 1}\limits_{{x_i} \to + \infty } \,\,({x_1},\, \ldots ,\,{x_n}) = {c_i}$, ci = cont. Working algorithms and C/C++ software functioning in Microsoft Visual Studio 2019 system in Microsoft Windows 10 environment were developed. The main studies of the authors were aimed at developing effective computational algorithms for constructing approximating functions of two variables from various given classes of three-dimensional data samples (three-dimensional interconnected time series). The article provides a detailed description of the problem statement, introduces classes of approximating functions, provides algorithms for estimating the parameters of approximating functions and a description of the software. The estimation algorithm considered in the article is constructed according to the scheme of the coordinate descent method with optimization of the step length (Gauss-Seidel method).

scholarly journals A Manipulation of Visual Feedback during Gait Training in Parkinson's Disease

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Quincy J. Almeida ◽  
Haseel Bhatt
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Optic Flow ◽  
Visual Cues ◽  
Step Length ◽  
Gait Training ◽  
Control Group ◽  
Training Interventions ◽  
Visual Cueing ◽  
Walking Velocity

Visual cues are known to improve gait in Parkinson's disease (PD); however, the contribution of optic flow continues to be disputed. This study manipulated transverse line cues during two gait training interventions (6 weeks). PD subjects (N=42) were assigned to one of three groups: treadmill (TG), overground (OG), or control group (CG). Participants walked across lines placed on either treadmills or 16-meter carpets, respectively. The treadmill (TG) offered a reduced dynamic flow from the environment, while lines presented on the ground (OG) emphasized optic flow related to the participant's own displacement. Both interventions significantly improved (and maintained through retention period) step length, thus improving walking velocity. Only the OG improved in the TUG test, while only the TG showed hints of improving (and maintaining) motor symptoms. Since gait improvements were found in both training groups, we conclude that by reducing optic flow, gait benefits associated with visual cueing training can still be achieved.

The Use of Numerical and Graphical Statistical Methods in the Analysis of Data on Learning to See Complex Random-Dot Stereograms

Perception ◽  
1978 ◽  
Vol 7 (1) ◽  
pp. 113-118 ◽  
Author(s):  
William S Cleveland ◽  
Roberta Guarino
Keyword(s):  
Statistical Methods ◽  
Visual Cues ◽  
Hypothesis Test ◽  
A Priori ◽  
A Priori Information ◽  
Verbal Cues ◽  
Random Dot Stereograms ◽  
Random Dot Stereogram ◽  
Priori Information ◽  
Exponential Probability

Several numerical and graphical statistical methods are illustrated in an analysis of data from an experiment that investigated a hypothesis of Julesz that giving a person a priori information about the structure of a complex random-dot stereogram reduces the time needed to perceive it when it is viewed. The data are divided into two groups, one consisting of those observers who received no cue or verbal cues (NV) and the other consisting of those who received verbal-visual cues (VV). A quantile-quantile plot shows that the NV times (mean = 7.6) are longer than the VV times (mean = 5.6). By using probability plots, it is shown that the perception times have an exponential probability distribution. A hypothesis test based upon this distribution is used to show that the differences between the NV and W times has significance slightly below 0.05.

Using patch and landscape variables to model bird abundance in a naturally heterogeneous landscape

2003 ◽  
Vol 81 (3) ◽  
pp. 441-452 ◽  
Author(s):  
Gaea E Crozier ◽  
Gerald J Niemi
Keyword(s):  
Spatial Scales ◽  
Remote Sensing Data ◽  
Landscape Composition ◽  
Training Data ◽  
Aerial Photographs ◽  
Habitat Patch ◽  
Bird Abundance ◽  
Landscape Characteristics ◽  
Heterogeneous Landscape ◽  
Study Sites

Regression models were developed to predict relative bird abundance in a naturally heterogeneous landscape using patch and landscape spatial scales. Breeding birds were surveyed with point counts on 140 study sites in 1997 and 1998. Aerial photographs were digitized to obtain habitat patch information, such as area, shape, and edge contrast. Classified remote-sensing data were gathered to provide information on landscape composition and configuration within a 1-km2 area around the study sites. Stepwise multiple linear regression was used to develop 40 species-specific models within specific habitat types using patch and landscape characteristics. In 38 out of the 40 models, area of the habitat patch was first selected as the most important predictor of relative bird abundance. Variables related to the landscape were retained in 6 of the 40 models. In this naturally heterogeneous region, the landscape surrounding the patch contributed little to explaining relative bird abundance. The models were evaluated by examining how well they predicted relative bird abundance in a test set not included in the original analyses. The results of the test data were reasonable: >79% of the test observations were within the prediction intervals established by the training data.

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