scholarly journals Deterministic, random, or in between? Inferring the randomness level of wildlife movements

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Teresa Goicolea ◽  
Aitor Gastón ◽  
Pablo Cisneros-Araujo ◽  
Juan Ignacio García-Viñas ◽  
M. Cruz Mateo-Sánchez
Keyword(s):  
Shortest Path ◽  
Least Cost Path ◽  
Point Selection ◽  
Validation Methods ◽  
Management Actions ◽  
Movement Data ◽  
Recent Approach ◽  
Connectivity Model ◽  
Traditional Approaches ◽  
Corridor Network

Abstract Background When assessing connectivity, it is crucial to rely on accurate modeling frameworks that consider species movement preferences and patterns. One important aspect is the level of randomness or unpredictability in the route selection. In this respect, traditional approaches (based on least-cost path or circuit theory) consider species movements unrealistically as totally deterministic or as totally random. A recent approach (randomized shortest path) advocates for choosing intermediate levels of randomness through a single parameter. This parameter may be optimized by validating connectivity surfaces developed from different levels of randomness against observed movement data. However, connectivity models are seldom validated, and it is still unclear how to approach this task. To address this knowledge gap, this paper aims at comparing different validation methods to infer the optimal randomness level in connectivity studies. Additionally, we aimed to disentangle the practical consequences of applying traditional connectivity approaches versus using an optimized level of movement randomness when delineating corridors. Methods These objectives were accomplished through the study case of the Iberian lynx, an endangered species whose maintenance and recovery depend on the current connectivity among its population nuclei. We firstly determined a conductance surface based on point selection functions accounting for the behavioral state (territorial or exploratory) of individuals. Secondly, we identified the level of randomness that better fits lynxes’ movements with independent GPS locations and different validation techniques. Lastly, we delineated corridors between lynx population nuclei through a) the randomized shortest path approach and the extreme and optimal levels of randomness of each validation method, and b) the traditional connectivity approaches. Results According to all used validation methodologies, models with intermediate levels of randomness outperformed those with extreme randomness levels representing totally deterministic or random movements. We found differences in the optimal randomness level among validation methods but similar results in the delineation of corridors. Our results also revealed that models with extreme randomness levels (deterministic and random walk) of the randomized path approach provided equivalent corridor networks to those from traditional approaches. Moreover, these corridor networks calculated with traditional approaches showed notable differences in patterns from the corridor network calculated with an optimized randomness level. Conclusions Here we presented a connectivity model with a solid biological basis that calibrates the level of movement randomness and is supported by comprehensive validation methods. It is thus a step forward in the search and evaluation of connectivity approaches that lead to improved, efficient, and successful management actions.

scholarly journals Space-Time Hierarchical Clustering for Identifying Clusters in Spatiotemporal Point Data

2020 ◽  
Vol 9 (2) ◽  
pp. 85 ◽  
Author(s):  
David Lamb ◽  
Joni Downs ◽  
Steven Reader
Keyword(s):  
Hierarchical Clustering ◽  
A Priori ◽  
Space Time ◽  
Moving Object ◽  
Agglomerative Hierarchical Clustering ◽  
Movement Data ◽  
Clustering Approach ◽  
Nested Structure ◽  
Point Data ◽  
Traditional Approaches

Finding clusters of events is an important task in many spatial analyses. Both confirmatory and exploratory methods exist to accomplish this. Traditional statistical techniques are viewed as confirmatory, or observational, in that researchers are confirming an a priori hypothesis. These methods often fail when applied to newer types of data like moving object data and big data. Moving object data incorporates at least three parts: location, time, and attributes. This paper proposes an improved space-time clustering approach that relies on agglomerative hierarchical clustering to identify groupings in movement data. The approach, i.e., space–time hierarchical clustering, incorporates location, time, and attribute information to identify the groups across a nested structure reflective of a hierarchical interpretation of scale. Simulations are used to understand the effects of different parameters, and to compare against existing clustering methodologies. The approach successfully improves on traditional approaches by allowing flexibility to understand both the spatial and temporal components when applied to data. The method is applied to animal tracking data to identify clusters, or hotspots, of activity within the animal’s home range.

scholarly journals Urban Ecological Corridor Network Construction: An Integration of the Least Cost Path Model and the InVEST Model

2020 ◽  
Vol 9 (1) ◽  
pp. 33 ◽  
Author(s):  
Yuhan Tang ◽  
Chi Gao ◽  
Xuefei Wu
Keyword(s):  
Urban Expansion ◽  
Path Model ◽  
Least Cost Path ◽  
Integrated Network ◽  
Invest Model ◽  
Terrestrial Mammals ◽  
External Threats ◽  
The Impact ◽  
Cost Factors ◽  
Corridor Network

Under the background of urban expansion, ecological protection cannot be delayed. The construction of ecological networks is of considerable significance to ecosystem services. However, in the process of constructing a corridor network, there is no uniform standard for the selection of ecological sources and the determination of cost factors. The InVEST model is an effective complement to ecosystem service assessment for sensitively measuring external threats and their threat intensity. Therefore, taking Wuhan as an example, we combined InVEST and the least cost path model (LCP) to construct a multi-target corridor network with comprehensive cost factors for birds and small terrestrial mammals. The results showed that: (1) The InVEST model provided a reliable basis for ecological source screening by demonstrating the distribution of habitat quality. (2) The corridor with a length of 12–25 km presented a “U” shape, and the impact of urbanization on small terrestrial mammals was more significant than that of birds. (3) The integrated network pattern proposed by the “point-line-plane” principle would provide a reference for urban ecological construction and sustainable development.

scholarly journals Updating movement estimates for American black ducks (Anas rubripes)

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e1787 ◽  
Author(s):  
Orin J. Robinson ◽  
Conor P. McGowan ◽  
Patrick K. Devers
Keyword(s):  
Atlantic Coast ◽  
The United States ◽  
Future Research ◽  
Harvest Management ◽  
Anas Rubripes ◽  
Management Actions ◽  
The North ◽  
Movement Data ◽  
Continental Population ◽  
American Black

Understanding migratory connectivity for species of concern is of great importance if we are to implement management aimed at conserving them. New methods are improving our understanding of migration; however, banding (ringing) data is by far the most widely available and accessible movement data for researchers. Here, we use band recovery data for American black ducks (Anas rubripes) from 1951–2011 and analyze their movement among seven management regions using a hierarchical Bayesian framework. We showed that black ducks generally exhibit flyway fidelity, and that many black ducks, regardless of breeding region, stopover or overwinter on the Atlantic coast of the United States. We also show that a non-trivial portion of the continental black duck population either does not move at all or moves to the north during the fall migration (they typically move to the south). The results of this analysis will be used in a projection modeling context to evaluate how habitat or harvest management actions in one region would propagate throughout the continental population of black ducks. This analysis may provide a guide for future research and help inform management efforts for black ducks as well as other migratory species.

A Primal Adjacency-Based Algorithm for the Shortest Path Problem with Resource Constraints

2020 ◽  
Vol 54 (5) ◽  
pp. 1153-1169
Author(s):  
Ilyas Himmich ◽  
Hatem Ben Amor ◽  
Issmail El Hallaoui ◽  
François Soumis
Keyword(s):  
Dynamic Programming ◽  
Shortest Path ◽  
Resource Constraints ◽  
Solution Space ◽  
Shortest Path Problem ◽  
Scheduling Problems ◽  
Least Cost Path ◽  
Major Drawback ◽  
Routing And Scheduling ◽  
Problem Instances

The shortest path problem with resource constraints (SPPRC) is often used as a subproblem within a column-generation approach for routing and scheduling problems. It aims to find a least-cost path between the source and the destination nodes in a network while satisfying the resource consumption limitations on every node. The SPPRC is usually solved using dynamic programming. Such approaches are effective in practice, but they can be inefficient when the network is large and especially when the number of resources is high. To cope with this major drawback, we propose a new exact primal algorithm to solve the SPPRC defined on acyclic networks. The proposed algorithm explores the solution space iteratively using a path adjacency–based partition. Numerical experiments for vehicle and crew scheduling problem instances demonstrate that the new approach outperforms both the standard dynamic programming and the multidirectional dynamic programming methods.

scholarly journals A Hybrid Approach for Providing Improved Link Connectivity in SDN

2019 ◽  
Vol 17 (2) ◽  
pp. 250-256
Author(s):  
Muthumanikandan Vanamoorthy ◽  
Valliyammai Chinnaiah ◽  
Harish Sekar
Keyword(s):  
Response Time ◽  
Shortest Path ◽  
Hybrid Approach ◽  
Link Failure ◽  
Use Case ◽  
Hybrid Scheme ◽  
Backup Path ◽  
The Past ◽  
Unique Approach ◽  
Traditional Approaches

Software-Defined Networking (SDN) is a unique approach to design and build networks. The networks services can be better handled by administrators with the abstraction that SDN provides. The problem of re-routing the packets with minimum overhead in case of link failure is handled in this work. Protection and restoration schemes have been used in the past to handle such issues by giving more priority to minimal response time or controller overhead based on the use case. A hybrid scheme has been proposed with per-link Bidirectional forwarding mechanism to handle the failover. The proposed method makes sure that the controller overhead does not impact the flow of packets, thereby decreasing the overall response time, even with guaranteed network resiliency. The computation of the next shortest backup path also guarantees that the subsequent routing of packets always chooses the shortest path available. The proposed method is compared with the traditional approaches and proven by results to perform better with minimal response time.

ON BENDS AND LENGTHS OF RECTILINEAR PATHS: A GRAPH-THEORETIC APPROACH

1992 ◽  
Vol 02 (01) ◽  
pp. 61-74 ◽  
Author(s):  
C.D. YANG ◽  
D.T. LEE ◽  
C.K. WONG
Keyword(s):  
Extreme Point ◽  
Shortest Path ◽  
Theoretic Approach ◽  
Least Cost Path ◽  
Unified Approach ◽  
Graph Theoretic ◽  
Bounded Number ◽  
Graph Theoretic Approach ◽  
Number Of Bends ◽  
The Cost

We consider the problem of finding a rectilinear path between two designated points in the presence of rectilinear obstacles subject to various optimization functions in terms of the number of bends and the total length of the path. Specifically we are interested in finding a minimum bend shortest path, a shortest minimum bend path or a least-cost path where the cost is defined as a function of both the length and the number of bends of the path. We provide a unified approach by constructing a path-preserving graph. guaranteed to preserve all these three kinds of paths and give an O(K+e log e) algorithm to find them, where e is the total number of obstacle edges, and K is the number of intersections between tracks from extreme point and other tracks (defined in the text). K is bounded by O(et), where t is the number of extreme edges. In particular, if the obstacles are rectilinearly convex, then K is O(ne), where n is the number of obstacles. Extensions are made to find a shortest path with a bounded number of bends and a minimum-bend path with a bounded length. When a source point and obstacles are pre-given, queries for the assorted paths from the source to given points can be handled in O( log e+k) time after O(K+e log e) preprocessing, where k is the size of the goal path. The trans-dichotomous algorithm of Fredman and Willard8 and the running time for these problems are also discussed.

Pragmatic versus Morphological/Syntactic Criteria for Language Referrals

1980 ◽  
Vol 11 (2) ◽  
pp. 85-94 ◽  
Author(s):  
Jack Damico ◽  
John W. Oller
Keyword(s):  
Grade Level ◽  
The State ◽  
Verb Agreement ◽  
Remedial Programs ◽  
Service Training ◽  
Traditional Approaches ◽  
Communicative Effectiveness

Two methods of identifying language disordered children are examined. Traditional approaches require attention to relatively superficial morphological and surface syntactic criteria, such as, noun-verb agreement, tense marking, pluralization. More recently, however, language testers and others have turned to pragmatic criteria focussing on deeper aspects of meaning and communicative effectiveness, such as, general fluency, topic maintenance, specificity of referring terms. In this study, 54 regular K-5 teachers in two Albuquerque schools serving 1212 children were assigned on a roughly matched basis to one of two groups. Group S received in-service training using traditional surface criteria for referrals, while Group P received similar in-service training with pragmatic criteria. All referrals from both groups were reevaluated by a panel of judges following the state determined procedures for assignment to remedial programs. Teachers who were taught to use pragmatic criteria in identifying language disordered children identified significantly more children and were more often correct in their identification than teachers taught to use syntactic criteria. Both groups identified significantly fewer children as the grade level increased.

Age Differences in Eye Movements During Reading: Degenerative Problems or Compensatory Strategy?

2019 ◽  
Vol 24 (4) ◽  
pp. 297-311
Author(s):  
José David Moreno ◽  
José A. León ◽  
Lorena A. M. Arnal ◽  
Juan Botella
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Meta Analysis ◽  
Age Groups ◽  
Behavioral Changes ◽  
Aging Effects ◽  
Movement Data ◽  
Sentence Reading ◽  
The Difference ◽  
Eye Movements During Reading

Abstract. We report the results of a meta-analysis of 22 experiments comparing the eye movement data obtained from young ( Mage = 21 years) and old ( Mage = 73 years) readers. The data included six eye movement measures (mean gaze duration, mean fixation duration, total sentence reading time, mean number of fixations, mean number of regressions, and mean length of progressive saccade eye movements). Estimates were obtained of the typified mean difference, d, between the age groups in all six measures. The results showed positive combined effect size estimates in favor of the young adult group (between 0.54 and 3.66 in all measures), although the difference for the mean number of fixations was not significant. Young adults make in a systematic way, shorter gazes, fewer regressions, and shorter saccadic movements during reading than older adults, and they also read faster. The meta-analysis results confirm statistically the most common patterns observed in previous research; therefore, eye movements seem to be a useful tool to measure behavioral changes due to the aging process. Moreover, these results do not allow us to discard either of the two main hypotheses assessed for explaining the observed aging effects, namely neural degenerative problems and the adoption of compensatory strategies.

Sign in / Sign up

Export Citation Format

Share Document