scholarly journals Circular-Linear Copulae for Animal Movement Data

2021 ◽  
Author(s):  
Florian Hodel ◽  
John R. Fieberg
Keyword(s):  
Habitat Selection ◽  
Animal Movement ◽  
Small Step ◽  
Multivariate Distributions ◽  
Time Intervals ◽  
Movement Data ◽  
Pekania Pennanti ◽  
Large Step ◽  
Regular Time ◽  
Selection For

1. Animal movement is often modeled in discrete time, formulated in terms of steps taken between successive locations at regular time intervals. Steps are characterized by the distance between successive locations (step-lengths) and changes in direction (turn angles). Animals commonly exhibit a mix of directed movements with large step lengths and turn angles near 0 when traveling between habitat patches and more wandering movements with small step lengths and uniform turn angles when foraging. Thus, step-lengths and turn angles will typically be cross-correlated. 2. Most models of animal movement assume that step-lengths and turn angles are independent, likely due to a lack of available alternatives. Here, we show how the method of copulae can be used to fit multivariate distributions that allow for correlated step lengths and turn angles. 3. We describe several newly developed copulae appropriate for modeling animal movement data and fit these distributions to data collected on fishers (Pekania pennanti). The copulae are able to capture the inherent correlation in the data and provide a better fit than a model that assumes independence. Further, we demonstrate via simulation that this correlation can impact movement patterns (e.g. rates of dispersion overtime). 4. We see many opportunities to extend this framework (e.g. to consider autocorrelation in step attributes) and to integrate it into existing frameworks for modeling animal movement and habitat selection. For example, copula could be used to more accurately sample available locations when conducting habitat-selection analyses.

scholarly journals Using approximate Bayesian inference for a “steps and turns” continuous-time random walk observed at regular time intervals

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8452
Author(s):  
Sofia Ruiz-Suarez ◽  
Vianey Leos-Barajas ◽  
Ignacio Alvarez-Castro ◽  
Juan Manuel Morales
Keyword(s):  
State Space ◽  
Continuous Time ◽  
Time Scale ◽  
Animal Movement ◽  
State Space Model ◽  
Movement Direction ◽  
Time Intervals ◽  
Space Model ◽  
Regular Time ◽  
Approximate Bayesian

The study of animal movement is challenging because movement is a process modulated by many factors acting at different spatial and temporal scales. In order to describe and analyse animal movement, several models have been proposed which differ primarily in the temporal conceptualization, namely continuous and discrete time formulations. Naturally, animal movement occurs in continuous time but we tend to observe it at fixed time intervals. To account for the temporal mismatch between observations and movement decisions, we used a state-space model where movement decisions (steps and turns) are made in continuous time. That is, at any time there is a non-zero probability of making a change in movement direction. The movement process is then observed at regular time intervals. As the likelihood function of this state-space model turned out to be intractable yet simulating data is straightforward, we conduct inference using different variations of Approximate Bayesian Computation (ABC). We explore the applicability of this approach as a function of the discrepancy between the temporal scale of the observations and that of the movement process in a simulation study. Simulation results suggest that the model parameters can be recovered if the observation time scale is moderately close to the average time between changes in movement direction. Good estimates were obtained when the scale of observation was up to five times that of the scale of changes in direction. We demonstrate the application of this model to a trajectory of a sheep that was reconstructed in high resolution using information from magnetometer and GPS devices. The state-space model used here allowed us to connect the scales of the observations and movement decisions in an intuitive and easy to interpret way. Our findings underscore the idea that the time scale at which animal movement decisions are made needs to be considered when designing data collection protocols. In principle, ABC methods allow to make inferences about movement processes defined in continuous time but in terms of easily interpreted steps and turns.

Habitat selection by common brushtail possums in a patchy eucalypt-forestry environment.

2005 ◽  
Vol 27 (2) ◽  
pp. 119 ◽  
Author(s):  
Mar K le ◽  
C McArthur
Keyword(s):  
Habitat Selection ◽  
Population Density ◽  
Animal Movement ◽  
Brushtail Possum ◽  
Native Forest ◽  
Eucalyptus Nitens ◽  
North West ◽  
Movement Data ◽  
Selection Indices ◽  
Spatio Temporal

We investigated population density and patterns of habitat selection by the common brushtail possum (Trichosurus vulpecula fuliginosus) within a patchy forestry environment in north-west Tasmania. Population density was extremely low overall (0.04 animals.ha-1) and varied between habitats (0.01 ? 0.13 animals.ha-1). Selection indices from population surveys and animal movement data showed clear patterns for two closed habitats across two spatio-temporal scales: native forest was selected for, while 5 - 7 year old Eucalyptus nitens plantation was selected against, for both home range placement within the study area and habitats selectively used while foraging at night. Daytime habitat selection also showed the same pattern. We argue that native forest represented high quality habitat, offering both food and shelter (tree-hollows), while older plantation represented low quality habitat, lacking both of these resources. Results for open habitats (young Eucalyptus nitens plantation and grassland) were less clear. These patterns are discussed in relation to potential effects of a changing forestry landscape on this species.

scholarly journals Females roam while males patrol: divergence in breeding season movements of pack-ice polar bears ( Ursus maritimus )

2013 ◽  
Vol 280 (1752) ◽  
pp. 20122371 ◽  
Author(s):  
Kristin L. Laidre ◽  
Erik W. Born ◽  
Eliezer Gurarie ◽  
Øystein Wiig ◽  
Rune Dietz ◽  
...  
Keyword(s):  
Habitat Selection ◽  
Simulation Model ◽  
Polar Bears ◽  
Movement Behaviour ◽  
Breeding Range ◽  
Movement Data ◽  
Adult Females ◽  
Pack Ice ◽  
Selection For ◽  
Breeding Seasons

Intraspecific differences in movement behaviour reflect different tactics used by individuals or sexes to favour strategies that maximize fitness. We report movement data collected from n = 23 adult male polar bears with novel ear-attached transmitters in two separate pack ice subpopulations over five breeding seasons. We compared movements with n = 26 concurrently tagged adult females, and analysed velocities, movement tortuosity, range sizes and habitat selection with respect to sex, reproductive status and body mass. There were no differences in 4-day displacements or sea ice habitat selection for sex or population. By contrast, adult females in all years and both populations had significantly more linear movements and significantly larger breeding range sizes than males. We hypothesized that differences were related to encounter rates, and used observed movement metrics to parametrize a simulation model of male–male and male–female encounter. The simulation showed that the more tortuous movement of males leads to significantly longer times to male–male encounter, while having little impact on male–female encounter. By contrast, linear movements of females are consistent with a prioritized search for sparsely distributed prey. These results suggest a possible mechanism for explaining the smaller breeding range sizes of some solitary male carnivores compared to females.

scholarly journals Movement syndromes of a Neotropical frugivorous bat inhabiting heterogeneous landscapes in Brazil

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Patricia Kerches-Rogeri ◽  
Danielle Leal Ramos ◽  
Jukka Siren ◽  
Beatriz de Oliveira Teles ◽  
Rafael Souza Cruz Alves ◽  
...  
Keyword(s):  
Site Fidelity ◽  
Animal Movement ◽  
Radio Telemetry ◽  
Food Resource ◽  
Movement Behavior ◽  
Movement Activity ◽  
Landscape Features ◽  
Heterogeneous Landscapes ◽  
Movement Data ◽  
High Site

Abstract Background There is growing evidence that individuals within populations can vary in both habitat use and movement behavior, but it is still not clear how these two relate to each other. The aim of this study was to test if and how individual bats in a Stunira lilium population differ in their movement activity and preferences for landscape features in a correlated manner. Methods We collected data on movements of 27 individuals using radio telemetry. We fitted a heterogeneous-space diffusion model to the movement data in order to evaluate signals of movement variation among individuals. Results S. lilium individuals generally preferred open habitat with Solanum fruits, regularly switched between forest and open areas, and showed high site fidelity. Movement variation among individuals could be summarized in four movement syndromes: (1) average individuals, (2) forest specialists, (3) explorers which prefer Piper, and (4) open area specialists which prefer Solanum and Cecropia. Conclusions Individual preferences for landscape features plus food resource and movement activity were correlated, resulting in different movement syndromes. Individual variation in preferences for landscape elements and food resources highlight the importance of incorporating explicitly the interaction between landscape structure and individual heterogeneity in descriptions of animal movement.

Tree Swallow selection for wetlands in agricultural landscapes predicted by central-place foraging theory

The Condor ◽  
2020 ◽  
Author(s):  
Andrew S Elgin ◽  
Robert G Clark ◽  
Christy A Morrissey
Keyword(s):  
Habitat Selection ◽  
Central Place ◽  
Foraging Theory ◽  
Agricultural Landscapes ◽  
Tree Swallow ◽  
Field Margins ◽  
Central Place Foraging ◽  
Prairie Pothole ◽  
Prairie Wetlands ◽  
Selection For

Abstract Millions of wetland basins, embedded in croplands and grasslands, are biodiversity hotspots in North America’s Prairie Pothole Region, but prairie wetlands continue to be degraded and drained, primarily for agricultural activities. Aerial insectivorous swallows are known to forage over water, but it is unclear whether swallows exhibit greater selection for wetlands relative to other habitats in croplands and grasslands. Central-place foraging theory suggests that habitat selectivity should increase with traveling distance from a central place, such that foragers compensate for traveling costs by selecting more profitable foraging habitat. Using global positioning system (GPS) tags, we evaluated habitat selection by female Tree Swallows (Tachycineta bicolor) at 4 sites containing wetlands and where terrestrial land cover was dominated by grasslands (grass, herbaceous cover) and/or cultivated cropland. We also used sweep-net transects to assess the abundance and biomass of flying insects in different habitats available to swallows (wetland pond margins, grassy field margins, and representative uplands). As expected for a central-place forager, GPS-tagged swallows selected more for wetland ponds (disproportionate to availability), and appeared to increasingly select for wetlands with increasing distance from their nests. On cropland-dominated sites, insect abundance and biomass tended to be higher in pond margins or grassy field margins compared to cropped uplands, while abundance and biomass were more uniform among sampled habitats at sites dominated by grass and herbaceous cover. Swallow habitat selection was not clearly explained by the distribution of sampled insects among habitats; however, traditional terrestrial sampling methods may not adequately reflect prey distribution and availability to aerially foraging swallows. Overall, our results underscore the importance of protecting and enhancing prairie wetlands and other non-crop habitats in agricultural landscapes, given their disproportionate use and capacity to support breeding swallow and insect populations.

scholarly journals Speech rhythm: a metaphor?

2014 ◽  
Vol 369 (1658) ◽  
pp. 20130396 ◽  
Author(s):  
Francis Nolan ◽  
Hae-Sung Jeon
Keyword(s):  
Traditional View ◽  
Time Intervals ◽  
Speech Rhythm ◽  
Linguistic Structure ◽  
Regular Time ◽  
Linguistic Functions ◽  
Absence Of Evidence ◽  
Metaphorical Extension ◽  
Analogical Process

Is speech rhythmic? In the absence of evidence for a traditional view that languages strive to coordinate either syllables or stress-feet with regular time intervals, we consider the alternative that languages exhibit contrastive rhythm subsisting merely in the alternation of stronger and weaker elements. This is initially plausible, particularly for languages with a steep ‘prominence gradient’, i.e. a large disparity between stronger and weaker elements; but we point out that alternation is poorly achieved even by a ‘stress-timed’ language such as English, and, historically, languages have conspicuously failed to adopt simple phonological remedies that would ensure alternation. Languages seem more concerned to allow ‘syntagmatic contrast’ between successive units and to use durational effects to support linguistic functions than to facilitate rhythm. Furthermore, some languages (e.g. Tamil, Korean) lack the lexical prominence which would most straightforwardly underpin prominence of alternation. We conclude that speech is not incontestibly rhythmic, and may even be antirhythmic. However, its linguistic structure and patterning allow the metaphorical extension of rhythm in varying degrees and in different ways depending on the language, and it is this analogical process which allows speech to be matched to external rhythms.

Processing and Excellent Oxidation Resistance of Nanocrystalline Fe-Cr Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 1122-1125
Author(s):  
Rajeev K. Gupta ◽  
B.V. Mahesh ◽  
R.K. Singh Raman ◽  
Carl C. Koch
Keyword(s):  
Oxidation Resistance ◽  
Secondary Ion Mass Spectrometry ◽  
Nanocrystalline Alloy ◽  
High Energy ◽  
Processing Route ◽  
Protective Oxide ◽  
Time Intervals ◽  
Regular Time ◽  
Order Of Magnitude ◽  
Energy Ball

Nanocrystalline and microcrystalline Fe-10Cr alloys were prepared by high energy ball milling followed by compaction and sintering, and then oxidized in air for 52 hours at 400°C. The oxidation resistance of nanocrystalline Fe-10Cr alloy as determined by measuring the weight gain after regular time intervals was compared with that of the microcrystalline alloy of same chemical composition (also prepared by the same processing route and oxidized under identical conditions). Oxidation resistance of nanocrystalline Fe10Cr alloy was found to be in excess of an order of magnitude superior than that of microcrystalline Fe10Cr alloy. The paper also presents results of secondary ion mass spectrometry of oxidized samples of nanocrystalline and microcrystalline Fe-Cr alloys, evidencing the formation of a more protective oxide scale in the nanocrystalline alloy.

scholarly journals Running on empty: recharge dynamics from animal movement data

2018 ◽  
Author(s):  
Mevin B. Hooten ◽  
Henry R. Scharf ◽  
Juan M. Morales
Keyword(s):  
Animal Movement ◽  
Movement Data
Sign in / Sign up

Export Citation Format

Share Document