The Physics of Foraging Viswanathan, Gandhimohan. M.; da Luz, Marcos G. E.; Raposo, Ernesto P. ...
06/2011
eBook, Book
Do the movements of animals, including humans, follow patterns that can be described quantitatively by simple laws of motion? If so, then why? These questions have attracted the attention of ...scientists in many disciplines, and stimulated debates ranging from ecological matters to queries such as 'how can there be free will if one follows a law of motion?' This is the first book on this rapidly evolving subject, introducing random searches and foraging in a way that can be understood by readers without a previous background on the subject. It reviews theory as well as experiment, addresses open problems and perspectives, and discusses applications ranging from the colonization of Madagascar by Austronesians to the diffusion of genetically modified crops. The book will interest physicists working in the field of anomalous diffusion and movement ecology as well as ecologists already familiar with the concepts and methods of statistical physics.
Mechanistic home range analysis Moorcroft, Paul; Lewis, Mark A
2006, 2006., 20131031, 2013, 2006-01-01, Letnik:
43
eBook, Book
Spatial patterns of movement are fundamental to the ecology of animal populations, influencing their social organization, mating systems, demography, and the spatial distribution of prey and ...competitors. However, our ability to understand the causes and consequences of animal home range patterns has been limited by the descriptive nature of the statistical models used to analyze them. InMechanistic Home Range Analysis, Paul Moorcroft and Mark Lewis develop a radically new framework for studying animal home range patterns based on the analysis of correlated random work models for individual movement behavior. They use this framework to develop a series of mechanistic home range models for carnivore populations.
The authors' analysis illustrates how, in contrast to traditional statistical home range models that merely describe pattern, mechanistic home range models can be used to discover the underlying ecological determinants of home range patterns observed in populations, make accurate predictions about how spatial distributions of home ranges will change following environmental or demographic disturbance, and analyze the functional significance of the movement strategies of individuals that give rise to observed patterns of space use.
By providing researchers and graduate students of ecology and wildlife biology with a more illuminating way to analyze animal movement,Mechanistic Home Range Analysiswill be an indispensable reference for years to come.
It is not clear whether animals consistently change their home ranges in response to density reduction. This is important to understand for better management of pest species where sustained control ...is required. Our objective was to measure whether home ranges of Australian brushtail possums (Trichosurus vulpecula) change following density reduction, using global positioning system (GPS) tracking. We experimentally reduced the densities of 2 populations (1 high-density at 7 possums/ha and 1 low-density at 1.5 possums/ha) and did not manipulate another population. We then monitored home ranges of individual possums. The high-density manipulated population had a significant increase in home-range size and overlap within 5 weeks following reduction, whereas the other 2 populations did not. This research suggests that changes in possum home ranges following control are likely influenced by the initial density of the pest population.
Animals require a certain amount of habitat to persist and thrive, and habitat loss is one of the most critical drivers of global biodiversity decline. While habitat requirements have been predicted ...by relationships between species traits and home‐range size, little is known about constraints imposed by environmental conditions and human impacts on a global scale. Our meta‐analysis of 395 vertebrate species shows that global climate gradients in temperature and precipitation exert indirect effects via primary productivity, generally reducing space requirements. Human pressure, however, reduces realised space use due to ensuing limitations in available habitat, particularly for large carnivores. We show that human pressure drives extinction risk by increasing the mismatch between space requirements and availability. We use large‐scale climate gradients to predict current species extinction risk across global regions, which also offers an important tool for predicting future extinction risk due to ongoing space loss and climate change.
Extinctions due to space loss occur when the available habitat shrinks to a point where an animal struggles to meet its daily life‐supporting demands. By employing a global assessment of animal space use in an environmental context, we calculate the discrepancy between required and available habitat space. Thereby, we (1) show that human impacts drive extinction risks by reducing available habitat and (2) identify species and areas at risk of extinction worldwide.
Summary
Movement ecology has developed rapidly over the past decade, driven by advances in tracking technology that have largely removed data limitations. Development of rigorous analytical tools has ...lagged behind empirical progress, and as a result, relocation data sets have been underutilized.
Discrete‐time correlated random walk models (CRW) have long served as the foundation for analyzing relocation data. Unfortunately, CRWs confound the sampling and movement processes. CRW parameter estimates thus depend sensitively on the sampling schedule, which makes it difficult to draw sampling‐independent inferences about the underlying movement process. Furthermore, CRWs cannot accommodate the multiscale autocorrelations that typify modern, finely sampled relocation data sets.
Recent developments in modelling movement as a continuous‐time stochastic process (CTSP) solve these problems, but the mathematical difficulty of using CTSPs has limited their adoption in ecology. To remove this roadblock, we introduce the ctmm package for the R statistical computing environment. ctmm implements all of the CTSPs currently in use in the ecological literature and couples them with powerful statistical methods for autocorrelated data adapted from geostatistics and signal processing, including variograms, periodograms and non‐Markovian maximum likelihood estimation.
ctmm is built around a standard workflow that begins with visual diagnostics, proceeds to candidate model identification, and then to maximum likelihood fitting and AIC‐based model selection. Once an accurate CTSP for the data has been fitted and selected, analyses that require such a model, such as quantifying home range areas via autocorrelated kernel density estimation or estimating occurrence distributions via time‐series Kriging, can then be performed.
We use a case study with African buffalo to demonstrate the capabilities of ctmm and highlight the steps of a typical CTSP movement analysis workflow.
Mapping and measuring place attachment Brown, Greg; Raymond, Christopher M.; Corcoran, Jonathan
Applied geography (Sevenoaks),
February 2015, 2015-02-00, Letnik:
57
Journal Article
Recenzirano
The concept of place attachment has been studied extensively across multiple disciplines but only recently with empirical measurement using public participation GIS (PPGIS) and related crowd-sourcing ...mapping methods. This research trialed a spatially explicit method for identifying place attachment in a regional study in South Australia. Our research objectives were to (1) analyze and present the spatial results of the mapping method as a benchmark for future research, (2) compare mapped place attachment to the more common practice of mapping landscape values in PPGIS that comprise a values home range, (3) identify how participant socio-demographic and home location attributes influence place attachment, (4) provide some guidance for mapping place attachment in future research. We found large spatial variability in individual place attachment and mapped landscape values using both area and distance-based measures. The area of place attachment is influenced by occupational roles such as farming or conservation, as well as home location, especially in coastal versus non-coastal contexts. The spatial distribution of mapped landscape values or values home range is related to, but not identical to mapped place attachment with just over half of landscape values located outside the area of mapped place attachment. Economic livelihood values, as an indicator of place dependence, and social values, as an indicator of place identity, are more likely to be mapped within the place attachment area. Aggregated place attachment across participants in the region showed similar spatial intensity to aggregated values home range, but area-based assessment of place attachment and values home range are distorted by edge effects such as a coastline. To further develop the mapping of place attachment in PPGIS, we identify knowledge gaps from our study and offer suggestions for future research design.
•Operationalizes and implements a method for mapping place attachment in PPGIS.•Compares place attachment to mapped landscape values, called values home range.•Place attachment is a spatial subset of a values home range.•Place attachment area is influenced by occupation and home location.•Provides suggestions to advance spatial identification of place attachment.
Objectives
Territoriality refers to the consistent defense of an area within the home range (HR) against intrusions of conspecifics. It implies exclusive space use with low degree of overlap among ...neighboring groups, high site fidelity, specific ranging behavior such as high mobility relative to HR size and frequent visits of territory borders, and monitoring behavior. We examined ranging behavior and use of space to evaluate territoriality in Pithecia aequatorialis in Ecuador.
Materials and methods
Between 2005 and 2015, we monitored one main study group continuously and five additional groups for shorter periods (5 months to 2.5 years) at the Tiputini Biodiversity Station, in eastern Ecuador. We scored the location of the study groups at 20 min intervals during, on average, 5 days per month. We estimated saki HRs and core areas (CAs) using the fixed kernel density method (95 and 50%, respectively).
Results
The average HR size was 57 ha and the average CA 14 ha. The degree of overlap between HRs of neighboring groups was low (2–9%). For the main study group, the average overlap between annual HRs was 82%. Mean daily path length across groups was 1,151 m; the defensibility index varied between 1.1 and 2.3 (values >1 are suggestive of territoriality), and the fractional monitoring rate varied between 0.06 and 0.15 (values >0.08 are suggestive of territoriality). Groups did not visit their HR borders (100 m inner buffer) more often than would be expected by chance. Travel speed and directness were comparable between the borders and the centers of groups' HRs.
Discussion
Our multiyear study suggests that equatorial sakis show low degree of range overlap and high site fidelity and have the potential to be territorial, given their high mobility relative to HR size that allows for frequent border monitoring. Nevertheless, their movement patterns in border areas did not reveal evidence for monitoring behavior.
Home ranges are vitally important to an animal's behavior, survival, and reproduction. Variation in environmental conditions and landscape composition coupled with differences between sexes can ...influence home range structure, and understanding these differences is important for species management. Elk (Cervus canadensis Erxleben, 1777) are a widespread culturally important ungulate that has been well studied over portions of its range. Reintroduced populations in eastern North America, where conditions differ dramatically from those in the west, are comparatively understudied. Using Ornstein-Uhlenbeck movement models, we calculated season- and sex-specific home range and core areas for elk in Pennsylvania, USA. Results showed strong seasonal variation in sizes of core areas and home ranges, with summer ranges consistently smaller than other seasons. Home ranges were largely forested. However, forest cover of core areas was lower than home ranges. Proportion of open cover types was greater in core areas than home ranges. Use of timber harvests overall was low. However, among individuals with highly forested home ranges, timber harvests were strongly selected for in spring. This work highlights the regional specificity in the size, composition, and seasonality of elk home ranges, and stresses the need for additional context-specific research in understudied elk populations of forested eastern landscapes.
North American populations of Black Vultures Coragyps atratus have increased and expanded their distribution in the southern and eastern USA. In conjunction with these patterns has been a rise in ...human–vulture conflicts. To improve our understanding of space use patterns and better inform management, we evaluated the movements of Black Vultures (n = 23) in the southeastern USA using a long‐term GPS tracking database. Our specific objectives were to: (1) quantify home‐range sizes in relation to season and geographical study location and (2) examine within‐home‐range resource selection to identify landscape and anthropogenic factors influencing roost and diurnal space use. Home‐range sizes did not significantly differ between breeding and non‐breeding seasons. However, there were differences across geographical study locations, with the largest home‐ranges located in Florida. Similarly, there was limited seasonal variation in resource selection; however, use of anthropogenic features did vary by geographical study location. Overall Black Vultures avoided homogeneous landscapes regardless of season or activity and exhibited a strong selection for areas with increased landscape richness. Increased landscape richness, unlike homogeneous habitat, provides a diversity of resources for Black Vultures in a localized area, such as food, water, roosting and perch sites, and the creation of energy‐efficient flight opportunities. Contrasting with natural landscape feature selection, selection of anthropogenic features, such as landfill proximity and road density, was highly variable across individuals and study location. The high level of variation in selection for anthropogenic features provides further evidence of the propensity of Black Vultures to be flexible and opportunistic. The findings of this study stress the importance of using site‐specific studies effectively to understand and manage local vulture populations and mitigate associated human–vulture conflicts. Wildlife managers should exercise caution when implementing vulture management actions based on inferences from telemetry studies conducted in other geographical areas.
With rapid development and the spread of urbanized land, there is an increasing need to understand species' responses to urban conditions. Carnivores are considered to be sensitive to urbanization; ...however, there is ample evidence that some carnivore species successfully inhabit urban areas, and human‐modified habitats have recently been recognized as an important refuge for several species. Despite the increasing number of studies on urban carnivore ecology, no comprehensive cross‐species comparisons have been made in order to assess the effects of urbanization on the spatial ecology of carnivores and their population densities. Such a review could provide interesting insight into how some carnivore species respond to increasing urbanization. Specifically, we examine changes in population density and home range size of eight carnivore species that occur along the natural–urban environmental gradient. Using data from 411 articles, we provide evidence that the home range size of carnivores decreases in six out of eight species, and population density increases in three out of six species along the natural–urban habitat gradient. The density‐dependent pattern of variation in home range size is consistent in all species studied. Our results emphasize the remarkable ability of some carnivore species to adapt to novel environments through their behavioural flexibility and life history adaptations. We outline ideas for future research that could be adopted in addressing this phenomenon, namely comparative approaches and detailed studies of biotic and abiotic conditions along natural–urban gradients.
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