Добірка наукової літератури з теми "Dynamic Brownian bridge movement models"

Movement analyses were conducted for 50 goats across southern Australia using GPS satellite collars. A radio or satellite-tracked animal used to direct culling operations is generally called a ‘Judas’ animal. Goats used as ‘Judas’ animals in control operations were compared with non-‘Judas’ goats in the states of South Australia and Victoria, respectively. Their movement in two land systems were also compared. Dynamic Brownian Bridges Movement Models were used to calculate home ranges (95% utilisation areas). Changes in movement behaviour were identified to partition sedentary behaviour from long-distance movement events, defined here as ranging. Eleven goats exhibited ranging behaviour and moved from 9 to 33 km between their home ranges. After partitioning, their home ranges varied from 1.97 to 223.8 km2. In this study in the Southern Australian Mallee regions, non-‘Judas’ goats had significantly smaller home ranges than ‘Judas’ goats. However, no significant differences were found in the ranging distances between non-‘Judas’ goats and ‘Judas’ goats. Understanding these two distinct forms of goat movement is important in the planning and budgeting of removal operations. To demonstrate this a simple goat management decision tool is used to illustrate the biases that can result in the expected hours of removal operations when the assumptions about goat movement are ill-defined.

An understanding of the spatial ecology of species living in and around human-dominated habitats is needed to develop conflict mitigation strategies and predict how organisms cope with ongoing anthropogenic habitat alteration. Here we present the results of a six-month telemetry study in Thailand of the banded krait (Bungarus fasciatus), a venomous elapid snake. We quantified home range size and habitat use of three adult kraits (1 male, 2 females) in an agricultural habitat. The kraits travelled an average of 47.20 m ± 23.54 m between shelter sites and occupied home ranges of on average 21.45 ha ± 19.56 ha (95 % dynamic Brownian Bridge Movement Models). They preferred to seek day time refuge amongst less disturbed habitat features, including waterways and rice paddy dykes, while avoiding routinely disturbed monoculture fields. The two female kraits also exhibited reduced movement while simultaneously attending their nests in a shared burrow complex. Fifteen neonates were observed emerging from the nest site. We recommend further investigation of banded krait reproductive ecology and ability to persist in heavily disturbed habitats.

Feral cats are one of the most damaging predators on Earth. They can be found throughout most of Australia’s mainland and many of its larger islands, where they are adaptable predators responsible for the decline and extinction of many species of native fauna. Managing feral cat populations to mitigate their impacts is a conservation priority. Control strategies can be better informed by knowledge of the locations that cats frequent the most. However, this information is rarely captured at the population level and therefore requires modelling based on observations of a sample of individuals. Here, we use movement data from collared feral cats to estimate home range sizes by gender and create species distribution models in the Pilbara bioregion of Western Australia. Home ranges were estimated using dynamic Brownian bridge movement models and split into 50% and 95% utilisation distribution contours. Species distribution models used points intersecting with the 50% utilisation contours and thinned by spacing points 500 m apart to remove sampling bias. Male cat home ranges were between 5 km2 (50% utilisation) and 34 km2 (95% utilisation), which were approximately twice the size of the female cats studied (2–17 km2). Species distribution modelling revealed a preference for low-lying riparian habitats with highly productive vegetation cover and a tendency to avoid newly burnt areas and topographically complex, rocky landscapes. Conservation management can benefit by targeting control effort in preferential habitat.

A better understanding of the movement of feral dromedary camels (Camelus dromedarius) in Australia would be useful for planning removal operations (harvest or culling), because the pattern and scale of camel movement relates to the period they reside in a given area, and thus the search effort, timing and frequency of removal operations. From our results, we suspect that the dune direction influences how camels move across central Australia; particularly effects like the north–south longitudinal dune systems in the Simpson Desert, which appeared to elongate camel movement in the same direction as the dunes. We called this movement anisotropy. Research suggests camel movement in Australia is not migratory but partially cyclic, with two distinctive movement patterns. Our study investigated this further by using satellite tracking data from 54 camels in central Australia, recorded between 2007 and 2016. The mean tracking period for each animal was 363.9 days (s.e.m.=44.1 days). We used a method labelled multi-scale partitioning to test for changes in movement behaviour and partitioned more localised intensive movements within utilisation areas, from larger-scale movement, called ranging. This involved analysing the proximity of movement trajectories to other nearby trajectories of the same animal over time. We also used Dynamic Brownian Bridges Movement Models, which consider the relationship of consecutive locations to determine the areas of utilisation. The mean utilisation area and duration of a camel (n=658 areas) was found to be 342.6km2 (s.e.m.=33.2km2) over 23.5 days (s.e.m.=1.6 days), and the mean ranging distance (n=611 ranging paths) was a 45.1km (s.e.m.=2.0km) path over 3.1 days (s.e.m.=0.1 days).

Fire severity is an important control over regeneration of deciduous species and can influence the overall quality of habitat for herbivores, such as moose (Alces alces (Linnaeus, 1758)), but the relationships between availability and duration of biomass production and moose habitat use are largely unknown. We evaluate the relative influence of a regenerating burn, paying particular attention to fire severity, on winter forage production and duration, offtake, nutritional quality, and seasonal moose habitat use. We used data from 14 GPS collared male moose in the 20-year-old Hajdukovich Creek Burn (HCB) in interior Alaska, USA, to generate seasonal dynamic Brownian bridge movement models. Within HCB, moose selected for low-severity sites more than high- and moderate-severity sites during the winter. Over the past decade, willow (species of the genus Salix L.) biomass production in low-severity sites has doubled and is likely influencing winter habitat selection patterns. In summer, moose selected for high-severity sites where there is a more abundant understory layer (e.g., stem densities) providing both forage and cover. The initial pulse of biomass production in high-severity sites, as well as the delay in growth and maturation of vegetation in low-severity sites, indicate that differing distributions of wildfire severity can create a dynamic mosaic of habitat patches that may extend the value of burns over time for moose.

Reptiles are the most species-rich terrestrial vertebrate group with a broad diversity of life history traits. Biotelemetry is an essential methodology for studying reptiles as it compensates for several limitations when studying their natural history. We evaluated trends in terrestrial reptile spatial ecology studies focusing upon quantifying home ranges for the past twenty years. We assessed 290 English-language reptile home range studies published from 2000–2019 via a structured literature review investigating publications’ study location, taxonomic group, methodology, reporting, and analytical techniques. Substantial biases remain in both location and taxonomic groups in the literature, with nearly half of all studies (45%) originating from the USA. Snakes were most often studied, and crocodiles were least often studied, while testudines tended to have the greatest within study sample sizes. More than half of all studies lacked critical methodological details, limiting the number of studies for inclusion in future meta-analyses (55% of studies lacked information on individual tracking durations, and 51% lacked sufficient information on the number of times researchers recorded positions). Studies continue to rely on outdated methods to quantify space-use (including Minimum Convex Polygons and Kernel Density Estimators), often failing to report subtleties regarding decisions that have substantial impact on home range area estimates. Moving forward researchers can select a suite of appropriate analytical techniques tailored to their research question (dynamic Brownian Bridge Movement Models for within sample interpolation, and autocorrelated Kernel Density Estimators for beyond sample extrapolation). Only 1.4% of all evaluated studies linked to available and usable telemetry data, further hindering scientific consensus. We ultimately implore herpetologists to adopt transparent reporting practices and make liberal use of open data platforms to maximize progress in the field of reptile spatial ecology.

The Balkan populations of the European wildcat are among the least studied. This study reports the first findings on the spatial ecology and activity pattern of the wildcat in Greece and compares them to those of better studied northern populations. We fitted five wildcats (two males, three females) with collars containing GPS and accelerometer loggers (E-obs 1A) and collected data from fall to early summer. All animals moved within a mosaic of lowland agricultural fields, woodland patches, riparian forests and wetlands near the banks of a lake. The trapping rate was the highest reported for the species. The home range sizes, estimated using Brownian bridge movement models, ranged from 0.94 to 3.08 km2 for females and from 1.22 to 4.43 km2 for males. Based on overall dynamic body acceleration (ODBA) values estimated from the accelerometer data, the diel activity of male wildcats followed the species’ typical nocturnal pattern with crepuscular peaks. Female activity varied seasonally, at times being cathemeral. We found only weak effects of environmental variables on wildcat activity, and no significant difference in the activity in open versus forested areas. Our findings suggest that human modified landscapes can play a significant role in the conservation of this typically forest-associated species.

Malleefowl are iconic Australian birds that build large mounds to incubate their eggs using external sources of heat. Malleefowl numbers have drastically decreased since European settlement and they are now a nationally threatened species. Their decline is caused by habitat loss and fragmentation; predation by introduced species; inappropriate fire regimes and competition and habitat degradation through overabundant native and introduced herbivores. Climate change is expected to exacerbate these pressures by leading to more frequent and longer periods of high temperatures, reduced precipitation and increased frequency and intensity of wildfires. This thesis aimed to investigate how historic and recent habitat fragmentation and climatic variables influenced Malleefowl on the Eyre Peninsula and how climate change may exacerbate future impacts. The objectives were to assess population trends, investigate landscape genetics, study movement patterns and the influence of habitat variables. These objectives were addressed through a multidisciplinary approach to study discrete Malleefowl populations at study sites located on the Eyre Peninsula in South Australia. To assess population trends and the influence of environmental factors, 24 years of mound-based breeding activity data were modelled. Results showed a widespread and significant decline in Malleefowl breeding activity during the study period, driven by changes in vegetation cover and reduction in soil moisture. High throughput DNA sequencing was used to investigate past dispersal patterns and the effects of recent anthropogenic land cover changes. The results indicate that Malleefowl population structure on the Eyre Peninsula was not homogenous and that habitat fragmentation with subsequent isolation has caused the differentiation of at least two distinct populations. Further, there was preliminary genetic evidence of female dispersal. Solar-powered GPS trackers were used to determine individual movement patterns and the effects of habitat fragmentation and environmental factors. Malleefowl movement was tightly associated with breeding status, with breeding birds staying close to the mound and non-breeding birds disassociating from the mound and moving long distances. Movement was also influenced by patch size and fragmentation, with non-breeding birds in large patches moving further than birds in smaller patches, but Malleefowl were able to persist in small patches and breed successfully for many years. Malleefowl moved less with increasing temperatures. Malleefowl did not use cropping land and they avoided crossing open paddocks. Malleefowl also had high mortality rates with over 66% of tracked individuals dying within a year of trapping, mostly from cat and fox predation. Vegetation surveys were combined with GPS tracking data to investigate whether Malleefowl movement was influenced by vegetation composition or cover. Results indicate that Malleefowl seek out micropatches of tall mallee stands within a mature Eucalyptus matrix – likely as refuges from heat and predators – and that movement is less driven by a preference for plant species, reflecting the fact that Malleefowl have a highly variable and opportunistic diet. In summary, this thesis shows how anthropogenic habitat alteration and changing environmental conditions have reduced breeding activity, restricted movement, dispersal and gene flow of Malleefowl populations on the Eyre Peninsula, with noticeable long-term genetic effects. Further, we can expect climate change to exacerbate all existing pressures and possibly drive Malleefowl closer to extinction. This research provides valuable new information about Malleefowl movement ecology which supports increased efforts to protect even small patches of native vegetation in agricultural matrices and the creation of habitat corridors between patches, as well as the improvements of matrix habitat, to facilitate between-patch movement. This, combined with continued and improved predator-control efforts, may enhance the conditions for future survival of Malleefowl populations, and support biodiversity in general, which is vital when faced with increasing climate change pressures.
Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2022

A lack of understanding of the fluid-structure interactions has resulted in a number of infamous structural failures in the past. For example, the collapses of the Tay Bridge in Scotland in 1879, the Tacoma Bridge in 1948 and three tall cooling towers in Ferrybridge/England in 1965 have been intrinsically related to fluid forces acting on the structure. Flutter, flow-induced vibration, divergence and related phenomena may be studied using the Fluid-Solid-Interaction (FSI) approach. This paper gives three examples of the FSI approach and shows the innovative application of state-of-the-art computational methods to improve realism and accuracy in engineering analyses. Case 1: Study of Hydrodynamic Sloshing Loads: The sloshing of liquid in large vessels under seismic loads is a timely topic. The movement of the free surface of the liquid is simulated using a two-phase volume of fluid model at various liquid heights. The transient forces generated by the fluid on the vessel wall and internals are superimposed as loads on a dynamic non-linear calculation and the fatigue and stresses are computed in an explicit finite element analysis. This approach calculates the local sloshing effects on internals as opposed to the traditional approach of using spring-mass elements. Case 2: Bending of Large Pipes due to Temperature Differentials: Pipe temperature differentials can be caused by either extremely cold liquids or hot liquids flowing at the bottom of a piping system while the top is exposed to atmospheric conditions. Differential expansion can cause pipe deformation resulting in pipe lift-off at its supports and failure at the weld locations and T-joints. Heat transfer from complex multi-phase flows was simulated using CFD. The predicted pipe wall temperatures were then input to an FEA grid and analyzed for heat transfer and thermal stresses. These stresses were compared to ASME standard allowable limits. Based on this analytical approach, a design guide for various diameters of flare header pipes, supports and tees has been established. Details of this paper were previously published in [Ref 1] and are not described in this paper. Case 3: Establishing velocity limits and line sizing criteria in pipes: The original guidelines in Fluid Flow Manuals were developed over the last fifty years based on project experience and economic and best practices technology of the time. The criteria have proven out as good, but overly conservative with regards to line size. Compressor discharge guidelines are based on the erosion velocity limits. Based on a dynamic analysis approach — using unsteady flow rates from compressors — stresses due to flow-induced vibration, noise and fatigue, hydraulic transients such as waterhammer effects for long lines (greater than 1000 feet), flashing and control valve cavitations may be studied. FSI was used to determine if the velocity limit guidelines hold in the current designs and use a parametric approach to mitigate the bottlenecking by supplying a simple fix to the problem. Furthermore the approach was used to define the correct velocity limit and establish optimal layout for the piping network.

Designing and maintenance of pipeline cable bridge with dynamic loads is complex because this problem belongs to the geometrically nonlinear problems. Analysis shown that existing mathematics models of cables have restrictions in use and we can’t use these cable models for dynamic loads calculations of cable-suspended pipeline bridge. Movement, produced by motion of inspection pig inside pipeline is an example of such dynamic loads. During its motion through the pipeline cable bridge the inspection pig induces additional stresses in pipeline due its weight and finite velocity which induces the vibration of the bridge. Its stress state assessment requires a lot of modeling, measuring and calculating actions to be done. First of all the initial static stress state of the cable bridge should be evaluated. It depends on the existing tension forces in the cable elements. They approximately were derived from the optical measurement of their geometrical curvatures with accounting for known weight density of the cables. Then, existing software tool for piping stress calculation “3D Pipe Master”, which operates by 12 degrees of freedom in pipe elements, was modernized to be able to take into account the geometrically nonlinear behavior of 6 d.o.f. cable elements. The equations which relate the elongations and rotations of cable elements with tension forces in cables are written in the form convenient for application of the transfer matrix method in the linearized iteration procedure which adjusts the measured displacements of the elements of the bridge with calculated one. In this way the initial tension forces in cables, in particular, and the bridge state, in general were determined. The dynamic part of the problem is solved by expansion in terms of natural frequencies eigenfunctions. Given inspection pig velocity calculation allows to determine the time dependence of generalized loads for each of natural vibration mode as product of the pig weight multiplied by mode shape displacement in point of pig position at the given time moment. Eventually the technique of Duhamel integral is used to calculate the dynamic behavior of the bridge for each natural mode of vibration. Two examples of dynamic stress calculation are considered. First is primitive one and relate to calculation joint interaction pipeline and cable system at dynamic loading. The second example concerns dynamic calculation pipeline cable bridge through the river Svicha during movement inspection pig. This bridge consists of two support, two parallel pipelines (1220×15) with bends and cable system. Analysis shown possibility uses “3D Pipe Master” software for the solving problems of durability pipeline cable bridge any complexity in the conditions of static and dynamic loading.