resource selection
Recently Published Documents
TOTAL DOCUMENTS
H-INDEX
C-V2X Centralized Resource Allocation with Spectrum Re-Partitioning in Highway Scenario
Cellular Vehicle-to-Everything communication is an important scenario of 5G technologies. Modes 3 and 4 of the wireless systems introduced in Release 14 of 3GPP standards are intended to support vehicular communication with and without cellular infrastructure. In the case of Mode 3, dynamic resource selection and semi-persistent resource scheduling algorithms result in a signalling cost problem between vehicles and infrastructure, therefore, we propose a means to decrease it. This paper employs Re-selection Counter in centralized resource allocation as a decremental counter of new resource requests. Furthermore, two new spectrum re-partitioning and frequency reuse techniques in Roadside Units (RSUs) are considered to avoid resource collisions and diminish high interference impact via increasing the frequency reuse distance. The two techniques, full and partial frequency reuse, partition the bandwidth into two sub-bands. Two adjacent RSUs apply these sub-bands with the Full Frequency Reuse (FFR) technique. In the Partial Frequency Reuse (PFR) technique, the sub-bands are further re-partitioned among vehicles located in the central and edge parts of the RSU coverage. The sub-bands assignment in the nearest RSUs using the same sub-bands is inverted concerning the current RSU to increase the frequency reuse distance. The PFR technique shows promising results compared with the FFR technique. Both techniques are compared with the single band system for different vehicle densities.
AbstractCoexistence of competing species in the same foraging guild has long puzzled ecologists. In particular, how do small subordinate species persist with larger dominant competitors? This question becomes particularly important when conservation interventions, such as reintroduction or translocation, become necessary for the smaller species. Exclusion of dominant competitors might be necessary to establish populations of some endangered species. Ultimately, however, the goal should be to conserve whole communities. Determining how subordinate species escape competitive exclusion in intact communities could inform conservation decisions by clarifying the ecological conditions and processes required for coexistence at local or regional scales. We tested for spatial and temporal partitioning among six species of native, granivorous rodents using null models, and characterized the microhabitat of each species using resource-selection models. We found that the species’ nightly activity patterns are aggregated temporally but segregated spatially. As expected, we found clear evidence that the larger-bodied kangaroo rats drive spatial partitioning, but we also found species-specific microhabitat associations, which suggests that habitat heterogeneity is part of what enables these species to coexist. Restoration of natural disturbance regimes that create habitat heterogeneity, and selection of translocation sites without specific competitors, are among the management recommendations to consider in this case. More generally, this study highlights the need for a community-level approach to conservation and the usefulness of basic ecological data for guiding management decisions.
In northern Eurasia, large carnivores overlap with semi-domestic reindeer (Rangifer tarandus) and moose (Alces alces). In Scandinavia, previous studies have quantified brown bear (Ursus arctos) spring predation on neonates of reindeer (mostly in May) and moose (mostly in June). We explored if habitat selection by brown bears changed following resource pulses and whether these changes are more pronounced on those individuals characterised by higher predatory behaviour. Fifteen brown bears in northern Sweden (2010–2012) were fitted with GPS proximity collars, and 2585 female reindeers were collared with UHF transmitters. Clusters of bear positions were visited to investigate moose and reindeer predation. Bear kill rates and home ranges were calculated to examine bear movements and predatory behaviour. Bear habitat selection was modelled using resource selection functions over four periods (pre-calving, reindeer calving, moose calving, and post-calving). Coefficients of selection for areas closer to different land cover classes across periods were compared, examining the interactions between different degrees of predatory behaviour (i.e., high and low). Bear habitat selection differed throughout the periods and between low and high predatory bears. Differences among individuals’ predatory behaviour are reflected in the selection of habitat types, providing empirical evidence that different levels of specialization in foraging behaviour helps to explain individual variation in bear habitat selection.
Orientation: Technological innovations and developments in methods of productivity have resulted in an increased demand for technically-oriented artisans. However, the supply of qualified artisans is insufficient to meet the demand.Research purpose: This article is the product of a systematic investigation into the extent and nature of empirical literature related to human resource selection practices used for apprentices.Motivation for the study: The authors noted inadequate research into the selection practices used for apprentices. This investigation was motivated by the need to systematically verify the extent and nature of the empirical literature on apprentice selection, both internationally and nationally.Research design, approach and method: A systematic literature review of published empirical research articles (for the period 1990–2020) in scholarly databases was conducted. The literature was accessed through relevant databases within the business management, human resource management and industrial psychology fields. The literature was restricted to scholarly (i.e., peer reviewed journals), English full textual data. Twelve combinations of two clusters of key words were used in the search function. The first cluster was apprentice, apprenticeship and artisan, with the second cluster being selection, selection process, staffing and recruitment. Four exclusion categories were used to reject literature that were unrelated, dissimilar and unconnected with the purpose of the literature review.Main findings: From the comprehensive review of the literature, 12 articles were found to have content related to the selection of apprentices. Five core themes, with 11 sub-themes, were identified from this literature. A research agenda is proposed with research questions identified for each theme.Practical/managerial implications: This literature review has provided a synthesised summary of the available literature on apprentice selection. Through the provision of a research agenda, this article contributes by providing a foundation for further research in the field.Contribution/value-add: This article adds to the current literature available on apprentice selection practices. This should alert researchers of the need to further explore this area to enhance knowledge and understanding of the best practices employed in the selection of apprentices.
<p>Identifying the mechanisms causing population change is essential for conserving small and declining populations. Substantial range contraction of many carnivore species has resulted in fragmented global populations with numerous small isolates in need of conservation. Here I investigate the rate and possible agents of change in two threatened grizzly bear (Ursus arctos) populations in southwestern British Columbia, Canada. I use a combination of population vital rates estimates, population trends, habitat quality analyses, and comparisons to what has been described in the literature, to carefully compare among possible mechanisms of change. First, I estimate population density, realized growth rates (λ), and the demographic components of population change for each population using DNA based capture-recapture data in both spatially explicit capture-recapture (SECR) and non-spatial Pradel robust design frameworks. The larger population had 21.5 bears/1000km2 and between 2006 and 2016 was growing (λPradel = 1.02 ± 0.02 SE, λsecr = 1.01 ± 4.6 x10-5 SE) following the cessation of hunting. The adjacent but smaller population had 6.3 bears/1000km2 and between 2005 and 2017 was likely declining (λPradel = 0.95 ± 0.03 SE, λsecr = 0.98 ± 0.02 SE). Estimates of apparent survival and recruitment indicated that lower recruitment was the dominant factor limiting population growth in the smaller population. Then I use data from GPS-collared bears to estimate reproduction, survival and projected population change (λ) in both populations. Adult female survival was 0.96 (95% CI: 0.80-0.99) in the larger population (McGillvary Mountains or MM) and 0.87 (95% CI: 0.69-0.95) in the small, isolated population (North Stein-Nahatlatch or NSN). Cub survival was also higher in the MM (0.85, 95%CI: 0.62-0.95) than the NSN population (0.33, 95%CI: 0.11-0.67). This analysis identifies both low adult female survival and low cub survival as the demographic factors associated with population decline in the smaller population. By comparing the vital rates from these two populations with other small populations, I suggest that when grizzly bear populations are isolated, there appears to be a tipping point (de Silva and Leimgruber 2019) around 50 individuals, below which adult female mortality, even with intensive management, becomes prohibitive for population recovery. This analysis provides the first detailed estimates of population vital rates for a grizzly bear population of this size, and this information has been important for subsequent management action. To determine whether bottom-up factors (i.e. food) are limiting population growth and recovery in the small isolated population I use resource selection analysis from GPS collar data. I develop resource selection functions (RSF) for four dominant foraging seasons: the spring-early summer season when bears feed predominantly on herbaceous plants and dig for bulbs, the early fruit season where they feed on low elevation berries and cherries, the huckleberry season and the post berry season when foraging behaviours are most diverse but whitebark pine nuts are a relatively common food source. The differences in overall availability of high-quality habitats for different food types, especially huckleberries, between populations suggests that season specific bottom-up effects may account for some differences in population densities. Resource selections are a very common tool used for estimating resource distribution and availability, however, their ability to estimate food abundance on the ground are usually not tested. I assessed the accuracy of the resulting RSF models for predicting huckleberry presence and abundance measured in field plots. My results show that berry specific models did predict berry abundance in previously disturbed sites though varied in accuracy depending on how the models were categorized and projected across the landscape. Finally, I combine spatially explicit capture-recapture methods and models developed from resource selection modelling to estimate the effect of seasonal habitat availability and open road density, as a surrogate for top-down effects, on the bear density in the two populations. I found that population density is most strongly connected to habitats selected during a season when bears fed on huckleberries, the major high-energy food bears eat during hyperphagia in this area, as well as a large baseline difference between populations. The abundance of high-quality huckleberry habitat appears to be an important factor enabling the recovery of the larger population that is also genetically connected to other bears. The adjacent, smaller and genetically isolated population is not growing. The relatively low abundance of high-quality berry habitat in this population may be contributing to the lack of growth of the population. However, it is likely that the legacy of historic mortality and current stochastic effects, inbreeding effects, or other Allee effects, are also contributing to the continued low density observed. While these small population effects may be more challenging to overcome, this analysis suggests that the landscape can accommodate a higher population density than that currently observed.</p>
<p>Identifying the mechanisms causing population change is essential for conserving small and declining populations. Substantial range contraction of many carnivore species has resulted in fragmented global populations with numerous small isolates in need of conservation. Here I investigate the rate and possible agents of change in two threatened grizzly bear (Ursus arctos) populations in southwestern British Columbia, Canada. I use a combination of population vital rates estimates, population trends, habitat quality analyses, and comparisons to what has been described in the literature, to carefully compare among possible mechanisms of change. First, I estimate population density, realized growth rates (λ), and the demographic components of population change for each population using DNA based capture-recapture data in both spatially explicit capture-recapture (SECR) and non-spatial Pradel robust design frameworks. The larger population had 21.5 bears/1000km2 and between 2006 and 2016 was growing (λPradel = 1.02 ± 0.02 SE, λsecr = 1.01 ± 4.6 x10-5 SE) following the cessation of hunting. The adjacent but smaller population had 6.3 bears/1000km2 and between 2005 and 2017 was likely declining (λPradel = 0.95 ± 0.03 SE, λsecr = 0.98 ± 0.02 SE). Estimates of apparent survival and recruitment indicated that lower recruitment was the dominant factor limiting population growth in the smaller population. Then I use data from GPS-collared bears to estimate reproduction, survival and projected population change (λ) in both populations. Adult female survival was 0.96 (95% CI: 0.80-0.99) in the larger population (McGillvary Mountains or MM) and 0.87 (95% CI: 0.69-0.95) in the small, isolated population (North Stein-Nahatlatch or NSN). Cub survival was also higher in the MM (0.85, 95%CI: 0.62-0.95) than the NSN population (0.33, 95%CI: 0.11-0.67). This analysis identifies both low adult female survival and low cub survival as the demographic factors associated with population decline in the smaller population. By comparing the vital rates from these two populations with other small populations, I suggest that when grizzly bear populations are isolated, there appears to be a tipping point (de Silva and Leimgruber 2019) around 50 individuals, below which adult female mortality, even with intensive management, becomes prohibitive for population recovery. This analysis provides the first detailed estimates of population vital rates for a grizzly bear population of this size, and this information has been important for subsequent management action. To determine whether bottom-up factors (i.e. food) are limiting population growth and recovery in the small isolated population I use resource selection analysis from GPS collar data. I develop resource selection functions (RSF) for four dominant foraging seasons: the spring-early summer season when bears feed predominantly on herbaceous plants and dig for bulbs, the early fruit season where they feed on low elevation berries and cherries, the huckleberry season and the post berry season when foraging behaviours are most diverse but whitebark pine nuts are a relatively common food source. The differences in overall availability of high-quality habitats for different food types, especially huckleberries, between populations suggests that season specific bottom-up effects may account for some differences in population densities. Resource selections are a very common tool used for estimating resource distribution and availability, however, their ability to estimate food abundance on the ground are usually not tested. I assessed the accuracy of the resulting RSF models for predicting huckleberry presence and abundance measured in field plots. My results show that berry specific models did predict berry abundance in previously disturbed sites though varied in accuracy depending on how the models were categorized and projected across the landscape. Finally, I combine spatially explicit capture-recapture methods and models developed from resource selection modelling to estimate the effect of seasonal habitat availability and open road density, as a surrogate for top-down effects, on the bear density in the two populations. I found that population density is most strongly connected to habitats selected during a season when bears fed on huckleberries, the major high-energy food bears eat during hyperphagia in this area, as well as a large baseline difference between populations. The abundance of high-quality huckleberry habitat appears to be an important factor enabling the recovery of the larger population that is also genetically connected to other bears. The adjacent, smaller and genetically isolated population is not growing. The relatively low abundance of high-quality berry habitat in this population may be contributing to the lack of growth of the population. However, it is likely that the legacy of historic mortality and current stochastic effects, inbreeding effects, or other Allee effects, are also contributing to the continued low density observed. While these small population effects may be more challenging to overcome, this analysis suggests that the landscape can accommodate a higher population density than that currently observed.</p>
<p>Black-tailed deer (BTD, Odocoileus hemionus columbianus), a socio-economically important deer species in western North America is steadily declining throughout much of its range over the last century. Though a large number of studies have been carried out on forage availability, predation pressure, and population dynamics of the species, there still remain broad gaps in current understanding of the underlying causes, mechanisms, and spatio-temporal patterns of habitat use which can affect the population dynamics and distribution of BTD. So, the central aim of my thesis was to identify the spatial and temporal scale that may affect habitat selection, movement and ultimately long-term persistence of the BTD population in the Mendocino National Forest, California. Understanding population structuring in BTD is vital to underpin the spatial scale for conservation. So, I tested for presence of population sub-structuring among female BTD in the study area by analysing the combined effect of site fidelity and philopatry on the population. Fidelity analyses from radio-telemetry data revealed BTD to have extremely small seasonal home ranges (0.71 km²) and very high site fidelity to these ranges. Direct fitness benefits of fidelity were observed as individuals with decreased site fidelity to their ranges suffered elevated risks of mortality. Results from mtDNA sequencing revealed high genetic differentiation (FST > 0.30) and low haplotype sharing even among geographic areas separated by as little as 4–10 km. Combined, the results indicated prolonged period of philopatric behaviour resulting in demographic isolation and very small scale population sub-structuring that can impact the population dynamics at a finer spatial scale than previously assumed. Next, I examined the effect of temporal scale on resource selection by BTD, through comparing habitat characteristics selected by BTD from a pooled model (all telemetry locations pooled across activity states) versus habitat characteristics associated with foraging (active state) and resting or ruminating (inactive state). The main factors that influenced resource selection in BTD were: 1) seasonal changes associated largely with variable selection towards slope, aspect, and elevation and 2) activity states influenced fine-scale selection towards vegetation type, edge density, and cover within the home-ranges. The comparative analysis also revealed that due to larger proportion of resting and ruminating locations, the pooled model frequently failed to identify critical foraging habitats and reflected habitats associated with resting. The frequent misidentification for important ecological covariates associated with foraging was a testimony that pooling data across activity states in BTD can negatively impact our understanding about habitat selection by the species. Finally, I developed a movement model to understand the spatial and temporal patterns of risk-forage trade-offs by female BTD as a function of landscape familiarity. The results showed that familiarity affects the trade-off patterns by BTD in a heterogeneous landscape, with differential selection towards productivity and risk that also varied largely with habitat types. The results further revealed strong selection towards highly familiar areas by BTD during the night time and at dawn while stepping into less familiar areas during the daytime. The demonstrated preference for familiar locations within their home ranges when their primary predator (puma) is most active emphasizes that spatial familiarity is important not only for large scale processes like selection of home range, but also for striking fine-scale trade-offs between forage and risk within individual home ranges. The knowledge of this fine scale selection pattern is critical for maintaining habitat heterogeneity at a spatial scale comparable to the size of their home ranges, as they have vital consequences on fitness of BTD that ultimately affects the population dynamics of the species.</p>
<p>Black-tailed deer (BTD, Odocoileus hemionus columbianus), a socio-economically important deer species in western North America is steadily declining throughout much of its range over the last century. Though a large number of studies have been carried out on forage availability, predation pressure, and population dynamics of the species, there still remain broad gaps in current understanding of the underlying causes, mechanisms, and spatio-temporal patterns of habitat use which can affect the population dynamics and distribution of BTD. So, the central aim of my thesis was to identify the spatial and temporal scale that may affect habitat selection, movement and ultimately long-term persistence of the BTD population in the Mendocino National Forest, California. Understanding population structuring in BTD is vital to underpin the spatial scale for conservation. So, I tested for presence of population sub-structuring among female BTD in the study area by analysing the combined effect of site fidelity and philopatry on the population. Fidelity analyses from radio-telemetry data revealed BTD to have extremely small seasonal home ranges (0.71 km²) and very high site fidelity to these ranges. Direct fitness benefits of fidelity were observed as individuals with decreased site fidelity to their ranges suffered elevated risks of mortality. Results from mtDNA sequencing revealed high genetic differentiation (FST > 0.30) and low haplotype sharing even among geographic areas separated by as little as 4–10 km. Combined, the results indicated prolonged period of philopatric behaviour resulting in demographic isolation and very small scale population sub-structuring that can impact the population dynamics at a finer spatial scale than previously assumed. Next, I examined the effect of temporal scale on resource selection by BTD, through comparing habitat characteristics selected by BTD from a pooled model (all telemetry locations pooled across activity states) versus habitat characteristics associated with foraging (active state) and resting or ruminating (inactive state). The main factors that influenced resource selection in BTD were: 1) seasonal changes associated largely with variable selection towards slope, aspect, and elevation and 2) activity states influenced fine-scale selection towards vegetation type, edge density, and cover within the home-ranges. The comparative analysis also revealed that due to larger proportion of resting and ruminating locations, the pooled model frequently failed to identify critical foraging habitats and reflected habitats associated with resting. The frequent misidentification for important ecological covariates associated with foraging was a testimony that pooling data across activity states in BTD can negatively impact our understanding about habitat selection by the species. Finally, I developed a movement model to understand the spatial and temporal patterns of risk-forage trade-offs by female BTD as a function of landscape familiarity. The results showed that familiarity affects the trade-off patterns by BTD in a heterogeneous landscape, with differential selection towards productivity and risk that also varied largely with habitat types. The results further revealed strong selection towards highly familiar areas by BTD during the night time and at dawn while stepping into less familiar areas during the daytime. The demonstrated preference for familiar locations within their home ranges when their primary predator (puma) is most active emphasizes that spatial familiarity is important not only for large scale processes like selection of home range, but also for striking fine-scale trade-offs between forage and risk within individual home ranges. The knowledge of this fine scale selection pattern is critical for maintaining habitat heterogeneity at a spatial scale comparable to the size of their home ranges, as they have vital consequences on fitness of BTD that ultimately affects the population dynamics of the species.</p>
ABSTRACT The southern limit of the Golden Eagle's (Aquila chrysaetos) breeding range in North America is Mexico, where the eagle is the national symbol yet designated as a threatened, high priority species for conservation action. Movement information needed for conserving Mexico's Golden Eagles is sparse; knowledge of dispersal from natal areas is essential to understand the eagle's ecology and help provide for its management. Using satellite telemetry data, we analyzed movements of three males and one female from central Mexico during their first year of life; we documented (1) timing and distance of initial dispersal movements, (2) total distance traveled and maximum distance from natal site by month of age following fledging, and (3) size of areas (based on 95% adaptive local convex hulls) across which eagles ranged following initial dispersal. Individual eagles dispersed from their natal areas between mid-September and mid-November, at 6–8 mo of age. Monthly total distance traveled by males reached approximately 350–1350 km at 8–11 mo; the female's peak monthly travel was 3000 km, at age 7 mo. Monthly proximity to natal sites by individuals at ages 8–12 mo was relatively constant, averaging 17.9 km (SD = 5.7) to 129.1 km (SD = 11.3). After dispersal, the monthly ranging areas overall increased during the first year of life for all eagles, especially the female, due mainly to multiple long-distance excursions. Our data suggest that movement behavior of juvenile Golden Eagles from Mexico is mostly similar to that of conspecifics from nonmigratory populations elsewhere. Our study may help serve as a foundation for future work to better understand movement dynamics and resource selection by Mexico's Golden Eagles.
<p>Urban areas and human populations are growing. Cities provide highly modified habitat for species that can adapt their feeding and other behaviours. The growth of urban landscapes and human populations may result in an increase in human-wildlife conflict. Businesses which prepare and sell food (food establishments) may be more likely to encounter conflict with urban wildlife, which may lead to negative attitudes towards urban wildlife. Negative attitudes towards wildlife could create polarised communities and possibly affect the success of environmental initiatives. This study sought to understand (1) how feral pigeons use urban environments and the resources key to their distribution and congregation; (2) whether feral pigeons are food limited in Wellington City; and (3) how the interactions of owners and managers of food establishments with feral pigeons influence their attitudes to feral pigeons. I used 8 transects through the central City which covered a representative sample of urban habitats, including the central business district, green space, and waterfront to estimate resource selection. Bird capture and banding were used to determine feral pigeon condition at a range of sites across the City and included a mix of high, medium and low anthropogenic fed sites. A written survey of owners and managers of food establishments in Wellington was conducted to evaluate attitudes to feral pigeons (n = 62). Feral pigeon resource selection is mainly influenced by people and where they choose to eat (∆AIC ≤ W = 0.999), such as sites with outdoor seating where people may directly feed feral pigeons. However, once a site has been selected, areas with tertiary vegetation and disposed food (W = 0.324 and W = 0.297) are the most likely to attract larger flocks of feral pigeons (although a number of other variables also influence flock size, such as availability of freshwater). Feral pigeons do not appear to be food limited in Wellington as condition was not significantly different between sites (n=48, body condition, (body mass/tarsus length) Kruskal-Wallis = 2.06, p = 0.36; keel condition, Kruskal-Wallis = 0.7283, p = 0.6948; feather condition Kruskal-Wallis = 2.7943, p = 0.2473). Attitudes of food establishment owners and managers towards feral pigeons are most influenced by how often they see feral pigeons (∆AICc ≤ W = 0:465). Therefore, direct experience rather than knowledge, engagement, action or socio-demographics has the most influence on attitudes of owners and managers of food establishments. These results suggest that feral pigeon populations are largely dependent on the availability of anthropogenic foods. Reducing the food provided by people may limit feral pigeon populations. Reductions in pigeon populations are also likely to change attitudes of business owners and reduce conflict because they will be less likely to encounter pigeons. Limiting feeding and access to food waste is probably the most effective way of managing pigeon populations.</p>
