-
Sensors (Basel, Switzerland) Sep 2023Farm tractors have become a key part of daily routine agriculture, converting complex and time-consuming tasks into tasks that are easier to perform and less dependent...
Farm tractors have become a key part of daily routine agriculture, converting complex and time-consuming tasks into tasks that are easier to perform and less dependent on human labor, contributing directly to increasing the economic value generated by this activity sector, either by increasing the productivity or by making certain agricultural crops viable, which otherwise would not be sustainable. However, despite all the advantages, accidents with this type of equipment are common, often with critical and sometimes fatal consequences. The evolution of safety requirements of these machines has occurred at a good level; however, a significant part of the agricultural tractors in use are older models that do not have such solutions. Even in the new models, which contain such solutions, these are not always correctly used, and it is even common that they are turned off or simply not used at all. It is therefore natural that accidents continue to occur, a situation that is aggravated by other factors. Lack of situational awareness of the operators, which can result from advanced age, inadequate training, reduced sensitivity/respect for safety rules, or working on irregular terrain like mountainous areas, contribute to high-risk contexts that end in the loss of human life. The consequences of such accidents are clearly aggravated by the time it takes to assist the victims-either because accidents are simply not identified/reported immediately, or by the time it takes to locate and provide help to the victims. This is a scenario that is more common in mountainous regions and regions with low population density. The current paper, using NB-IoT, a set of sensors, and a web application, presents a conceptual toolset conceived to prevent accidents and minimize consequences (human and material) that can be applied to old and new farm tractors. The development was carried out taking the characterization of the farmers and the land in the region in which the authors' research institution is located into account, which has the highest rate of fatal accidents with agricultural tractors in the country; it is a region of mountainous with a very low population density.
Topics: Humans; Farms; Population Density; Accidents; Agriculture; Awareness
PubMed: 37765868
DOI: 10.3390/s23187811 -
PloS One 2023Large carnivores face numerous threats, including habitat loss and fragmentation, direct killing, and prey depletion, leading to significant global range and population...
Large carnivores face numerous threats, including habitat loss and fragmentation, direct killing, and prey depletion, leading to significant global range and population declines. Despite such threats, leopards (Panthera pardus) persist outside protected areas throughout most of their range, occupying diverse habitat types and land uses, including peri-urban and rural areas. Understanding of leopard population dynamics in mixed-use landscapes is limited, especially in South Africa, where the majority of leopard research has focused on protected areas. We use spatially explicit capture-recapture models to estimate leopard density across a mixed-use landscape of protected areas, farmland, and urban areas in the Overberg region of the Western Cape, South Africa. Data from 86 paired camera stations provided 221 independent captures of 25 leopards at 50 camera trap stations with a population density estimate of 0.64 leopards per 100 km2 (95% CI: 0.55-0.73). Elevation, terrain ruggedness, and vegetation productivity were important drivers of leopard density in the landscape, being highest on elevated remnants of natural land outside of protected areas. These results are similar to previous research findings in other parts of the Western Cape, where high-lying natural vegetation was shown to serve as both a refuge and a corridor for leopard movement in otherwise transformed landscapes. Given the low leopard density and the prevalence of transformed land intermixed with patches of more suitable leopard habitat, prioritising and preserving connectivity for leopards is vital in this shared landscape. Ecological corridors should be developed in partnership with private landowners through an inclusive and multifaceted conservation strategy which also incorporates monitoring of and rapid mitigation of emerging threats to leopards.
Topics: Animals; Panthera; South Africa; Anthropogenic Effects; Ecosystem; Population Density; Conservation of Natural Resources
PubMed: 37889916
DOI: 10.1371/journal.pone.0293445 -
Microbiological Research May 2022Acclimation and flexible response mechanisms are survival adaptations allowing prokaryotic cells to colonize diverse habitats and maintain viability in nature. Lack of...
Acclimation and flexible response mechanisms are survival adaptations allowing prokaryotic cells to colonize diverse habitats and maintain viability in nature. Lack of water significantly impacts cellular response, which can be partially compensated for through community interactions and accessing survival means beyond the cell's boundaries. In the present study, higher numbers of cultivable Gram-positive Arthrobacter sp. and Gram-negative Pseudomonas stutzeri cells were found on surfaces when high population density was used after prolonged periods of desiccation and nutrient starvation. Total cell counts during desiccation periods decreased slower than culturable cell counts independently from initial population density. The presence of homogenate, prepared by filtering homogenized cultures through a 0.2 µm filter, extended culturability of Arthrobacter sp. cells, while intact heat-killed cells extended the culturability of Arthrobacter sp. and P. stutzeri. Our results suggest very slow cell membrane breakdown for desiccated bacterial cells at solid-air interfaces over extended time spans, which may serve as reservoirs of nutrients, and may potentially provide trace amounts of water for surviving cells. Higher initial population density and recycling of resources from "zombie"-like cells, may support growth in a similar fashion as access to cell lysates or the contents of heat-killed cells analogous to dead-phase cultures where some cells experience cryptic growth.
Topics: Arthrobacter; Desiccation; Nutrients; Population Density; Water
PubMed: 35247798
DOI: 10.1016/j.micres.2022.126997 -
Current Biology : CB Oct 2011
Review
Topics: Biological Evolution; Gene Frequency; Genetic Drift; Genetics, Population; Humans; Mutation; Population Density; Selection, Genetic
PubMed: 22032182
DOI: 10.1016/j.cub.2011.08.007 -
Proceedings. Biological Sciences Dec 2020Understanding factors affecting the functional diversity of ecological communities is an important goal for ecologists and conservationists. Previous work has largely...
Understanding factors affecting the functional diversity of ecological communities is an important goal for ecologists and conservationists. Previous work has largely been conducted at the community level; however, recent studies have highlighted the critical importance of considering intraspecific functional diversity (i.e. the functional diversity of phenotypic traits among conspecifics). Further, a major limitation of existing literature on this topic is the lack of empirical studies examining functional diversity of -including animal personalities. This is a major shortcoming because personality traits can affect the fitness of individuals, and the composition of personalities in a population can have important ecological consequences. Our study aims to contribute to filling this knowledge gap by investigating factors affecting the functional diversity of personality traits in wild animal populations. Specifically, we predicted that the richness, divergence and evenness associated with personality traits would be impacted by key components of forest structure and would vary between contrasting forest types. To achieve our objective we conducted a fully replicated large-scale field experiment over a 4 year period using small mammal populations as a model system. We found that greater heterogeneity in the cover of shrubs, coarse woody debris and canopy cover was associated with a greater richness, lower divergence and lower evenness in personality traits. Greater population density was associated with greater functional richness and lower functional divergence and evenness of personality traits. To maintain a behaviourally diverse population and its associated functions, managers may promote heterogeneity in vegetation and increased population density, which we found to be the most important determinants driving functional diversity of personality traits.
Topics: Animals; Behavior, Animal; Biodiversity; Ecosystem; Forestry; Forests; Mammals; Personality; Phenotype; Population Density
PubMed: 33290673
DOI: 10.1098/rspb.2020.1713 -
PeerJ 2023Density-dependent regulation is ubiquitous in population dynamics, and its potential interaction with environmental stochasticity complicates the characterization of the...
BACKGROUND
Density-dependent regulation is ubiquitous in population dynamics, and its potential interaction with environmental stochasticity complicates the characterization of the random component of population dynamics. Yet, this issue has not received attention commensurate with its relevance for descriptive and predictive modeling of population dynamics. Here we use a Bayesian modeling approach to investigate the contribution of density regulation to population variability in stochastic environments.
METHODS
We analytically derive a formula linking the stationary variance of population abundance/density under Gompertz regulation in a stochastic environment with constant variance to the environmental variance and the strength of density feedback, to investigate whether and how density regulation affects the stationary variance. We examine through simulations whether the relationship between stationary variance and density regulation inferred analytically under the Gompertz model carries over to the Ricker model, widely used in population dynamics modeling.
RESULTS
The analytical decomposition of the stationary variance under stochastic Gompertz dynamics implies higher variability for strongly regulated populations. Simulation results demonstrate that the pattern of increasing population variability with increasing density feedback found under the Gompertz model holds for the Ricker model as well, and is expected to be a general phenomenon with stochastic population models. We also analytically established and empirically validated that the square of the autoregressive parameter of the Gompertz model in AR(1) form represents the proportion of stationary variance due to density dependence.
DISCUSSION
Our results suggest that neither environmental stochasticity nor density regulation can alone explain the patterns of population variability in stochastic environments, as these two components of temporal variation interact, with a tendency for density regulation to amplify the magnitude of environmentally induced population fluctuations. This finding has far-reaching implications for population viability. It implies that intense intra-specific resource competition increases the risk of environment-driven population collapse at high density, making opportune harvesting a sensible practice for improving the resistance of managed populations such as fish stocks to environmental perturbations. The separation of density-dependent and density-independent processes will help improve population dynamics modeling, while providing a basis for evaluating the relative importance of these two categories of processes that remains a topic of long-standing controversy among ecologists.
Topics: Animals; Bayes Theorem; Population Dynamics; Population Density; Computer Simulation
PubMed: 36751641
DOI: 10.7717/peerj.14701 -
Journal of Evolutionary Biology Jan 2017Many animals exhibit social plasticity - changes in phenotype or behaviour in response to experience with conspecifics that change how evolutionary processes like sexual...
Many animals exhibit social plasticity - changes in phenotype or behaviour in response to experience with conspecifics that change how evolutionary processes like sexual selection play out. Here, we asked whether social plasticity arising from variation in local population density in male advertisement signals and female mate preferences influences the form of sexual selection. We manipulated local density and determined whether this changed how the distribution of male signals overlapped with female preferences - the signal preference relationship. We specifically look at the shape of female mate preference functions, which, when compared to signal distributions, provide hypotheses about the form of sexual selection. We used Enchenopa binotata treehoppers, a group of plant-feeding insects that exhibit natural variation in local densities across individual host plants, populations, species and years. We measured male signal frequency and female preference functions across the density treatments. We found that male signals varied across local social groups, but not according to local density. By contrast, female preferences varied with local density - favouring higher signal frequencies in denser environments. Thus, local density changes the signal-preference relationship and, consequently, the expected form of sexual selection. We found no influence of sex ratio on the signal-preference relationship. Our findings suggest that plasticity arising from variation in local group density and composition can alter the form of sexual selection with potentially important consequences both for the maintenance of variation and for speciation.
Topics: Animal Communication; Animals; Biological Evolution; Female; Hemiptera; Male; Population Density; Sexual Behavior, Animal
PubMed: 27749022
DOI: 10.1111/jeb.12994 -
PloS One 2013We explore the large spatial variation in the relationship between population density and burned area, using continental-scale Geographically Weighted Regression (GWR)...
We explore the large spatial variation in the relationship between population density and burned area, using continental-scale Geographically Weighted Regression (GWR) based on 13 years of satellite-derived burned area maps from the global fire emissions database (GFED) and the human population density from the gridded population of the world (GPW 2005). Significant relationships are observed over 51.5% of the global land area, and the area affected varies from continent to continent: population density has a significant impact on fire over most of Asia and Africa but is important in explaining fire over < 22% of Europe and Australia. Increasing population density is associated with both increased and decreased in fire. The nature of the relationship depends on land-use: increasing population density is associated with increased burned are in rangelands but with decreased burned area in croplands. Overall, the relationship between population density and burned area is non-monotonic: burned area initially increases with population density and then decreases when population density exceeds a threshold. These thresholds vary regionally. Our study contributes to improved understanding of how human activities relate to burned area, and should contribute to a better estimate of atmospheric emissions from biomass burning.
Topics: Biomass; Climate; Ecosystem; Fires; Humans; Population Density
PubMed: 24358108
DOI: 10.1371/journal.pone.0081188 -
Annual Review of Animal Biosciences Feb 2023Deleterious mutations decrease reproductive fitness and are ubiquitous in genomes. Given that many organisms face ongoing threats of extinction, there is interest in... (Review)
Review
Deleterious mutations decrease reproductive fitness and are ubiquitous in genomes. Given that many organisms face ongoing threats of extinction, there is interest in elucidating the impact of deleterious variation on extinction risk and optimizing management strategies accounting for such mutations. Quantifying deleterious variation and understanding the effects of population history on deleterious variation are complex endeavors because we do not know the strength of selection acting on each mutation. Further, the effect of demographic history on deleterious mutations depends on the strength of selection against the mutation and the degree of dominance. Here we clarify how deleterious variation can be quantified and studied in natural populations. We then discuss how different demographic factors, such as small population size, nonequilibrium population size changes, inbreeding, and gene flow, affect deleterious variation. Lastly, we provide guidance on studying deleterious variation in nonmodel populations of conservation concern.
Topics: Animals; Genetics, Population; Models, Genetic; Inbreeding; Mutation; Population Density; Genetic Variation
PubMed: 36332644
DOI: 10.1146/annurev-animal-080522-093311 -
PloS One 2023The present study aimed to assess the population density, structure, and population change of nine wild prey species in the semi-arid landscape of Saurashtra, Gujarat,...
The present study aimed to assess the population density, structure, and population change of nine wild prey species in the semi-arid landscape of Saurashtra, Gujarat, India. A total of eight sites, representing a gradient from highly protected woodlands and grasslands to unreserved grasslands, were selected for sampling. We employed the road transect methodology under a distance sampling framework to achieve our objectives. We evaluated the realized growth rate of the Gir ungulate population through linear regression analysis. Our findings revealed that deer species exhibited higher density and biomass in woodlands compared to grasslands and coastal forests. On the other hand, antelopes showed higher density and biomass in grasslands and coastal forests compared to woodlands. The density gradient of wild prey species was influenced by various factors, including habitat structure, social organization, grouping tendencies, and topography. Over the last four decades, the population of wild prey species in Gir showed minimal changes. Our study provides a comprehensive understanding of wild prey species' density and biomass patterns at the landscape level. The inclusion of findings from ecologically significant and unique areas, such as coastal forests, further enhances the importance of this study. The implications of this study extend beyond the conservation of wild prey species alone; they also contribute to the conservation of the large carnivore guild in the Saurashtra landscape.
Topics: Animals; Ecosystem; Biomass; Lions; Population Density; Conservation of Natural Resources; Deer; Forests; Carnivora
PubMed: 37768920
DOI: 10.1371/journal.pone.0292048