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1.
TERESE E. MCINTOSH RICHARD C. ROSATTE JOSEF HAMR DENNIS L. MURRAY 《The Journal of wildlife management》2009,73(4):580-585
ABSTRACT The status of recolonizing elk (Cervus elaphus) populations in Ontario, Canada, is unclear and there is a need for effective population survey methods that can be applied locally. We sought to develop a sightability model that could account for both low densities of elk and dense forest cover in elk-release areas in Ontario. We corrected winter aerial survey counts for sightability based on radiocollared animals known to be within observable distance of the aircraft. The multivariate model with the highest Akaike's Information Criterion corrected for sample size weight (wi = 0.427) revealed that elk group size, elk activity, dominant tree type, percent canopy cover, and percent conifer cover were significant predictors of elk sightability. The group-size effect indicated that odds of sighting an elk increased by 1.353 (95% CI = 0.874-3.689) for every additional elk. Standing elk were 5.033 (95% CI = 0.936-15.541) times more likely to be observed than were resting elk, and those located in conifer cover were 0.013 (95% CI = 0.001-0.278) times less likely to be sighted than elk in deciduous cover. Furthermore, elk located in >50% canopy cover and >50% conifer cover were 0.041 (95% CI = 0.003-0.619) times and 0.484 (95% CI = 0.024-9.721) times less likely to be sighted than elk in more open habitat, respectively. During model validation, observers detected 79% (113/143) of known elk in any given area, and population and sightability model predictions (±90% CI) overlapped with the population estimate, implying that our predictive model was robust. Unsurprisingly, large groups of elk in open habitat increased model precision, which highlights difficulties of counting Ontario elk in their northern range. We conclude that our model provided increased reliability for estimating elk numbers in Ontario compared to existing methods, and that the estimator may be useful in other areas where elk density is low and sightability is poor due to dense forest cover. 相似文献
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Abstract: Estimates of wildlife population sizes are frequently constructed by combining counts of observed animals from a stratified survey of aerial sampling units with an estimated probability of detecting animals. Unlike traditional stratified survey designs, stratum-specific estimates of population size will be correlated if a common detection model is used to adjust counts for undetected animals in all strata. We illustrate this concept in the context of aerial surveys, considering 2 cases: 1) a single-detection parameter is estimated under the assumption of constant detection probabilities, and 2) a logistic-regression model is used to estimate heterogeneous detection probabilities. Naïve estimates of variance formed by summing stratum-specific estimates of variance may result in significant bias, particularly if there are a large number of strata, if detection probabilities are small, or if estimates of detection probabilities are imprecise. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):837–844; 2008) 相似文献
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Daniel P. Walsh Henry Campa III Dean E. Beyer Jr. Scott R. Winterstein 《The Journal of wildlife management》2011,75(5):1228-1235
Measurement error of explanatory variables used in sightability models can result in biased population estimates and associated measures of precision. We developed a Monte Carlo simulation procedure that can be implemented within the sightability model framework when measurement error is present. Additionally, we developed simulation and sample survey methods, for determining the optimal allocation of survey effort to maximize precision of population estimates for a fixed survey cost, when a complete survey of a study area is not feasible. We used data from aerial surveys of elk during 2004–2006 in Michigan to demonstrate the application of these techniques. By accounting for measurement error and applying appropriate survey design practices, managers employing sightability models may be able to generate more accurate and cost-effective population estimates and accompanying measures of precision than is possible if these techniques are ignored. © 2011 The Wildlife Society. 相似文献
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Scott M. McCorquodale Shannon M. Knapp Michael A. Davison Jennifer S. Bohannon Chris D. Danilson W. Chris Madsen 《The Journal of wildlife management》2013,77(2):359-371
The North Cascades (Nooksack) elk (Cervus elaphus) population declined during the 1980s, prompting a closure to state and tribal hunting in 1997 and an effort to restore the herd to former abundance. In 2005, we began a study to assess the size of the elk population, judge the effectiveness of restoration efforts, and develop a practical monitoring strategy. We concurrently evaluated 2 monitoring approaches: sightability correction modeling and mark-resight modeling. We collected data during February–April helicopter surveys and fit logistic regression models to predict the sightability of elk groups based on group and environmental variables. We used an information-theoretic criterion to compare 9 models of varying complexity; the best model predicted sightability of elk groups based on 1) transformed (log2) group size, 2) forest canopy cover (%), and 3) a categorical activity variable (active vs. bedded). The sightability model indicated relatively steady and modest herd growth during 2006–2011, but estimates were less than minimum-known-alive counts. We also used the logit-normal mixed effects (LNME) mark-resight model to generate estimates of total elk population size and the sizes of the adult female and branch-antlered male subpopulations. We explored 15 LNME models to predict total population size and 12 models to predict subpopulations. Our results indicated individual heterogeneity in resighting probabilities and variation in resighting probabilities across sexes and some years. Model-averaged estimates of total population size increased from 639 (95% CI = 570–706) in spring 2006 to 1,248 (95% CI = 1,094–1,401) in 2011. We estimated the adult female subpopulation increased from 381 (95% CI = 338–424) in spring 2006 to 573 (95% CI = 507–639) by 2011. The branch-antlered male subpopulation estimates increased from 87 (95% CI = 54–119) to 180 (95% CI = 118–241) from spring 2006 to spring 2011. The LNME model estimates were greater than sightability model estimates and minimum-known-alive counts. We concluded that mark-resight performed better and was a viable approach for monitoring this small elk population and possibly others with similar characteristics (i.e., small population and landscape scales), but this approach requires periodic marking of elk; we estimated mark-resight costs would be about 40% greater than sightability model application costs. The utility of sightability-correction modeling was limited by a high proportion of groups with low detectability on our densely forested landscape. © 2012 The Wildlife Society. 相似文献
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Daniel J. Twedt 《Journal of Field Ornithology》2015,86(4):352-368
Estimating the size of bird populations is central to effective conservation planning and prudent management. I updated estimated regional bird populations for the East Gulf Coastal Plain of Mississippi using data from 275 North American Breeding Bird Surveys from 2009 to 2013. However, regional bird populations estimated from count surveys of breeding birds may be biased due to lack of empirical knowledge of the distance at which a species is effectively detected and the probability of detecting a species if it is present. I used data recorded within two distance classes (0–50 m and >50–400 m) and three 1‐min time intervals on 130 Breeding Bird Surveys to estimate detection probability and effective detection distance for 77 species. Incorporating these empirical estimates of detection probability and detection distance resulted in estimated regional populations for these species that were markedly greater than regional populations estimated without species‐specific estimates of detection parameters. Using the same Breeding Bird Survey data, I also estimated probability of site occupancy for 66 species and extrapolated this to the proportion of area occupied in the East Gulf Coastal Plain of Mississippi. I combined the area occupied with the reported range of breeding territory size for 54 species to obtain independent estimates of regional bird populations. Although the true population of these species is unknown, estimated populations that incorporated empirical estimates of detection probability and detection distance were more likely to be within the range of independently estimated, occupancy‐based, regional population estimates than were population estimates that lacked empirical detection and distance information. 相似文献
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Eric Vander Wal Philip D. McLoughlin Ryan K. Brook 《The Journal of wildlife management》2011,75(6):1521-1526
Few tracking studies consider seasonal changes in ability to re-sight wildlife, despite potential for biases in sightability to mislead our interpretation of models of movement and abundance. We developed seasonal sightability models based on visual observations of radio-collared elk (Cervus elaphus) in Manitoba, Canada, through 6 seasons. We located 377 elk 8,862 times using aerial telemetry from 2002 to 2009. We tested the hypothesis that sites where we were able to visually observe radio-collared elk during aerial telemetry differed from sites where collared elk were known to be present but could not be sighted. Relationships varied with season and elk sightability was influenced by forest type, habitat openness, distance to edge, and time of day. Our results confirm that observers have the highest probability of detecting elk in early and late winter. However, factors such as day length, which increases by 64% during this period, suggest that fewer impediments to detection exist in late winter. Our findings reinforce the need to account for seasonal as well as spatial changes in habitat-specific sightability models. © 2011 The Wildlife Society. 相似文献
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ABSTRACT The long-tailed goral (also called the Amur goral) Naemorhedus caudatus (subfamily Caprinae), a vulnerable and protected species designated by IUCN and CITES, has sharply been declining in the population size and is now becoming critically endangered in South Korea. This species has been conserved as a natural monument by the Korean Cultural Heritage Administration since 1968. In this study, using 78 fecal DNA samples with a non-invasive genetic approach, we assessed the genetic integrity and individual identification-based population size for the goral population from Seoraksan National Park representing the largest wild population in Korea. Using the successfully isolated 38 fecal DNA, phylogeographic and population genetic analyses were performed with mitochondrial DNA control region (CR) sequences and nine microsatellite loci. We found seven CR haplotypes, of which five were unique to the Seoraksan population, considering previously determined haplotypes in Korean populations. The Seoraksan population showed higher haplotype diversity (0.777?±?0.062) and mean number of alleles (4.67?±?1.563) relative to southern populations in Korea reported from previous studies, with no signal of a population bottleneck. Microsatellite-based individual identification estimate based on probability of identity (PID) indicated a population size of ≥30 in this population. Altogether, we suggest that for future management efforts of this species in the Seoraksan National Park, conserving its genetic integrity as an ‘endemic’ lineage, and curbing a decrease in its number through mitigating habitat destruction might be key to secure the population for the long term. 相似文献
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An increasing number of studies have demonstrated relationships between climate trends and body size change of organisms. In many cases, climate might be expected to influence body size by altering thermoregulation, energetics or food availability. However, observed body size change can result from a variety of ecological processes (e.g. growth, selection, population dynamics) or imperfect observation of biological systems. We used two extensive datasets to evaluate alternative mechanisms for recently reported changes in the observed body size of plethodontid salamanders. We found that mean adult body size of salamanders can be highly sensitive to survey conditions, particularly rainfall. This systematic bias in the detection of larger or smaller individuals could result in a signature of body size change in relation to reported climate trends when it is simply observation error. We also identify considerable variability in body size distributions among years and find that individual growth rates can be strongly influenced by weather. Finally, our study demonstrates that measures of mean adult body size can be highly variable among surveys and that large sample sizes may be required to make reliable inferences. Identifying the effects of climate change is a critical area of research in ecology and conservation. Researchers should be aware that observed changes in certain organisms can result from multiple ecological processes or systematic bias due to nonrandom sampling of populations. 相似文献
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Caitlin Karniski Eric M. Patterson Ewa Krzyszczyk Vivienne Foroughirad Margaret A. Stanton Janet Mann 《Marine Mammal Science》2015,31(3):839-852
Activity budget data are essential for determining behavioral responses to physiological and ecological variables. Yet, few studies are available to investigate the robustness, accuracy, and biases of the methods used to estimate activity budgets for cetaceans. In this study, we compare activity budgets of 55 adult female bottlenose dolphins in Shark Bay, Australia derived from two methods: surveys (n = 6,903) and focal follows (n = 1,185, totaling 2,721 h of observation). Activity budgets estimated from survey data differed in all behavioral states compared to focal follow data. However, when controlling for temporal autocorrelation, only time spent socializing and time spent traveling remained disparate between the methods. To control for biases associated with assigning group‐level behavior to individuals, we also compared survey and focal follow activity budgets for lone females. Here we found differences between methods in time spent foraging and traveling regardless of whether we controlled for temporal autocorrelation, which suggests detection biases likely play a role in explaining differences in activity budget estimates between the two methodologies. Our results suggest that surveys are less representative of individual‐level activity budgets, and thus, when individual‐level knowledge about behavior is needed, focal follows are preferred. 相似文献
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Synonymous codons are not used at equal frequency throughout the genome, a phenomenon termed codon usage bias (CUB). It is often assumed that interspecific variation in the intensity of CUB is related to species differences in effective population sizes (Ne), with selection on CUB operating less efficiently in species with small Ne. Here, we specifically ask whether variation in Ne predicts differences in CUB in mammals and report two main findings. First, across 41 mammalian genomes, CUB was not correlated with two indirect proxies of Ne (body mass and generation time), even though there was statistically significant evidence of selection shaping CUB across all species. Interestingly, autosomal genes showed higher codon usage bias compared to X‐linked genes, and high‐recombination genes showed higher codon usage bias compared to low recombination genes, suggesting intraspecific variation in Ne predicts variation in CUB. Second, across six mammalian species with genetic estimates of Ne (human, chimpanzee, rabbit, and three mouse species: Mus musculus, M. domesticus, and M. castaneus), Ne and CUB were weakly and inconsistently correlated. At least in mammals, interspecific divergence in Ne does not strongly predict variation in CUB. One hypothesis is that each species responds to a unique distribution of selection coefficients, confounding any straightforward link between Ne and CUB. 相似文献
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Phillip R. England Jean-Marie Cornuet Pierre Berthier David A. Tallmon Gordon Luikart 《Conservation Genetics》2006,7(2):303-308
Effective population size (N
e) is a central concept in evolutionary biology and conservation genetics. It predicts rates of loss of neutral genetic variation, fixation of deleterious and favourable alleles, and the increase of inbreeding experienced by a population. A method exists for the estimation of N
e from the observed linkage disequilibrium between unlinked loci in a population sample. While an increasing number of studies have applied this method in natural and managed populations, its reliability has not yet been evaluated. We developed a computer program to calculate this estimator of N
e using the most widely used linkage disequilibrium algorithm and used simulations to show that this estimator is strongly biased when the sample size is small (<‰100) and below the true N
e. This is probably due to the linkage disequilibrium generated by the sampling process itself and the inadequate correction for this phenomenon in the method. Results suggest that N
e estimates derived using this method should be regarded with caution in many cases. To improve the method’s reliability and usefulness we propose a way to determine whether a given sample size exceeds the population N
e and can therefore be used for the computation of an unbiased estimate. 相似文献
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Christopher Gast John R. Skalski Dean E. Beyer 《The Journal of wildlife management》2013,77(6):1258-1270
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Kelly M. Proffitt Justin A. Gude Julee Shamhart Fred King 《The Journal of wildlife management》2012,76(4):847-856
In the Greater Yellowstone Ecosystem, growing concern over increasing rates of brucellosis seroprevalence in wildlife has challenged wildlife managers to develop strategies for minimizing the potential for pathogen exchange within and between wildlife populations. Recent evidence suggests that increases in elk seroprevalence may be associated with increasing elk densities and/or increasing size of elk aggregations. However, the interactions between elk population density, landscape factors, and elk aggregation patterns are not well-understood, making appropriate management responses challenging. Using a unique, long-term elk aggregation dataset collected across a wide range of elk population sizes, we investigated relationships between elk population size, landscape factors, and elk aggregation responses (group size and group density) with goals of clarifying how changes in elk population size may affect elk aggregation patterns. Overall, landscape attributes and weather had a stronger influence on elk aggregation patterns than factors such as elk population size that are within management control. We found little evidence that elk population size affected mean elk group sizes, but we did find evidence that the size and density of the largest elk aggregations increased as elk population size increased. We also found some evidence that group densities increased following the establishment of wolves. However, across the relatively wide range of elk population sizes observed in this study, only modest changes in elk group density were observed, suggesting that dramatic reductions in population sizes would be necessary to produce measureable reductions in elk group density to affect frequency-dependent transmission. Management actions designed to lower disease transmission are likely to negatively affect other objectives related to elk management and conservation. We therefore suggest that a first step in managing disease transmission risk is agreement among stakeholders interested in elk management of all objectives related to elk management, including acknowledgment that disease transmission is undesirable. © 2011 The Wildlife Society. 相似文献
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Ellen M. Pero Donovan A. Bell Zachary L. Robinson M. Colter Chitwood Aaron M. Hildreth Leah K. Berkman Barbara J. Keller Jason A. Sumners Lonnie P. Hansen Jason L. Isabelle Lori S. Eggert Chelsea L. Titus Joshua J. Millspaugh 《Conservation Science and Practice》2022,4(2):e598
Population restoration is an inherently costly conservation practice typically reliant on animal translocations. There are many approaches to translocation and consideration is paid to understanding how various translocation models influence restoration success. Translocation strategies are often designed to meet site-specific objectives, minimize cost, and maximize success. We investigated genetic diversity retention associated with the low-founder, multi-release, single admixed stock translocation model of the Missouri elk (Cervus canadensis) restoration in 2011–2013. We further estimated effective population size and projected future losses in genetic diversity if the restored Missouri elk herd is maintained at the population size objective with no immigration from neighboring states. We observed relatively high levels of genetic diversity retention as evidenced by minimal losses in allelic richness and expected heterozygosity. Our projections indicated 90% genetic diversity retention within the Missouri population for roughly 130 years. Where number of progeny or source stocks are limited by resource or disease considerations, use of a relatively low-founder, single admixed source may enable retention of genetic variation, while minimizing costs. 相似文献
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Benjamin N. Sacks Taylor M. Davis Thomas J. Batter 《The Journal of wildlife management》2024,88(3):e22539
California, USA, is home to 3 subspecies of North American elk (Cervus canadensis): Roosevelt (C. c. roosevelti), Rocky Mountain (C. c. nelsoni), and tule (C. c. nannodes). Effective management requires a baseline understanding of each subspecies' range, admixture zones, and geographic patterns of genetic diversity. To address these questions, we genotyped 1,271 individual elk from California (n = 1,204) and reference populations of Rocky Mountain and Roosevelt elk from Nevada (n = 32) and Oregon (n = 35), USA. Using 19 polymorphic microsatellite loci, we detected admixture between Roosevelt and Rocky Mountain elk at a contact zone in northern California, and between Roosevelt and tule elk in north-coastal California and central-coastal California. We identified a genetically distinct population of Roosevelt elk in northwestern California, likely reflecting the remnant population that survived a large demographic decline from overhunting during the 1800s. Tule elk exhibited lower levels of heterozygosity (0.44 ± 0.03 [SD]) and allelic richness (2.9 ± 0.2) than Rocky Mountain (0.58 ± 0.05, 4.9 ± 0.4, respectively) and Roosevelt (0.50 ± 0.06, 4.4 ± 0.6, respectively) elk. Among tule elk populations, heterozygosity varied, with the lowest heterozygosity (0.23 ± 0.05) corresponding to the oldest enclosed herd used over the past century as a source of translocations. Among tule elk populations, genetic structure revealed several cases of successful and unsuccessful reintroduction or augmentation attempts. Results provide an essential baseline for future monitoring and decisions about harvest management, translocations to preserve genetic diversity, and landscape-level conservation planning to maintain, enhance, or obstruct connectivity of elk populations. Genome-wide sequencing and analyses are needed to quantify inbreeding absolutely and assess genetic load and the age of admixture where subspecies currently exchange genes. 相似文献
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Floriane Plard;Hélder Araújo;Amaia Astarloa;Maite Louzao;Camilo Saavedra;José Antonio Vazquez Bonales;Graham John Pierce;Matthieu Authier; 《Marine Mammal Science》2024,40(3):e13104
Estimates of population abundance are required to study the impacts of human activities on populations and assess their conservation status. Despite considerable effort to improve data collection, uncertainty around estimates of cetacean densities can remain large. A fundamental concept underlying distance sampling is the detection function. Here we focus on reducing the uncertainty in the estimation of detection function parameters in analyses combining data sets from multiple surveys, with known effects on the precision of density estimates. We developed detection functions using infinite mixture models that can be applied on data collating multiple species and/or surveys. These models enable automatic clustering by fusing the species and surveys with similar detection functions. We present a simulation analysis of a multisurvey data set in a Bayesian framework where we demonstrated that distance sampling models including fusion effects showed lower uncertainty than classical distance sampling models. We illustrated the benefits of this new model using data of line transect surveys from the Bay of Biscay and Iberian Coast. Future estimates of abundance using conventional distance sampling models on large multispecies surveys or on data sets combining multiple surveys could benefit from this new model to provide more precise density estimates. 相似文献