Quantifying patch distribution at multiple spatial scales: Applications to wildlife-habitat models     

Johnson  Chris J.  Boyce  Mark S.  Mulders  Robert  Gunn  Anne  Gau  Rob J.  Cluff  H. Dean  Case  Ray L. 《Landscape Ecology》2004,19(8):869-882

Multiscale analyses are widely employed for wildlife-habitat studies. In most cases, however, each scale is considered discrete and little emphasis is placed on incorporating or measuring the responses of wildlife to resources across multiple scales. We modeled the responses of three Arctic wildlife species to vegetative resources distributed at two spatial scales: patches and collections of patches aggregated across a regional area. We defined a patch as a single or homogeneous collection of pixels representing 1 of 10 unique vegetation types. We employed a spatial pattern technique, three-term local quadrat variance, to quantify the distribution of patches at a larger regional scale. We used the distance at which the variance for each of 10 vegetation types peaked to define a moving window for calculating the density of patches. When measures of vegetation patch and density were applied to resource selection functions, the most parsimonious models for wolves and grizzly bears included covariates recorded at both scales. Seasonal resource selection by caribou was best described using a model consisting of only regional scale covariates. Our results suggest that for some species and environments simple patch-scale models may not capture the full range of spatial variation in resources to which wildlife may respond. For mobile animals that range across heterogeneous areas we recommend selection models that integrate resources occurring at a number of spatial scales. Patch density is a simple technique for representing such higher-order spatial patterns.  相似文献   

Epidemiology of porcine non-specific colitis on Scottish farms     

Chase-Topping ME  Gunn G  Strachan WD  Edwards SA  Smith WJ  Hillman K  Stefopoulou SN  Thomson JR 《Veterinary journal (London, England : 1997)》2007,173(2):353-360

The objective of this study was to investigate epidemiological risk factors for porcine non-specific colitis (NSC). Forty-seven Scottish pig farms, with and without a clinical history of diarrhoea during the growing period (15-40 kg), were selected. The study included farm visits, clinical inspection of pigs, completion of farm management questionnaires, pathological tests into the cause of the diarrhoea and analysis of the non-starch polysaccharide (NSP) content of feeds. The results from 17 farms designated as NSC and 10 control farms suggest dietary associations with NSC. Farms with NSC fed diets with significantly higher levels of NSPs, especially containing the sugars glucose, arabinose and xylose. Few management factors were identified, although the high prevalence of infectious colitis reduced the power of the study.  相似文献   

Quantifying patch distribution at multiple spatial scales: Applications to wildlife-habitat models     

Chris J. Johnson  Mark S. Boyce  Robert Mulders  Anne Gunn  Rob J. Gau  H. Dean Cluff  Ray L. Case 《Landscape Ecology》2005,19(8):869-882

Multiscale analyses are widely employed for wildlife-habitat studies. In most cases, however, each scale is considered discrete and little emphasis is placed on incorporating or measuring the responses of wildlife to resources across multiple scales. We modeled the responses of three Arctic wildlife species to vegetative resources distributed at two spatial scales: patches and collections of patches aggregated across a regional area. We defined a patch as a single or homogeneous collection of pixels representing 1 of 10 unique vegetation types. We employed a spatial pattern technique, three-term local quadrat variance, to quantify the distribution of patches at a larger regional scale. We used the distance at which the variance for each of 10 vegetation types peaked to define a moving window for calculating the density of patches. When measures of vegetation patch and density were applied to resource selection functions, the most parsimonious models for wolves and grizzly bears included covariates recorded at both scales. Seasonal resource selection by caribou was best described using a model consisting of only regional scale covariates. Our results suggest that for some species and environments simple patch-scale models may not capture the full range of spatial variation in resources to which wildlife may respond. For mobile animals that range across heterogeneous areas we recommend selection models that integrate resources occurring at a number of spatial scales. Patch density is a simple technique for representing such higher-order spatial patterns.  相似文献   

The Treatment of Limb Bone Fractures in Animals.*     

R. M. C. Gunn 《Australian veterinary journal》1936,12(4):139-146

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NOTE ON THE RADIAL MAGNETIC GRADIENT OF THE SUN     

Gunn R 《Science (New York, N.Y.)》1928,68(1760):273-274

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EFFECTS OF FLUID AND COMPUTED TOMOGRAPHIC TECHNICAL FACTORS ON CONSPICUITY OF CANINE AND FELINE NASAL TURBINATES          下载免费PDF全文

Raimonda Uosyte  Darren J. Shaw  Danielle A. Gunn‐Moore  Eduardo Fraga‐Manteiga  Tobias Schwarz 《Veterinary radiology & ultrasound》2015,56(5):494-502

Turbinate destruction is an important diagnostic criterion in canine and feline nasal computed tomography (CT). However decreased turbinate visibility may also be caused by technical CT settings and nasal fluid. The purpose of this experimental, crossover study was to determine whether fluid reduces conspicuity of canine and feline nasal turbinates in CT and if so, whether CT settings can maximize conspicuity. Three canine and three feline cadaver heads were used. Nasal slabs were CT‐scanned before and after submerging them in a water bath; using sequential, helical, and ultrahigh resolution modes; with images in low, medium, and high frequency image reconstruction kernels; and with application of additional posterior fossa optimization and high contrast enhancing filters. Visible turbinate length was measured by a single observer using manual tracing. Nasal density heterogeneity was measured using the standard deviation (SD) of mean nasal density from a region of interest in each nasal cavity. Linear mixed‐effect models using the R package ‘nlme’, multivariable models and standard post hoc Tukey pair‐wise comparisons were performed to investigate the effect of several variables (nasal content, scanning mode, image reconstruction kernel, application of post reconstruction filters) on measured visible total turbinate length and SD of mean nasal density. All canine and feline water‐filled nasal slabs showed significantly decreased visibility of nasal turbinates (P < 0.001). High frequency kernels provided the best turbinate visibility and highest SD of aerated nasal slabs, whereas medium frequency kernels were optimal for water‐filled nasal slabs. Scanning mode and filter application had no effect on turbinate visibility.  相似文献   

Adaptations of skeletal muscle that favour athletic ability     

H.M. Gunn H.M.Gunn M.V.B. M.R.C.V.S. 《New Zealand veterinary journal》2013,61(11):249-254

The preparation and use of a blowgun apparatus is described for injection of animals which cannot readily be physically restrained. The apparatus has been in use at Taronga Zoo for some months, providing a reliable and economical alternative to commercially available systems.  相似文献   

SCIENCE AND LITERATURE     

Gunn S 《Science (New York, N.Y.)》1911,34(878):550-556

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Diagnostic accuracy of PCR for Jaagsiekte sheep retrovirus using field data from 125 Scottish sheep flocks     

F.I. Lewis  F. Brülisauer  C. Cousens  I.J. McKendrick  G.J. Gunn 《Veterinary journal (London, England : 1997)》2011,187(1):104-108

Using a representative sample of Scottish sheep comprising 125 flocks, the sensitivity and specificity of PCR for Jaagsiekte sheep retrovirus (JSRV) was estimated. By combining and adapting existing methods, the characteristics of the diagnostic test were estimated (in the absence of a gold standard reference) using repeated laboratory replicates. As the results of replicates within the same animal cannot be considered to be independent, the performance of the PCR was calculated at individual replicate level.The median diagnostic specificity of the PCR when applied to individual animals drawn from the Scottish flock was estimated to be 0.997 (95% confidence interval [CI] 0.996–0.999), whereas the median sensitivity was 0.107 (95% CI 0.077–0.152). Considering the diagnostic test as three replicates where a positive result on any one or more replicates results in a positive test, the median sensitivity increased to 0.279. Reasons for the low observed sensitivity were explored by comparing the performance of the test as a function of the concentration of target DNA using spiked positive controls with known concentrations of target DNA. The median sensitivity of the test when used with positive samples with a mean concentration of 1.0 target DNA sequence per 25 μL was estimated to be 0.160, which suggests that the PCR had a high true (analytical) sensitivity and that the low observed (diagnostic) sensitivity in individual samples was due to low concentrations of target DNA in the blood of clinically healthy animals.  相似文献   

Practice-based health assurance.     

G J Gunn  J S Simpson  I McCulloch  A G Masson  G F Swanson  A G Rafferty 《The Veterinary record》2001,149(14):430-431

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