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   

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   

Perceptions of state public health officers and state veterinarians regarding risks of bioterrorism in the United States     

Tharratt RS  Case JT  Hird DW 《Journal of the American Veterinary Medical Association》2002,220(12):1782-1787

OBJECTIVE:To assess perceptions of state public health officers and state veterinarians in the United States regarding the risks of bioterrorism and determine the degree of support provided for activities related to bioterrorism. DESIGN: Cross-sectional survey. SAMPLE POPULATION: State public health officers and state veterinarians. PROCEDURE: A questionnaire was sent between April and June 2001 to the state public health officer and state veterinarian in each of the 50 states and the District of Columbia. RESULTS: Perceptions of the risk of bioterrorism attacks were similar for state public health officers and state veterinarians. Veterinarians perceived the risks associated with foot-and-mouth disease and Newcastle disease to be higher than did physicians. State veterinarians perceived the risks associated with an anthrax hoax, brucellosis, and ricin toxicosis to be lower than did state public health officers. Risk posed by agents that affected animals exclusively was perceived to be higher than risk posed by agents that affected humans exclusively and zoonotic agents. Number of full-time-equivalent positions devoted to bioterrorism surveillance and percentage of the budget devoted to bioterrorism activities were significantly lower for offices run by state veterinarians than for offices run by state public health officers. State veterinarians were significantly less likely to have knowledge of bioterrorism incidents within their state or district than were state public health officers. CONCLUSIONS AND CLINICAL RELEVANCE: Provision of additional resources to state veterinarians and explicit integration of their expertise and surveillance capabilities may be important to effectively mitigate the risk of bioterrorism.  相似文献   

Comparison of the trotting gaits of Labrador Retrievers and Greyhounds     

Bertram JE  Lee DV  Case HN  Todhunter RJ 《American journal of veterinary research》2000,61(7):832-838

OBJECTIVE: To compare the trotting gaits of Labrador Retrievers and Greyhounds to determine whether differences in locomotion are attributable to differences in their manner of moving or to body size and shape differences between these 2 breeds. ANIMALS: 8 healthy 5-month-old Greyhounds and 5 healthy Labrador Retrievers between 6 and 18 months old. PROCEDURE: A series of 4 force platforms was used to record independent ground reaction forces on the forelimbs and hind limbs during trotting. Values of stride parameters were compared between breeds before and after normalization for size differences. Standard values of absolute and normalized stride period and stride length were determined from linear regressions of these parameters on relative (normalized) velocity. Forces were normalized to body weight and compared at the same relative velocity. RESULTS: Greyhounds used fewer, longer strides than the Labrador Retrievers to travel at the same absolute speed. After normalization for body size differences, most measurable differences between breeds were eliminated. Subtle differences that did persist related to proportion of the stride that the forefoot was in contact with the ground, timing of initial hind foot contact relative to initial forefoot contact, and distribution of vertical force between the forelimbs and hind limbs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that apparent differences in the trotting gait between Labrador Retrievers and Greyhounds are mainly attributable to differences in size, and that dogs of these 2 breeds move in a dynamically similar manner at the trot.  相似文献   

THE USE OF BAKELITE IN THE PRESERVATION OF FOSSIL MATERIAL     

Case EC 《Science (New York, N.Y.)》1925,61(1586):543-544

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Perception of Teaching and Assessing Technical Proficiency in American College of Veterinary Surgeons Small Animal Surgery Residency Programs          下载免费PDF全文

Stanley E. Kim BVSc  MS  DACVS  J. Brad Case DVM  MS  DACVS  Daniel D. Lewis DVM  DACVS  Gary W. Ellison DVM  MS  DACVS 《Veterinary surgery : VS》2015,44(6):790-797

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Pericardioscopic imaging findings in cadaveric dogs: Comparison of an apical pericardial window and sub‐phrenic pericardectomy     

Owen T. Skinner BVSc  J. Brad Case DVM  MS  Diplomate ACVS  Gary W. Ellison DVM  MS  Diplomate ACVS  Eric L. Monnet DVM  PhD  Diplomate ACVS & ECVS 《Veterinary surgery : VS》2014,43(1):45-51

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NATURE STUDY     

Case EC 《Science (New York, N.Y.)》1904,19(483):550-551

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Big questions in ecology     

Case TJ 《Science (New York, N.Y.)》1992,256(5059):1056-1057

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Spatial and temporal clustering of Salmonella serotypes isolated from adult diarrheic dairy cattle in California.     

K Sato  T E Carpenter  J T Case  R L Walker 《Journal of veterinary diagnostic investigation》2001,13(3):206-212

Electronic records from the California Animal Health and Food Safety Laboratory System between January 1, 1991, and June 30, 1998, were reviewed, and data on 593 Salmonella serotypes isolated from feces or intestinal contents of adult dairy cattle with diarrhea were analyzed to determine spatial and temporal clustering. A statistically significant clustering in space was detected with 10 (Typhimurium, Montevideo, Muenster, Anatum, Give, Menhaden, Kentucky, Agona, Derby, and Newport) of the 13 serotypes examined. Significant temporal clustering was also detected with 10 serotypes (Typhimurium, Montevideo, Muenster, Anatum, Give, Newbrunswick, Menhaden, Kentucky, Derby, and Newport). Six serotypes (Anatum, Menhaden, Montevideo, Muenster, Newbrunswick, and Newport) were significantly spatially and temporally clustered. A difference in temporal and spatial distribution patterns of some serotypes associated with diarrhea in adult dairy in California was found. Knowledge of the specific type of clustering, if present, should improve our understanding of the transmission and control of salmonellosis in the field.  相似文献