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Understanding the processes that underlie bat distribution and activity patterns requires examination of habitat associations at multiple scales. We examined the association of both local structure and landscape context with bat activity in forested stands using ultrasonic detectors. Forty-eight stands in western Oregon and Washington were monitored for bat activity on at least six occasions for each of two field seasons. At the stand level, bat activity was negatively associated with tree density. The standard deviation of tree density and the density of newly created snags were positively associated with bat activity. In combination, these three variables explained 46% of the total variance in bat activity among stands. Landscape-level variables did not explain any significant variation among a subset of stands (n=22). Our study suggests that management of forest-dwelling bats should focus primarily on structural attributes at the stand level and the effects of these features on feeding and roosting opportunities. more...

We examined the influence of average climatic conditions and nightly weather variations using bat detectors on the summer activity of bats. Average summer precipitation was the principal climate variable correlated with differences in bat activity along a latitudinal array of sites, with the highest activity levels occurring at sites located in montane rain shadows. On a nightly basis, the occurrence of rain and low temperatures had strong negative correlations with flight activity. However, the variation in nightly activity at a site that was explained by weather was relatively small. Our results suggest that the use of long-term climatic data offers potential to predict variations in bat activity among sites. Such information may be useful in recognizing conservation priorities for the management of bats in the Pacific Northwest where topography is complex and climate conditions are variable. more...

Although bats are a group with high species richness in shrub-steppe areas of the Columbia Basin, limited information is available on distributions, species occurrence, and habitat use. We surveyed bat populations of the Hanford Site, which has provided a refuge for shrub-steppe flora and fauna in Washington State. We used Anabat detectors, harp traps, mist nets, and auditory-visual observations during 1997 and 1998 to document the occurrence of bat species and to compare activity levels among major habitat types on the site. Across both years, we recorded 6,470 bat calls during 302 bat detector survey-nights at 66 locations. Bats of the genus Myotis constituted 84 to 88% of total calls each year. The hoary bat (Lasiurus cinereus), silver-haired bat (Lasionycteris noctivagans), western pipistrelle (Pipistrellus hesperus), big brown bat (Eptesicusfuscus), and pallid bat (Antrozous pallidus) also were recorded. Big brown bats have not been reported previously at the Hanford Site. Detection rates were highest near potential roosting structures and riparian foraging areas, and lowest in upland shrub-steppe cover types. During 133 trap nights across both years, we captured 81 bats of 5 species: the western smallfooted myotis (Myotis ciliolabrum), little brown myotis (M. lucifugus), Yuma myotis (M. yumanensis), silver-haired bat, and pallid bat. The site supports at least 3 arid-land bats (western small-footed myotis, western pipistrelle, and pallid bat) that are near the northern edge of their species distributions. By protecting large patches of undisturbed habitat, the Hanford Site has helped maintain a diverse bat fauna in Washington's shrub-steppe. In addition, some habitat modifications at the site may have benefited bats, as evidenced by heavy use of old buildings, irrigation run-off wetlands, and planted trees. more...

Recognized risk factors for metrizamide myelography are seizure disorder, seizure-threshold-lowering drugs, dehydration, and possibly age. After observing serious neurologic complications in diabetic patients after routine metrizamide myelography, a retrospective study was conducted to determine if diabetes should be considered another independent and important risk factor. Forty-one diabetic patients who had lumbar metrizamide myelograms were compared with a control group of 110 nondiabetic patients. A significantly higher incidence was found of severe vomiting (15% vs. 3%, p less than 0.01) and neurologic complications (20% vs. 2%, p less than 0.001) in the diabetic population. Neurologic complications included one case each of seizure, severe encephalopathy, auditory and visual hallucinations, and prolonged somnolence and four cases of confusion-anxiety. Four of the diabetic patients had major transient elevations of blood pressure. These findings suggest that diabetics are a high-risk population for metrizamide myelography. The dose of metrizamide should be minimized, whenever possible. The new nonionic myelographic agents may prove to be safer in this population, but caution and careful follow-up should be exercised in the initial trials with these patients. more...

High field strength MR imaging systems may require several kilowatts of RF power to obtain images. A fraction of this power is absorbed by the patient, and changes in body temperature have been measured in experimental animals. The purpose of this study was to quantify changes in body surface temperature and other physiologic parameters in humans during MR scanning at 1.5 T. Blood pressure, heart rate, respiration, and axillary temperature measurements were obtained on 27 normal volunteers. Measurements were made at RF power levels of 0, 0.2, and 0.8 W/kg, with the power sequence randomized. In 14 volunteers receiving lumbar scans, statistically significant increases in temperature were observed at RF power levels of 0.2 (+0.2 +/- 0.1 degree C) and 0.8 (+0.5 +/- 0.1 degree C) W/kg. No significant changes related to RF power were observed in blood pressure or respiratory rate. At the 0.8 W/kg level there was a slight increase in heart rate (3 +/- 1.3 beats per minute). In the 13 patients receiving head scans, physiologic changes were substantially smaller. The temperature increases and other physiologic changes observed during MR scanning with the 1.5 T imager at RF powers of 0.2 and 0.8 W/kg were small and of no clinical concern. Additional studies should be performed in patients with cardiac failure, vascular occulusion, and metallic implants or prostheses. more...