Cattle grazing in semiarid forestlands: Habitat selection during periods of drought.

Climate change models are predicting increased frequency and severity of droughts in arid and semiarid environments, and these areas are responsible for much of the world's livestock production. Because cattle (Bos Taurus) grazing can impact the abundance, distribution, and ecological function of native plant and animal communities, it is important to understand how cattle might respond to increasingly arid conditions. Here, we evaluate changes in habitat selection by cattle across an 8-yr period as a function of rainfall and other environmental covariates. Using resource selection functions, we evaluated habitat selection based on 2 behaviors, stationary and mobile. Models revealed similarity in cattle habitat selection across years, with only modest changes in selection as a function of precipitation, despite marked seasonal and interannual differences in rainfall. Cattle preferred gentle slopes, forest edges, wet meadows, and areas near water as well as areas far from water on plateaus. Cattle avoided areas at intermediate distances from water, typically associated with steep slopes. As conditions became drier during the late season, cattle did not switch selection patterns but instead contracted their selection around water. Cattle also selected similar habitats whether they were mobile or stationary, possibly making microsite decisions therein. This consistent pattern of selection across years could be particularly problematic for riparian communities as climates become drier; however, it may also simplify cattle management, as range managers can focus vegetation monitoring efforts on riparian areas. Due to the uncertainty surrounding future climatic conditions, it is imperative that both range and wildlife managers develop long-term plans to continue managing these multiuse landscapes in an ecologically sustainable manner based on expected patterns of livestock grazing.

Comparing the toxicity of digoxin and digitoxin in a geriatric population: should an old drug be rediscovered?

BACKGROUND: Little information is available regarding toxicity rates of the two available forms of cardiac glycosides (digoxin, digitoxin) when used in elderly patients. METHODS: We retrospectively analyzed the charts of all patients more than 60 years of age who were chronically managed with a cardiac glycoside and were hospitalized during the period January 1995 through January 1998. Toxicity was defined as any clinical event that required either a reduction in dose of the drug or its discontinuance. RESULTS: Toxicity occurred among 7.6% of hospitalizations in which digitoxin was used, compared with 18.3% of hospitalizations in which digoxin was used. In multivariate analysis, the odds of toxicity adjusted for other clinical characteristics were three times greater for patients taking digoxin than for patients taking digitoxin. CONCLUSION: Hospitalized elderly patients taking digitoxin had a lower rate of toxicity than those taking digoxin.