1. Predicting the spatial pattern of disease risk in wild animal populations is important for implementing effective control programmes. We developed a risk model predicting the probability that a deer harvested in a wild population was chronic wasting disease positive (CWD+) and evaluated the importance of landscape connectivity based on deer movements. 2. We quantified landscape connectivity from deer 'resistance' to move across the landscape similar to the flow of electrical current across a hypothetical electronic circuit. Resistance values to deer movement were derived as the inverse of step selection function values constructed using movement data from GPS-collared deer. 3. The top CWD risk model indicated risk increased over time was higher among mule deer Odocoileus hemionus than white-tailed deer Odocoileus virginianus, males than females, and was greater in areas with high stream density and abundant agriculture. A metric of connectivity derived from mule deer movements outperformed models including Euclidean distance, with high connectivity being associated with high CWD risk. 4. The CWD risk model was a good predictor of CWD occurrence among an independent set of surveillance data collected in subsequent years. 5. Synthesis and applications. We found that landscape connectivity was a major contributor to the spatial pattern of chronic wasting disease (CWD) risk on a heterogeneous landscape. For this reason, future disease surveillance programmes and models of disease spread should consider landscape connectivity. In the aspen parkland ecosystem, we recommend managers focus surveillance and control efforts along river valleys surrounded by agriculture where mule deer abound, because of the high risk of CWD infection. Fig. 4. (a) Chronic wasting disease (CWD) risk weighted by species and sex composition within wildlife management unit 730 in Alberta, and (b) forest/shrub cover, streams and agriculture within 730, where streams and agriculture are covariates in the CWD risk model.
Woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)) populations have declined throughout their range. With the goal of better understanding habitat selection and fidelity during the neonatal calving period (0-4 weeks), we applied a noninvasive method that estimates calving events and subsequent survival based on changes in movement rates among GPS-collared female caribou. We examined a long-term GPS-collar data set (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014) collected from 81 adult female caribou in two central mountain herds in Alberta and British Columbia, Canada. Although we were unable to validate our results with aerial surveys and pregnancy tests, our estimates of parturition rates, survival rates, calving dates, and habitat selection were consistent with previous studies. We identified 83 calving sites. Female caribou selected calving sites and postparturition habitat on high-elevation ridgetops with gradual slopes and avoided anthropogenic linear features. Female caribou displayed low fidelity to interannual calving ranges with a mean distance of 8.7 km between calving ranges. Fidelity was lower in areas with high seismic-line density. Conservation of high-elevation habitat with limited anthropogenic disturbance is likely to provide the greatest benefit to central mountain caribou during the neonatal calving period, and represents a potential management strategy for population recovery efforts.
Mountain pine beetle (MPB) has become an invasive forest pest of mature pine in western North America as it spreads beyond its former endemic range. Management actions such as timber harvest can reduce the spread of MPB but may affect species of conservation concern like woodland caribou. Our goal was to inform MPB management within caribou ranges by exploring the impacts of MPB on caribou habitat-focusing on terrestrial lichens, an important winter food for caribou. We evaluated differences in lichen cover among four MPB management actions: timber harvest, wildfires, leaving MPB killed trees as-is, and single-tree cut-and-burn control. We found little evidence that leaving MPB killed trees as-is or controlling MPB using single-tree cut-and-burn impacted lichen cover. However, we found that lichen cover was lower in timber harvested and burned areas compared to intact undisturbed forest but only 10 to 20 years post-disturbance, respectively. Our results suggest that despite short-term reductions in lichen cover, using timber harvesting and prescribed burns to control MPB may balance management needs for MPB while maintaining lichen cover over time. However, using timber harvesting and prescribed burns to manage MPB is likely to have detrimental population-level effects on caribou by increasing the proportion of disturbed habitat and thus predators within caribou ranges. Among the four management actions that we evaluated, the cut-and-burn control program balances the need to limit the spread of MPB while also limiting negative impacts on caribou food. Our work addresses some of the challenges of managing competing forest and ecosystem values by evaluating the consequence of forest pest management actions on an important food resource for a species-at-risk.
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