No abstract

Summary1. The effects of harvest on the annual and seasonal survival of willow ptarmigan Lagopus lagopus L. were tested in a large-scale harvest experiment. Management units were randomly assigned to one of three experimental treatments: 0%, 15% or 30% harvest. Seasonal quotas were based on the experimental treatment and estimates of bird density before the hunting season. Survival rates and hazard functions for radio-marked ptarmigan were then estimated under the competing risks of harvest and natural mortality. 2. The partially compensatory mortality hypothesis was supported: annual survival of ptarmigan was 0AE54 ± 0AE08 SE under 0% harvest, 0AE47 ± 0AE06 under 15% harvest, and was reduced to 0AE30 ± 0AE05 under 30% harvest. Harvest mortality increased linearly from 0AE08 ± 0AE05, 0AE27 ± 0AE05 and 0AE42 ± 0AE06 from 0% to 30% harvest, whereas natural mortality was 0AE38 ± 0AE08, 0AE25 ± 0AE05 and 0AE28 ± 0AE06 under the same treatments. 3. Realized risk of harvest mortality was 0AE08-0AE12 points higher than our set harvest treatments of 0-30% because birds were exposed to risk if they moved out of protected areas. The superadditive hypothesis was supported because birds in the 30% harvest treatment had higher natural mortality during winter after the hunting season. 4. Natural mortality was mainly because of raptor predation, with two seasonal peaks in fall and spring. Natural and harvest mortality coincided during early autumn with little potential for compensation during winter months. Peak risk of harvest mortality was 5· higher than natural mortality. Low natural mortality during winter suggests that most late season harvest would be additive mortality. 5. Environmental correlates of natural mortality of ptarmigan included seasonal changes in snow cover, onset of juvenile dispersal, and periods of territorial activity. Natural mortality of ptarmigan was highest during autumn movements and nesting by gyrfalcons Falco rusticolus L. Mortality was low when gyrfalcons had departed for coastal wintering sites, and during summer when ptarmigan were attending nests and broods. 6. Our experimental results have important implications for harvest management of upland gamebirds. Seasonal quotas based on proportional harvest were effective and should be set at £15% of August populations for regional management plans. Under threshold harvest of a reproductive surplus, 15% harvest would be sustainable at productivity rates ‡2AE5 young per pair. Impacts of winter harvest could be minimized by closing the hunting season in early November or by reducing late season quotas.

Despite much criticism, black-or-white null-hypothesis significance testing with an arbitrary P-value cutoff still is the standard way to report scientific findings. One obstacle to progress is likely a lack of knowledge about suitable alternatives. Here, we suggest language of evidence that allows for a more nuanced approach to communicate scientific findings as a simple and intuitive alternative to statistical significance testing. We provide examples for rewriting results sections in research papers accordingly. Language of evidence has previously been suggested in medical statistics, and it is consistent with reporting approaches of international research networks, like the Intergovernmental Panel on Climate Change, for example. Instead of re-inventing the wheel, ecology and evolution might benefit from adopting some of the 'good practices' that exist in other fields.

Variation in size of home range is among the most important parameters required for effective conservation and management of a species. However, the fact that home ranges can vary widely within a species makes data transfer between study areas difficult. Home ranges of Eurasian lynx Lynx lynx vary by a factor of 10 between different study areas in Europe. This study aims to try and explain this variation in terms of readily available indices of prey density and environmental productivity. On an individual scale we related the sizes of 52 home ranges, derived from 23 (9:14 male:female) individual resident lynx obtained from south-eastern Norway, with an index of density of roe deer Capreolus capreolus. This index was obtained from the density of harvested roe deer within the municipalities covered by the lynx home ranges. We found a significant negative relationship between harvest density and homerange size for both sexes. On a European level we related the sizes of 111 lynx (48:63 male: female) from 10 study sites to estimates derived from remote sensing of environmental productivity and seasonality. A multiple linear regression model indicated that productivity of the study site had a clear negative relationship with home-range size. At both scales, sex emerged as a significant explanatory variable with males having larger home ranges than females. In addition, the size of male home-ranges increased faster with decreasing prey density than for females. These analyses support widely held predictions that variation in home-range size is due to variation in prey density.