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2.  Should hunting mortality mimic the patterns of natural mortality? 
Biology Letters  2008;4(3):307-310.
With growing concerns about the impact of selective harvesting on natural populations, researchers encourage managers to implement harvest regimes that avoid or minimize the potential for demographic and evolutionary side effects. A seemingly intuitive recommendation is to implement harvest regimes that mimic natural mortality patterns. Using stochastic simulations based on a model of risk as a logistic function of a normally distributed biological trait variable, we evaluate the validity of this recommendation when the objective is to minimize the altering effect of harvest on the immediate post-mortality distribution of the trait. We show that, in the absence of compensatory mortality, harvest mimicking natural mortality leads to amplification of the biasing effect expected after natural mortality, whereas an unbiased harvest does not alter the post-mortality trait distribution that would be expected in the absence of harvest. Although our approach focuses only on a subset of many possible objectives for harvest management, it illustrates that a single strategy, such as hunting mimicking natural mortality, may be insufficient to address the complexities of different management objectives with potentially conflicting solutions.
PMCID: PMC2610045  PMID: 18292053
demography; life history; simulation; management; selection; vulnerability
3.  Bigger teeth for longer life? Longevity and molar height in two roe deer populations 
Biology Letters  2007;3(3):268-270.
The role of tooth wear as a proximate cause of senescence in ruminants has recently been highlighted. There are two competing hypotheses to explain variation in tooth height and wear; the diet-quality hypothesis predicting increased wear in low-quality habitats, and the life-history hypothesis predicting molar height to be related to expected longevity. We compared tooth height and wear from roe deer of known age from two contrasting populations of roe deer (Capreolus capreolus) in France: Trois Fontaines (TF) with good habitat and shorter animal life expectancy and Chizé (CH) with poor habitat and longer animal life expectancy. There was no population difference in tooth wear, leading to rejection of the diet-quality hypothesis. However, despite their smaller body size, initial molar height for animals from CH was larger than for animals from TF. This provides the first evidence that variation in longevity between populations can lead to differences in molar height within a species.
PMCID: PMC2464678  PMID: 17311776
longevity; Capreolus capreolus; intraspecific variation; molar; selective browser
4.  Positive short-term effects of sheep grazing on the alpine avifauna 
Biology Letters  2006;3(1):109-111.
Grazing by large herbivores may negatively affect bird populations. This is of great conservation concern in areas with intensive sheep grazing. Sheep management varies substantially between regions, but no study has been performed in less intensively grazed systems. In a fully replicated, landscape scale experiment with three levels of sheep grazing, we tested whether the abundance and diversity of an assemblage of mountain birds were negatively affected by grazing or if grazing facilitated the bird assemblage. Density of birds was higher at high sheep density compared with low sheep density or no sheep by the fourth grazing season, while there was no clear effect on bird diversity. Thus, agricultural traditions and land use politics determining sheep density may change the density of avifauna in either positive or negative directions.
PMCID: PMC2373819  PMID: 17443979
ecosystem function; livestock; biodiversity; birds; facilitation; trophic cascades
5.  Harvesting of males delays female breeding in a socially monogamous mammal; the beaver 
Biology Letters  2006;3(1):106-108.
Human exploitation may skew adult sex ratios in vertebrate populations to the extent that males become limiting for normal reproduction. In polygynous ungulates, females delay breeding in heavily harvested populations, but effects are often fairly small. We would expect a stronger effect of male harvesting in species with a monogamous mating system, but no such study has been performed. We analysed the effect of harvesting males on the timing of reproduction in the obligate monogamous beaver (Castor fiber). We found a negative impact of harvesting of adult males on the timing of parturition in female beavers. The proportion of normal breeders sank from over 80%, when no males had been shot in the territories of pregnant females, to under 20%, when three males had been shot. Harvesting of males in monogamous mammals can apparently affect their normal reproductive cycle.
PMCID: PMC2373813  PMID: 17443978
Castor fiber; life history; management; phenology; seasonality
6.  Selectivity of harvesting differs between local and foreign roe deer hunters: trophy stalkers have the first shot at the right place 
Biology Letters  2006;2(4):632-635.
Harvesting represents a major source of mortality in many deer populations. The extent to which harvesting is selective for specific traits is important in order to understand contemporary evolutionary processes. In addition, since such data are frequently used in life-history studies, it is important to know the pattern of selectivity as a source of bias. Recently, it was demonstrated that different hunting methods were selected for different weights in red deer (Cervus elaphus), but little insight was offered into why this occurs. In this study, we show that foreign trophy stalkers select for larger antlers when hunting roe deer (Capreolus capreolus) than local hunters, but that close to half of the difference in selectivity was due to foreigners hunting earlier in the season and in locations with larger males. The relationship between antler size and age was nevertheless fairly similar based on whether deer was shot by foreign or local hunters.
PMCID: PMC1833986  PMID: 17148307
antlers; Capreolus capreolus; life history; trophy stalking; management; selection
7.  The relative role of winter and spring conditions: linking climate and landscape-scale plant phenology to alpine reindeer body mass 
Biology Letters  2005;1(1):24-26.
The relative importance of winter harshness and early summer foraging conditions are of prime interest when assessing the effect of global warming on Arctic and mountainous ecosystems. We explored how climate and vegetation onset (satellite-derived normalized difference vegetation index data) determined individual performance in three reindeer populations (data on 27 814 calves sampled over 11 years). Snow conditions, spring temperatures and topography were the main determinants of the onset of the vegetation. An earlier onset positively affected the body mass of calves born the following autumn, while there was no significant direct negative impact of the previous winter. This study underlines the major impact of winter and spring climatic conditions, determining the spring and summer food availability, and the subsequent growth of calves among alpine herbivores.
PMCID: PMC1629060  PMID: 17148119
Rangifer tarandus; normalized difference vegetation index; environmental variations; North Atlantic Oscillation

Results 1-7 (7)