No abstract

Animals selecting habitats often have to consider many factors, e.g., food and cover for safety. However, each habitat type often lacks an adequate mixture of these factors. Analyses of habitat selection using resource selection functions (RSFs) for animal radiotelemetry data typically ignore trade-offs, and the fact that these may change during an animal's daily foraging and resting rhythm on a short-term basis. This may lead to changes in the relative use of habitat types if availability differs among individual home ranges, called functional responses in habitat selection. Here, we identify such functional responses and their underlying behavioral mechanisms by estimating RSFs through mixed-effects logistic regression of telemetry data on 62 female red deer (Cervus elaphus) in Norway. Habitat selection changed with time of day and activity, suggesting a trade-off in habitat selection related to forage quantity or quality vs. shelter. Red deer frequently used pastures offering abundant forage and little canopy cover during nighttime when actively foraging, while spending much of their time in forested habitats with less forage but more cover during daytime when they are more often inactive. Selection for pastures was higher when availability was low and decreased with increasing availability. Moreover, we show for the first time that in the real world with forest habitats also containing some forage, there was both increasing selection of pastures (i.e., not proportional use) and reduced time spent in pastures (i.e., not constant time use) with lowered availability of pastures within the home range. Our study demonstrates that landscape-level habitat composition modifies the trade-off between food and cover for large herbivorous mammals. Consequently, landscapes are likely to differ in their vulnerability to crop damage and threat to biodiversity from grazing.

We present a model on plant^deer^climate interactions developed for improving our understanding of the temporal dynamics of deer abundance and, in particular, how intrinsic (density-dependent) and extrinsic (plants, climate) factors in£uence these dynamics. The model was tested statistically by analysing the dynamics of ¢ve Norwegian red deer populations between 1964 and 1993. Direct and delayed densitydependence signi¢cantly in£uenced the development of the populations: delayed density-dependence primarily operated through female density, whereas direct density-dependence acted through both female and male densities. Furthermore, population dynamics of Norwegian red deer were signi¢cantly a¡ected by climate (as measured by the global weather phenomenon, the North Atlantic Oscillation: NAO). Warm, snowy winters (high NAO) were associated with decreased deer abundance, whereas the delayed (two-year) e¡ect of warm, snowy winters had a positive e¡ect on deer abundance. Our analyses are argued to have profound implications for the general understanding of climate change and terrestrial ecosystem functioning.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. Density-independent weather effects can have important consequences for the demography of terrestrial herbivores because precipitation, temperature and insolation influence plant phenology, forage quality and biomass production, which in turn affects the habitat carrying capacity. Since forage digestibility influences intake and weight gain, life-history traits of young, growing animals are likely to reflect variation in the prevailing weather. 2. This paper specifically investigates spatial and temporal variation in age at maturation in female red deer (Cervus elaphus) in Norway in relation to climate variables known to influence primary production. Our findings are corroborated by analysing differences in age at maturation in 21 cohorts of red deer on the Isle of Rum, Scotland. 3. In Norway the majority of females ovulated as yearlings and calved for the first time as 2-year-olds. The proportion calving for the first time at two years varied from 0 23 to 0 67 between regions and fluctuated from 0 46 to 0 76 between cohorts. On Rum, where age of maturation was delayed at least a year, the proportion calving for the first time as 3-year-olds varied between cohorts from 0 0 to 0 89. 4. In a subset of yearlings culled in Norway at the time of conception, the spatial and temporal differences in ovulation rates were related to the geographical and annual variation in body weight. 5. Both the spatial and temporal variation in the proportion of 2-year-olds calving in Norway, and cohort differences in the proportion calving as 3-year-olds on Rum, were negatively related to variation in May-June degree days 12 months earlier. 6. Although primary production on the preferred herb-rich Agrostis-Festuca grasslands was positively correlated with temperature in May and June on Rum, the proportion of females calving as three years old, was negatively correlated with annual differences in May-June primary production. 7. We argue that retarded phenological development, during periods of cooler weather, enhances diet quality because leaf:stem ratios and digestibility of plant parts decline more slowly. Thus, weight gain during the early summer growth spurt should be rapid during cool May-June weather, increasing the probability of conception in the autumn. 8. Since density-independent variation in food availability also influences fitness components which commonly have a more pronounced influence on population demography, for example offspring survival, we argue that our results highlight the potential importance of variation in weather on herbivore abundance.

1. A central concept in ruminant foraging ecology is that even slight changes in plant quality affect body growth substantially, because ruminants not only gain more protein and energy but also use less time for rumination when eating high-quality forage. Increased access to highly nutritious forage is thus regarded as an important driving force in the evolution of migration in large herbivores, because the temporal and spatial variation in plant quality is huge. Body weight is in turn a major determinant of reproductive performance and survival in ungulates, and therefore important for population dynamics. 2. In the temperate region, the vertical movement of cervids from a low-elevation winter range to a high-elevation summer range is the most common pattern of migration. Migration to high elevations during summer is regarded as a strategy to increase energy intake among northern temperate ungulates. 3. It has been suggested that there is increased forage quality at high elevation. This leads to the prediction that body weights are positively correlated with the proportion of high-altitude habitat. Alternatively, cervids may benefit due to prolonged access to newly emerged forage as they migrate along an altitudinal gradient. If so, it can be predicted that body weights are highest in regions with the highest diversity of different altitudes. 4. The facing of slopes, i.e. the aspect, is also regarded as an important part of the habitat for deer. Access to north-facing slopes is regarded as favourable because plant quality may be higher on north-facing slopes; access to a variety of different aspects is also favourable because this may lead to a variable snow melt and thus a longer time period with access to high-quality forage. 5. In order to test the above predictions (under points 3 and 4), we analysed the spatial variability of body weight of 8452 female and 12 474 male red deer harvested during 1975-98 from 105 municipalities in Norway. 6. Body weight of red deer was positively related to the diversity of altitudes, and negatively related to the proportion of high-altitude habitat per se. This demonstrated that the altitudinal migration of cervids is not necessarily due to increased forage quality at high elevation, but rather that migrating cervids gain from prolonged access to newly emerging forage along an altitudinal gradient as they migrate to high elevation during early summer. 7. There was also no support for the hypothesis that access to a high proportion of north-facing slopes was favourable; rather, body weight of red deer was correlated with access to a diversity of aspects. There was thus clear evidence that a variable topography, measured as different altitude levels and aspects, was positively related to body weight of red deer.

Large-scale climatic fluctuations, such as the North Atlantic Oscillation (NAO), have been shown to affect many ecological processes. Such effects have been typically assumed to be linear. Only one study has reported a nonlinear relation; however, that nonlinear relation was monotonic (that is, no reversal). Here we show that there is a strong nonlinear and non-monotonic (that is, reversed) effect of the NAO on body weight during the subsequent autumn for 23,838 individual wild red deer (Cervus elaphus) and 139,485 individual domestic sheep (Ovis aries) sampled over several decades on the west coast of Norway. These relationships are, at least in part, explained by comparable nonlinear and non-monotonic relations between the NAO and local climatic variables (temperature, precipitation and snow depth). The similar patterns observed for red deer and sheep, the latter of which live indoors during winter and so experience a stable energy supply in winter, suggest that the (winter) climatic variability (for which the index is a proxy) must influence the summer foraging conditions directly or indirectly.

Even though theoretical models show that parasites may regulate host population densities, few empirical studies have given support to this hypothesis. We present experimental and observational evidence for a host-parasite interaction where the parasite has sufficient impact on host population dynamics for regulation to occur. During a six year study of the Svalbard reindeer and its parasitic gastrointestinal nematode Ostertagia gruehneri we found that anthelminthic treatment in April-May increased the probability of a reindeer having a calf in the next year, compared with untreated controls. However, treatment did not influence the over-winter survival of the reindeer. The annual variation in the degree to which parasites depressed fecundity was positively related to the abundance of O. gruehneri infection the previous October, which in turn was related to host density two years earlier. In addition to the treatment effect, there was a strong negative effect of winter precipitation on the probability of female reindeer having a calf. A simple matrix model was parameterized using estimates from our experimental and observational data. This model shows that the parasite-mediated effect on fecundity was sufficient to regulate reindeer densities around observed host densities.

Aim  To investigate the phylogeographical patterns of red deer (Cervus elaphus) in Europe, and to disentangle the influence of ancient (e.g. Pleistocene ice ages) from more recent processes (e.g. human translocations). Location  Europe. Methods  In this study we provide by far the most extensive analysis of genetic structure in European red deer, based on analyses of variation at two mitochondrial markers (cyt b and D‐loop) in a large number of individuals from 39 locations. Relationships of mitochondrial DNA haplotypes were determined using minimum spanning networks and phylogenetic analyses. Population structure was examined by analyses of molecular variance. Historical processes shaping the present patterns were inferred from nested clade analysis and nucleotide diversity statistics. Results  Within Europe, we detected three deeply divergent mitochondrial DNA lineages. The three lineages displayed a phylogeographical pattern dividing individuals into western European, eastern European and Mediterranean (Sardinia, Spain and Africa) groups, suggesting contraction into three separate refugia during the last glaciation. Few haplotypes were shared among these three groups, a finding also confirmed by FST values. Calculations of divergence times suggest that the groups probably split during the Pleistocene. Main conclusions  The observed pattern is interpreted to result from isolation in different refugia during the last glaciation. The western and eastern European lineages could be linked to an Iberian and Balkan refugium, respectively. The third lineage might originate from a Sardinian or African refugium. We link local phylogeographical patterns observed in Europe to the post‐glacial recolonization process, shaped by the geographical localization of refugia and barriers to gene flow. Regardless of the importance of red deer as a game species and the tradition of translocating red deer in Europe, we detected few individuals that did not match the trichotomous pattern, suggesting that translocations have occurred mainly at smaller spatial scales.