Contrasting effects of summer and winter warming on body mass explain population dynamics in a food-limited Arctic herbivore.

The cumulative effects of climate warming on herbivore vital rates and population dynamics are hard to predict, given that the expected effects differ between seasons. In the Arctic, warmer summers enhance plant growth which should lead to heavier and more fertile individuals in the autumn. Conversely, warm spells in winter with rainfall (rain-on-snow) can cause 'icing', restricting access to forage, resulting in starvation, lower survival and fecundity.

Congruent responses to weather variability in high arctic herbivores.

Assessing the role of weather in the dynamics of wildlife populations is a pressing task in the face of rapid environmental change. Rodents and ruminants are abundant herbivore species in most Arctic ecosystems, many of which are experiencing particularly rapid climate change. Their different life-history characteristics, with the exception of their trophic position, suggest that they should show different responses to environmental variation.

Icing events trigger range displacement in a high-arctic ungulate.

Despite numerous studies of how climate change may affect life history of mammals, few have documented the direct impact of climate on behavior. The Arctic is currently warming, and rain-on-snow and thaw-freeze events leading to ice formation on the ground may increase both in frequency and spatial extent. This is in turn expected to be critical for the winter survival of arctic herbivores.

Maturation trends in red deer females over 39 years in harvested populations.

1. There is increasing awareness that heavy harvesting can lead to rapid evolution towards earlier sexual maturation. With increased harvest pressure, individuals that begin reproduction at light weights have a greater chance of reproducing at least once compared with individuals that begin reproduction at heavier weights and hence later in life.

Negative density-dependent emigration of males in an increasing red deer population.

In species with polygynous mating systems, females are regarded as food-limited, while males are limited by access to mates. When local density increases, forage availability declines, while mate access for males may increase due to an increasingly female-biased sex ratio. Density dependence in emigration rates may consequently differ between sexes.

Temporal scales, trade-offs, and functional responses in red deer habitat selection.

Animals selecting habitats often have to consider many factors, e.g., food and cover for safety.

The timing of male reproductive effort relative to female ovulation in a capital breeder.

1. In large herbivores, the timing of breeding is important for females to hit peak plant protein levels. For males, the timing of reproductive effort is important to maximize the number of females they can mate during autumn rut in competition with other males.

Hierarchical path analysis of deer responses to direct and indirect effects of climate in northern forest.

A problem in climate studies has been on how to treat causal chains of explanations and both direct and indirect effects. Mammals in strongly seasonal environments of the boreal forest typically lose condition during winter and gain mass (and reproduce) during the summer season when biomass and plant quality peak. Mass decay of large herbivores during winter is due to direct effects of winter weather, such as increased costs of movement, thermoregulation and reduced access to food when snow is deep.

Evidence for a trade-off between early growth and tooth wear in Svalbard reindeer.

Ruminants depend on efficient physical degradation of forage through chewing to increase the surface area of the food particles presented to the microflora. Fossil evidence suggests that increased molar height is an adaptation for wear tolerance in dry ecosystems with sparse vegetation, but no study has shown selection pressure for hypsodonty in contemporary ruminants. We explored the relationships between particle size in rumen, tooth wear (scanned molar occlusal topography), age and body mass of female Svalbard reindeer living in an arctic desert at 78 degrees latitude on Svalbard.

Activity pattern of arctic reindeer in a predator-free environment: no need to keep a daily rhythm.

Arctic Cervids face considerable challenges in sustaining life in a harsh and highly seasonal environment, and when to forage is a key component of the survival strategy. We predict that a cervid maximizes net intake of energy to change the duration of feeding-ruminating cycles depending on season, and pays no attention to light or other activity-entraining cues. Still, in periods of bad weather it may pay energetically to reduce exposure and heat loss.

Testing five hypotheses of sexual segregation in an arctic ungulate.

1. Sexual segregation occurs in most species of sexually dimorphic ungulates. At least five not mutually exclusive hypotheses have been formulated to explain patterns of social, habitat and spatial segregation; the indirect competition hypothesis (H1), the nutritional needs hypothesis (H2), the activity budget hypothesis (H3), the weather sensitivity hypothesis (H4), and the predation risk hypothesis (H5).

Increased effect of harsh climate in red deer with a poor set of teeth.

Teeth are vital for mammal performance and especially in ungulates relying on mechanical decomposition of plant material for effective microbial digestion and energy uptake. The main focus of the role of teeth in ungulate life histories has been on tooth wear, while no one has addressed to what extent deviation from the natural set of teeth (maldentition) causes variation in individual fitness components. Based on mandibles from 41,066 individual red deer (Cervus elaphus L.

Resistance to abomasal nematodes and individual genetic variability in reindeer.

Resistance to parasites is believed to have a widespread influence on demographic and adaptive processes. In systems where parasites impose a fitness cost on their host, heterozygotes may be selected because they are more resistant to parasites than homozygotes. Our objective was to assess the relationships between genomewide individual heterozygosity and abomasal nematode burdens in female Svalbard reindeer (Rangifer tarandus platyrhynchus) after the effects of host age, locality, season, and year had been accounted for.

Importance of climatological downscaling and plant phenology for red deer in heterogeneous landscapes.

Understanding how climate influences ecosystems represents a challenge in ecology and natural resource management. Although we know that climate affects plant phenology and herbivore performances at any single site, no study has directly coupled the topography-climate interaction (i.e.

Multiple causes of sexual segregation in European red deer: enlightenments from varying breeding phenology at high and low latitude.

Sexual segregation outside the mating season occurs in most species of sexually dimorphic ungulates and has been extensively described in the literature, but the mechanisms causing segregation are still debated. The detailed pattern of sexual segregation throughout the year has rarely been presented for mammals, and no study, to our knowledge, has used latitudinal-related variation in breeding phenology to shed light on the underlying mechanisms. Recent methodological developments have made it possible to quantify separate components of segregation (social, habitat) and activity synchrony in animal groups, but these major improvements have so far been little used.

Timing and synchrony of ovulation in red deer constrained by short northern summers.

Iteroparous mothers often face a trade-off between further investments in current offspring at the expense of the start of the next reproductive cycle. In the strongly seasonal environments at northern latitudes, large herbivores are typically calving in early summer each year to get a long growth season and to hit peak protein levels of vegetation. Late-born offspring are more likely to die since they are smaller in autumn.

Social rank, feeding and winter weight loss in red deer: any evidence of interference competition?

During winter at northern latitudes, large herbivores often exploit patches of concentrated, relatively high quality forage, which may lead to interference competition. The factors affecting success in contests and subsequent dominance rank, such as age and body weight, remain key issues in ungulate behavioural ecology. Maternal effects on offspring body weight are well known, but few studies have investigated if mother's social rank influence offspring rank.

Decelerating and sex-dependent tooth wear in Norwegian red deer.

In ungulates, tooth wear is often suggested as a proximate cause of senescence. Tooth wear is expected to be sex-dependent since energetic requirements and food selection varies largely between sexes in sexually dimorphic ungulates. Furthermore, tooth wear may lower mastication efficiency, and we predict a negative correlation between tooth wear and body weight or condition.

Age- and density-dependent reproductive effort in male red deer.

Reproductive effort in female ungulates originates from gestation and lactation and has been studied extensively; however, no comparable studies of reproductive effort in males (due to fighting for access to mates) have, to our knowledge, previously been reported. Here, we report on weight loss of male red deer during the annual mating season--a direct measure of male reproductive effort (or somatic reproductive costs). The 'terminal investment' hypothesis predicts that reproductive effort should increase with age, given that costs remain stable.

Extrinsic Modification of Vertebrate Sex Ratios by Climatic Variation.

Evidence for the influences of climate on early development, maternal condition, and offspring viability in terrestrial vertebrates suggests that climatic change has the potential to induce variation in offspring sex ratios in such organisms. Using long-term data at individual and population levels, we investigated the influence of global climatic variation, as a result of the North Atlantic Oscillation (NAO), on offspring sex ratios of red deer in Norway. The state of the NAO during the fetal development of hinds influenced the mass of their sons, but not daughters, and increasingly warmer and snowy winters led to increasingly male-biased offspring sex ratios, independently of changes in the mean age of hinds.

Short- and long-term effects of winter and spring weather on growth and survival of red deer in Norway.

Populations of red deer (Cervus elaphus) in Norway have increased continuously over the last decades. We tested the possible effects of climate and increase in population size on the survival rates and body condition of individuals in one of the northernmost populations of red deer in Europe. Based on 678 individuals of known age marked between 1977 and 1995, we estimated annual survival rates, the probabilities of being harvested and the recapture probability according to sex, age, year, winter and spring weather, population size, and, body weight and body condition, using capture-mark-recapture models.

Feeding-patch choice by red deer in relation to foraging efficiency : An experiment.

We tested the idea that ruminants allocate their feeding time to habitat patches in relation to foraging efficiency. We used five tame red deer (Cervus elaphus) in an enclosure planted with four treatment of timothy grass (Phleum pratense) differing in their stage of growth. Older swards offered higher biomass but lower nutritional quality than younger swards.