Most evidence for advances in phenology of in response to recent climate warming in wild vertebrate populations has come from long-term studies of birds. Few studies have either documented phenological advances or tested their climatic causes and demographic consequences in wild mammal systems. Using a long-term study of red deer on the Isle of Rum, Scotland, we present evidence of significant temporal trends in six phenological traits: oestrus date and parturition date in females, and antler cast date, antler clean date, rut start date and rut end date in males. These traits advanced by between 5 and 12 days across a 28-year study period. Local climate measures associated with plant growth in spring and summer (growing degree days) increased significantly over time and explained a significant amount of variation in all six phenological traits, largely accounting for temporal advances observed in some of the traits. However, there was no evidence for temporal changes in key female reproductive performance traits (offspring birth weight and offspring survival) in this population, despite significant relationships between these traits and female phenology. In males, average antler weights increased over time presumably as a result of improved resource availability and physiological condition through spring and summer. There was no evidence for any temporal change in average male annual breeding success, as might be expected if the timing of male rutting behaviour was failing to track advances in the timing of oestrus in females. Our results provide rare evidence linking phenological advances to climate warming in a wild mammal and highlight the potential complexity of relationships between climate warming, phenology and demography in wild vertebrates.
A growing literature now documents the presence of fine-scale genetic structure in wild vertebrate populations. Breeding population size, levels of dispersal and polygyny--all hypothesized to affect population genetic structure--are known to be influenced by ecological conditions experienced by populations. However the possibility of temporal or spatial variation in fine-scale genetic structure as a result of ecological change is rarely considered or explored. Here we investigate temporal variation in fine-scale genetic structure in a red deer population on the Isle or Rum, Scotland. We document extremely fine-scale spatial genetic structure (< 100 m) amongst females but not males across a 24-year study period during which resource competition has intensified and the population has reached habitat carrying capacity. Based on census data, adult deer were allocated to one of three subpopulations in each year of the study. Global F(ST) estimates for females generated using these subpopulations decreased over the study period, indicating a rapid decline in fine-scale genetic structure of the population. Global F(ST) estimates for males were not different from zero across the study period. Using census and genetic data, we illustrate that, as a consequence of a release from culling early in the study period, the number of breeding females has increased while levels of polygyny have decreased in this population. We found little evidence for increasing dispersal between subpopulations over time in either sex. We argue that both increasing female population size and decreasing polygyny could explain the decline in female population genetic structure.
T. H. 2006. Cumulative reproduction and survival costs in female red deer. Á Oikos 115: 241 Á252.Successful reproduction in a single breeding event has consistently been shown to reduce condition, fecundity and survival to the following breeding season. Few studies have examined the cumulative costs of frequent reproduction on survival. Here we use a dataset of female red deer (Cervus elaphus ) from the Isle of Rum, Scotland, to model survival probability within a mark Árecapture framework. By including both recent reproduction and long-term cumulative reproductive effort in the models we tested whether knowledge of lifetime reproductive effort improves our estimates of survival probability. We found that the fit of the model was significantly improved with the inclusion of longer-term measures of reproductive history. Heterogeneity in the reproductive performance of individuals influenced the expected survival cost of reproduction, with high cumulative reproductive effort associated with high survival, except with individuals reproducing in their first year where reproduction was associated with a decrease in survival. This work emphasises the need to account for reproductive history when estimating the survival probabilities of animals. K. Moyes
Demographic senescence is increasingly recognised as an important force shaping the dynamics of wild vertebrate populations. However, our understanding of the processes that underpin these declines in survival and fertility in old age remains limited. Evidence for age-related changes in foraging behaviour and habitat use is emerging from wild vertebrate studies, but the extent to which these are driven by within-individual changes, and the consequences for fitness, remain unclear. Using longitudinal census observations collected over four decades from two long-term individual-based studies of unmanaged ungulates, we demonstrate consistent within-individual declines in home range area with age in adult females. In both systems, we found that within-individual decreases in home range area were associated with increased risk of mortality the following year. Our results provide the first evidence from the wild that age-related changes in space use are predictive of adult mortality.
Parasitism in wild mammals can vary according to myriad intrinsic and extrinsic factors, many of which vary seasonally. However, seasonal variation in parasitism is rarely studied using repeated samples from known individuals. Here we used a wild population of individually recognized red deer (Cervus elaphus) on the Isle of Rum to quantify seasonality and intrinsic factors affecting gastrointestinal helminth parasitism over the course of a year. We collected 1020 non-invasive faecal samples from 328 known individuals which we then analysed for propagules of three helminth taxa: strongyle nematodes, the common liver fluke Fasciola hepatica and the tissue nematode Elaphostrongylus cervi. Zero-inflated Poisson models were used to investigate how season, age and sex were associated with parasite prevalence and count intensity, while Poisson models were used to quantify individual repeatability within and between sampling seasons. Parasite intensity and prevalence varied according to all investigated factors, with opposing seasonality, age profiles and sex biases between parasite taxa. Repeatability was moderate, decreased between seasons and varied between parasites; both F. hepatica and E. cervi showed significant between-season repeatability, while strongyle nematode counts were only repeatable within-season and showed no repeatability within individuals across the year.
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