Mast seeding is a well-known example of pulsed resources in terrestrial ecosystems. Despite the large literature available so far on the effects of mast seeding on the dynamics of seed consumer populations, it remains unknown whether heterogeneity in demographic responses to mast seeding exists both within a population of consumers and among consumer populations. Here, we fill this knowledge gap by assessing the effects of acorn production (i.e., oak mast) on all stage-specific demographic rates (i.e., survival, growth, reproduction) in several consumer populations. From long-term capture-mark-recapture data collected in three wild boar populations in Europe and detailed information on annual acorn production, we quantified the effects of acorn production on body mass-specific demographic rates in these populations. We then built a body mass-structured population model for each population and assessed the effect of acorn production on generation time-the mean age of mother at childbirth-and population growth rate using a combination of prospective and retrospective demographic analyses. Within populations, acorn production had a positive effect on reproduction (proportion of breeding females) and growth of small-sized females. Survival remained buffered against environmental variation, in accordance with the demographic buffering hypothesis. Thus, all stage-specific demographic rates were not influenced in the same way by acorn production. In turn, higher reproduction and growth probabilities involved higher population growth rates and shorter generation times. Despite these common demographic responses to mast seeding among populations, we highlighted marked among-population variation in the magnitude of these responses. Also, while populations inhabiting resource-rich environments took advantage of current acorn conditions, populations under resource-poor environments stored and allocated acorns produced the preceding year to reproduction indicating contrasting breeding tactics along the capital-income continuum. Our results suggest heterogeneity in demographic responses to mast seeding, within and among populations. This is an important finding for our understanding of the effects of mast seeding on the dynamics of seed consumer populations.
Weather conditions and population density individuals experience at birth influence their life‐history traits and thereby population dynamics. Early‐life individual growth is a key fitness‐related trait; however, how it is affected by such conditions at birth remains to be explored. Taking advantage of long‐term monitoring of three wild boar (Sus scrofa) populations living in contrasting ecological contexts, we assess how weather conditions (temperature and precipitation) and the number of removed individuals at birth influence early‐life growth rates. We found that the number of individuals removed before the early‐growth period had a positive effect on early‐life growth rate across sites. This might be interpreted as a density‐dependent response involving an increase in food availability per capita that favors faster growth. Alternatively, if the number of removed individuals increases with population density, this result might be attributable to decreasing litter sizes at high density, leading mothers to allocate more resources to individual offspring, which favors higher juvenile growth rates. Early‐life growth rates also increased with springtime temperature and decreasing precipitation. Thus, early‐life growth is expected to increase in response to warmer and drier springs, which should become more frequent in the future under current climate change. We found that conditions at birth explained very little among‐year variation in early‐life growth rates (i.e., weak cohort effects) and that within‐year variation in early‐life growth rates was more likely caused by strong individual differences.
From current theories on life-history evolution, fast early-life growth to reach early reproduction in heavily hunted populations should be favored despite the possible occurrence of mortality costs later on. However, fast growth may also be associated with better individual quality and thereby lower mortality, obscuring a clear trade-off between early-life growth and survival. Moreover, fast early-life growth can be associated with sex-specific mortality costs related to resource acquisition and allocation throughout an individual's lifetime. In this study, we explore how individual growth early in life affects age-specific mortality of both sexes in a heavily hunted population. Using longitudinal data from an intensively hunted population of wild boar (Sus scrofa), and capture-mark-recapture-recovery models, we first estimated age-specific overall mortality and expressed it as a function of early-life growth rate. Overall mortality models showed that faster-growing males experienced lower mortality at all ages. Female overall mortality was not strongly related to early-life growth rate. We then split overall mortality into its two components (i.e., non-hunting mortality vs. hunting mortality) to explore the relationship between growth early in life and mortality from each cause. Faster-growing males experienced lower non-hunting mortality as subadults and lower hunting mortality marginal on age. Females of all age classes did not display a strong association between their early-life growth rate and either mortality type. Our study does not provide evidence for a clear trade-off between early-life growth and mortality.
1 9 2 0 3 1 marine and terrestrial populations of vertebrates. As individual measures of body mass at both 3 2 capture and death are often collected in fish and terrestrial game species, our model integrates 3 3 capture-mark-recapture-recovery data and data collected at death into a body mass-structured 3 4 population model. It allows the observed number of individuals harvested to be compared 3 5with the expected number and provides accurate estimates of demographic parameters. 3 63. We illustrate the usefulness of this IPM using an emblematic game species distributed 3 7 worldwide, the wild boar Sus scrofa, as a case study. For this species that has increased in 3 8 distribution and abundance over the last decades, the model provides accurate and precise 3 9 annual estimates of key demographic parameters (survival, reproduction, growth) and of 4 0 population size while accounting for imperfect detection and observation error.4 1 3 4. To avoid an overexploitation of declining populations or an under-exploitation of 4 2 increasing populations, it is crucial to gain a good understanding of the dynamics of exploited 4 3 populations. When managers or conservationists have limited demographic data, the IPM 4 4 offers a powerful framework to assess population dynamics. Being highly flexible, the 4 5 approach is broadly applicable to both terrestrial and marine exploited populations for which 4 6 measures of body mass are commonly recorded and more generally, to all populations 4 7 suffering from anthropogenic mortality causes. 4 8 4 9
Despite their importance in shaping life history tactics and population dynamics, individual growth trajectories have only been rarely explored in the wild because their analysis requires multiple measurements of individuals throughout their lifetime and some knowledge of age, a key timer of body growth. The availability of long‐term longitudinal studies of two wild boar populations subjected to contrasting environments (rich vs. poor) provided an opportunity to analyze individual growth trajectories. We quantified wild boar growth trajectories at both the population and the individual levels using standard growth models (i.e., Gompertz, logistic, and monomolecular models) that encompass the expected range of growth shapes in determinate growers. Wild boar is a rather altricial species, with a polygynous mating system and is strongly sexually dimorphic in size. According to current theories of life history evolution, we thus expect wild boar to display a sex‐specific Gompertz type growth trajectory and lower sexual size dimorphism in the poorer environment. While wild boar displayed the expected Gompertz type trajectory in the rich site at the population level, we found some evidence for potential differences in growth shapes between populations and individuals. Asymptotic body mass, growth rate and timing of maximum growth rate differed as well, which indicates a high flexibility of growth in wild boar. We also found a cohort effect on asymptotic body mass, which suggests that environmental conditions early in life shape body mass at adulthood in this species. Our findings demonstrate that body growth trajectories in wild boar are highly diverse in relation to differences of environmental context, sex and year of birth. Whether the intermediate ranking of wild boar along the precocial–altricial continuum of development at birth may explain the ability of this species to exhibit this high diversity of growth patterns remains to be investigated.
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