Pulsed resources influence the demography and evolution of consumer populations and, by cascading effect, the dynamics of the entire community. Mast seeding provides a case study for exploring the ...evolution of life history traits of consumers in fluctuating environments. Wild boar (Sus scrofa) population dynamics is related to seed availability (acorns/beechnuts). From a long-term monitoring of two populations subjected to markedly different environmental contexts (i.e., both low vs. high frequency of pulsed resources and low vs. high hunting pressure in Italy and in France, respectively), we assessed how pulsed resources shape the reproductive output of females. Using path analyses, we showed that in both populations, abundant seed availability increases body mass and both the absolute and the relative (to body mass) allocation to reproduction through higher fertility. In the Italian population, females equally relied on past and current resources for reproduction and ranked at an intermediate position along the capital-income continuum of breeding tactics. In contrast, in the French population, females relied on current more than past resources and ranked closer to the income end of the continuum. In the French population, one-year old females born in acorn-mast years were heavier and had larger litter size than females born in beechnut-mast years. In addition to the quantity, the type of resources (acorns/beechnuts) has to be accounted for to assess reliably how females allocate resources to reproduction. Our findings highlight a high plasticity in breeding tactics in wild boar females and provide new insight on allocation strategies in fluctuating environments.
Hunting can be used as a tool for wildlife management, through limitation of population densities and dissuading game from using sensitive areas. The success of these approaches requires in depth ...knowledge of prey movement. Indeed, movement decisions of game during hunting may affect the killing success of hunters as well as the subsequent location of surviving animals. We thus investigated red deer movement responses to drive hunts and their causal factors. We studied 34 hunting events in the National Estate of Chambord (France) and thereby provided a fine-scale characterization of the immediate and delayed movement responses of red deer to drive hunts. Red deer responded to drive hunts either by immediately fleeing the hunted area, or by initially remaining before ultimately fleeing after the hunters had departed. A few hours after the hunt, all individuals were located in distant areas (> 2 kilometres) from the hunted area. Immediate flight responses were less common when drive hunts occurred in areas with dense understorey. However, neither beater/dog densities nor site familiarity influenced the immediate flight decision. Following a drive hunt, red deer remained outside the hunted areas for periods twice as long compared to periods when no hunting occurred (34 hours vs. 17 hours). Such knowledge of game movement rates in response to drive hunts may help the development of informed management policy for hunted red deer populations.
•Monitoring exploited population trends is a timely issue for sustainable management.•Some hunter associations collect routinely hunting logs of wild boar drive hunting.•A simple reproductible ...Bayesian catch-effort conceptual framework was used.•Catchability allows to link hunting components in order to assess population trends.•Our framework can be used immediately by manager to adapt their wild boar harvest.
For sustainable management of exploited populations, it is required to have good knowledge on temporal trends in population density to adapt the harvest. In this regard, hunting statistics are often collected routinely by government agencies and associations. These data are used to assess demographic trends through the development of indices, which are in turn used to manage exploited populations in a sustainable way. However, these population indices depend on features of the hunting process (e.g. hunting effort, hunting conditions, probability of catch). In this study, we show how to use hunting logs to assess demographic trends in exploited populations while accounting for the components of the hunting process. In particular, we developed a catch-effort model to study how the hunting effort leads to mortality rate – hunting pressure – within a given habitat type and during a given period. We illustrated the usefulness of this approach using exploited wild boar (Sus scrofa) populations as a case study. We used a large hunting logs dataset to perform our study, with several hundreds of thousands hunting events for more than 10 years in two French departments in France, including information about the number of hunters, of wild boars culled and the date of the hunt. We showed that catchability is a key parameter to assess hunting pressure at a given time and place. This parameter varies both within the hunting season and between habitat types. Once this variation in catchability was accounted for, our catch-effort model allowed us to obtain estimates of relative densities of wild boar populations over the study period at the management unit scale. Thus, catch-effort models are powerful tools to assess population density and to understand the underlying hunting process. Our study offers straightforward and reproducible conceptual framework that can be applied routinely by wildlife managers on exploited populations and practitioners from hunting statistics logs.
Grow fast at no cost Veylit, Lara; Sæther, Bernt-Erik; Gaillard, Jean-Michel ...
Oecologia,
04/2020, Letnik:
192, Številka:
4
Journal Article
Recenzirano
Odprti dostop
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. Identifying which factors influence age and size at maturity is crucial for a better understanding of the evolution of life-history strategies. In particular, populations intensively harvested, ...hunted or fished by humans often respond by displaying earlier age and decreased size at first reproduction. 2. Among ungulates wild boar (Sus scrofa scrofa L.) exhibit uncommon life-history traits, such as high fertility and early reproduction, which might increase the demographic impact of varying age at first reproduction. We analysed variation in female reproductive output from a 22-year long study of an intensively hunted population. We assessed how the breeding probability and the onset of oestrus responded to changes of female body mass at different ages under varying conditions of climate and food availability. 3. Wild boar females had to reach a threshold body mass (27-33 kg) before breeding for the first time. This threshold mass was relatively low (33-41% of adult body mass) compared to that reported in most other ungulates (about 80%). 4. Proportions of females breeding peaked when rainfall and temperature were low in spring and high in summer. Climatic conditions might act through the nutritional condition of females. The onset of oestrus varied a lot in relation to resources available at both current and previous years. Between none and up to 90% of females were in oestrus in November depending on the year. 5. Past and current resources accounted for equivalent amount of observed variations in proportions of females breeding. Thus, wild boar rank at an intermediate position along the capital-income continuum rather than close to the capital end where similar-sized ungulates rank. 6. Juvenile females made a major contribution to the yearly reproductive output. Comparisons among wild boar populations facing contrasted hunting pressures indicate that a high demographic contribution of juveniles is a likely consequence of a high hunting pressure rather than a species-specific life-history pattern characterizing wild boar.
Herbivorous ungulates are key species in the functioning of terrestrial ecosystems, and their recent demographic and geographic expansion in some temperate regions is likely to influence ecological ...processes, particularly if we consider plants and the frequency of mobile links among plant populations. In forests, long-distance seed dispersal essentially relies on animal movements. Owing to their ability to cover daily long distances, large herbivorous ungulates are assumed to be important vectors for long-distance seed dispersal (hundreds to thousands of metres). To quantify patterns of seed dispersal, we analysed the paths of roe deer (Capreolus capreolus), red deer (Cervus elaphus) and wild boar (Sus scrofa) which had been equipped with GPS collars. We used seed gut passage times from a recent companion paper (Picard et al., Ecology and Evolution, 2015;5:2621–2632). We combined the animal movements and seed gut passage times to estimate seed dispersal curves for herbivorous ungulates. On average, the forest ungulates might disperse consumed seeds over distances greater than 2km, during a 48-h path in the forest. Maximal dispersal distance was longer for red deer (3.5km) and wild boar (3.2km) than for roe deer (2.0km). By combining high excretion rates and long dispersal distance, wild boar appears to be potentially an efficient seed disperser. Seed dispersal by common herbivorous ungulates is likely to play a crucial role in the today's context of rapid environmental changes such as global warming and landscape fragmentation. Differences in the distribution of seed gut passage times and seasonal distances covered underline the relevance of cross comparative approaches and the complementarity of herbivorous ungulates in long-distance seed dispersal.
Pflanzenfressende Huftiere sind Schlüsselarten für das Funktionieren von terrestrischen Ökosystemen. Ihre jüngste demographische und geographische Expansion in einigen gemäßigten Regionen wird vermutlich ökologische Prozesse beeinflussen, insbesondere, wenn wir Pflanzen und die Häufigkeit von mobilen Verbindungen zwischen Pflanzenpopulationen betrachten. In Wäldern beruht die weiträumige Samenausbreitung im Wesentlichen auf den Bewegungen von Tieren. Aufgrund ihrer Fähigkeit, täglich lange Strecken zurücklegen zu können, nimmt man an, dass große Huftiere wichtige Vektoren für die Samenausbreitung über hunderte und tausende von Metern sind. Um die Muster der Samenausbreitung zu quantifizieren analysierten wir die Laufwege von Rehen (Capreolus capreolus), Hirschen (Cervus elaphus) and Wildschweinen (Sus scrofa), die mit GPS-Halsbändern ausgerüstet waren.
Wir nutzten die Darmpassagezeiten von Samen aus einer neuen Parallelstudie (Picard et al., Ecology and Evolution, 2015;5:2621–2632) und kombinierten die Bewegungen der Tiere und die Darmpassagezeiten der Samen, um Samenausbreitungskurven für die Herbivoren zu errechnen. Im Durchschnitt können die Waldhuftiere aufgenommene Samen innerhalb von 48 Stunden über Entfernungen von mehr als 2km transportieren. Die maximalen Ausbreitungsentfernungen waren für Hirsche (3.5km) und Wildscheine (3.2km) größer als für Rehe (2.0km). Indem hohe Exkretionsraten und weite Ausbreitungsentfernungen kombiniert werden, scheinen Wildschweine effektive Samenausbreiter zu sein. Die Samenausbreitung durch häufige herbivore Ungulaten spielt wahrscheinlich eine entscheidende Rolle im gegenwärtigen Kontext von schnellen Umweltveränderungen wie der globalen Erwärmung und der Landschaftsfragmentierung. Unterschiede bei den Darmpassagezeiten und saisonal unterschiedliche Wanderentfernungen unterstreichen die Wichtigkeit vergleichender Forschungsansätze und die Komplementarität der herbivoren Ungulaten.
Spatial variation of the ‘predation risk’ due to human activities or distribution may increase the sexual difference in habitat selection. Indeed, females with offspring are usually more risk adverse ...than males. Based on a long-term wild boar study, we analysed the diurnal distribution of female and male wild boar before, during and after the hunting period. Hunting, food and foliation were investigated as factors affecting patterns of forest parcel selection. As expected, dense vegetative covers were selected during resting periods, but wild boar decreased this pattern of habitat selection in response to hunting disturbance. Moreover, the habitat selection of wild boar did not fit with the variation of food availability (presence or absence of mast) and the vegetation cycle. As expected, sows responded more to the hunting disturbance than males, leading to a more pronounced sexual difference during the riskier season. The unexpected decrease of bush use may be explained either by the increased hunting effort in this habitat or by the increased movements between resting sites due to disturbance, leading to a more random habitat selection pattern. The observed difference between sexes could result from a higher response of females with offspring to hunting, leading to an increased frequentation of secondary habitats, whereas males can tolerate more risks and remain hidden in thicket plots. Our results highlight how hunting disturbance can lead game species to change their patterns of refuge habitat selection and may affect the habitat segregation between the sexes.
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.
There is a relative rarity of long‐term studies documenting lifetime body growth trajectories. Using long‐term longitudinal data on two wild boar populations subjected to contrasting environments (rich vs. poor), we demonstrate body growth trajectories in wild boar are context‐, sex‐, and cohort‐specific, differing between populations and among individuals within a population. These findings are novel as they demonstrate that it may be difficult to generalize the shape of a species’ body growth trajectory.
In stochastic environments, a change in a demographic parameter can influence the population growth rate directly or via a resulting impact on age structure. Stochastic elasticity of the long‐run ...stochastic growth rate λₛ to a demographic parameter offers a suitable way to measure the overall demographic response because it includes both the direct effect of changing the demographic parameter and its indirect effect through changes in the age structure. From 25 mammalian populations with contrasting life histories, we investigated how pace of life and population growth rate influence the demographic responses (measured as the relative contributions of the direct and indirect components of stochastic elasticity on λₛ). We found that in short‐lived species, the change in population structure resulting from an increase in yearling survival leads to an additional increase in λₛ, whereas in long‐lived species, the same change in population structure leads to a decrease. Short‐lived species thus display a boom‐bust life history strategy contrary to long‐lived species, for which the long lifespan dampens the demographic consequences of changing age structure. Irrespective of the species’ life history strategy, the change in population age structure resulting from an increase in adult survival leads to an additional increase in λₛ due to an increase of the proportion of mature individuals in the population. On the contrary, a change in population age structure resulting from an increase of reproductive performance leads to a decrease in λₛ that is due to the increase of the proportion of immature individuals in the population. Our comparative analysis of stochastic elasticity patterns in mammals shows the existence of different demographic responses to changes in age structure between short‐ and long‐lived species, which improves our understanding of population dynamics in variable environments in relation to the species‐specific pace of life.
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