Modification de la structure des populations de sangliers par la chasse et influence sur les processus de reproduction

The wild boar (Sus scrofa scrofa) is a peculiar species. It is an appreciated game species for hunters, a nightmare for farmers and a subject of debate for the society in general. The tenfold increase of the population over the last decades in France and all over Europe, despite increased hunting pressure, generated great human-wildlife conflict. The wild boar is responsible for great economic losses due to vehicle collision, diseases transmission and damaged crops and ecosystems. Improving management strategies becomes a prime interest to avoid such conflicts, or at least keep them under control. Obtaining information on the species is a first step toward good management strategies. The objective of my work is, in a first part, to characterize the mating system of the wild boar and to identify some parameters, especially hunting, influencing the reproductive processes. The second part focus on the investigation of the influence of the mating system on wild boar life history traits. My researches are based on the study of several populations contrasting in their hunting practices and on longitudinal data of a highly monitored population. The study is based on data collected on wild boars killed by hunting. Genotypes were obtained for pregnant females and their litter and paternity analyses were realized to measure the number of fathers in a litter and estimate multiple paternity rates (proportion of litter sired by more than one father). I was able to show that the mating system is mainly promiscuous (several males mate with several females) contrasting with the polygyny (a dominant male monopolizing a group of females) usually described in this species. Moreover, reproductive processes, estimated by the number of mates of a female and the multiple paternity rates, are influenced by hunting variations in a population. I also showed that number of fathers has positive effect on female fecundity. High rates of multiple paternity together with high genetic diversity were found in a heavily hunted population, suggesting multiple paternity may buffer yearly bottlenecks. However, the increase of number of fathers is not associated with increase of within-litter variationLe sanglier (Sus scrofa scrofa) est une espèce à part entière. C'est une espèce de gibier particulièrement appréciée des chasseurs, un cauchemar pour les agriculteurs et un sujet de débat pour la société en général. La multiplication par dix des populations au cours des dernières décennies en France et dans toute l'Europe, malgré une pression de chasse accrue, a engendré de nombreux conflits entre les humains et la faune sauvage. Le sanglier est responsable de grandes pertes économiques dues aux collisions avec les véhicules, à la transmission de maladies et de dommages aux cultures et écosystèmes. L'amélioration des stratégies de gestion devient un intérêt majeur pour éviter, ou contrôler, de tels conflits. La récolte d'informations sur l'espèce problématique est un premier pas vers de bonnes stratégies de gestion. L'objectif de mon travail est, dans un premier temps, de caractériser le système d’appariement du sanglier et d'identifier certains paramètres influençant les processus de reproduction, notamment la chasse. Dans un deuxième temps, mon travail se concentre sur l'étude de l'influence du système d’appariement sur les traits d'histoire de vie du sanglier. Mes recherches sont basées sur l'étude de plusieurs populations contrastées dans leurs pratiques de chasse et sur des données longitudinales d'une population intensivement suivie. L'étude est basée sur des données recueillies sur des sangliers tués à la chasse. Les génotypes ont été obtenus pour les femelles gestantes et leur portée et des analyses de paternité ont été réalisées pour mesurer le nombre de pères dans une portée et estimer les taux de paternité multiples (proportion de portées engendrées par plus d'un père). J'ai été en mesure de montrer que le système d’appariement est principalement de promiscuite (plusieurs mâles s'accouplent avec plusieurs femelles) contrastant avec la polygynie (un mâle dominant monopolisant un groupe de femelles) habituellement décrite chez cette espèce. De plus, les processus de reproduction, estimés par le nombre de partenaires d'une femelle et les taux de paternité multiples, sont influencés par les variations de chasse dans une population. J'ai aussi montré que le nombre de pères avait un effet positif sur la fécondité des femelles. Des taux élevés de paternité multiple et une grande diversité génétique ont été constatés ensemble dans une population fortement chassée, ce qui suggère que la paternité multiple peut tamponner les goulots d'étranglement annuels. Cependant, l'augmentation du nombre de père n'est pas associée à une augmentation de la variation intraporté

Modification de la structure des populations de sangliers par la chasse et influence sur les processus de reproduction

The wild boar (Sus scrofa scrofa) is a peculiar species. It is an appreciated game species for hunters, a nightmare for farmers and a subject of debate for the society in general. The tenfold increase of the population over the last decades in France and all over Europe, despite increased hunting pressure, generated great human-wildlife conflict. The wild boar is responsible for great economic losses due to vehicle collision, diseases transmission and damaged crops and ecosystems. Improving management strategies becomes a prime interest to avoid such conflicts, or at least keep them under control. Obtaining information on the species is a first step toward good management strategies. The objective of my work is, in a first part, to characterize the mating system of the wild boar and to identify some parameters, especially hunting, influencing the reproductive processes. The second part focus on the investigation of the influence of the mating system on wild boar life history traits. My researches are based on the study of several populations contrasting in their hunting practices and on longitudinal data of a highly monitored population. The study is based on data collected on wild boars killed by hunting. Genotypes were obtained for pregnant females and their litter and paternity analyses were realized to measure the number of fathers in a litter and estimate multiple paternity rates (proportion of litter sired by more than one father). I was able to show that the mating system is mainly promiscuous (several males mate with several females) contrasting with the polygyny (a dominant male monopolizing a group of females) usually described in this species. Moreover, reproductive processes, estimated by the number of mates of a female and the multiple paternity rates, are influenced by hunting variations in a population. I also showed that number of fathers has positive effect on female fecundity. High rates of multiple paternity together with high genetic diversity were found in a heavily hunted population, suggesting multiple paternity may buffer yearly bottlenecks. However, the increase of number of fathers is not associated with increase of within-litter variationLe sanglier (Sus scrofa scrofa) est une espèce à part entière. C'est une espèce de gibier particulièrement appréciée des chasseurs, un cauchemar pour les agriculteurs et un sujet de débat pour la société en général. La multiplication par dix des populations au cours des dernières décennies en France et dans toute l'Europe, malgré une pression de chasse accrue, a engendré de nombreux conflits entre les humains et la faune sauvage. Le sanglier est responsable de grandes pertes économiques dues aux collisions avec les véhicules, à la transmission de maladies et de dommages aux cultures et écosystèmes. L'amélioration des stratégies de gestion devient un intérêt majeur pour éviter, ou contrôler, de tels conflits. La récolte d'informations sur l'espèce problématique est un premier pas vers de bonnes stratégies de gestion. L'objectif de mon travail est, dans un premier temps, de caractériser le système d’appariement du sanglier et d'identifier certains paramètres influençant les processus de reproduction, notamment la chasse. Dans un deuxième temps, mon travail se concentre sur l'étude de l'influence du système d’appariement sur les traits d'histoire de vie du sanglier. Mes recherches sont basées sur l'étude de plusieurs populations contrastées dans leurs pratiques de chasse et sur des données longitudinales d'une population intensivement suivie. L'étude est basée sur des données recueillies sur des sangliers tués à la chasse. Les génotypes ont été obtenus pour les femelles gestantes et leur portée et des analyses de paternité ont été réalisées pour mesurer le nombre de pères dans une portée et estimer les taux de paternité multiples (proportion de portées engendrées par plus d'un père). J'ai été en mesure de montrer que le système d’appariement est principalement de promiscuite (plusieurs mâles s'accouplent avec plusieurs femelles) contrastant avec la polygynie (un mâle dominant monopolisant un groupe de femelles) habituellement décrite chez cette espèce. De plus, les processus de reproduction, estimés par le nombre de partenaires d'une femelle et les taux de paternité multiples, sont influencés par les variations de chasse dans une population. J'ai aussi montré que le nombre de pères avait un effet positif sur la fécondité des femelles. Des taux élevés de paternité multiple et une grande diversité génétique ont été constatés ensemble dans une population fortement chassée, ce qui suggère que la paternité multiple peut tamponner les goulots d'étranglement annuels. Cependant, l'augmentation du nombre de père n'est pas associée à une augmentation de la variation intraporté

From hybridization to introgression between two closely related sympatric ant species

International audienc

Consistently high multiple paternity rates in five wild boar populations despite varying hunting pressures

International audienc

Data from: On the evolutionary consequences of increasing litter size with multiple paternity in wild boar (Sus scrofa scrofa)

Understanding how some species may be able to evolve quickly enough to deal with anthropogenic pressure is of prime interest in evolutionary biology, conservation and management. Wild boar (Sus scrofa scrofa) populations keep growing all over Europe despite increasing hunting pressure. In wild boar populations subject to male-selective harvesting, the initially described polygynous mating system may switch to a promiscuous/polyandrous one. Such a change in the mating system, where potentially more males sire a litter at one reproductive event, may be associated with the retention of high genetic diversity and an increase of litter size. We tested these hypotheses by estimating the number of sires per litter based on a 6-year long monitoring of a wild boar population subject to particularly high harvesting pressure. Our results show a high and stable genetic diversity and high rates of multiple paternity compared to other populations, thus depicting a promiscuous/polyandrous mating system in this population. We also show that litter size is positively linked to the number of sires, suggesting that multiple paternity increases fecundity. We finally discuss that multiple paternity may be one of the factors allowing rapid evolution of this population by maintaining both genetic and phenotypic diversity

Does multiple paternity explain phenotypic variation among offspring in wild boar?

During pregnancy, littermates compete to extract maternal resources from the placenta. Unequal extraction of resources leads to developmental differences among offspring and thus within-litter variation in offspring mass. Because competition among littermates can be stronger among half-sibs, multiple paternity may represent an adaptive strategy allowing females to increase within-litter phenotypic variation among offspring when facing variable environments. Wild boar (Sus scrofa) females produce large litters with diversified offspring in terms of body mass. Additionally, multiple paternities within a litter have been observed in this promiscuous species. One can hypothesize that multiple paternity represents the mechanism by which females increase within-litter phenotypic variation. Combining long-term monitoring data with paternity analyses in a wild boar population, we tested whether the increase in the number of fathers within a litter explained the increase in within-litter variation in offspring mass observed in large litters. We showed that heavy females mated earlier during the rut, produced larger litters with a higher number of fathers and more variable fetus mass than lighter females. Within-litter variation of offspring mass increased with gestation stage and litter size, suggesting differential allocation of maternal resource among offspring “in utero.” However, we found only a weak paternal effect on offspring mass and no direct effect of the number of fathers on the within-litter variation in offspring mass. These results indicate that differential maternal allocation to offspring during pregnancy is unlikely related to paternal identity in this species

Does multiple paternity explain phenotypic variation among offspring in wild boar?

During pregnancy, littermates compete to extract maternal resources from the placenta. Unequal extraction of resources leads to developmental differences among offspring and thus within-litter variation in offspring mass. Because competition among littermates can be stronger among half-sibs, multiple paternity may represent an adaptive strategy allowing females to increase within-litter phenotypic variation among offspring when facing variable environments. Wild boar (Sus scrofa) females produce large litters with diversified offspring in terms of body mass. Additionally, multiple paternities within a litter have been observed in this promiscuous species. One can hypothesize that multiple paternity represents the mechanism by which females increase within-litter phenotypic variation. Combining long-term monitoring data with paternity analyses in a wild boar population, we tested whether the increase in the number of fathers within a litter explained the increase in within-litter variation in offspring mass observed in large litters. We showed that heavy females mated earlier during the rut, produced larger litters with a higher number of fathers and more variable fetus mass than lighter females. Within-litter variation of offspring mass increased with gestation stage and litter size, suggesting differential allocation of maternal resource among offspring “in utero.” However, we found only a weak paternal effect on offspring mass and no direct effect of the number of fathers on the within-litter variation in offspring mass. These results indicate that differential maternal allocation to offspring during pregnancy is unlikely related to paternal identity in this species

Wild boar population, sex, age, weigh, litter size, maximal number of paternal allele, number of father estimated with Gerud, number of father estimated with Cervus, ID of father identified by Cervus

Wild boar population, sex, age, weigh, litter size, maximal number of paternal allele, number of father estimated with Gerud, number of father estimated with Cervus, ID of father identified by Cervu

Wild boar genotypes

Wild boar genotype