The influence of landscape structure on female roe deer home-range size

10 pagesInternational audienceAnimal distribution and abundance are greatly affected by the availability of their food resources, which also depends on landscape structure. Lothar hurricane in 1999 had profoundly modified the structure of the forests in France, affecting the habitat quality of ungulates. We tested whether the variations in home-range size of 23 female roe deer were influenced by the fragmentation of the landscape caused by Lothar in the Chize´ forest, namely by the increase in heterogeneity associated with the localized massive tree felling. Home-range size was studied in the summers of 2001 and 2002 and we found that variation in home-range size was mainly explained by only one landscape variable: edge density. Home-range size decreased as edge density increased, which is consistent with the fact that edges are good browsing habitats for roe deer. The result of this study suggests that, after 2 years, the hurricane had improved the quality of the home ranges by creating more forest heterogeneity and increasing the contacts between the different vegetation patches within the home range. These results highlight the fact that spatial heterogeneity is likely to be a key factor influencing the distribution and local population density

Estimating population size of migrating adults of salmonids : a unifying approach

International audienc

SIZE DIFFERENCE IN WHOOPING CRANES REARED FOR TWO REINTRODUCTION METHODS

We investigated a possible size difference in whooping cranes (Grus americana) captive-reared for 2 reintroduction methods to establish a migratory population in eastern North America. Cranes reared for ultralight aircraft-led migration (UL) to Florida were significantly larger than cranes reared for direct autumn release (DAR) on the natal area in central Wisconsin. Mean tarsal length was 315.5 ± 0.98 (1 SE) and 308.1 ± 1.87 mm, respectively, for UL and DAR males and 296.9 ± 1.03 and 290.8 ± 2.60 mm, respectively, for UL and DAR females. Because of the different rearing schedules, eggs for the DAR method were generally laid later than eggs for UL. Eggs later in the laying sequence had lower weights and resulted in smaller birds, although this overall effect was small. Size difference did not appear related to genetic factors. Although survival to 5 years after release was not significantly related to size within groups of the same sex and release method, captive-rearing effects such as size on survival and behavior of released birds should be considered in assessment of reintroduction programs

Dynamique d'une population chassée de sangliers (Sus scrofa scrofa) en milieu forestier

Au sein des Ongulés sauvages, le Sanglier (Sus scrofa scrofa) se distingue par une combinaison bien particulière de traits d histoire de vie associant une fécondité élevée et un âge de première reproduction précoce à, une grande taille et une forte espérance de vie potentielle. De plus, au contraire de la plupart des autres ongulés qui sont des herbivores assez stricts, le Sanglier est omnivore. Cette stratégie d histoire de vie peu commune est associée à un fort succès en terme d effectifs, puisqu en Europe, les populations de Sanglier sont en pleine expansion et sont à l origine de problèmes socio-e conomiques principalement en raison des dégâts occasionnés aux activités humaines. Il est donc indispensable de déterminer les facteurs explicatifs de cette augmentation des effectifs et de développer un modèle de fonctionnement de populations pour réussir à mieux gérer la situation. Ce travail s appuie sur une étude à long terme (25 ans) d une population chassée de l Est de la France (Haute-Marne). L analyse de l allocation maternelle dans la reproduction met en évidence que la sexe ratio in utero varie en fonction de la taille de la portée avec : une sexe ratio biaisée envers les mâles pour les portées de taille inférieure ou égale à six et une sexe ratio biaisée envers les femelles pour les portées de plus de six fœtus. Ce patron de variation peu commun pourrait avoir évolué sous la pression de sélection contre les grandes tailles de portée au sein desquelles une trop forte compétition apparaît entre frères et sœurs et ce, afin de maximiser le nombre de jeunes recrutés. Le poids seuil pour que les femelles puissent se reproduire est d environ 28 kg (poids vif) et une fois la maturité sexuelle acquise, ces femelles sont susceptibles de se reproduire chaque année. Les ressources disponibles influencent cependant la phénologie de la reproduction qui varie d une année à l autre. La mortalité naturelle a pu être différenciée de celle due à la chasse grâce à l emploi des modèles récemment développés de Capture-Recapture Multi-Etats. Les mâles ont une survie constante au cours du temps mais différente selon leur âge et une probabilité d être tués à la chasse qui augmente avec l âge jusqu à atteindre près de 70%. La survie des femelles varient plus fortement entre années et diffère aussi selon l âge avec, des femelles de moins de un an qui ont un taux de survie annuel inférieur aux femelles les plus âgées. Relativement aux autres grands mammifères, la survie des femelles adultes est plus faible et plus variable au cours du temps, peut-être en réponse à un investissement plus fort dans la reproduction, en particulier pour les jeunes adultes. Ces spécificités démographiques démontrent que le Sanglier ne peut donc être soumis aux mêmes règles de gestion que les autres Ongulés. Nous avons développé un modèle de gestion de population structuré en classe de sexe et de poids afin que les gestionnaires puissent comparer les résultats du modèle avec la distribution observée dans le tableau de chasse et apprécier ainsi l efficacité des modalités de gestion qu ils appliquentAmong Ungulates, the wild boar (Sus scrofa scrofa) is characterised by a mixture of particular life history traits which associate a high fecundity and an early age at first reproduction with a large body size and a potential long life expectancy. Moreover, unlike most ungulates which are rather strict herbivores, the wild boar is an omnivore. This uncommon life-history strategy is associated with an increase in population size. Indeed, in Europe, wild boar populations are currently still growing and cause some socio-economical problems due to the damage that wild boars generate to the human activities. Hence the understanding of the factors primarily involved in this increase in population size as well as the modelling of population dynamics is now essential to better manage wild boar populations. This work rely on a long term data set (25 years) of a hunted wild boar population in the eastern part of France (Haute-Marne). The analyses of maternal allocation in reproduction highlighted that in utero, the sex ratio decreased as litter size increased. Sex ratio was male-biased for litter size up to 6 and then became female-biased in larger litters. Producing large female-biased litters may be an adaptive adjustment to avoid strong sibling competition during lactation and therefore to maximise the number of recruited offspring. The threshold weight above which females can reproduce is around 28 kg live weight but once females become sexually mature, they will reproduce every year. However, the onset of oestrus may be delayed according to the available resources and vary year-to-year. Natural mortality was disentangled from hunting mortality by using Capture-Recapture multi-states models. Males survival did not vary yearly but did vary with age-classes and the probability to be hunted increased with age up to around 70%. Females survival did vary yearly and also differed between age-classes with the yearly survival probability of females younger than one-year old being smaller than that of older females. Compared to other large mammals, adult females survival was lower and more variable over time possibly because of higher reproductive investment, especially in young adults. Those demographic characteristics reveal that wild boars could not be managed like other ungulate species. So, we developed a new modelling approach and retained a sex-specific body mass-dependent model to assist managers. In this way, managers have the possibility to directly test the outcome of the model by comparing observed and expected distributions of wild boars killed by hunters among sex- and body mass-specific classes. They can assess the performance of a given hunting rule and simulate the respective efficiency of management scenariosLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Supplement 1. JAGS code for fitting the state-space implementation of a multi-state mark–recapture model and calculating demographic estimates.

<h2>File List</h2><div> <p><a href="JAGS-code.txt">JAGS-code.txt</a> (MD5: a5de8f40e6a2872bd83bba1baec10619) </p> </div><h2>Description</h2><div> <p>JAGS-code.txt enables to fit the state-space implementation of a multi-state mark–recapture model and get demographic estimates. </p> </div

Appendix A. Supplementary results tables for demographic estimation in the Whooping Crane eastern migratory population.

Supplementary results tables for demographic estimation in the Whooping Crane eastern migratory population

Data from: High hunting pressure selects for earlier birth date: wild boar as a case study

Exploitation by humans affects the size and structure of populations. This has evolutionary and demographic consequences that have typically being studied independent of one another. We here applied a framework recently developed applying quantitative tools from population ecology and selection gradient analysis to quantify the selection on a quantitative trait - birth date - through its association with multiple fitness components. From the long-term monitoring (22 years) of a wild boar (Sus scrofa scrofa) population subject to markedly increasing hunting pressure, we found that birth dates have advanced by up to 12 days throughout the study period. During the period of low hunting pressure, there was no detectable selection. However, during the period of high hunting pressure, the selection gradient linking breeding probability in the first year of life to birth date was negative, supporting current life history theory predicting selection for early births to reproduce within the first year of life with increasing adult mortality