Global ETD Search

1	Reported & Reported: differences among local and international game hunting data and potential reasons on the example of South Africa Johanisová, Lucie January 2020 (has links) The South African wildlife tourism industry is based on trophy hunting and together with international wildlife trade it can represent a major treat to biodiversity conservation. Annually, thousands of hunters participate in hunting activities in South Africa and thousands of trophy items are traded across international borders. This research is a result of comprehensive quantitative analysis in how far data of trophy hunting kills and data of trophy export are consistent on the example of South Africa. Data were extracted from 2 different sources: trade data reported under the CITES Trade Database on export of trophy items from South Africa within the year 2018; South African Professional Hunting statistics (SAPHs) containing trophy kills information for each species and the country of origin of the hunter. In the year 2018, a total of 3,126 hunting trophy items of 28 endangered taxa were exported out of South Africa to 37 countries that contributed to trophy hunting trade in South Africa. However, 64 countries participated in trophy hunting of endangered taxa in South Africa and a total of 4,726 trophy kills of 28 trophy-hunted endangered taxa were reported. Therefore, the level of inconsistence in data of trophy hunting kills and data of trophy hunting export is significant and differs to varying degrees across the countries contributing to trophy hunting and CITES-listed trophy-hunted species. This research provides possible reasons for the inconsistency and propose recommendations for improving the CITES reporting system. / <p>2020-06-10</p> CITES Trade Database Trophy hunting South Africa Environmental Sciences Miljövetenskap
2	Cycles of voles, predators, and alternative prey in boreal Sweden Hörnfeldt, Birger January 1991 (has links) Bank voles, grey-sided voles, and field voles had synchronous 3-4 year density cycles with variable amplitudes which averaged about 200-fold in each species. Cycles of vole predators (red fox and Tengmalm's owl), and their (foxes') alternative prey (mountain hare and forest grouse) lagged behind the vole cycles. The nomadic Tengmalm's owl responded with a very rapid and strong numerical increase to the initial cyclic summer increase of voles (the owl’s staple food). Owl breeding densities in the springs were highly correlated with vole supply in the previous autumns. This suggested that the number of breeding owls was largely determined in the autumn at the time of the owl's nomadic migrations, and that immigration was crucial for the rapid rise in owl numbers. The owl's numerical response was reinforced by the laying of earlier and larger clutches when food was plentiful. In addition, the owl has an early maturation at one year of age. The transition between subsequent vole cycles was characterized by a distinct shift in rate of change in numbers from low to high or markedly higher values in both summer and winter. Regulation increased progressively throughout the cycle since the rate of change decreased continuously in the summers. Moreover, there was a similar decrease of the rate of change in winter. Rate of change was delayed density-dependent. The delayed density-dependence had an 8 month time-lag in the summers and a 4 month time-lag in the winters relative to the density in previous autumns and springs, respectively. These findings suggest that vole cycles are likely to be generated by a time-lag mechanism. On theoretical grounds, it has been found that a delayed density- dependence of population growth rate with a 9 month time-lag caused stable limit cycles with a period between 3 and 4 years. Some mechanisms for the delayed density-dependence are suggested and discussed. The mechanisms are assumed to be related to remaining effects of vole populations past interactions with predators, food supplies, and/or diseases. Unlike the other voles, the bank vole had regular and distinct seasonal declines in density over winter. These declines are proposed to be due to predation, mainly by Tengmalm's owl. Supranivean foraging for epiphytic tree lichens and conifer seeds most likely explains why this species was frequently taken by the owl under snow-rich conditions. The alternative prey hypothesis predicts that a reduction of predator numbers should increase the number of alternative prey. Alternative prey should be less effectively synchronized to the vole cycle by predation at declining and low vole (main prey) densities; they may also lose their 3-4 year cyclicity. The appearance of sarcoptic mange among foxes in northern Sweden in the mid 1970s provided an opportunity to "test" these ideas, and these were found to be supported. In areas with highest mange infection rates, foxes declined markedly from the late 1970s to mid 1980s, whereas hare numbers rose rapidly and appeared non-cyclic. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1991, härtill 7 uppsatser</p> / digitalisering@umu 3-4 year cycles Clethrionomys glareolus Clethrionomys rufocanus Microtus agrestis snap-trapping rate of change population regulation delayed density-dependence time-lag mechanism seasonality predation food predator avoidance foraging behaviour Aegolius funereus nest boxes numerical response nomadism Vulpes vulpes Sarcoptes scabiei vulpes Lepus timidus Francisella tularensis Tetraonidae hunting statistics
3	Pression d'herbivorie et dynamique des communautés végétales : influence à court et moyen termes des populations de cervidés sur la diversité des communautés végétales en forêt / Herbivory pressure and vegetation community dynamics : short- and mid-term impacts of deer populations on the diversity of forest vegetation communities Boulanger, Vincent 27 April 2010 (has links) Les cervidés, animaux mobiles et herbivores, peuvent influencer les distributions, assemblages et dynamiques d'espèces végétales. L'objectif de cette thèse est d'évaluer le rôle joué par les cervidés sur la composition, stratification et dynamique de la végétation forestière. Le ré-échantillonnage de relevés couplant composition et abroutissement de la flore, implantés en 1976 en Forêt d'Arc-en-Barrois (52) a permis d'identifier (i) des espèces ligneuses préférées (Cornus sp., Rosa arvensis) ou au contraire évitées par les cervidés qui sélectionnent les espèces arbustives et à bois dense et (ii) le niveau trophique et la pression d'abroutissement comme gradients structurant la végétation et déterminant les dynamiques des espèces et des communautés. Nous analysons plus précisément le rôle des cervidés dans la progression spectaculaire de Cynoglossum germanicum, espèce rare, épizoochore et toxique.A partir d'un réseau national d'enclos/exclos suivis sur 10 ans, nous montrons que les cervidés limitent la croissance des arbustes et des espèces compétitrices, ce qui profite à la richesse spécifique de la strate herbacée. La valeur écologique et patrimoniale des espèces en progression est discutée. A l'aide de données de chasse, nous tentons d'isoler les rôles des différentes espèces d'ongulés dans ces dynamiques.Ces résultats exposent la complexité et la diversité des effets des cervidés sur la végétation forestière. Enfin, ce travail met l'accent sur la nécessité des suivis temporels intégrant toutes les composantes de l'écosystème forestier pour mieux appréhender les changements en cours. / This thesis aims at assessing the impacts of deer on forest vegetation composition, stratification and dynamics.We resampled a network of relevés coupling vegetation and browsing surveys, settled in 1976 in the national forest of Arc-en-Barrois. We identified (i) ligneous species that are either preferred (Cornus sp., Rosa arvensis) or avoided by deer, which tend to select shrubs species with dense wood and (ii) trophic level and browsing pressure as gradients that determine plant communities structures and dynamics. Then, we highlight the roles of deer in the spectacular expansion of Cynoglossum germanicum, a rare, epizoochorous and toxic species. According to a national network of exclosures, monitored for over 10 years, we show that deer limit shrubs and competing species growth, which in turn benefits to the herbaceous species richness probably through an increased light availability. Ecological and patrimonial value of the benefitting species is discussed. Using hunting statistics, we try to isolate the role of the various ungulate species in these dynamics.These results provide evidence for the diversity and complexity of deer impacts on forest vegetation. Finally, we demonstrate the need for long term monitoring programs, including all the forest ecosystem components so that we could better appreciate the forces driving the current changes Forêt Végétation Herbivorie Cerf Chevreuil Ongulés Changements Communautés végétales Espèces ligneuses Étude diachronique Suivi à long terme Ré-échantillonnage Flore Gestion forestière Abroutissement Sélectivité Épizoochorie Perturbations Enclos/exclos Réseau Rénécofor Arc-en-Barrois Plan de chasse Traits de vie Valeurs indicatrices Forest Vegetation Herbivory Red deer Roe deer Ungulates Shifts Vegetation communities Woody species Diachronic study Long-term monitoring Resampling Ground ﬂora Forest management Browsing pressure Selectivity Epizoochory Disturbance Intermediate disturbance hypothesis Enclosure Network Rénécofor Arc-en-Barrois Hunting statistics Plant traits Indicator values

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