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Projecting the impact of climate change on ungulate population dynamics : the importance of trophic interactionsDavis, Miranda Lynn January 2013 (has links)
Many projections of climate change impacts on ecological communities do not consider population dynamics or trophic interactions in species responses to climate. Therefore, they do not produce the estimates of population growth needed by wildlife managers. As herbivores, roe deer (Capreolus capreolus) are clearly affected by climate and by interactions with other trophic levels. They are dependent on vegetation for food and subject to predation by multiple species. Consequently, long-term datasets on this ungulate provide the opportunity to explore the importance of trophic interactions while estimating how population dynamics respond to changing climatic conditions. I used the relationship between temporal variation in climate and an index of net primary productivity to project increases in vegetation production for three study sites under future climate scenarios. Analyses of annual variation in the survival and reproductive rates of roe deer at two sites in Sweden demonstrated the importance of indirect effects of climate via changes in vegetation, in addition to the effects of predation and harvest on roe deer demography. Roe deer population growth in response to climate change was estimated using models incorporating both vegetation changes and vital rates into mechanistic simulations. These simulations highlighted the potential for climate change to increase deer population growth and for an increase in harvest and predation to reduce that growth. However, the uncertainty surrounding each level of these analyses was high. Additionally, an investigation of the factors affecting predation of roe deer by the wolf (Canis lupus) identified additional ecological complexities and sources of uncertainty that warrant consideration. This pervasive uncertainty indicates a need for cautious interpretation of results in this thesis, but also provides insight into priorities for future research. Collectively, these analyses demonstrate the theoretical and management value of taking a holistic and demographically explicit approach to estimating species responses to climate change.
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Foot design, locomotor impact dynamics and pathology in large mammalsWarner, Sharon Elaine January 2014 (has links)
No description available.
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La chasse aux trophées : conséquences comportementales, démographiques, et évolutives chez les populations d'ongulés : l’exemple des ongulés des savanes africaines / Trophy hunting : behavioral, demographic, and evolutionary consequences in ungulate populations : the example of the ungulates of African savannahsCrosmary, William Georges 11 May 2012 (has links)
La chasse aux trophées peut contraindre les ongulés à ajuster leur comportement pourréduire le risque de mortalité. De plus, comme cette chasse est basée sur des critères detaille, et biaisée en faveur des mâles, elle peut causer des changements morphologiquesvers des individus plus petits, et altérer la structure et la dynamique des populations. Lachasse aux trophées est l’un des modes de conservation des habitats naturels. Son potentielde conservation est encore incertain parce qu’il y a peu d’études en dehors des parcsnationaux, notamment en Afrique. Cette thèse examine les effets de cette chasse sur lesongulés africains, i.e. sur leur comportement, la longueur des cornes, la proportion de mâlesadultes, la taille de groupe, et la densité des populations. J’ai travaillé à partird’observations comportementales et de données populationnelles de suivis à long terme.Pour plusieurs espèces (surtout l’impala Aepyceros melampus, le grand koudouTragelaphus strepsiceros, et l’hippotrague noir Hippotragus niger), j’ai comparé lecomportement, la structure et la densité des populations entre le Parc National de Hwangeet les zones de chasse adjacentes, Zimbabwe. Dans les zones de chasse, j’ai analysé lestendances de longueur des cornes au cours des 30 dernières années. Les ongulés venaientdavantage de nuit aux points d’eau, et étaient plus vigilants dans les zones de chasse quedans le parc national. L’amplitude de ces ajustements en revanche, était limitée par lebesoin en eau, et par le risque de prédation naturelle. La longueur des cornes a décliné, plusparticulièrement pour les espèces prisées des chasseurs et subissant une pression de chasseélevée. Il n’y avait pas de différence significative de la proportion de mâles adultes, ou dela taille de groupe, entre les populations du parc national et des zones de chasse. Au coursdes 30 dernières années, les densités de population ont globalement davantage diminuédans le parc national que dans les zones de chasse. Ceci suggère que la chasse aux trophéesn’a eu qu’un effet minime sur les densités de population par rapport à d’autres facteurscomme les précipitations, ou possiblement la prédation naturelle et l’éléphant. Malgré lesajustements comportementaux, le déclin de la longueur des cornes, et le prélèvement biaiséen faveur des mâles adultes, les densités d’ongulés étaient aussi élevées dans les zones dechasse que dans le Parc National de Hwange. Cette étude illustre comment les zones dechasse aux trophées, lorsque rigoureusement gérées, peuvent jouer un rôle dans laconservation des ongulés africains. / Like predation, trophy hunting may constrain ungulates to adjust their behaviour todecrease mortality risk. Moreover, because this removal is size selective and male-biased, itmay induce morphological changes towards individuals with smaller traits, alter populationstructure and dynamics. Trophy hunting is one of the conservation modes of naturalhabitats, particularly in Africa. However, its conservation potential is still unclear becausethere are few studies outside National Parks. This thesis aimed to investigate the subtleeffects of trophy hunting on African ungulates, i.e. on their behaviour, horn length ofharvested males, proportion of adult males, group size, and population densities. I workedfrom behavioural observations, and from population data of long-term surveys. For severalspecies (mainly impala Aepyceros melampus, greater kudu Tragelaphus strepsiceros, andsable antelope Hippotragus niger), I compared behaviour, population structure, anddensities between Hwange National Park and adjacent hunting areas, Zimbabwe. In huntingareas, I analysed trends in horn length of harvested males over the past 30 years. This thesisshows that ungulates drank more often at night, and were more vigilant in hunting areasthan in the national park. However, the amplitude of these adjustments was constrained bythe need of surface water, and by natural predation risk. Trophy hunting caused a decline inhorn length, particularly for species that experienced high hunting pressure and were ofhigh value for hunters. Trophy hunting tended to decrease proportion of adult males,though not significantly, and did not affect group size. Moreover, during the last 30 years,ungulate densities generally declined more in the national park than in neighbouringhunting areas. This suggests that trophy hunting played a minor role on densities comparedto other factors, i.e. rainfall, and possibly natural predation and elephant densities. Despitebehavioural adjustments induced by hunting risk, decline of horn length, and harvestskewed towards adult males, ungulate densities in hunting areas adjacent to HwangeNational Park remained comparable to densities within the national park. This studyillustrates how trophy hunting areas, when rigorously managed, may play a significant rolein the conservation of ungulates in Africa.
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