Search for dissertations about: "predators"

Showing result 6 - 10 of 179 swedish dissertations containing the word predators.

2. 6. Predator induced phenotypic plasticity in a freshwater snail

   Author : Thomas Lakowitz; Biologiska institutionen; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; dispersal; Radix balthica; shell morphology; reaction norm; multiple predators; cost of plasticity; intraspecific competition; inerspecific competition;

   Abstract : In this thesis I examined a phenotypically plastic defence in a common freshwater snail, Radix balthica. Adaptive prey defences may involve behavioural, life-history or morphological changes. Snails are important species in freshwater systems. READ MORE

4. 7. Invading Herbivory. Effects of the Golden Apple Snail (Pomacea canaliculata) in Asian Wetlands

   Author : Nils Carlsson; Biologiska institutionen; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; gastropoda; invasive species; golden apple snail; herbivory; wetland functioning; biodiversity; sustainable control; indigenous predators; size-dependent competitive ability; akvatisk ekologi; limnologi; Marinbiologi; limnology; Hydrobiology; aquatic ecology; marine biology;

   Abstract : The South American golden apple snail (Pomacea canaliculata) was intentionally introduced to aquacultures in South East Asia to produce snails for human consumption, but the aquatic snails soon escaped and started to consume large amounts of rice seedlings. The aim of this thesis was to quantify the effects of this invasive herbivore on aquatic plants in natural wetlands since previous research has focused on effects of the snail in rice fields. READ MORE

5. 8. Cycles of voles, predators, and alternative prey in boreal Sweden

   Author : Birger Hörnfeldt; S. Erlinge; Umeå universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; 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; zooekologi; Animal Ecology;

   Abstract : 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. READ MORE

6. 9. Causes and consequences of niche differentiation between color morphs of pygmy grasshoppers

   Author : Einat Karpestam; Anders Forsman; Birgitta Tullberg; Linnéuniversitetet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; color polymorphism; visual predators; Tetrix subulata; differential habitat use; niche; thermoregulation; feeding preferences; stable isotopes; Evolutionary Biology; Evolutionsbiologi;

   Abstract : In this thesis, I used the color polymorphic pygmy grasshopper, Tetrix subulata, as a model system in order to investigate the degree of niche differentiation between alternative color morphs that are present within a single population. First, I hypothesized that individuals belonging to different color morphs differ in their innate food preference due to somewhat dissimilar physiology, and in their actual food consumption due in part to differential habitat use. READ MORE

7. 10. Anthropogenic impact on predator guilds and ecosystem processes : Apex predator extinctions, land use and climate change

   Author : Marianne Pasanen Mortensen; Bodil Elmhagen; Francisco Palomares; Stockholms universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Mesopredators; apex predators; top-down; bottom-up; interspecific killing; red fox; Eurasian lynx; grey wolf; wolverine; productivity; winter severity; cropland; zoologisk ekologi; Animal Ecology;

   Abstract : Humans affect ecosystems by changing species compositions, landscape and climate. This thesis aims to increase our understanding of anthropogenic effects on mesopredator abundance due to changes in apex predator status, landscape and climate. READ MORE