Browsing by Subject "habitat selection"

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  • Byholm, Patrik; Burgas, Daniel; Virtanen, Tarmo; Valkama, Jari (2012)
  • Aben, J.; Adriaensen, F.; Thijs, K. W.; Pellikka, P.; Siljander, M.; Lens, L.; Matthysen, E. (2012)
  • Riipinen, Katariina; Mikkola, Salla; Ahola, Milla K.; Aalto, Milla M.; Olkinuora, Alisa; Vesakoski, Outi (2017)
    Information on the habitat selection by non-indigenous species is crucial for understanding their effects on the communities to which they are introduced, since the effects are often focused on the invaded habitats. The North American mud crab Rhithropanopeus harrisii is a new invader in the northern Baltic Sea, on the coasts of Finland and Estonia. In the Finnish Archipelago Sea, it has been found in two very distinct habitats: reed belts of Phragmites australis and algal zones with Fucus vesiculosus as the main habitat-forming species. In previous studies in the Baltic Sea, R. harrisii has preferred F. vesiculosus and has locally driven a shift in the structure of F. vesiculosus-associated invertebrate communities. Here, we disentangled whether habitat choice was determined by habitat structure or the availability of food. First, we conducted a habitat selection experiment with P. australis and F. vesiculosus habitats and varying food availability, and found that R. harrisii preferred F. vesiculosus, with food having no effect on the habitat choice. Second, we studied if the preference for F. vesiculosus was due to the alga itself or the rocks it grows on. We found that R. harrisii preferred the shelter of the rock habitat, indicating that R. harrisii choose their habitat based on habitat structure rather than food availability in the habitat. However, the preference for sheltered rocky bottom habitats also exposes the associated F. vesiculosus communities to the impacts of R. harrisii through predation.
  • Nikula, Ari; Nivala, Vesa; Matala, Juho; Heliövaara, Kari Tapani (2019)
    We modelled the effect of habitat composition and roads on the number and occurrence of moose (Alces alces L.) damage in Ostrobothnia and Lapland using a zero-inflated count model. Models were developed for 1 km(2), 25 km(2) and 100 km(2) landscapes consisting of equilateral rectangular grid cells. Count models predict the number of damage, i.e. the number of plantations and zero models the probability of a landscape being without damage for a given habitat composition. The number of moose damage in neighboring grid cells was a significant predictor in all models. The proportion of mature forest was the most frequent significant variable, and an increasing admixture of mature forests among plantations increased the number and occurrence of damage. The amount of all types of plantations was the second most common significant variable predicting increasing damage along with increasing amount of plantations. An increase in thinning forests as an admixture also increased damage in 1 km(2) landscapes in both areas, whereas an increase in pine-dominated thinning forests in Lapland reduced the number of damage in 25 km(2) landscapes. An increasing amount of inhabited areas in Ostrobothnia and the length of connecting roads in Lapland reduced the number of damage in 1 and 25 km(2) landscapes. Differences in model variables between areas suggest that models of moose damage risk should be adjusted according to characteristics that are specific to the study area.
  • Lehikoinen, Aleksi; Virkkala, Raimo (2016)
    There is increasing evidence that climate change shifts species distributions towards poles and mountain tops. However, most studies are based on presence-absence data, and either abundance or the observation effort has rarely been measured. In addition, hardly any studies have investigated the direction of shifts and factors affecting them. Here, we show using count data on a 1000km south-north gradient in Finland, that between 1970-1989 and 2000-2012, 128 bird species shifted their densities, on average, 37km towards the north north-east. The species-specific directions of the shifts in density were significantly explained by migration behaviour and habitat type. Although the temperatures have also moved on average towards the north north-east (186km), the species-specific directions of the shifts in density and temperature did not correlate due to high variation in density shifts. Findings highlight that climate change is unlikely the only driver of the direction of species density shifts, but species-specific characteristics and human land-use practices are also influencing the direction. Furthermore, the alarming results show that former climatic conditions in the north-west corner of Finland have already moved out of the country. This highlights the need for an international approach in research and conservation actions to mitigate the impacts of climate change.
  • Huusko, Jari (Helsingfors universitet, 2012)
    The non-lethal effects of predation, i.e. predation risk, can significantly affect the prey population by inducing changes in behavior to reduce the risk of predation. Vigilance, hiding, and fleeing are common responses in order to lower predation risk while changes in habitat selection, habitat use, and changes in activity patterns are more severe changes and can profoundly affect prey fitness. Prey may begin to avoid habitats frequented by predators and may begin to reduce their activity during the time of day when predators are active. Human disturbance can be comparable to predation risk as it may induce similar changes in behavior. Therefore, human activity can be compared to predation risk even though the risk posed by humans may rarely be lethal. For many large vertebrates, however, humans do pose a direct and lethal threat. This is especially true for large predators whose severe decline has been attributed to centuries of persecution and habitat loss and whose populations have only recently began to increase following more favourable management plans and conservation efforts. Similarly, brown bear (Ursus arctos) populations have only recently began to increase in many parts of Europe and North America. In Finland brown bears survived extinction only in the wilderness areas in the north and in the east but have recolonized much of the country in the past decades. These solitary, opportunistic omnivores prefer forested habitats and usually try to avoid humans who they may view as predators. The limited availability of ideal habitats and extensive human activity means that bears may have to use spatio-temporal avoidance of humans rather than large scale spatial avoidance in order to reduce the risk of encountering humans. This should be evident in bear daybed selection whereby bears should select daybed sites away from human activity and select sites that provide good cover against humans while the bear rests during the day i.e. peak period of human activity. Additionally the daybed concealment should be higher closer to human activity. I studied bear daybed selection using GPS location data from collared bears from Central Finland and North Karelia regions and identifying possible daybed sites. Habitat of the daybeds was studied both by visiting daybeds in the field to assess the tree height, tree species composition, and concealment (visibility and canopy cover) and by using GIS software to identify large scale habitat preference. Effects of human activity (house, small roads, large roads) were studied by comparing the concealment of the daybed to a nearby random site and by comparing the bears' early morning locations' distance to human activity with subsequent daybed locations. Further tests were performed to test if season, bear sex, or the study area affected bear daybed selection. The results indicate that bears strongly preferred forested habitats in daybed selection and preferred mixed forests and woodland shrub habitat over the dominant coniferous forests possibly due to their higher proportion and availability of spruce (Picea abies) and deciduous trees (e.g. Betula spp. and Populus tremula) that can offer better cover than pine (Pinus sylvestris) which is dominant in coniferous forests. Mixed forests and woodland shrub may also be preferred as they provide bears with more nutritious vegetation as a food source. Both males and females preferred sites with shorter trees for better concealment while females with cubs preferred sites with taller trees with less concealment. Thus females with cubs may have to trade high concealment for better escape chances for the cubs to avoid potentially infanticidal males. Human activity was shown to affect daybed selection as daybed sites were more concealed than nearby random sites and bears were also closer to human activity during early morning but selected their daybeds farther away. Daybeds were considerably farther away from houses and large roads than from small roads which were often scarcely used forestry roads. Concealment did not change with distance to human activity indicating that bears may not be able to avoid human activity at a large spatial scale even in areas of low human population density. Due to low sample sizes and individual bias the results of this study should be considered more indicative than of high probability. Nevertheless they provide largely new information on bear daybed selection that may be of public interest in reducing human bear conflicts and of use in bear conservation and management.