Öst, M. & Kilpi, M. 1999: Parental care influences the feeding behaviour of female eiders Somateria mollissima. — Ann. Zool. Fennici 36: 195–204.
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Tolonen, A., Kjellman, J. & Lappalainen, J. 1999: Diet overlap between burbot (Lota lota (L.)) and whitefish (Coregonus lavaretus (L.)) in a subarctic lake. — Ann. Zool. Fennici 36: 205–214.
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Johannesen, E. & Mauritzen, M. 1999: Habitat selection of grey-sided voles and bank voles in two subalpine populations in southern Norway. — Ann. Zool. Fennici 36: 215–222.
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Basquill, S. & Bondrup-Nielsen S. 1999: Meadow voles (Microtus pennsylvanicus) in farm landscapes, I. Population parameters in different habitats. — Ann. Zool. Fennici 36: 223–230.
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Basquill, S. & Bondrup-Nielsen S. 1999: Meadow voles (Microtus pennsylvanicus) in farm landscapes, II. Movements among habitats. — Ann. Zool. Fennici 36: 231–238.
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Chaline, J., Brunet-Lecomte, P., Montuire, S., Viriot, L. & Courant, F. 1999: Anatomy of the arvicoline radiation (Rodentia): palaeogeographical, palaeoecological history and evolutionary data. — Ann. Zool. Fennici 36: 239–267.
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Öst, M. & Kilpi, M. 1999: Parental care influences the feeding behaviour of female eiders Somateria mollissima. — Ann. Zool. Fennici 36: 195–204.
We compared the feeding behaviour of lone tenders, multi-female tenders and postbreeding, non-tending eider females Somateria mollissima in the northern Baltic. Few prey species are available for eiders in the Baltic; in the non-breeding season adults prefer blue mussels Mytilus edulis, whereas small ducklings feed primarily on gammarids Gammarus spp. Infections by the acanthocephalan parasite Polymorphus minutus occur when eiders feed on gammarids and this infection may be fatal if the host's resistance is low. The mussel beds and areas with gammarids are close together but do not overlap. Assuming that females always should prefer blue mussels to gammarids we tested the following predictions: (i) non-tending females should exclusively feed on mussels, (ii) lone tenders may be forced to feed like their young, and (iii) multi-female tenders may occasionally utilise mussels, thereby mitigating constraints associated with consumption of unprofitable gammarid prey. Tending females foraged like their young, whereas non-tending females fed on mussels throughout the brood-rearing season. Individually marked females fed on mussels immediately after losing their brood, suggesting that a conflict between female and duckling feeding needs exists during early brood-rearing. However, later in the season all females and young fed on mussels. Multi-female tenders achieved no obvious foraging benefits compared to lone tenders, indicating that crèching in eiders may have primarily evolved for other reasons.
Tolonen, A., Kjellman, J. & Lappalainen, J. 1999: Diet overlap between burbot (Lota lota (L.)) and whitefish (Coregonus lavaretus (L.)) in a subarctic lake. — Ann. Zool. Fennici 36: 205–214.
The growth of burbot in ultraoligotrophic Kilpisjärvi, a lake in northern Finland, is slow. The mean lengths of age-5 and age-9 burbot were 198 mm and 217 mm, respectively. Stomach contents of 45 burbot (144–274 mm) and 331 whitefish (117–345 mm) were analysed to determine any possible diet overlap between the studied species. According to logistic regressions, the main diet of burbot longer than 257 mm was fish, whereas the smallest burbot (< 165 mm) ingested mainly insect larvae. The length-dependent probabilities of burbot ingesting certain food items did not differ between the ice-covered and open-water periods. During the ice-covered period burbot preferentially preyed on molluscs, insect larvae and benthic crustaceans, while most whitefish smaller than 274 mm ingested zooplankton. During the open-water period, more than 50% of whitefish smaller than 191 mm ingested zooplankton, while those in the length interval 127–244 mm preferred benthic crustaceans. The largest whitefish (> 294 mm) ingested insect larvae during the ice-covered period and insect pupae during the open-water period. Independently of season, most large whitefish (> 274 mm) ingested molluscs. The diet overlap between burbot and whitefish was thus highest during the ice-covered period.
Johannesen, E. & Mauritzen, M. 1999: Habitat selection of grey-sided voles and bank voles in two subalpine populations in southern Norway. — Ann. Zool. Fennici 36: 215–222.
Bank voles and grey-sided voles occur in sympatry in large parts of boreal and subalpine Fennoscandia. The bank vole has been studied throughout its range, whereas the grey-sided vole has primarily been studied in northern Fennoscandia. We compared habitat selection of grey-sided and bank voles close to the southern edge of the grey-sided vole’s range. Voles were live trapped in the summers of 1995 and 1996 in two plots located in boulder fields in birch forest. We used Principal Component Analysis based on six habitat variables to describe the habitat in the plots. In general, the grey-sided voles preferred areas with boulders and Vaccinium spp., whereas the bank voles avoided such areas, being found in association with herbs and grass. When the grey-side voles decreased and bank voles increased in abundance, bank voles used the habitat more according to the habitat availability within the plots, which suggests that competition affected habitat selection.
Basquill, S. & Bondrup-Nielsen S. 1999: Meadow voles (Microtus pennsylvanicus) in farm landscapes, I. Population parameters in different habitats. — Ann. Zool. Fennici 36: 223–230.
Two microlandscapes were constructed for use in a live trapping study, designed to investigate how meadow vole populations are affected by habitat. Each microlandscape (105 x 35 m) consisted of barley and forage crops (white clover, alfalfa, Canada bluegrass and Kentucy bluegrass), separated by a center plot of undisturbed meadow. Differences in population parameters among habitats were used as indices of habitat suitability. Population parameters were found to differ among habitats; population density, population growth rate, and recruitment showed the greatest variations. Meadow was the highest quality habitat, forage crop was second highest in quality and barley was a low quality habitat. With intensive farming practices, an undisturbed meadow habitat is often rare and highly fragmented. Although forage crops may be common, these habitats are harvested, and are thus only suitable as vole habitats in early summer and late autumn. Persistence of vole populations in farm landscapes hinges on voles not being prevented from disperse among suitable habitats by agricultural crops and tilling practices.
Basquill, S. & Bondrup-Nielsen S. 1999: Meadow voles (Microtus pennsylvanicus) in farm landscapes, II. Movements among habitats. — Ann. Zool. Fennici 36: 231–238.
Two microlandscapes were constructed for use in a live trapping study designed to investigate how meadow vole movement behaviour is affected by landscape structure. Each experimental system was composed of both barley and forage habitats separated by a central habitat of old-field successional meadow. Vole movement patterns in the landscapes were related to differences in the quality and boundary characteristics of each habitat. Habitat quality was shown to be an important determinant of both within- and between-habitat vole movement dynamics. Meadow voles preferred moving within habitats of higher quality and perceived boundaries between habitats of more similar quality as more permeable. Boundaries were in general avoided, thus affecting the voles' spatial distribution. Meadow voles functioning in farm mosaics will be limited in their ability to fulfill their resource needs by the presence of low quality habitats and by increase in the numbers of distinct boundaries.
Chaline, J., Brunet-Lecomte, P., Montuire, S., Viriot, L. & Courant, F. 1999: Anatomy of the arvicoline radiation (Rodentia): palaeogeographical, palaeoecological history and evolutionary data. — Ann. Zool. Fennici 36: 239–267.
Voles and lemmings (Arvicolinae subfamily) diversified throughout the northern hemisphere over five million years into 140 lineages. Attempts have been made to identify relationships within the Arvicolinae on the basis of biochemical, chromosomal and morphological characteristics as well as on the basis of palaeontological data. Arvicolines are thought to have originated from among the Cricetidae, and the history of voles can be divided into two successive chronological phases occurring in Palaearctic and Nearctic areas. The history of lemmings is not well documented in the fossil record and their Early Pleistocene ancestors are still unknown. The arvicoline dispersal is one of the best known and provides an opportunity to test the anatomy of the radiation and more particularly the punctuated equilibrium model. Study of arvicolines reveals three modes of evolution: stasis, phenotypic plasticity and phyletic gradualism. Clearly the punctuated equilibrium model needs to be supplemented by a further component covering disequilibrium in phenotypic plasticity and phyletic gradualism, suggesting a punctuated equilibrium/disequilibrium model. In terms of palaeogeography, study of arvicolines shows that Quaternary climatic fluctuations led to long-range faunal migrations (3000 km) and study of these patterns is a significant factor in mapping past environments and climates. Some studies attest to the prevailing influence of ecological and ethological factors on skull morphology in arvicoline rodents sometimes inducing morphological convergences.