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1

Fluorescent powder as dye in bait for studying foraging areas in small mammals

100%
Hovland N., Andreassen H. P.
Acta Theriologica
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1995
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tom 40
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nr 3
We examined the characteristics of fluorescent powder as dye in bait for the purpose of studying individual foraging areas of the root vole Microtus oeconomus (Pallas, 1776). Colours were visible in the faeces 2-3 h after consumption, and were still evident 36-48 h after the removal of bait. It was possible to distinguish up to four different colours in faeces from one individual if the appropriate combination of coloured powder was used. The method is a better alternative to other markers commonly used in bait because only a small extra sampling effort is needed during trapping, and the observation of colours is relatively easy in UV-light. Because the persistance of the colour powder in the animal is relatively short, the method facilitates studies of short-term changes in foraging areas.
2

Density-dependent variation in body mass of voles

100%
Johannesen E., Andreassen H. P.
Acta Theriologica
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2008
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tom 53
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nr 2
We studied inter-annual, spatial and sexual variation in the body mass of bank volesMyodes glareolus Schreber, 1780 and grey-sided volesMyodes rufocanus Sundevall, 1846 using live trappings from two grids on the southand north-facing slopes of a mountain valley in Southern Norway. Variation in spring density of the four populations was consistent with cyclic dynamics (n=7,s-values >0.5). Individuals caught on the south-facing slope were larger than those caught on the north-facing slope. Reproductively mature bank vole males were smaller than females, whereas reproductively mature grey-sided vole males were larger than females. Body mass was related to density in both species. In bank voles, we found a direct positive density dependence caused by a higher rate of survival at higher densities resulting from individual allocation of resources from reproduction to survival and growth. In grey-sided voles, we found a negative delayed density dependence resulting from grazing on preferred plants that determined the resource available for individual vole growth the following year.
3

Spatial organization in a small population of the root vole Microtus oeconomus in a linear habitat

81%
Fauske J., Andreassen H. P., Ims R. A.
Acta Theriologica
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1997
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tom 42
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nr 1
We studied demography and spatial organization in a population of root voles Microtus oeconomus (Pallas, 1776) inhabiting a fenced, linear habitat (560 x 1.5 m) during the breeding season, using live trapping and radiotelemetry. There were no establishments of new reproductive individuals. Compared to root voles in non-linear habitats, home ranges were extremely small and no male home ranges overlapped. A short term removal and reintroduction experiment (2 days removal of every second individual on the study area) produced no changes in home range size, indicating that home range borders were not defended by daily contact between neighbours.
4

Intersexual attraction in natal dispersing root voles Microtus oeconomus

71%
Gundersen G., Moe J. A., Andreassen H. P., Carlsen R. G., Gundersen H.
Acta Theriologica
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1999
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tom 44
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nr 3
By an enclosure experiment we tested whether natal dispersing root voles Microtus oeconomus (Pallas, 1776) were prevented from colonising already occupied habitat patches or if they were attracted to habitat patches by potential mates. The treatment consisted of manipulating the presence of animals in immigration patches, either with the presence of a solitary sexually mature male or female, whereas empty patches were used as a control. Immigration patches were separated from a patch used for release of a matriline (mother with her newly weaned titter) by a semipermeable fence allowing only interpatch movements of young animals. We predicted that either a social fence would prevent immigration to treatment patches, or that potential mates would attract dispersing individuals. In particular we expected fewer dispersing males to colonise male occupied patches, and fewer dispersing females to colonise female occupied patches due to intrasexual competition, ie an intrasexual social fence. We found that a higher proportion of females settled in male treatment patches than in female patches, whereas male dispersal was unaffected by treatment. Thus, the observed female immigration pattern appeared to be an attraction to patches occupied by the opposite sex We found no sign that immigration was prevented by a social fence.
5

Visual cues as determinants of perceptual range in root voles Microtus oeconomus

71%
Andreassen H. P., Bjornbom E., Carlsen R. G., Gundersen G., Gundersen H.
Acta Theriologica
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1998
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tom 43
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nr 4
We tested whether the perceptual range of male root voles Microtus oeconomus (Pallas, 1776) could be determined by visual objects in the landscape. This was done by giving single mates the choice between three different sized visual cardboard patches randomly arranged around the perimeter of a circle located in agricultural fields. Effects of distance were tested by varying the diameter of the circle. The root voles were able to orient towards patches, but did not choose patches relative to their size. The ability to orient towards patches decreased with increasing distance between the release point and the patches.
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