Agrell, J., Erlinge, S., Nelson, J. & Sandell, M. 1996: Shifting spacing behaviour of male field voles (Microtus agrestis) over the reproductive season. — Ann. Zool. Fennici 33: 243–248
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Bergeron, J.-M. 1996: Chemical constituents of vole feces as indicators of bark use in sapling plantations. — Ann. Zool. Fennici 33: 249–257.
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Bergeron, J.-M. 1996: The use of seedling bark by voles sustained by high proteinic content of food. — Ann. Zool. Fennici 33: 259–266.
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Cavallini, P. & Santini, S. 1996: Reproduction of the red fox Vulpes vulpes in Central Italy. — Ann. Zool. Fennici 33: 267–274.
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Kaitala, V., Ranta, E. & Lindström, J. 1996: External perturbations and cyclic dynamics in stable populations. — Ann. Zool. Fennici 33: 275–282.
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Kauhala, K. 1996: Distributional history of the American mink (Mustela vison) in Finland with special reference to the trends in otter (Lutra lutra) populations. — Ann. Zool. Fennici 33: 283–291.
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Koivunen, V., Korpimäki, E. & Hakkarainen, H. 1996: Differential avian predation on sex and size classes of small mammals: doomed surplus or dominant individuals? — Ann. Zool. Fennici 33: 293–301.
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ERRATA: Spence, J. R., Langor, D. W., Niemelä, J., Cárcamo, H. A. & Currie, C. R.: Northern forestry and carabids: the case for concern about old-growth species. — Ann. Zool. Fennici 33: 302.
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Agrell, J., Erlinge, S., Nelson, J. & Sandell, M. 1996: Shifting spacing behaviour of male field voles (Microtus agrestis) over the reproductive season. — Ann. Zool. Fennici 33: 243–248
Spacing behaviour of male field voles was studied by radio-telemetry during spring and autumn. Spacing patterns were different during the two periods with great overlap between ranges in spring, and exclusive ranges during autumn. Regarding movement activity males were stationary and made regular excursions in the surroundings during spring, whereas they continuously moved around in their exclusive ranges during autumn. Contradictory to the theoretical models on male spacing behaviour, the shift in male spacing behaviour could neither be attributed to distribution of females nor to female reproductive synchrony. Instead female density seemed to be the most influential factor, although sex ratio, dominance relations and predation may also be important.
Bergeron, J.-M. 1996: Chemical constituents of vole feces as indicators of bark use in sapling plantations. — Ann. Zool. Fennici 33: 249–257.
Population density of meadow voles (Microtus pennsylvanicus ) and amount of bark removal of conifer and deciduous seedlings were estimated in a young meadow and in an old-field community used as tree plantations. Vole feces were sampled to assess the changes in neutral detergent solubles, total phenolics, total non-structural carbohydrates, and protein from fecal matter. In 1992, voles reached peak densities with similar population characteristics in both meadows. This was followed in the spring 1993 by bark removal on deciduous seedlings in the young meadow and on wild shrubs (not spruce trees) in the old-field community. Chemical components measured in the fall 1992 feces contained significantly more phenolics and carbohydrates than fall samples collected the year after peak density. Fecal matter from voles trapped in the young meadow in the spring of 1993 contained high levels of phenolics and carbohydrates after the winter use of bark tissues. Chemical analyses of fecal matter may be useful in predicting the nutritional status of voles in tree plantations before bark removal, and might be developed as a tool to aid in management of rodent populations.
Bergeron, J.-M. 1996: The use of seedling bark by voles sustained by high proteinic content of food. — Ann. Zool. Fennici 33: 259–266.
Meadow voles (M. pennsylvanicus) are known to select herbaceous plants with high protein contents and low phenolic values. However, they eat the bark of coniferous and deciduous seedlings with low dosages of protein and high phenolic contents. We tested the hypothesis that voles can use bark of red oak seedlings (Q. rubra) when their regular diet contains high proteinic components (> 8% dry matter). Three groups of 10 non reproducing female meadow voles were maintained on 15%, 8%, and 4% protein diets supplemented with red oak seedlings during two weeks. Variations in body mass, total food intake, ingestion of bark and the assigned diets, chemical constituents of fecal matter, protein digestibility, and phenolic recovery rates in fecal matter were compared between the experimental groups. Animals of all groups used extensively the bark of red oak seedlings. Ingestion of bark tissues explained 46% and 20% of the body mass variation of voles maintained on the 15% and 4% protein diets, respectively. Fecal matter yielded significantly higher contents of phenolics and total nonstructural carbohydrates and lower dosages of protein for voles maintained on the 4% proteinic diet. The opposite was true for animals maintained on the 15% proteinic diet. Protein digestibility was similar for every treatment which indicates that voles maintained on a 4% proteinic diet can keep an excellent proteinic balance if they have access to seedlings with high proteinic values in bark. Phenolic recovery rates from fecal matter varied between 12 and 23% for the three vole categories but were not statistically different. These results suggest that low proteinic content of food does not regulate the use of bark by voles. Bark tissues during short periods can be added to the vole diet without any apparent costs.
Cavallini, P. & Santini, S. 1996: Reproduction of the red fox Vulpes vulpes in Central Italy. — Ann. Zool. Fennici 33: 267–274.
The reproductive output (ovulation rate, fertility, barrenness, productivity, pre-natal mortality) of the red fox Vulpes vulpes (n = 317) has been studied in a Mediterranean region (Pisa province, Central Italy) in 1992 by post-mortem analysis. On average, female foxes shed 5.03 ± 1.27 ova, had 3.95 ± 1.25 placental scars and 3.88 ± 1.55 live embryos. Twenty percent of foxes were barren, and intra-uterine mortality was common: 47% of females lost at least one ovum before implantation; 43.5% of yearlings (less than or equal to1 year old) lost at least one foetus, whereas only 16.7% of adults did so. Male yearlings had lower testis mass than adults. The reproductive output was higher for heavier females, but marginally so for those with greater head and body length. Barrenness and intra-uterine mortality were not related to body size. Amount of body fat and age were unrelated to reproductive output, with the exception of post-implantation mortality (higher for yearlings). All these results suggest that the reproduction of the red fox was not limited directly by food availability, but rather by social modulation. The reproductive output in this population was low in comparison with other populations, in spite of faster physical development. A review of the literature suggests compensatory reproduction in the red fox, litter size being larger in areas of higher mortality.
Kaitala, V., Ranta, E. & Lindström, J. 1996: External perturbations and cyclic dynamics in stable populations. — Ann. Zool. Fennici 33: 275–282.
We show that sustained population oscillations do not necessarily stem from the dynamic properties of a population, or from periodic environmental fluctuations. In particular, we demonstrate that population fluctuations may be sustained by random non-cyclic environmental disturbances. These perturbations reduce breeding success in otherwise stable populations with overshootings in their transient dynamics. When the transition phase from non-equilibrium to equilibrium states is slow, as compared with the frequency and strength of the random fluctuations, and includes overshootings, the dynamics may show fluctuating patterns that are hard to tell apart from regular fluctuations. Population dynamics which include overshootings during transient phases are common in a large variety of population models. As a specific example, we consider the effect of delayed density dependence in a Ricker type model. However, to show that the process can be generalized to different types of models, we also use a nonlinear autoregressive model containing density dependence.
Kauhala, K. 1996: Distributional history of the American mink (Mustela vison) in Finland with special reference to the trends in otter (Lutra lutra) populations. — Ann. Zool. Fennici 33: 283–291.
The distributional history of the American mink (Mustela vison) in Finland in 1951–93 was studied by means of game inquiries and compared to the trends in otter (Lutra lutra) populations. Minks were brought to fur farms in the late 1920s and the first minks were observed in the wild in 1932. In the early 1950s minks occurred mainly in the western and southwestern coast of Finland, but two decades later minks were found in most parts of the country. Today minks are found almost everywhere in Finland; only few observers report that minks are not found in their area. The relative density of the mink is now highest in eastern Finland, rather high in southern Finland and quite low in Lapland. The data from the archipelago are, however, sparce. Otter density declined in the 1970s, but increased again in some areas in the 1980s, is now highest in the provinces of Kymi, Mikkeli and Central Finland, and almost lacking from SW Finland, especially from the coast. Among the reasons behind the decline in the otter populations may have been environmental pollutants, like dieldrin in inland areas and PCBs in the coast and archipelago. Human disturbance may also have had an effect, especially in the archipelago. The role of the mink is not clear; it seems probable that if there is competition between these species, the otter is the stronger one.
Koivunen, V., Korpimäki, E. & Hakkarainen, H. 1996: Differential avian predation on sex and size classes of small mammals: doomed surplus or dominant individuals? — Ann. Zool. Fennici 33: 293–301.
Predators of small mammals may selectively kill either large individuals, usually male or the old, or small individuals, often females and young. We studied the prey choice of breeding male Tengmalm's owls (Aegolius funereus) in western Finland. The owls fed mainly on sibling voles (Microtus rossiaemeridionalis), field voles (M. agrestis), bank voles (Clethrionomys glareolus) and common shrews (Sorex araneus). We identified, sexed and weighed prey items cached by the owls in their nest-boxes, and compared characteristics of these prey to small mammals trapped in the same study area during 1985–1992. For each of the three vole species, owls captured more males than females, but we did not find that owls preferred one sex of common shrews. Our long-term data indicated that male-bias of two Microtus species in the diet of owls was highest in the low phase of the vole cycle, and decreased through the increase and peak phases. This suggests that the two sexes of voles behave differently, but that these differences change over the course of the 3-yr cycle. The proportion of prey individuals with a small body mass was greater in owl caches compared to trapping censuses, irrespective of species or sex. Large dominant individuals may occupy safe habitats with dense vegetation cover, where avian predation risk is minimal.