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  • 1.
    Elmhagen, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Kindberg, Jonas
    Changes in vole and lemming fluctuations in northern Sweden 1960-2008 revealed by fox dynamics2011In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 48, no 3, p. 167-179Article in journal (Refereed)
    Abstract [en]

    Cyclic dynamics with extensive spatial synchrony has long been regarded as characteristic of key herbivores at high latitudes. This contrasts to recent reports of fading cycles in arvicoline rodents in boreal and alpine Fennoscandia. We investigate the spatio-temporal dynamics of boreal red fox and alpine arctic fox in Sweden as a proxy for the dynamics of their main prey, voles and Norwegian lemming, respectively. We analyse data from five decades, 1960-2008, with wavelets and autocorrelation approaches. Cyclic dynamics were identified with at least one method in all populations (arctic fox n = 3, red fox n = 6). The dynamics were synchronous between populations, or coupled with a 1-yr lag, in 8 of 13 pairwise comparisons. Importantly though, the dynamics were heterogeneous in space and time. All analytical approaches identified fading cycles in the three arctic fox populations and two northern red fox populations. At least one method identified similar patterns in three southern red fox populations. Red fox dynamics were cyclic in the 1970s primarily, while arctic fox dynamics was cyclic until the late 1980s or early 1990s. When cyclic, 4-yr cycles dominated in arctic fox and northern red fox, whilst 3-4-yr cycles was found in southern red foxes. Significant cyclic regimes reappeared in the 1990s or 2000s in two red fox populations and one arctic fox population. Cycles and regionally coupled dynamics appeared associated in northern arctic and red foxes. This study supports accumulating evidence which suggests that cyclic and synchronous patterns in the dynamics of lemmings and voles are nonstationary in space and time. Furthermore, the similar patterns of change in both fox species indicate that persistence of cycles is governed by similar mechanisms in lemmings and voles.

  • 2. Kaikusalo, A.
    et al.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology.
    The Arctic Fox Population in Finnish Lapland During 30 Years, 1964-931995In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 32, no 1, p. 69-77Article in journal (Refereed)
    Abstract [en]

    We have monitored the number of arctic foxes and microtine rodents in northern Finland for 30 years. Arctic fox densities were estimated by inventories at den sites, and microtine abundance by snap trapping. Time series analyses showed that the arctic fox population fluctuated widely but always close together with the microtines in a five year cycle. However, there was no time lag in the numerical response of foxes on microtines. The strong dependence on microtines was confirmed by analyses of faecal droppings and food remains at dens. In summer time microtines consisted in average of 45% of the diet and reindeer 30%, but during winters reindeer was the most important food source with 45% compared to 15% for microtines. There was a surprising positive correlation between number of voles and reindeer carcasses, suggesting competition or alternatively an external correlation from e.g. weather. Mean litter size of the arctic fox was also highly dependent on microtine abundance but decreased during the study period despite that food resources had not changed. Further, when microtines had high densities during two consecutive years, arctic foxes only responded to the first year. A feeding experiment resulted in an increase in number of red foxes but had no or little effect on arctic foxes. So, it is difficult to single out one explanation to the decline and second year effect. Food was probably not involved and we do not know if diseases and parasites have been involved. However, both competition and predation, primarily from the red fox, may be responsible together with climatic or weather changes.

  • 3.
    Rautio, Pasi
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Bergvall, Ulrika A.
    Stockholm University, Faculty of Science, Department of Zoology. Swedish University of Agricultural Sciences, Sweden.
    Tuomi, Juha
    Kesti, Kari
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Food selection by herbivores and neighbourhood effects in the evolution of plant defences2012In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 49, no 1-2, p. 45-57Article in journal (Refereed)
    Abstract [en]

    A number of studies have reported how neighbouring plants may influence herbivory on palatable or unpalatable plants. Such neighbourhood effects can have important evolutionary consequences as they may either promote the evolutionary stability of plant defences or, alternatively, select against the fixation of plant defences and instead promote a stable polymorphism of palatable and unpalatable plants. These consequences depend on whether the difference in herbivore damage between unpalatable and palatable plants is smaller or, alternatively, greater when the neighbours are unpalatable instead of palatable. Such relations can arise when the neighbourhood effects are non-parallel among palatable and unpalatable plants. We outline two basic situations of non-parallel neighbourhood effects and illustrate how they can come about. A detailed dissection of these interactions reveals that there are several qualitatively distinct mechanisms that promote either evolutionary stability of plant defences or alternatively polymorphism. Our classification of mechanisms can be used to clarify and explain observations obtained in the field of plant herbivore interactions and predator prey interactions, both at the population and the community level.

  • 4.
    Taylor, Alexandra K.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Hellström, Peter
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Angerbjörn, Anders
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Effects of trap density and duration on vole abundance indices2011In: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 48, no 1, p. 45-55Article in journal (Refereed)
    Abstract [en]

    This study aims to investigate if patterns of immigration by voles into removal plots on the third day of trapping are evident in the grey-sided vole, and if altering the number of traps at each station will result in increased precision of the vole abundance estimate. Traps were placed using the small quadrat method, with one, three, or five traps placed at each corner. Traps were checked twice a day for five days. Mixed-effect models were used to investigate the relationship between the number of traps and the length of time the traps were out on the abundance index. There was no difference between having three or five traps. Having one trap resulted in an inflated estimate. Five traps had the highest number of successful trapping events, reducing the number of zeros in the data set and leaving fewer individuals unaccounted. There was a peak in catches on the third day, driven by younger individuals and by males. These are suspected immigrants that are exploiting the territories left by individuals trapped in the first two days, suggesting this is not a closed system.

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