title: Physiological condition of bank voles (Myodes glareolus) during the increase and decline phases of the population cycle.
abstract: The dynamics of animal populations are greatly influenced by interactions with their natural enemies and food resources. However, quantifying the relative effects of these factors on demographic rates remains a perpetual challenge for animal population ecology. Food scarcity is assumed to limit the growth and to initiate the decline of cyclic herbivore populations, but this has not been verified with physiological health indices. We hypothesized that individuals in declining populations would exhibit signs of malnutrition-induced deterioration of physiological condition. We evaluated the association of body condition with population cycle phase in bank voles (Myodes glareolus) during the increase and decline phases of a population cycle. The bank voles had lower body masses, condition indices and absolute masses of particular organs during the decline. Simultaneously, they had lower femoral masses, mineral contents and densities. Hemoglobin and hematocrit values and several parameters known to respond to food deprivation were unaffected by the population phase. There were no signs of lymphopenia, eosinophilia, granulocytosis or monocytosis. Erythrocyte counts were higher and plasma total protein levels and tissue proportions of essential polyunsaturated fatty acids lower in the population decline. Ectoparasite load was lower and adrenal gland masses or catecholamine concentrations did not suggest higher stress levels. Food availability seems to limit the size of voles during the decline but they can adapt to the prevailing conditions without clear deleterious health effects. This highlights the importance of quantifying individual health state when evaluating the effects of complex trophic interactions on the dynamics of wild animal populations.
authors.affiliation: University of Eastern Finland, Faculty of Health Sciences, School of Medicine, Institute of Biomedicine/Anatomy, P.O. Box 1627, FI-70211 Kuopio, Finland; University of Eastern Finland, Faculty of Science and Forestry, Department of Biology, P.O. Box 111, FI-80101 Joensuu, Finland. Electronic address: Petteri.Nieminen@uef.fi.
authors.forename: Petteri
authors.initials: P
authors.lastname: Nieminen
authors.affiliation: Natural Resources Institute Finland, Suonenjoki Unit, Juntintie 154, FI-77600 Suonenjoki, Finland.
authors.forename: Otso
authors.initials: O
authors.lastname: Huitu
authors.affiliation: Natural Resources Institute Finland, Vantaa Unit, P.O. Box 18, FI-01301 Vantaa, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Henttonen
authors.affiliation: University of Oulu, Faculty of Medicine, Institute of Biomedicine, Department of Medical Technology, P.O. Box 5000, FI-90014 Oulu, Finland.
authors.forename: Mikko A J
authors.initials: MA
authors.lastname: Finnilä
authors.affiliation: Natural Resources Institute Finland, Vantaa Unit, P.O. Box 18, FI-01301 Vantaa, Finland; University of Helsinki, Department of Virology, P.O. Box 21, FI-00014 Helsinki, Finland.
authors.forename: Liina
authors.initials: L
authors.lastname: Voutilainen
authors.affiliation: University of Oulu, Faculty of Science, Department of Biology, Biodiversity Unit, Zoological Museum, P.O. Box 3000, FI-90014 Oulu, Finland.
authors.forename: Juhani
authors.initials: J
authors.lastname: Itämies
authors.affiliation: Kuopio University Hospital, Department of Pathology, P.O. Box 1777, FI-70211 Kuopio, Finland.
authors.forename: Vesa
authors.initials: V
authors.lastname: Kärjä
authors.affiliation: University of Oulu, Faculty of Science, Department of Biology, P.O. Box 3000, FI-90014 Oulu, Finland.
authors.forename: Seppo
authors.initials: S
authors.lastname: Saarela
authors.affiliation: Eastern Finland Laboratory Centre (ISLAB), P.O. Box 1700, FI-70211 Kuopio, Finland.
authors.forename: Toivo
authors.initials: T
authors.lastname: Halonen
authors.affiliation: Municipal Veterinary Clinic of Joensuu, Takilatie 5, FI-80110 Joensuu, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Aho
authors.affiliation: University of Eastern Finland, Faculty of Health Sciences, School of Medicine, Institute of Biomedicine/Anatomy, P.O. Box 1627, FI-70211 Kuopio, Finland; University of Eastern Finland, Faculty of Science and Forestry, Department of Biology, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: Anne-Mari
authors.initials: AM
authors.lastname: Mustonen
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000502:physiology*; D005260:Female; D008297:Male; D011157:Population Dynamics
keywords: Arvicolinae; Bone mineral density; Ectoparasitism; Fatty acid signature; Hematology; Puumala hantavirus