title: Immunocompetence and high metabolic rates enhance overwinter survival in the root vole, Microtus oeconomus.
abstract: Despite its presumed significance, the association between immune defence, energy expenditures and overwinter survival is rarely studied. We analysed individual variation in immunocompetence quantified as neutrophil-to-lymphocyte ratio (N/L), total white blood cells (WBC) and natural antibody levels, along with resting (RMR) and peak metabolic rates (PMR) and mortality during three consecutive winter seasons in a natural population of the root vole, Microtus oeconomus. In early winter, WBC count was negatively correlated with RMR, whereas N/L ratio was negatively correlated with swim-elicited PMR. We suggest that while the first correlation reflected the trade-off between energy allocation in immunocompetence and other metabolically demanding processes, the latter correlation stemmed from stress-induced immunosuppression elicited by the necessity to cope with swimming in frequently flooded habitat. In addition, the analysis carried out during the first year of study characterized by a high population density and prevalence of infestation with a blood parasite--Babesia spp., showed that its intensity was inversely correlated with the N/L ratio. In summary, our results suggest that elevated N/L ratio increases the winter survival of free-ranging rodents by increasing their ability to cope with parasitic infections.
authors.affiliation: Institute of Biology, University of Białystok, Świerkowa 20B, 15-950 Białystok, Poland anetak@uwb.edu.pl.
authors.forename: Aneta
authors.initials: A
authors.lastname: Książek
authors.affiliation: Mammal Research Institute, Polish Academy of Sciences, Waszkiewicza 1, 17-230 Białowieża, Poland.
authors.forename: Karol
authors.initials: K
authors.lastname: Zub
authors.affiliation: Mammal Research Institute, Polish Academy of Sciences, Waszkiewicza 1, 17-230 Białowieża, Poland.
authors.forename: Paulina A
authors.initials: PA
authors.lastname: Szafrańska
authors.affiliation: Mammal Research Institute, Polish Academy of Sciences, Waszkiewicza 1, 17-230 Białowieża, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Wieczorek
authors.affiliation: Institute of Biology, University of Białystok, Świerkowa 20B, 15-950 Białystok, Poland.
authors.forename: Marek
authors.initials: M
authors.lastname: Konarzewski
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D004734:Energy Metabolism; D007121:Immunocompetence; D012621:Seasons; D013534:Survival
keywords: N/L ratio; innate immunity; metabolic rates; overwinter survival; trade-off; white blood cell count