Microhabitat use by the snow vole Chionomys nivalis in alpine environments reflects rock-dwelling preferences

Environmental conditions in mountainous regions have influenced the nature of some adaptations among small mammals and this may apply to strategies of habitat use in alpine biotopes. In the present paper, microhabitat use in relation to microhabitat availability of a population of snow voles Chionomys nivalis Martins, 1842, a nonhibernating microtine rodent that inhabits high-mountain environments exclusively, was studied. The results show that C. nivalis did not use microhabitats in proportion to availability, suggesting a preference for certain habitat charac - teristics. Chionomys nivalis strongly used scree areas at all times, whereas the use of available areas of mixed shrubs (Juniperus communis and Cytisus oromediterraneus) and Scots pine (Pinus sylvestris) was lower than expected. Factors other than food, such as favourable microclimate or refuge from predators, might determine regular use of rocky microhabitats. The results also revealed differences in the use of rocky structures related to sex and reproductive condi - tion, suggesting different strategies of spatial use related to reproductive tasks. Juveniles and reproductive females used central zones of the scree and areas with scree junipers (J. communis) significantly more than expected, whereas repro- ductive males and nonreproductive adults used scree areas in proportion to availability. Based on its unique morpholog - ical, physiological, and ecological characteristics, C. nivalis can be considered a rock-dwelling specialist of alpine environments. Resume : Dans les zones montagneuses, les conditions environnementales ont influence la nature de certaines adapta- tions chez les petits mammiferes et cela peut etre vrai des strategies d'utilisation de l'habitat dans les biotopes alpins. On trouvera ici les resultats d'une etude sur l'utilisation des microhabitats en fonction de leur disponibilite chez une population de campagnols des neiges Chionomys nivalis Martins, 1842, un rongeur microtine qui n'hiberne pas et qui vit exclusivement dans les habitats de haute montagne. Les resultats indiquent que C. nivalis n'utilise pas les microha- bitats proportionnellement a leur disponibilite, ce qui laisse supposer l'existence d'une preference pour certaines carac- teristiques de l'habitat. Les campagnols frequentent beaucoup les zones d'eboulis en tout temps, alors qu'ils utilisent les zones buissonneuses mixtes (Juniperus communis et Cytisus oromediterraneus) et les zones de pins sylvestres (Pinus sylvestris) moins que prevu. Des facteurs autres que la nourriture, par exemple un microclimat favorable ou une protection contre les predateurs, peuvent expliquer l'utilisation reguliere des microhabitats rocheux. I l y a aussi des dif- ferences d'utilisation des structures rocheuses entre mâles et femelles et entre individus de statuts reproducteurs diffe - rents, ce qui suggere des strategies variables d'utilisation de l'espace selon les tâches reproductrices. Les juveniles et les femelles reproductrices frequentent les zones centrales des eboulis et les zones d'eboulis-genevriers ( J. communis) significativement plus que prevu, alors que les mâles reproducteurs et les adultes non reproducteurs utilisent les zones d'eboulis en fonction de leur disponibilite. Des caracteristiques morphologiques, physiologiques et ecologiques particu - lieres font de C. nivalis une espece specialiste des zones rocheuses des milieux alpins.

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