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Mammalian Biology

, Volume 73, Issue 6, pp 415–422 | Cite as

Can environmental factors explain size variation in the common shrew (Sorex araneus)?

  • Karl FrafjordEmail author
Original Investigation

Abstract

Shrews are small mammals with a high metabolic rate and may potentially be greatly influenced by environmental factors. Several studies have indicated both morphological and genetical variation in the common shrew (Sorex araneus). The aims of this study were to study patterns in size variation and to test which environmental factors influence body size most. Most study sites were located to northern Norway, between 65° and 70°N, one study site in south Norway was also included (60°N). At one site shrews were studied for 10 consecutive years. Three body measurements (body length, tail length and body mass) and two combined estimates (tail proportion and body condition) were compared, where appropriate, among populations (sites), years and months, and along gradients of altitude (habitat), coast-inland and north–south. Effects of summer climate (temperature and precipitation) were also tested. Size variations among populations of common shrews were found in a number of respects; yearly, seasonal, local and regional. Regional variation was most significant, followed by yearly and seasonal variation. The results suggest a strong link between body size and a coast–inland gradient, with smallest shrews (up to 13% smaller) on inland locations. The main differences between coastal and inland sites are lower winter temperatures and less snow cover at inland sites (factors which are also associated with habitat productivity), which could favour smaller shrews with less energetic demands. Most other variation was relatively small (<5%). Most of the results indicate climate and habitat productivity as the most important factors, which may also vary between years at a single site. Bergmanns’s rule, Allen’s rule or Dehnel’s phenomenon were not supported by this study. The insular syndrome was partly supported. Smaller variations in size may only be proximate adaptations to local food supply, but larger variations are likely to be ultimate adaptations.

Keywords

Sorex araneus Body size Environmental gradients 

Können Umweltfaktoren Größenunterschiede bei der Waldspitzmaus (Sorex araneus) erklären?

Zusammenfassung

Spitzmäuse sind Kleinsäuger mit hoher Stoffwechselrate, die potentiell stark von äußeren Faktoren beeinflusst werden. Mehrere Studien haben sowohl morphologische als auch genetische Variabilität bei Waldspitzmäusen (Sorex araneus) nachgewiesen. Ziel der vorliegenden Studie war die Ermittlung von Mustern in der Größenvariation und zu testen, welche Umweltfaktoren sich am stärksten auf die Körpergröße auswirken. Die meisten untersuchten Gebiete befanden sich im Norden Norwegens (65–70°N), doch wurde auch eines aus dem Süden des Landes (60°N) mit einbezogen. Die Spitzmäuse wurden in 10 aufeinander folgenden Jahren untersucht. Drei Maße (Körperlänge, Schwanzlänge und Körpergewicht) sowie zwei kombinierte Parameter (Schwanzproportion und körperliche Verfassung) wurden zwischen Populationen, Jahren und Monaten, entlang der Höhe über NN, zwischen Küste und Inland sowie zwischen Norden und Süden verglichen. Effekte des Sommerklimas (Temperatur und Niederschlag) wurden ebenfalls überprüft. Größenvariationen wurden für verschiedene Vergleiche gefunden: jährlich, jahreszeitlich, lokal und regional. Die regionale Variation war am stärksten, gefolgt von Variation in Abhängigkeit vom Jahr und der Jahreszeit. Die Ergebnisse legen eine starke Variation der Körpergröße entlang eines Küste-Inlandgradienten nahe, wobei die kleinsten Tiere (Größenreduktion um bis zu 13%) im Inland gefunden wurden. Die wesentlichen Unterschiede zwischen den Küsten- und Inlandhabitaten sind die niedrigere Wintertemperatur und die dünnere Schneedecke im Inland (was mit Habitatproduktivität in Verbindung gebracht wird), wodurch möglicherweise kleinere Tiere mit geringerem Energiebedarf einen Selektionsvorteil haben. Die übrige Variation war meist gering (<5%). Die meisten Ergebnisse deuten auf Klima und Habitatproduktivität als die wichtigsten Faktoren hin, die auch innerhalb von Standorten zwischen den Jahren variieren können. Weder Bergmannsche oder Allensche Regel noch das Dehnelsche Phänomen wurden in der vorliegenden Studie bestätigt, wogegen das Inselsyndrom teilweise bestätigt wurde. Geringere Größenvariationen sind wahrscheinlich nur proximate Adaptationen an das lokale Nahrungsangebot, wogegen größere Variationen eher ultimate Anpassungen darstellen.

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Copyright information

© Deutsche Gesellschaft für Säugetierkunde 2007

Authors and Affiliations

  1. 1.Tromsø MuseumUniversity of TromsøTromsøNorway

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