THE RED FOX IN NORWAY - MORPHOLOGICAL ADAPTATION OR RANDOM VARIATION IN SIZE

LUND (1959) collected red foxes Vulpes vulpes from different sites in Norway. We reanalysed his data on body mass, body length, tail length and condition in an attempt to Study some factors influencing size var iation in foxes. Sexual dimorphism was most significant, with regional variation followed by yearly and seasonal variation. Males were large r (4-5%) and heavier (14%) than females, but not in better condition. Foxes increased in size from south to mid Norway, but were smallest in north Norway. Sexual dimorphism in mass decreased progressively from south to north, Yearly variation was greatest in males. Both males and females were in better condition during autumn and Minter. and in poo rer condition in the spring. Seasonal changes in mass were similar, bu t less systematic. Environmental factors that ch;change most from sout h/mid Norway to north Norway are climatic with lower temperatures, lon ger winters and lover;er primary productivity to the north. A smaller northern fox may need a shorter period of growth and conserve energy d uring the winter.