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Starting from data obtained by scat prospection in 500 river stretches we discuss wich are the main distribution factors of Iberian Desman in Catalonia, a peripheral part of the species global area. The most important factors are: 1) Lack of great geographical barriers which have historically impede individuals exchange (colonization or recolonization after local extinctions) between river basins; this could explain the species absence in Noguera Rib-agorgana’s basin and suggests a post-glacial colonization of Southern Pyrenees rivers from NW. 2) An upper basin’s surface superior to 300 km2; this fact probably shows that a long-term viable population needs a minimum length of suitable rivers. 3) An important winter snow-covering of upper basin mountains which in areas of strong mediterranean influence is the main guarantee for a regular water flow. Reduced basin’s surface and little snow fall would explain the absence of Desman in the smallest basins of Eastern Pyrenees (Llo-bregat, Fluvia and Muga). Climate and altitude seem to condition distribution mainly for its incidence over rivers flow, whereas other factors (physicochemical water parameters, river slope, river banks, anthropic disturbance) would only influence at a local scale.

Тэги: Galemys pyrenaicus, Pyrenees, distribution, historical factors, basin surface, snow-fall, climate.

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