From 1993–1998, we monitored a 24.1 km long concrete water canal in northern Spain for drowned mammals. Along the canal, 14 concrete bridges and 9 small bridges permitted crossing by humans and livestock. Our objective was to test whether those bridges could be used as passages for wild animals to prevent drowning. We used tracks recorded in sand on bridges to identify species passing. Of the bridges, 65% were used by wild mammals; the 9 small bridges accounted for 57% of crossings by wild animals. Wild and domestic canids (Canis lupus, C.l. domesticus, Vulpes vulpes) were the main users (85%), followed by wild ungulates (mainly wild boar, Sus scrofa) at 71% of the crossings. Proximity to a mountain slope did not increase crossing in deer species, but did not hinder wild boars, foxes and wolves from doing so. Palabras clave: Mammal, Mortality