© 2020 Elsevier LtdSome of the most arid environments inhabited by the Eurasian otter (Lutra lutra) are the river systems draining the southern slopes of the High Atlas Mountains into the Sahara Desert, where we have studied otter distribution, habitat use and feeding ecology. We found signs of otter presence in 61% of 80 sampled sites. The species was widespread at intermediate elevations within the study area, being rarer at high altitudes (above 2000 m a.s.l.) and, especially, in the arid lowlands. The intensity of habitat use, estimated from spraint counts, also peaked at intermediate elevations. Otter diet, described through the analysis of 554 spraints, was dominated by fish in general (found in 97% of the spraints) and Luciobarbus barbels in particular (86% of spraints). The otter positively selected barbels of intermediate sizes (100–160 mm in length), avoiding the smallest size classes and consuming larger ones according to their availability. Our results suggest that otter may be vulnerable to the harsh environmental conditions in arid areas. This aridity-driven vulnerability is expected to increase in the area and to expand to other peri-Mediterranean regions in the future.