Many mammals, such as otters, live in close association with rivers and streams, feeding in them, or using them as a place of safety or means of escape from predators. The distinct adaptations that riparian mammals have evolved in order to live in these environments also handicap them for living elsewhere. These animals are therefore threatened by alterations to their environment. In recent years, our rivers have become highly polluted, and have been subject to bankside modifications for agriculture and forestry, enhanced or decreased water flow, and recreation. As a result, they have become...