Revised by Pohle (1920a), Pocock (1940b), van Zyll de Jong (1972, 1987, 1991a), Koepfli and Wayne (1998), and Bininda-Emonds et al. (1999). Reviewed by Harris (1968) and Sokolov (1973). Foster-Turley et al. (1990) reviewed the conservation status and distribution of otters.