Hydromys chrysogaster, commonly known as rakali, rabe or water-rat, is an Australian native rodent first described in 1804. The change to the aboriginal name Rakali was intended to foster a positive public attitude by Environment Australia. It is the only member of the genus Hydromys with a range extending beyond Papua New Guinea and Indonesian West Papua. Having effectively adapted and colonised a unique niche of semiaquatic and nocturnal lifestyle, this