THE STATUS OF SHIP-RATS RATTUS-RATTUS ON THE SHIANT-ISLANDS, OUTER-HEBRIDES, SCOTLAND

Ship rats Rattus rattus are amongst the rarest mammals in Britain and yet they are officially classified as pests. They exist independently of contemporary human settlement at only two sites both of which are i mportant seabird breeding colonies. There may be a conflict between co nserving this rare species while ensuring the welfare of seabirds. We present a case study of the potential conservation dilemma of ship rat management on the Shiant Islands. Using capture-mark-recapture the pr e-breeding rat population in May 1996 was estimated to be between 230 and 400. Evidence of rat predation on eggs and chicks was scarce at th e time of our survey. The small number of rats was not thought to have a substantial effect on the nesting success of the comparatively larg e seabird populations. We suggest that the scientific interest of the rat population may outweigh the conservation needs of the seabirds and that formal control measures are currently unwarranted. (C) 1997 Else vier Science Ltd.