Range and diet of Eurasian otters Lutra lutra (L.) in the catchment of the River Lee (south-east England) since re-introduction

1. After re-introduction in 1991 of Eurasian otters Lutra lutra (L.) to the River Lee catchment (England), changes in range were assessed from spraint collections in the periods 1991-1994, 1995 1997 and 1998-2000. Diet, assessed from concerted spraint sampling within the first two periods, was compared between 1992-1994 and 1996-1997, with dietary preferences assessed for the initial phase using available fish stock data for that period. 2. In 1991-1994, range encompassed much of the catchment, but reduced in 1995-1997 to a small area around the initial release site, when the otters were joined/replaced by natural immigrants presumed to come from a contiguous catchment. Range expanded in 1998-2000 to upper reaches of the catchment's major tributaries. 3. Fish, mainly cyprinids, were the major prey taken in 1992-1994 and 1996-1997. In 1996-1997, fish abundant near the initial release site became more prominent, in particular chub Leuciscus cephalus, and (upstream) species characteristic of the initial range decreased in importance. 4. Despite confirmed and unconfirmed sightings of females with cubs, it remains unclear whether the presence and apparent expansion of otters in the Lee catchment is the result of the reintroduction or of natural immigration/recolonization. Copyright (C) 2003 John Wiley Sons, Ltd.