Otters have made a remarkable recovery in Britain following persecution and organochlorine pesticide bans, but territorial behaviour, road mortality, and fish availability continue to shape individual welfare.
Otter welfare is primarily shaped by food availability and safe movement through their territory. Rivers with low fish biomass force otters to range more widely, increasing road crossing frequency and mortality risk. Otter cubs are particularly vulnerable - born in holts and dependent on the female for food provision for several months, their welfare is directly linked to the mother's fishing success. Road mortality is the leading unnatural cause of otter death in the UK, with bridges creating predictable fatal bottlenecks where otters cross roads rather than entering culverts. Installing otter ledges inside bridge culverts is a proven mitigation costing a few hundred pounds that prevents road mortality at known crossing points.