Eurasian and North American otters have recovered significantly following pollution controls, but road mortality, habitat fragmentation, and emerging pollutants continue to threaten individual welfare and population health.
Otter welfare today is shaped by the legacy of the pesticide crisis and the ongoing challenge of road mortality and emerging chemical threats. Road casualties cause traumatic injury and death — otters following river corridors cross roads at bridges and culverts, and without adequate otter passes (tunnels beneath roads) these crossings are fatal. The welfare consequence of road mortality is acute: crushing injuries from vehicles cause deaths that may not be instantaneous. PFAS contamination is a more diffuse welfare threat — these persistent chemicals accumulate in fish that otters eat and have been found in otter livers at concentrations associated with immune and reproductive effects in other species, suggesting chronic welfare impacts we cannot yet fully quantify. Otter passes — tunnels beneath road bridges with ledges connecting both banks — are a well-proven intervention that dramatically reduces otter road mortality and should be standard in all new and replacement bridge construction over watercourses.