There was a time, not long ago in historical terms, when otters had effectively disappeared from most of England’s rivers. By the 1970s, decades of hunting, habitat loss, and the widespread use of organochlorine pesticides had reduced the otter population to a handful of scattered survivors, mostly in the west of Wales and parts of Scotland.
The pesticides, particularly aldrin and dieldrin used in sheep dipping, accumulated in fish and then in the otters that ate them. The rivers that should have sustained them had been straightened, drained, and stripped of the bankside vegetation that otters need for cover and denning. The combination was close to lethal for the species across most of Britain.
The recovery that followed is one of the quieter conservation success stories of the past four decades.
Organochlorine pesticides were banned. Water quality improved as agricultural practices changed and sewage treatment standards tightened. Otter hunting was banned in 1978. Bankside habitat restoration programmes began to restore some of the cover that had been stripped away.
The otters did the rest themselves.
By the mid 2000s, otters had been recorded in every English county for the first time since records began. The population has continued to expand since then. Urban rivers that would have been considered uninhabitable thirty years ago now support breeding pairs. The River Thames has otters. The rivers running through Birmingham have otters.
The recovery is not complete. Road casualties remain the single biggest threat to otters in the UK, and the interaction between otters and fish farming creates ongoing conflict in some areas. Water quality improvements, while real, are uneven, and the agricultural runoff that continues to affect many rivers is a persistent problem.
But the otters came back. In most of the places from which they had gone, they returned without being reintroduced, following the rivers as water quality improved and finding the habitat that had been restored for them.
That is worth knowing.
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