What If Gone

Species → Eurasian Otter

Eurasian Otter

Lutra lutra

not quantified at the continental scale; sharply increasing in…
Extinction risk Near Threatened
WaterwayPredatorScientific controversy
Eurasian Otter (Lutra lutra)
Photo: Alexander Leisser, Wikimedia Commons (CC BY-SA 4.0)

What if it disappeared?

Impact Moderate
Over 75 years (Europe)

The dramatic decline of the Eurasian otter between the 1950s and 1970s, culminating in its disappearance from most of central and northern Europe, closely tracked the bioaccumulation of organochlorine pollutants (PCBs, DDT, dieldrin) in waterways. Their ban in the 1970s, followed by legal protection of the species, enabled measurable recovery in several countries since the 1990s.

Documented
Detail

IUCN SSC Otter Specialist Group — Eurasian Otter in Europe: Conservation Success (2025) ; Mammal Society — The Eurasian otter: an at risk species and indicator of chemical contamination of freshwaters.

The recovery remains uneven and has not yet restored the species' full historical range, but it is documented in several countries by long-term monitoring programs and several successful reintroductions.

Meta-analysis

While the otter's historical collapse did track water pollution, a meta-analysis of 21 diet studies concludes that the otter remains a poor day-to-day indicator of water quality: its ability to feed on a very wide range of prey, and the strong influence of habitat type on its diet, blur the signal its feeding habits are supposed to reveal.

Insufficient
Detail

Reid, N., Lundy, M.G., Hayden, B., Waterman, T., Looney, D., Lynn, D. & Marnell, F. (2012). Review and quantitative meta-analysis of diet suggests the Eurasian otter (Lutra lutra) is likely to be a poor bioindicator. Ecological Indicators, 26, 5–13. This is an important nuance, not a contradiction of the previous point: that the species' population trend over decades tracked the history of pollution is one thing; that case-by-case analysis of its droppings (spraints) faithfully reveals the condition of a given river is another — and it is this second use, common in biomonitoring programs, that the meta-analysis calls into question.

Documentation

Last verified: August 14, 2026