The current conservation status of the otter (Lutra lutra) in Ireland

The European otter (Lutra lutra) is listed as near threatened requiring regular reporting of its conservation status under Article 17 of the EU Habitat and Species Directive. The Standard Otter Survey method searches 600m of river bank, lake or coastal shore for spraint (conspicuous droppings used to mark their territory), tracks (footprints) or other field signs. Throughout Ireland, a total of 1,033 sites were surveyed (919 in the Republic of Ireland and 114 in Northern Ireland) during June 2023 to October 2024. Evidence of otters was found at 64% [95%CI 61 - 67%] of sites in Republic of Ireland with no change in incidence since the last survey in 2010-12 when occurrence was 63% [95%CI 60 - 66%]. This was highly comparable with Northern Ireland where otters occurred at 65% [95%CI 57 - 73%] of sites. Otters remain widespread. Further, 480 environmental or eDNA water samples were screened using an otter-specific ddPCR (droplet digital polymerase chain reaction) assay at 10 focal rivers in County Galway and 6 rivers in County Waterford: each sampled 30 times during three seasons to assess the false negative rate of traditional surveys. Survey method limitations, results and the impact of potential bias and error will be discussed.