Abstract
Invasive alien animal species (IAAS) are the second leading cause of global biodiversity loss after habitat destruction, yet
their conservation implications vary enormously with invasive species identity, invaded ecosystem type, and the
vulnerability of native assemblages. This study quantifies the conservation impacts of twelve IAAS on native fauna in
Spain, France, and Italy -- three countries with among the highest invasive species richness in Europe -- using camera
trap surveys, diet analysis, population modelling, and structured competition experiments at 72 study sites (2020-2024; n = 18,641 native species records). Twelve focal IAAS span predatory mammals (American mink Neovison vison, raccoon
Procyon lotor, red fox domestic lineage), fish (Lepomis gibbosus, Gambusia holbrooki), reptiles (Trachemys scripta
elegans, Iguana iguana), invertebrates (Procambarus clarkii, Vespa velutina), and birds (Psittacula krameri, Myiopsitta
monachus, Columba livia feral). GLMM analysis confirmed that American mink caused the greatest per-site reduction in
native waterbird breeding density (-58.4 +- 7.8%; z = -7.48, p < 0.001) and amphibian community richness (-42.4 +-
6.8%) of any focal IAAS. Trachemys scripta reduced Emys orbicularis occupancy probability by 74.8% at invaded sites.
Procambarus clarkii generated multi-trophic cascades reducing macroinvertebrate richness by 38.4% and waterbird
foraging success by 28.4%. Control intervention analysis at 18 management sites showed that trapping-based mink
removal achieved 87.4% activity reduction within 2 years, associated with significant native waterbird breeding recovery.
These findings support priority listing of American mink, Trachemys scripta, and Procambarus clarkii for mandatory
management under EU Invasive Alien Species Regulation (2024/1991) implementation.