Background Over the past century, populations of otter (Lutra lutra) decreased considerably across Europe. The causes of this have ranged from trapping by humans, the destruction of habitat, poor water quality, invasive species, road deaths and human encroachment into sensitive areas. A particular feature has been that, principally due to land use changes, the western and eastern European subpopulations of the otter were now separated. As a result of the species becoming protected in 1972 and recent mitigation measures carried out in several European countries, the situation is slowly changing. In France and Germany, the otter populations and their range have been increasing. In the project area, signs of otter presence had been occasionally observed until 2003, suggesting a very limited population of a few isolated individuals. However, at that time, a very small otter population still existed in the Belgian Ardennes and the neighbouring part of Luxembourg had potential to be reconnected to the increasing German and French populations. This could play a major role in establishing an important connecting gap for the species on a European scale. Objectives The Loutre BeLu project aimed to safeguard the existing otter (Lutra lutra) population and encourage recolonisation in a cross-border area between Belgium and the Grand Duché de Luxembourg. The project sought specifically to restore habitat over an area of 300 000 ha, including the basins of the Rivers Our, Sûre and Ourthe, with the ultimate aim of improving the possibility for contact and genetic exchanges between the currently separated otter populations. The project foresaw several actions to provide long-term protection and appropriate conservation management for key sites: Land purchase of 57 ha Management agreements signed with landowners for 50 ha Restoration of riverbanks, including planting deciduous species along 28 km and fences along 54 km Installing 96 drinking troughs to provide cattle with an alternative source of water Cutting of 133 ha of spruce plantations along the floodplains Removal of invasive species from 35 ha Establishment of 25 otter havens for reproduction Equipping seven road-bridges with passageways for otters Restoring 20 disconnected channels to increase the natural supply of fish Planting 24 km of hedges along ridges and digging 40 small ponds to provide corridors reconnecting river basin habitats.The project intended to work with the full range of local stakeholders, and landowners in particular, to plan and carry out these actions. It foresaw regular monitoring of indicators of otter presence, the creation of a data base and a geographical information system. The project planned a wide-ranging communication effort with specific actions toward different target groups. Results This ambitious project exceeded most of its objectives for the different technical actions affecting more than 600 km of watercourse, and 21 Natura 2000 sites in Belgium and eleven in Luxembourg. It successfully involved seven partners across this border and should constitute an important step forward in the restoration of the river basin habitats for the benefit of the otter (Lutra lutra) in the two countries and to help recreate links with populations in France and Germany. The project purchased 105 ha – 84 ha in Wallonia and 21.4 ha in Luxembourg – whilst a further 15.3 ha was purchased outside the scope of the project, in support of it. These areas reinforce the areas that were already have under official protection along the river basins. Actions were undertaken to successfully protect and restore riverbanks. Fences were constructed along 61 km to prevent access by livestock to riverbanks, 23 footbridges constructed for cattle, 262 drinking troughs established and 23 km of riparian forest planted. Further restoration worked included the removal of 150 ha of spruce plantations from floodplains, with 44 ha of this felling area cleaned up with the restoration of indigenous plants such as broad-leaved alluvial forest and a patchwork of meadows and marshes. The project created 178 ponds and 33 otter havens. Invasive species were directly tackled on 189 ha, with different methods tested and assessed. To restore water quality in the rivers for the otter and fish, the project: reconnected seven backwaters and spawning grounds to the main river channel; removed or modified 21 obstacles to the migration of fish up and down the river; and installed nine passageways for otters under road bridges. The project sites will enjoy ongoing management. The purchased Walloon territory was made Natural Reserves under the regional authority, whilst a Nature Foundation will manage the Luxembourg area. Work to monitor otter numbers was facilitated by the training of several dozen naturalists in otters tracking. This ongoing monitoring work was supported by the elaboration of an excellent tracking guide and a teaching manual. The project exceeded the initially set outputs despite serious delays to the start of the project due to administrative and capacity issues. Once these were resolved the project was highly successful, including in developing effective synergies with other nature conservation projects in the area, notably the three LIFE projects concerned with: conservation of pearl mussel (Margaritifera margaritifera) habitats (LIFE02 NAT/B/008590); the rehabilitation of natural habitats on the Tailles Plateau (LIFE05 NAT/BE/000089); and the restoration of raised bogs (LIFE03 NAT/B/000019). Awareness-raising was an important aspect of this LIFE Nature project, too. For schools, the project provided an educational file and a travelling exhibition, "On the tracks of the otter", which is also aimed at the general public, with a focus on interactivity and audience participation. Further information on the project can be found in the project's layman report and After-LIFE Conservation Plan (see "Read more" section).