- © Craig Llewellyn
- © Arbeco Ltd.
Encourage otters to recolonise and breed
Carefully sited and constructed artificial holts may encourage otters to recolonise and breed along stretches of waterways from which they are at present absent or re-locate otters where there is a threat as a consequence of development. Arbeco can competently construct artificial holts to enhance river banks for this European Protected Species.
A simple artificial holt can be made using log piles. In the wild otters will use piles of various sizes from structures as large as 40m long, 10m wide and 4m high to small features of 5m x 3m x 4m. Large logs should be used for the base, which will form a series of chambers, thinner logs can be used to roof the chambers and debris piled on top to make the structure waterproof.
Artificial holts must have two or three entrances below, at or above water level. No above ground entrance should be too high above the water level, they should be about 20cm across, and flush with the bank. Some vegetation cover should be present surrounding the holt.
Breezeblocks or unmortared bricks and paving stones can be used for the walls and roof of the chamber, and wood is a suitable alternative, providing the site is on dry soil.
Corrugated tin or polythene of bigger dimensions than the roof is often placed over the chamber to ensure that it keeps dry in the wettest weather. The chamber roof is usually covered with soil.