A third artificial otter holt has been built at the Co-op farm in fenland.

Co-operative Farms, which runs a ground-breaking scheme to protect otters on its Coldham estate, near Wisbech, called 'Habitat Heroes', is working with the Middle Level Commissioners (MLC) to help preserve the protected mammals in fenland waterways.

The holt was designed and built into the banks by Cliff Carson, environmental officer for the MLC, and features an infra-red 'otter-cam' to view the animals when they visit the holt without disturbing them.

Built to last more than 20 years, it is made with blocks and paving slabs with two entrance pipes at the water's edge, which are the only parts visible on completion.

It is one of a network of 73 otter holts installed throughout the Middle Level, a drainage area in the Cambridgeshire and Norfolk Fens, managed by the Middle Level Commissioners. It is adjacent to a drain managed by Waldersey Internal Drainage Board, which is one of over 25 drainage boards administered by the MLC.

Mr Carson, said: 'We have monitored otter activity at the Coldham site since we installed the first holt in 2011 as part of the Habitat Heroes project and we are thrilled with the results so far.

'We have captured some great footage in the holts, which have been visited by both males and also females with their young. The holts are being used, so there is definitely a need for them, and there are positive signs that there is an increase in otters in the area.'

Habitat Heroes was launched in 2011 to identify where investments and adaptations could be made on six farms across the country, owned or managed by Co-op Farms.

Tom Paybody, farm manager at Coldham, added: 'It's great news that there is increased otter activity on the farm and that they are using the holts. All the signs are very encouraging and if this latest holt also proves a success, there is the potential to build others at Coldham and provide a safe haven for even more otters in the future.'

It has been farming at the Coldham site since 1912 and grows onions, potatoes, shallots, sugar beet, beans, wheat and oilseed rape.

producing honey.

It is also the site of the Co-op's first windfarm, which was set up by the group in 2005 with Scottish Power.

Clips of otters using the original holt can be seen at www.co-operative.coop/farms/habitatheroes/Habitat-heroes-videos/