Water voles are one of the key species on drains and other waterways within the Middle Level. A UK Biodiversity Action Plan species, water voles have suffered over 90% reduction in their distribution country wide. This was in part due to the loss of their habitat from human activity but mainly due to the introduction of American mink, an invasive non-native predator for which water voles did not have an escape strategy. The Fens have however remained a stronghold for water voles and the Middle Level has one of the largest populations in the UK spread along 1,000 kilometres (620 miles) of ditches, drains and rivers in its catchment.
Water voles look like miniature beavers. They are vegetarian, nocturnal and industrious waterside engineers.
Several different surveys of water voles have been carried out in the Middle Level at different locations over the years. The Drainage Districts of Curf Fen and Ransonmoor have been surveyed three times over a 10 year period, in 2005, 2010 and 2015. A report written by Ruth Hawksley, Water for Wildlife Officer for the Bedfordshire, Cambridgeshire and Northamptonshire Wildlife Trust details the 2015 survey results and compares them with the two previous surveys.
It can be downloaded here: Curf & Ransonmoor 2015 Water Vole Survey Final Report
The 2010 survey report can be downloaded here: Curf & Ransonmoor Water Vole Survey 2010
The 2005 survey report can be downloaded here: Curf & Ransonmoor Water Vole Survey 2005
The 2015 survey confirmed the results of previous surveys that the Internal Drainage Board (IDB) managed ditches had high levels of occupancy by water vole with 70% positive at Curf Fen and 93% positive at Ransonmoor. The privately managed ditches are less frequently cleaned out and had lower levels of use but even so 52% at Curf Fen had water voles present and 68% at Ransonmoor. The results also confirmed that cleaning out of drains on a regular basis (typically on a four year cycle) is a positive benefit for water voles. It promotes the growth of a diverse selection of young water plants, providing the age and variety they prefer.
One of the most effective methods of surveying for water vole signs is from a canoe. Ransonmoor 2010.