As the volunteers make their way down stream, gently parting the riverside vegetation looking for signs of water voles, frequent finds are shouted back to Reeves.
The constant updates of today’s chart perhaps masks the spectacular decline of what was once a constant along our waterways.
It is estimated the spread of non native American mink saw 90% of water voles wiped out since the 1970s.
Together with the loss of habitat it now has the unenviable title of the fastest declining mammal in Britain.
But on the River Meon the future of the water vole is looking a little brighter.
More than 2,800 water voles have been released as part of the Meon Valley Partnership since 2013.
The joint project between the South Downs National Park Authority, conservation groups and landowners appears to have halted and reversed the dramatic decline.
Regular surveys have shown they are breeding and thriving with no sign of American mink along the waterway.
