Birth control measures for Wensleydale grey squirrels
Grey squirrels in North Yorkshire are being given contraceptives in their food in a bid to control their population.
The move is being made in Wensleydale to help the red squirrels which live there thrive.
The red squirrel has been in severe decline in the UK as the greys, which are not a native species, increase.
It is believed that greys act as carriers of squirrel pox - which kills reds.
Watch the full report on Inside Out Yorkshire and Lincolnshire on BBC One at 19:30 on Monday 6 February or via the BBC iPlayer for seven days after the initial broadcast.