Large-scale culls have taken place since the mid-20th century. In the 1950s, an estimated 1.5 million grey squirrels were killed in Britain through bounty schemes, trapping and shooting.2 Recolonisation was extremely rapid, with populations returning to pre-cull levels within a few years.2 This pattern has been repeated ever since: local reductions are temporary, and neighbouring grey populations quickly fill the gaps. 

There are no comprehensive public records of the total number of greys killed in the UK each year, but independent analyses estimate tens of thousands—likely hundreds of thousands annually.3 Yet despite the scale of killing, there is no long-term national decline in grey numbers. 

Scientific studies indicate that culling often worsens ecological conditions. Removing greys can:

• cause increased local breeding and migration, raising grey density in the area soon after culling;4

• increase bark-stripping damage in commercial woodlands;4

• disrupt territorial stability and raise disease transmission—similar to the well-documented “perturbation effect” seen in badger culling.4

Further studies across Europe support this:

• Italy (Piedmont & Liguria): After culls, grey squirrels recolonised rapidly unless entire landscapes were repeatedly treated—an impossible, unethical and enormously costly approach.5
  
  

• Ireland (Ulster): Grey-squirrel removal only produced short-lived benefits; habitat quality remained the determining factor for red survival.6
  
  

• England & Scotland: Modelling consistently shows that habitat structure, connectivity and conifer dominance—not grey density—predict long-term red-squirrel viability.7

The scientific consensus is clear:

Culling greys is expensive, cruel and ineffective, and it fails to secure the future of red squirrels. 

Killing greys on an industrial scale has not helped red squirrels for 70 years—and it never will. 

Text has been kindly reproduced, with a few minor alterations, from:  

https://viva.org.uk/animals/other-animals/squirrels/