The plight of the cats, which live in a woodland area, came to light after one was killed by a snare trap last month. Such traps are legally permitted if used to catch species classed as vermin, which feral cats are.
However, members of the public expressed shock at the action taken by estate staff, pointing out that it would be easy for a pet cat with an owner to be culled unintentionally.
Yorkshire Cat Rescue, Cat Action Trust, Keighley Cat Rescue and campaign group Ban Bloodsports on Yorkshire's Moors have all since approached the estate offering to safely round up the cats at their own expense. The animals would then be neutered and attempts made to re-home them, possibly on farms.
None of the charities were given permission to undertake such an operation, although the estate management has confirmed it is exploring options for future cat control with an unspecified external organisation.
Cats Protection's veterinary director Dr Maggie Roberts also wrote to the estate expressing concern over the practice on behalf of members and volunteers and advising humane and effective solutions to feral cat control issues.
Dr Roberts warned that it can actually be counter-productive to remove feral cats entirely from an area, as they are territorial animals whose place will immediately be taken by encroaching rivals. Instead, she condones neutering all of the cats and then returning a manageable number to the woodland to prevent the colony's numbers from expanding further.
A spokesperson for the Bolton Abbey estate said: "Bolton Abbey is currently in discussions with an external organisation to examine alternative, effective means of preventing feral cats from threatening endangered animals on the estate. This is a complex issue relating to a very large area and we will provide a further update in due course as these discussions progress."
Although large areas of the estate are open to visitors, there is also managed game shooting on the moors of Bolton Abbey. No shoots took place in 2020.