Campaigners who want grouse shooting banned in Scotland have been accused of subjecting gamekeepers and moor owners to a "campaign of intimidation".
Gamekeepers have reported vandalism, abuse and having their family homes filmed by wildlife activists, with one estate employing security guards to protect staff.
Ahead of the start of the grouse-shooting season on Monday, estate owners have expressed fear that licensing could be the "first step" to banning the controversial activity.
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Citing about 300 allegations of vandalism and trap thefts, moorland groups have claimed "no estate is safe" as the Scottish Government considers whether to introduce licensing for grouse shooting.
Shooting estate representatives argue that campaigners opposed to grouse hunting would use a licensing system to make false claims in an attempt to strip them of their licence.
Lianne MacLennan, a spokeswoman for Scotland's regional moorland groups, said a Grampian estate has employed a security firm after "covert cameras" were allegedly used to record footage of gamekeepers' homes and GPS trackers were illegally attached to their vehicles.
Describing the situation as a campaign of intimidation, Ms MacLennan said: "It should be everyone's right to work without fear. That is no longer the case for a gamekeeper in Scotland.
"The strain on them, partners and kids would not be tolerated in any other walk of life.
"If licensing is introduced, this will only escalate. Campaigners want grouse shooting banned. This is their green light. Licensing is their first step.
"People have a right to know what protection they are going to have, if this comes in.
"If anyone is breaking the law, they deserve to be punished, but no estate is safe and we ask Scottish Government to consider evidence carefully before making decisions which will affect families' lives.
"Because nothing is being done to protect estates just now, it is becoming passively accepted in Scotland that people can go on to land, cause wilful damage and manufacture problems for those involved in occupations that campaigners don't like."
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A gamekeeper, quoted anonymously by the pressure group, said: "I've been filmed, verbally abused, verbally threatened and had very unpleasant messages left for me.
"On most occasions, I have a firearm so I never respond as I would put myself in a difficult position, no matter how innocent I am.
"We've had 33 incidents of damage since last July and on most occasions, the police don't even know if a crime has been committed, nor do the Wildlife Crime Unit. We've lost countless work hours and thousands of pounds in revenue."