Footage of mountain hares being killed on a Scottish estate has prompted animal rights charities to call for immediate action.
An investigation by OneKind, League Against Cruel Sports and Lush shows "military style" mass killing of the animals on grouse moors.
Mountain hare shooting is among of the activities offered by Scottish game estates and managers to protect red grouse for sport shooting.
Campaigners, supported by broadcaster Chris Packham, are calling on the Scottish Government to take immediate action and end the killings.
Harry Huyton, director of OneKind, said: "Our investigation has revealed that instead of restraining themselves, as the Scottish Government has asked them to do, some estates seem to be at war with mountain hares.
"We filmed large groups of armed men moving around the mountains in convoys, killing hares and filling their pick-ups with dead animals as they go.
"The voluntary approach has failed, and the Scottish Government must take urgent action if it is to prevent further killing before the open season starts once again in August."
Chris Packham, conservationist, naturalist and TV presenter, said: "It is clear that self-restraint is not preventing large-scale culls of mountain hares on grouse moors and, as such, the law should be changed before we lose another iconic species from our uplands."
Mountain hare killing is not monitored in Scotland, however a Scottish National Heritage study estimates 25,000 mountain hares were killed in 2006/07.
This is understood to be between 5-14% of the total population.
Animal campaigners say approximately 40% of those killed are shot for sport shooting, and 50% as part of organised culls.
Robbie Marsland, director of the League Against Cruel Sports Scotland, added: "Mass killing of mountain hares is just one part of the intensification of grouse moor management in Scotland.
"Any animal that appears to threaten the red grouse is targeted by traps and snares or shot."
The charities are calling on the Scottish Government to impose an all year-round close season on hare shooting until a review by Lord Werity on the issue concludes.
A Scottish Government spokesman said: "The large-scale culling of Scotland's iconic mountain hares has the potential to put the conservation status of the species at risk.
"Video evidence and eye-witness reports indicate these culls are continuing, despite an agreement with land management organisations which was designed to ensure landowners showed voluntary restraint.
"The Scottish Government is now seeking urgent meetings with relevant stakeholders, while considering all available options for additional protections."
Tim Baynes, director of the Scottish Moorland Group, added: "This footage has been filmed by animal rights activists, who actively campaign against this type of land management, and have no interest in managing the balance of species and habitat on Scotland's heather moorland.
"Mountain hare management is not only legal but necessary and is carried out within a regulatory framework of closed seasons and licences administered by Scottish Natural Heritage."