An advertisement on their website says: "We are dedicated to finding our clients the best quality trophy's [sic].
"We hunt several concessions dependent on the game desired.
"We offer you tranquillity and a unique opportunity for hunting all year round."
"Hunting safaris" are priced at up to $9850 per person, with costs rising for more dangerous game and being lower for smaller wildlife including impalas and wildebeest.
Company founder and owner Fredrik du Toit told The Independent Mr Ermey had hunted with them two years ago.
He added: "The lions he shot were wild. There are certain rules everybody abides by in South Africa.
"The lions must be life-sustained and feeding for themselves.
"It's all regulated with permits and everything is legal."
Mr du Toit said his firm only shoots old animals and those that can no longer reproduce.
He claimed he and his family had received death threats because of his work.
Dr Kat said there is a lucrative hunting tourism trade in South Africa, which is one of the only places in the world where it is legal to kill lions.
Some hunts use animals bred in captivity that are released by firms for paying customers to shoot, he said.
Speaking to The Independent, Dr Kat said: "It's not hunting. You're not tracking these animals through the savannah or anything like that, there's no skill involved.
"It's about as difficult as shooting a cow in a field - it's just an ego trip.
"It's not hunting, it's just killing."
Because the animals are used to human contact, they are easier to catch than wild animals, he added.
The campaigner said: "You can even choose what lion you want to kill beforehand from pictures, like a menu."
In some cases, captive lion cubs can also be used to attract gap year students into paying to volunteer at "animal orphanages", he claimed.
A report by Lion Aid estimated that there are only 15,000 lions left in the world.
The charity is campaigning to illegalise lion hunting and stop the EU and USA allowing lion corpses and trophies to be imported.
- Independent
