"We're nearly 100% sure this is connected to rhino poaching", reserve owner Nick Fox said.
Fox said he thinks the poachers got onto the reserve on Sunday night or early Monday morning. At the same time he'd heard a commotion coming from the lions so he suspected that's what prompted a reaction from the dog.
"The lions are our watchers and guardians and they picked the wrong pride and became a meal", said Nick Fox, 60, who owns the reserve.
The horns are prized for their medicinal value and used in traditional Chinese medicines, though there is no science to back up their touted "cure-all" powers.
The reserve is one of the most popular game serves in the Eastern Cape and is home to Africa's big five - elephants, buffalos and leopards as well as rhinos and lions.
"We thought they must have been rhino poachers but the ax confirmed it", Fox said.
"We found enough body parts and three pairs of empty shoes which suggest to us that the lions ate at least three of them but it is thick bush and there could be more", Fox said.
The reserve's anti-poaching team arrived on the scene after a field guide alerted them to the human remains.
The reserve is still open to guests.
"They were clearly intent on killing rhinos and cutting off their horns".
The poaching problem has gotten so bad that some conservationists have begun flying black rhino - the most endangered type of South African rhino - through the air, upside down, by helicopter to safer turf. It was getting too dark to search the area, so police came back the next day with the reserve's anti-poaching unit and other specialists.
So far this year, more than nine rhinos have been killed in the Eastern Cape province, according to the BBC.
More than 1,000 rhinos were killed illegally in South Africa a year ago, a shocking rise since 2007, when only 13 were killed. "At this stage, we're unable to speculate as to how the remains ended up at the scene".
"They were obviously poachers".