“They strayed into a pride of lions – it’s a big pride so they didn’t have too much time,” Mr Fox told AFP news agency.
“We’re not sure how many there were – there’s not much left of them.”
The remains were first spotted at 16:30 local time on Tuesday (14:30 GMT).
An anti-poaching team arrived on the scene, where a hunting rifle with silencer, a long axe and wire-cutters – equipment generally used by rhino poachers – were also found.
Police have been patrolling the area in case any of the suspected poachers survived.
Nine rhinos were killed by poachers in Eastern Cape province, where the reserve is located, this year alone.
More than 7,000 have been killed in South Africa in the past decade.