Poachers have killed 158 rhinos in South Africa's national parks since the beginning of the year, a rate of more than two a day, environment officials said on Friday.
The vast Kruger National Park which borders Mozambique has registered 116 killings, despite beefed up anti-poaching initiatives by park authorities.
In December, Kruger acquired a military aircraft equipped with sophisticated surveillance technology to detect poachers.
"A total of 61 people have been arrested, 38 of them alleged poachers and three alleged couriers," said a statement.
Parks in the mining province of North West and the eastern KwaZulu-Natal reported 12 and nine killings respectively.
Poaching figures have reached alarming levels. Only 13 rhino were killed in 2007.
Amid the crisis, the South African government is mulling the legalisation of rhino horn trade in a bid to curb the slaughter.
South Africa has had a moratorium on rhino horn sales since 2009.
Rhino poaching is driven by a booming demand for their horns in the Asian black market where the fingernail-like substance is falsely believed to have powerful healing properties.
Explore further: Nearly 200 rhinos killed this year in South Africa: WWF