Conservationists wept in joy as the healthy female calf was born on western Sumatra island on Thursday, just the fifth rhino of its kind born in a breeding facility.
The newborn was walking within hours and has since grown stronger, feeding and bonding with its mother, a conservationist at the rhino sanctuary in Sumatra told AFP.
Sumatran rhinos are extremely rare, with just 100 believed to exist worldwide.
"Every birth counts," she told AFP from Sumatra.
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"One birth doesn't save the species, but it's one more Sumatran rhino."
Sumatran rhinos are targeted by poachers as their horns and other body parts fetch high prices on the black market for use in traditional Chinese medicine.
Their rainforest habitat on Sumatra island is also being destroyed due to the rapid expansion of palm oil and pulp and paper plantations.
Last year, they were declared extinct in Malaysia.
The remaining rhinos, distinctive for their woolly hair and twin horns, often exist in small herds of two to five within their jungle habitats in Indonesia.
It will be at least six or seven years before the newborn is ready to mate. For now the calf -- which has not yet been named -- will remain in the sanctuary where she's under 24-hour observation.
"She seems to be healthy," Ellis said.
"They come out and they're so skinny, but she's started to fill out a little bit today."
It was the second time the newborn's mother, Ratu, had given birth at the facility.