A Sumatran rhino has given birth to a record-setting third calf, again raising hopes among conservationists that the critically endangered species could be on the road to recovery.

The Cincinnati Zoo & Botanical Garden announced Monday that Emi delivered a healthy, 86-pound male calf at 10:59 p.m. on Sunday.

No other rhino has given birth to more than one calf while in captivity, a zoo statement said.

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Emi's first delivery, to a 72-pound male in 2001, was the first by a Sumatran rhino bred in captivity since the 19th century. That calf was sent to Indonesia earlier this year to take part in another breeding program.

A 75-pound female, delivered by Emi in 2004, remains at the zoo, the statement said.

The zoo's breeding program grew out of an international recognition in the early 1980s that the Sumatran rhinos were disappearing at a rapid pace, due to poaching and dwindling rain forest habitat in Malaysia and Indonesia. It's believed that fewer than 300 Sumatran rhinos survive.

A decade ago, little was known about caring for the Sumatran rhinos in captivity, let alone their mating habits and reproductive cycles.

But zoo staff have relied on the use of ultrasound, close monitoring of hormone levels and years of patient observation and trial-and-error to learn how to successfully mate the Sumatran rhinos.

The zoo is home to the only four Sumatran rhinos in the United States. Emi and the zoo's male, Ipuh, are on loan from the Indonesian government, the statement said.