Two Sumatran rhinos are pregnant at an Indonesian sanctuary, raising hopes and inbreeding concerns

Two critically endangered Sumatran rhinos are pregnant at the Sumatran Rhino Sanctuary in Way Kambas, Indonesia, a rare boost for a species with only a few dozen animals left in the wild.

Indonesia's Ministry of Forestry and Yayasan Badak Indonesia (YABI), the nonprofit that runs the sanctuary, announced Oct. 3 that a female named Ratu is carrying her fourth calf and her daughter Delilah her second. Both are due around May 2027. If Ratu's calf is born healthy, she would become the first known Sumatran rhino to give birth four times.

The pregnancies also expose the program's narrow gene pool. Ratu's calf was fathered by Andalas and Delilah's by Harapan, full brothers born at the Cincinnati Zoo. Because Andalas is also Delilah's father, the father of her calf is her paternal uncle. All the males among the 11 rhinos in the program, the only captive Sumatran rhinos in the world, are related.

"The current critical situation outweighs the genetic diversity considerations," Nina Fascione, executive director of the International Rhino Foundation, told Mongabay.

A specialist group at the International Union for Conservation of Nature (IUCN) estimates that 34 to 47 Sumatran rhinos remain in the wild, scattered in isolated groups. Because the animals are solitary, small populations struggle to find mates. Only five calves have been born at the sanctuary since captive breeding began in 1984, and miscarriages are common: Ratu lost two pregnancies before her first calf was born in 2012.

This brief is based on reporting by Basten Gokkon, published Oct. 14, 2026, in Mongabay. Read the original: https://news.mongabay.com/2026/10/two-rare-pregnancies-spark-hope-for-sumatran-rhinos-but-also-concerns-about-inbreeding/