Normally zoos wouldn’t even consider captive breeding of related animals. But with the total world population of Sumatran rhinos estimated at fewer than 100, Cincinnati Zoo says the hope they could produce young rhinos outweighs any potential risk.

 

Sumatran rhinos are possibly the most endangered large mammals on the planet. Fifty percent of the population has disappeared in the past two decades, the result of human encroachment on their forest habitat and poaching for their valuable horns. The smallest of the rhino species, Sumatrans rhinos have two horns and a light coat of brown fur. They are the only surviving member of their genus and are closely related to the woolly rhinoceros (Coelodonta antiquitatis), which went extinct several thousand years ago.

 

Cincinnati zookeepers hope that Harapan (a.k.a Harry), a six-year-old male, and his older sister Suci, an eight-year-old female, can help reverse their species’ population decline. To increase the chances of successful breeding, zookeepers will use a technique of captive breeding which requires them to monitor Harapan’s testosterone levels and use ultrasound to figure out when Suci is ovulating. The animals—which are solitary by nature—will be kept apart and only introduced to each other during potential breeding windows.