Scientists have found signs of four Javan rhinos born in recent weeks in Indonesia, a surprising baby boom for a species that may be reduced to fewer than 60 individuals worldwide.

Signs of the rhino calves were discovered in Indonesia’s Ujung Kulon National Park by a team of biologists, including park rangers and WWF staff, and local people checking on the rhinos after the recent earthquake on the island of Java. These are the first known births for the Javan rhinos in three years.

“Javan rhinos are probably the rarest large mammal species in the world and they are on the very brink of extinction,” said Arman Malolongan, Director General of Forest Protection and Nature Conservation at Indonesia’s Ministry of Forestry. “To discover that this population is breeding – and even slowly growing – gives us hope for the species’ future.”

Javan rhinos are the rarest of the world’s five rhino species and are critically endangered. It is estimated that between 28 and 56 Javan rhinos live in Ujung Kulon. The only other known population is in Cat Tien National Park in Vietnam, where no more than eight rhinos likely survive.

The team found the first sign of a calf a few weeks ago, with the discovery of a small footprint (about 16-17 cm) along with a larger footprint belonging to the mother. One day after this first discovery, another set of mother and calf footprints of slightly different size was found in a different area.

Both signs were estimated to be three days old or less. On the same day, a second team came face-to-face with another calf, which they were able to identify as a female, and her mother. And the following day, the team found a fourth small footprint in a different location.

“Javan rhinos live deep inside the rain forest and it’s very unusual to catch a glimpse of them,” said Adhi Rahmat Hariyadi, Site Manager for WWF-Indonesia in Ujung Kulon National Park.

“Our team was lucky to actually be able to observe a mother and calf on the regular route from north to south of Ujung Kulon Peninsula when checking camera trap installed in the area.” Because of the distance between the four areas where the discoveries were made and the differences in the size of the footprints, the team concluded they are evidence of four different calves.

WWF and park staff hope to capture photos of the newborns from remote-triggered camera traps used to monitor the rhinos. With this new evidence that the Javan rhino population in Ujung Kulon is breeding, WWF recommends that the park authorities find ways to reduce the main threats to this rare species, such as habitat and food competition with wild cattle within the park, and invasive vegetation that limits the expansion of the rhinos’ favourite plants. WWF also calls for the establishment of a second population of Javan rhinos outside the park to protect the species from disease or natural disasters that could wipe out the entire population.