Saving rhinos from extinction
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THE Javan rhino (Rhinoceros sondaicus) is found only at the very western tip of the Indonesian island of Java, in the rainforest habitats of Ujung Kulon National Park (UKNP). This wasn’t always so.
Many species have small natural ranges, but Javan rhinos once inhabited much of Southeast Asia. Now landscape changes, habitat loss and hunting have reduced their numbers to a precarious few. The last known Javan rhino in mainland Asia was poached in 2009. Today Javan rhinos are listed as critically endangered by the International Union for the Conservation of Nature.
Recovering any wild animal population with so few individuals remaining is difficult. Small populations grow slowly even in the best of circumstances. And even if a few animals are lost to poaching, disease or other factors, the loss means a large share of the population.
It also is hard to count small populations and characterize their distribution accurately. Often this critical information is poorly known, which makes it challenging for scientists to track the population and evaluate whether their actions are having positive effects. Nonetheless, scientists and the Indonesian government are forming a plan to rescue this imperiled species.
Why counting rhinos is hard
The rhino lineage has survived 50 million years through ice ages and attacks from prehistoric animals, such as the “dog-bear.” Rhinos play a significant role in structuring ecosystems. The Javan rhino creates unique habitats within the rainforest by dispersing seeds, creating mud wallows and removing large amounts of understory plants. Losing it would mean a less diverse forest.
The first estimate of the rhino population in UKNP, made in 1937, put their numbers at 20 to 25. Since then, at least 36 surveys have attempted to count the rhinos, but most have failed to provide much insight.
Recently, scientists set up camera traps to capture images of rhinos, but without high-quality images it was hard to tell individual animals apart.
Over the past four years, I have worked as an external scientific advisor with researchers and biologists from World Wildlife Fund Indonesia and the United States, UKNP biologists, Global Wildlife Conservation and the Indonesian nongovernment agency YABI to help create a strategy for monitoring Javan rhinos.
Building on past efforts, my colleagues developed a systematic approach to deploy camera traps throughout the rhino habitat of UKNP. Expert field biologists trekked over intense rainforest terrain to install cameras at 178 locations.
Each camera was set to record a high-quality video clip of any animal that walked past. My role was to work with these expert biologists to gather statistics to provide estimates of population size and distribution.
Most importantly, we were able to precisely estimate the population of Javan rhinos at 62 animals. Javan rhino populations generally do not grow very fast. Females typically reach sexual maturity by three to four years of age, but males typically aren’t mature until six years of age. Using our statistical model, we also found that male rhinos range over larger areas than females and that both sexes prefer low-elevation areas, often near the coastline. They almost completely avoid mountainous regions of the national park. Rhinos also prefer to be close to mud wallows.
Forming a conservation plan
With this new information in hand, we are working to help the Indonesian government and its conservation partners take steps to further protect Javan rhinos in UKNP and preserve the species. Our research shows that the rhinos are at serious risk from tsunamis, since their preferred habitat is near the coastline.
Protecting the Javan rhino from extinction will require establishing additional populations, which in turn will require removing some rhinos from UKNP. Translocating wild animals is a common approach in conservation, although it can pose notable risks to the animals. But given the risks to Javan rhinos as a species, doing nothing is not a viable solution.
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