The Javan rhino, Rhinoceros sondaicus, is critically endangered in a small area of Ujung Kulon National Park, Indonesia, with a population of about 70 individuals. Threats such as tsunamis, disease, and poachers exacerbate the risk to their survival. NGO Auriga Nusantara's reports of mismanagement in the park raise concerns, including claims of rhinos that should be dead but are still officially listed as alive.
A recent paper in the journal Gazella suggests new measures, detailing the idea of cutting down large trees in national parks to expand rhino foraging areas. The research also highlighted concerns about inbreeding in the population, leading to proposals for the establishment of captive breeding facilities as a preventative measure.
Francesco Nardelli, study author from IUCN's Asian Rhino Specialist Group, said genetic studies of Javan rhinos showed low genetic diversity in the population. This is often associated with inbreeding depression, increased disease risk, and reduced fitness.
In line with his findings, the government's management program for endangered Javan rhinos, which details plans for the period 2023-2029, revealed that 13 Javan rhinos had "congenital defects," most likely caused by decades of breeding in small groups.
Food or tree felling?
The gender imbalance in the Javan rhino population, with fewer adult females than males, is another concern. According to Francesco Nardelli, there are only about "a dozen" adult females capable of breeding, and although they continue to give birth, the process may not be fast enough to increase or sustain a population that has now bottomed out at around 70 individuals.
To address the genetic problem, Jan Robovský, a biologist at the University of Southern Bohemia in the Czech Republic, suggests that creating a larger population is the best way to go. However, concerns have been raised that the current population may already be at its lowest limit, around 70 individuals and that the existing habitat may not be able to support an increase in numbers.
Robovský compared the Javan rhino to the Indian rhino, a larger rhino species of the same genus. While the Indian rhino population recovered quickly after poaching was stopped, the Javan rhino population has not experienced a similar recovery. Whether this is due to continued poaching in the park or limited space and food resources remains a question that needs to be answered.
Nardelli and Robovský recommended that one way to address Javan rhino food scarcity is to cut down some of the large trees in Ujung Kulon National Park. Nardelli emphasized that as foragers, Javan rhinos rely on foliage as their main food source. Creating open land is expected to stimulate the growth of forage plants, provide a more abundant food source, and make it easier for rhinos to access food, especially given the limited habitat within the park.
Although park management has attempted to cut down fast-growing palm trees to make way for plants favored by rhinos, Nardelli and Robovský expressed the need to continue felling trees in areas not yet overrun by palm trees.
The government's Javan rhino management plan for 2023-2029 states that "a new management system will be designed to optimize the carrying capacity of the Javan rhino habitat," but provides no further details.
Nina Fascione, head of the International Rhino Foundation (IRF), which is working with the Indonesian government on rhino conservation in Ujung Kulon, said that additional improvements in habitat management would make a significant contribution, but asked for a more detailed explanation of the researchers' proposals.
Robovský also suggested removing some banteng from the national park to reduce competition with Javan rhinos for food. Although banteng is listed as an endangered species, Fascione emphasized that the current focus is on protecting the wild, naturally reproducing rhino population.
Talking about captive breeding, Nardelli and Robovský also recommended the establishment of a captive breeding center for Javan rhinos, following the model successfully used for Sumatran rhinos (Dicerorhinus sumatrensis).
Although captive breeding is on the agenda of the government's management plan, experts are hopeful that it will not be implemented any time soon. According to Fascione, captive breeding has the potential to be a critical tool in Javan rhino conservation efforts. He added, a captive conservation program with careful genetic management and rapid population growth could be one of the best solutions to this challenge.
Currently, the Indonesian government is developing a new complex within the national park known as the Javan Rhino Study and Conservation Area (JRSCA). Once this project is completed, the government's plan states that it will consider "translocation of selected individuals.
Nardelli explained that introducing some rhinos into a semi-wild captive breeding program could contribute to the scientific understanding that improves the survival of the species. In a controlled environment, researchers can monitor reproductive behavior, conduct reproductive physiology studies, and collect valuable data to support conservation efforts in captivity and natural habitats.
Although Sumatran rhinos are more vulnerable, with a population that may number fewer than 50 individuals, more in-depth knowledge is being gained through years of research in captivity. In contrast, the Javan rhino has not been recorded in captivity for more than a century, making it one of the least understood rhino species.
For example, the paper notes ongoing misunderstandings regarding a Javan rhino specimen in Italy that was previously misidentified as a larger one-horned rhino. This error is recognized as common and, according to the authors, requires a re-evaluation of all specimens in museums and collections around the world.
Addressing the lack of knowledge about the reproductive behavior of Javan rhinos, Nardelli emphasized the importance of such information for the development of effective conservation strategies, which can only be assessed through captive breeding programs outside their habitat.
Efforts to establish a second site for Javan rhinos in the Indonesian wild have been advocated by conservationists, with the goal of expanding the population beyond Ujung Kulon. However, the Indonesian government has yet to decide on a location, and plans to search for "another area" have been halted since 2019, with no sign of resumption.