On the Ground in Ujung Kulon: Rhino conservation

An ongoing struggle to increase the rhino population

Today, between 50 and 60 rhinos are found in the Park according to WWF's estimates. This in itself is remarkable, since almost 40 years ago when WWF first started work in Ujung Kulon, the total population was estimated at only 25 animals.

As a result of strict conservation measures adopted by the Directorate of Forest Protection and Nature Conservation (PHPA) in conjunction awith WWF, the Javan rhino population would seem to have recovered.

» Find out about the population status of the rhino

 Population growth stalled?
But since the end of 1970s, population numbers appear to be stable. While the numbers of rhinos vary slightly from one census to another, this is thought to be because of imperfect data gathering rather than actual population fluctuations.

So why isn't the population growing? Adhi Rachmat, WWF Project Executant, outlines the possibilities.

"Carrying capacity of the rhino habitat may have been reached, meaning that space and food restrictions are preventing more rhinos from occupying their current territory within the Park". Although data suggest that the Park could support up to 100 rhinos, there is evidence that other parameters are limiting the growth of the population.

When langkap gets in the way
A palm species called langkap (Arenga obtusifolia) is spreading fast inside the Park. Its seeds are distributed by the faeces of a civet species that feeds on them. What’s happening however, is that langkap shades out food plants in the undergrowth layer, depleting the rhinos’ food base.

To counter the phenomenon, WWF is investigating ways to control the spreading of the plant species in collaboration with the Yayasan Mitra Rhino (Rhino Friend Foundation, an Indonesian NGO).
» Find out more about the habitat study

Rhinos vs Banteng?
There are other possible causes for the lackluster rhino population. Studies in the early 1980s reported that rhinos and banteng, an endangered wild cattle species, had 23 species of food plant in common (which represented approximately 12% of rhino's diet and 34% of the banteng's).

Although both animals specialize on different plant species, competition between them is likely, particularly if the availability of food plant is low. Such competition may well become severe when banteng numbers reach high numbers. The banteng population is currently estimated to be at least 500 individuals, while in 1971, only 200 banteng occurred in the Park. A study commissioned by WWF recently indicated that banteng and rhinos are now competing for space.

Potential genetic issues
Other possibilities to account for the stalling in rhino population growth include a skewed sex ratio, which would lead to difficulties in mating, and inbreeding depression (it should be kept in mind that the population has approached a bottleneck situation for at least 30 years). Indeed, data from camera trapping research suggests that there are more males than females (2:3 ratio).

Relocation not an option…
While there are insufficient numbers of rhinos to relocate some outside the Park – a minimum population of 100 would be needed - serious thought is given to move a few individuals within the boundaries of the Park. And for that, more research is necessary.

Because of its small size, the rhino population is very susceptible to disease. From December 1981 to February 1982, at least five rhinoceros died when a viral infection that first hit water buffaloes in villages surrounding Ujung Kulon park spread to the population of the Javan rhinoceros. Many Javan rhinos also died in 1935 because of anthrax.

…and neither is captive breeding
Because of the poor performance of past captive breeding efforts, WWF opposes the practice of capturing wild Javan or Sumatran rhinos for captive breeding, and fully supports conservation activities in the species' natural habitat (in-situ). In the 1980s, an attempt to breed 40 Sumatran rhinoceros in various zoos was not very successful - most of the rhinos died, and two calves were born only in the last two years.

Weighing solutions carefully
Adhi is more than aware of the weight of WWF's decisions regarding rhino management. With such a small population, any error in judgement could wipe out the subspecies, along with 40 years of gruelling work. However, the cumulative knowledge of these very 40 years of work forms the backbone of sound management for the recovery of the animal.

"It's a species we are emotionally bound to protect", concludes Adhi.