In that case, if they have (historically) remained undisturbed, free of poaching and well protected over the last fifty years or so, the rhino population should be approaching that sort of level anyway. Maybe these surveys just don't show all the animals that are actually there- its not exactly easy terrain for scientists to work in.
I can't really see how the population can be effectively be determined but its good to know there are young animals present.
The rhinos have been relatively well protected over the last 35 years or so. WWF has been involved in the project's inception and has continued supporting the sanctuary and its staff with rhino conservation measures and ecological research over this entire time frame.
However, ecological research in a dense jungle environment requires is a long term effort requiring well trained scientific staff and adequate (in numbers and intensity), continued patrolling and report documentation by both scientists, forestry staff and rangers as well as adequate standardised equipment and technological resources to effectively study the rhino and other faunal and floral as well as environmental factors in the sanctuary.
Whereas intensive research has been done since its inception, technological advances (camera trapping, non-invasive genetic biological materials and statistical absence/abundance studies) have only been applied since the early 2000's. These have allowed for far more detailed data on the rhino population than previously possible. Earlier estimates were more or less based on anecdotal evidence (spoor, track width-length, mudbath, feeding areas and other rhino activities) as well as some but rare actual sightings and were essentially/could have been either over- or underestimates.
The new technology has allowed for more accurate data on the structure and make-up of the rhino population. Not unimportantly so the current estimate of the potential of the sanctuary to accomodate 100 Javan rhinos is based on the best case assumption of optimum habitat and ecological/environmental conditions. The optimum conditions for this number of Javan rhino have not yet been fully addressed and several negative factors are impacting the potential for growth in the rhino population.
Habitat surveys have determined that there is some evidence that a native plant species is an obstacle to major rhino food plants from flourishing and thus impacting the possibilities for population increase and frequency of births. Another outcome of the habitat surveys is that the density of Javan banteng in the sanctuary may actually negatively impact the rhino numbers in the sanctuary through food source competition. Sanctuary management has embarked on a programme to remove some of these potentially negative factors by proposing to relocate a significant portion of the local Javan banteng to other reserves with no or low banteng numbers and large scale removal of the competitor plant species. and equally has increased the research capacities of its research staff.
An outcome of the earlier scientific research has shown that patrolling of the sanctuary requires more manpower and a well-trained ranger force. Hence, the number of rangers has increased, the number of patrols has increased, the area of patrolling has been extended (to also include the sea entry points for the sanctuary), training has improved and financial recompense has been improved (allthough just part of the ranger force enjoys this benefit under the Rhino Patrolling Unit programme supported by WWF/IUCN and EAZA/AZA zoos).
The camera trapping, visual sightings and anecdotal rhino sign have underlined that the sex ratio in the rhino population may be somewhat skewed towards the bulls. However, this could equally be a reflection of the fact that cows generally tend to be even more secretive nature ... lest they attend to calves etcetera).
All the above factors exemplify that only in the last few years have estimates of the rhino population been anywhere more reliable and yet not 100% fool-proof. Only more intensive ecological research can provide an accurate estimate of current rhino numbers and population structure and sex ratio. If all these population data are known within a 90-95% confidence limit, then sanctuary management can actually decide to transfer out Javan rhinos for establishment of a second rhino population. It is hence a long term project and in a very dense and remote rainforest environment that provides extreme challenges to both scientific and ranger/forestry staff.
Hence, we may be a long way off yet from achieving the optimum number of Javan rhinos in Ujung Kulon. However, I do think that the setting up of a satellite rhino population within central Java and absorption into this sanctuary of some Ujung Kulon Javan rhinos may be closer than we might think. Alltogether, the outlook for Javan rhinos at Ujung Kulon is much more positive than the Vietnamese population (which may well now be functionally extinct ... allthough that is not a reason not to continue trying to increase their numbers through better habitat and species conservation). A formative estimate of 55-60 Javan rhinos and continued breeding over an extended time-frame (since 2000 at least 11 calves ...) bodes well for this taxon.
I'm going to be in Ujung Kulon next year, probably around October some time (if all things go to plan)
