Goats, banteng, boars, camels and water buffalo - all are present and are doing significant damage, particularly the buffalo. Adding another large mammal into the mix is just stupid, and in contravention of Australian laws. They can be prevented by not importing rhinos. Everything you've said. The largest mammals up that way are kangaroos. They move through the forest without damaging it, and they feed on grasses. Possums and gliders feed on leaves, usually in the treetops. A large bulky animal like a rhino will damage the substrate, trample the undergrowth and eat a lot of vegetation - assuming it can find something palatable. Australian forests are not the same as Javan rainforests - we have our own biota. Hix
The problem is that this will likely *never* happen - although stable, I believe the current population is at carrying capacity. This puts us in something of a catch-22; the species needs an ex-situ population to be secure, but at present the in-situ population is so low an ex-situ population is unfeasible and may put said population in risk. Moreover, the in-situ population cannot be expanded to new reserves and sites to allow it to grow to the point where an ex-situ project is within accepted margins of risk *because* in order to get individuals to these new sites we would have to capture individuals from the wild - which as already noted is deemed unfeasible until numbers are high enough. Or to summarise without the waffle; we can't capture individuals for an ex-situ population until the in-situ population is high enough, but the in-situ population won't be high enough until we capture individuals to allow further in-situ populations to be formed, but we cannot capture individuals for a new in-situ population until the existing in-situ population increases.... which it can never do until there are new populations to allow for expansion.
Various sources and relevant excerpts from each: Rhinos.org | Javan Rhino Conservation Program https://www.savetherhino.org/asia_programmes/jrsca Javan Rhino | WWF Indonesia
These are outdated info you are all quoting: the current identified population is in the low 60's and recent expansion into the new area - which is currently used by 7-8 rhinos (an area previously out of bounds and with unsuitable habitat, now with Arenga eradication et cetera new).
As TLD pointed out, the possiblity for expansion to a larger scale of the current population is limited, unless some individuals are going to be relocated to leave space in the national park for more Javan rhinos that will come (newborn to grow and then separate from their mothers). If not Northern tropical Australia (wich is more politicaly stable and safer for animals than Indonesia), then maybe some smaller near to Java islands (without endemic-for-that-island fauna/flora) of Indonesia or Australia can be used as relocating places (but the danger of natural disasters would remain). Of course this is just like optimistic enthusiatic idea of an animal lover, but can be considered as possiblity in the future, and thus I love to read different opinions.
As for method for capturing. It may be invented some less stressfull and less invasive procedure than traping in a classical hollow trap. Like for example fencing the forest wich fenced part would lead to narrower and narrower passage that will end up in a truck (decorated with trees, leaves on the floor) while herding a rhino(s), and translocation to the new location and releasing as soon as possible, without a rhino even to see a human (covered with leaves while working behind scenes). This just like one different hipothetic approach.
Why are you still hung up on trying to catch the animals when it's been shown by multiple people on here that leaving them in place for the time being is the safest thing to do? The more you harp on about catching wild animals or importing them from shady dealers, the more unethical you come across.
I think that leaving them in place is the safest thing to do, too. But because the possibility for future expansion of the population is very limited, I loved to discuss some alternatives for future (more distant future if you want). In no case when animal needs (including survival of the species) should be in the first place, I don't want to be unethical. So I will leave it now and read any other posts on this thread.