Ipuh's the males name and nowhere did anyone mention that they wouldn't mate anymore? I hope they'll try as many times as they can, which such low numbers any youngster would be invaluable.
If they stop breeding with Ipuh, perhaps he'd be better off in Sumatra together with Bina, Rosa and Ratu but he's also getting on in age.
And Ai for Suci will have to be with Torgamba's sperm to have any genetic effect (or else she could just be paired with Ipuh instead). But that sounds close to impossible for quite a few reasons:
1. Why would you attempt Ai in the USA when there are 2/3 better suitable females right NOW at Way Kambas? Wouldn't it be better to pioneer the proces right there?
2. Torgamba's sperm is of quiestionable quality
3. This is supposably an "induced ovulating" species, meaning that she would need to be with a male in order to ovulate? Perhaps an hormonal treatment would work?
Just my 2 cents anyways, i love this species and i hope everything will turn out okay for them (with a huge back-up population in captivity in the end)