Rabinowitz acknowledges the greater urgency for captive breeding, but disputes whether the data on population size, sex ratio and breeding success in the wild are good enough to say that wild populations are in terminal decline or that captive breeding — “an absolute last resort”, he says — is the only option. “When you lack information and just say there's no hope, then you're really writing the end of the book.”
Before her ultrasound scan, the unsuspecting Puntung is lured into a small pen by a bucketful of diced bananas. Hildebrandt's colleague Frank Göritz loads a syringe with a dose of sedative calculated to send her into a standing anaesthesia, then reaches through the bars to plunge the needle through her sparsely haired hide. Within seconds, she has relaxed into a sling, which supports her bulk and makes it easier to insert an endoscope into her uterus than if she were lying down.
When Robert Hermes, the third member of the team, slides his gloved arm into Puntung's rectum she barely flinches. She has undergone a period of intensive coaching to tolerate medical procedures. Now, it is impossible to tell that she's undergoing a transrectal ultrasound scan, were it not for the vet squatting at her rear.
Almost an hour later, however, the first signs of stress are showing — though not from Puntung. The ultrasound is over and Hildebrandt is struggling to insert the carbon-fibre catheter into her uterus. On his knees, with his right arm deep in her vagina and his cheek brushing up against her buttocks, his face is a picture of concentration and his scrubs are darkening with sweat. Puntung's cervix, tightly constricted owing to the phase of her menstrual cycle, is proving a serious obstacle to the catheter.
Eventually, Hildebrandt triumphs and is able to flush out the uterus with a sterile cell medium, which will be tested for any underlying infection. With the cervix so narrow, there is no hope of moving on to the bigger-bored endoscope, but before Hildebrandt removes the catheter he injects a highly concentrated penicillin solution. This will destroy any pathogenic bacteria, and is so concentrated that it may actually strip away some of the lining and cysts, possibly making it easier to attempt fertilization and embryo collection. Hildebrandt has successfully used this approach to boost the fertility of two tigers and a leopard. If it doesn't work, the favoured next step is to carry out a similar procedure at a future date, but to inject a more caustic chemical such as kerosene to attack the cysts. This carries a risk. The team has to make sure that the treatment “is not so aggressive that it destroys the uterus”, Hildebrandt says.
Before the vets call it a wrap, there is still time to take a cast of Puntung's stump, which will be used to fashion a prosthetic foot. This will allow her to move around with greater comfort. If she ever gets a chance to mate with Tam, the foot will also be handy for supporting his weight on her back during the half-hour encounter.
Even if embryo collection proves unsuccessful, it might not be the end of the road for Puntung. It should be possible to collect immature eggs, by inserting a fine needle through the wall of her rectum and into her ovaries. The challenge is getting them to mature and fertilize in vitro. The IZW vets have attempted this with white and black rhinos. They obtained 29 eggs and managed to fertilize one, but the embryo did not progress beyond the four-cell stage. The only attempt to harvest eggs in Sumatran rhinos — from Cincinnati Zoo's star female just after her death in 2009 — was unsuccessful.
There are other, more futuristic options. In theory, Puntung could be cloned, taking a nucleus from one of her cells and injecting it into an egg stripped of its own DNA. That rhino eggs are in short supply needn't be a problem, says Pasqualino Loi, a reproductive biologist at the University of Teramo in Italy, who, more than a decade ago, used domestic sheep as a source of eggs and surrogates to clone an endangered sheep relative, the mouflon. “Play around,” he suggests. “Inject some rhino mitochondria and a nucleus into a horse egg.” It's just possible, says Loi, that it could result in a viable embryo that could be successfully nurtured to term by a surrogate mare.