TARONGA Western Plains Zoo has a long-term plan to solve the mystery deaths of four female white rhinos almost a year ago.
Senior keeper of white rhinos Pascale Benoit yesterday revealed the zoo had frozen and stored samples in the hope that future scientific advances could make them useful in determining why the animals died.
Ms Benoit, who still wipes away tears when she speaks of the dead rhinos, has previously stood at the open-range zoo's white rhino exhibit and counted 10 of the "magnificent" and endangered creatures.
There were five females and two males in residence when the killer illness reared its ugly head in early 2012.
The only female to survive was Mopani, that, like staff at the zoo, has struggled to comprehend the dramatic loss.
Yesterday Ms Benoit reported that she was seeing the "old Mopani come back" thanks to a 2.5 tonne beauty that may kick-start the white rhino breeding program.
Female white rhino Likewizi was born at Taronga Western Plains Zoo but has lived most of her life at Victoria's Werribee Zoo.
Her return to Dubbo, to become a companion to Mopani and a mother, is lifting spirits.
Mopani and Likewizi are becoming thick as thieves.
"It was almost a godsend for Werribee to return Likewizi to us," Ms Benoit said.
"There has been a complete turnaround."
Motherhood it not a fait accompli for Likewizi, yet to produce a calf.
She left Dubbo in 1989 because her sire was the only male in the white rhino enclosure.
Across the next six months Likewizi will undergo a series of fertility tests.
"The plan is we'll do some hormone therapy just before she goes with the bull," Ms Benoit said.
"A little bit similar to what they do when preparing for IVF.
"If we get her to breed, that's going to be a bonus, and we can start increasing our numbers again."
The zoo has its eye to the future and across the world, searching for the reason why its treasured inhabitants died without explanation.
"We keep monitoring other populations and wild animals, the feelers are out there just in case we see it anywhere else," Ms Benoit said.
The senior keeper said all of the tests carried out after the white rhinos fell ill and died had been "inconclusive".
"But the zoo has a lot of material that we've frozen and stored, so that when new tests become available, we can use them," she said.
"One day we will find out why, hopefully."