Nabire was a 31-year-old Northern White Rhino who called Czech Republic’s Dvur Kralove Zoo home until her death, which was announced Tuesday. Nabire suffered from uterine cysts, which made it impossible for her to breed naturally, and a ruptured cyst led to her demise. In December 2014, the world’s Northern white rhino population dropped from six to five after the 44-year-old male named Angalifu died at the San Diego Zoo. With Nabire’s passing, there are now just four of the rhinos left on earth – three females and one male. Because none of the females are capable of carrying babies, there is a ticking clock on the survival of this subspecies.

northern white rhino, northern white rhinoceros, nabire, endangered species, extinct, ivf, in vitro fertilization for rhinos, can northern white rhinos be saved

Of the four surviving rhinos, the male, 42-year-old Sudan, and two of the females – Najin and Fatu – live on a reserve in Kenya. Najin is past reproductive age, and Fatu suffers a uterine condition which makes her unable to have babies. Nola, another female, is the fourth remaining white rhino and she lives at the San Diego Zoo, and is the only white rhino outside of Africa. She is also too old to reproduce.

Related: Only five Northern White Rhinos left in the world after aging male dies

Prior to Nabire’s passing, scientists had planned to harvest eggs from her healthy ovary in order to attempt an in vitro fertilization process, using sperm from Sudan and implanting the fertilized egg into a female southern white rhinoceros, the closest living relative to the dying breed. According to a statement from the Czech zoo, researchers did successfully harvest Nabire’s viable ovary following her death, so the IVF process could still be carried out. It’s uncertain whether such surrogate births would be enough to save the subspecies from extinction, but zoo officials believe they must try.

“It is our moral obligation to try to save them,” zoo director Přemysl Rabas said in a statement. “We are the only ones, perhaps with San Diego Zoo, who have enough of collected biological material to do so.”

Via Live Science

Images via Dvur Kralove Zoo and Wikipedia