Keeper Zachariah Mutai tends to Fatu, one of only two female northern white rhinos left in the world, in the pen where she is kept for observation at the Ol Pejeta Conservancy in Laikipia county in Kenya on March 2.

As the health of the world's last male northern white rhino declines in Kenya, a global team of scientists and conservationists is pushing ahead with an ambitious effort to save the subspecies from extinction with the help of the two surviving females.

Participants in the project to create northern white rhino embryos through in vitro fertilization say its success depends not on the sick, elderly male named Sudan, but on his daughter Najin and granddaughter Fatu, whose eggs would likely have to be extracted because the rhinos can't reproduce naturally.