We’ve all read about animals becoming extinct, but it’s heart-breaking to watch it play out in real time.

The northern white rhino is a species hanging on by a thread. Thousands of these animals have been killed for their horns, which are used in traditional Chinese medicine. Only five remain in the world: four females and one male, all living in captivity.

Now, desperate times call for desperate measures. Because northern white rhinos rarely breed in captive environments, four of them were flown from a European zoo to a Kenyan wildlife preserve where they could revert to wild behavior. But so far, breeding has been unsuccessful. Next steps might involve in vitro fertilization of a rhino egg and transferring into another rhino species to serve as a surrogate mother.

Prevention is the only tool we have against the forever of extinction.