In spring of 2017, guardians of the world's last male northern white rhino joined a dating app on his behalf to raise awareness about conservation efforts. But now, the health of this rare rhino is failing, and the subspecies might be one step closer to extinction.

Sudan, a 45-year-old male northern white rhino, is suffering from a nasty infection on his back right leg, which festered underneath an age-related ailment he developed last year. This new infection is not responding to treatment, and his keepers are considering euthanasia if the pain gets to be too much for him. (Read: "To Rescue or Not, That is the Question With Distressed Animals")

"It has been a struggle," says Kaddu Sebunya, president of the African Wildlife Foundation. "We're so concerned that the male rhino is now ailing, and we might lose him. We're in a hopeless situation."

View Images A platoon of armed guards watch over Sudan, one of the last northern white rhinoceroses brought from a zoo in the Czech Republic in an effort to save the almost extinct species. Photograph by Ami Vitale, Nat Geo Image Collection

"This is a very good example of Africa losing the heritage," says Sebunya, who is based in Nairobi, Kenya, but from Uganda. "How can we explain this to the next generation of Africans? We can't be so arrogant and neglect other African species."

Slipping Away

Even from this shrunken population, northern white rhino numbers continue to dwindle. In November 2015, a 41-year-old female northern white rhino named Nola had to be euthanized at the San Diego Zoo because of a string of painful illnesses. A few months earlier in July of that same year, Nabiré, a 31-year-old female, died at a zoo in the Czech Republic after complications from a ruptured cyst. A 34-year-old male named Suni died in October 2014 due to natural causes.

Natural breeding doesn't seem to be a viable option at this point, and it's practically impossible unless a male can be found in the wild. But that situation is unlikely, so scientists have turned to the lab for ideas on how to save this dying species. They've harvested sex cells from the living rhinos and have made steps toward in vitro fertilization with southern white rhino surrogates. But this effort could take more than a decade. (Related: read about how scientists get rare animals to mate.)

Orphaned By Poachers, a Baby Rhino Makes a New Friend WATCH: In South Africa's Pilanesberg National Park, a baby rhino was orphaned by poachers, but with the kindness and hard work of park staff and animal welfare organizations, she's now in a safe home, and even has a new friend.

What About Southern White Rhinos?

White rhinos are one of five species of rhinoceros. They're further divided into two subspecies: northern and southern white rhinos. Northern white rhinos are smaller than southern ones, with straight backs, flat skulls, no grooves between their ribs, hairy ears and tails, and squat front horns. Southern white rhinos are larger, have concave skulls and backs with pronounced shoulder humps, more overall body hair, grooves between their ribs, and longer front horns.

Like their northern counterparts, southern white rhinos have faced similar population declines. At the turn of the century, there were only a handful of the subspecies left—they're historically native to parts of southern Africa. Government conservation efforts have helped to revitalize the population in South Africa to some 20,000 rhinos, thanks to breeding and relocation programs, as well as controlled but controversial sport hunting. (Related: "Should We Kill Animals to Save Them?")

But in recent years, the legal rhino horn trade has returned to South Africa, and southern white rhinos are still considered near threatened by the International Union for Conservation of Nature.