This past Sunday, one of the world's last remaining six northern white rhinos died at the San Diego Zoo. According to the Washington Post, the rhino - named Angalifu - was 44 years old when he died, and passed away due to old age. Following his death, there are just five white rhinos left in the world, and all are in captivity.

Rancy Reiches, curator of mammals at the zoo's Safari Park, stated, "Angalifu's death is a tremendous loss to all of us." TIME Magazine reports that many attempts to breed Angalifu with the park's only other northern white rhino failed. Unfortunately, the species now faces complete extinction after decades of wide-scale poaching.

Back in 1960, there were more than 2,000 northern white rhinos living in the wild. However, because of poaching, that number scaled down dramatically to 15 in 1984. The LA Times reports that poachers are known to use helicopters, guns with silencers, and night-vision equipment to harvest rhinos' horns, which are in huge demand in Asia and sell for as much as $30,000 a pound.

What makes the northern white rhino so special? Well, it is the largest of all the rhino species and ranks as the second-largest mammal on land after the African elephant. Take a look at these staggering numbers: the white rhino can reach 6 feet in height at the shoulder, with females weighing about 3,500 pounds and males nearly 8,000. The head of the rhino alone can weigh as much as 1,000 pounds.

It seems now the only way to try and keep the species alive is to use artificial insemination techniques. The Washington Post reports that the San Diego Zoo has preserved some of Angalifu's testicular tissue and sperm for future attempts to artificially breed new members of the species. Hopefully, science will be able to come to the rescue.