The western black rhinoceros was officially declared extinct by the International Union for Conservation of Nature's (IUCN) Red List this week.

According to the nonprofit organization, Save The Rhino, however, the subspecies of the black rhinoceros was given the proclamation two years ago in 2011.

Even that status change was in some ways late. The IUCN had enough evidence to declare western black rhinos extinct in 2006, but the conservation group typically waits five years before making a significant change in case of new evidence, Save The Rhino reported.

To find the last time western black rhinos were seen in the wild, one has to go even further back to 2003, according to Save The Rhino (other breaking stories list the last sighting as 2006). Those rhinos were confined to a small region of Cameroon and eventually killed by poachers.

Poaching was the main reason for their demise and continues to threaten the remaining three subspecies of the black rhino (the eastern black, the south central black, and the southwestern black). Consumers in Asia, mostly Vietnam, covet the rhinos almost exclusively for their horns, which they hold as a symbol of status and believe to be a cure for cancer and hangovers, according to Save The Rhino.

"You've got to imagine an animal walking around with a gold horn; that's what you're looking at, that's the value and that's why you need incredibly high security," Simon Stuart, chair of the IUCN Species Survival Commission, told BBC News in 2011 when the organization made its first public announcement of the western black rhinoceros' extinction.

Stuart said 25 percent of all mammals on earth are at risk for extinction, according to the same article.

Killing animals like the western black rhinoceros for sport and for their resources has increased by 5,000 percent since 2007, according to One Green Planet.

If poaching continues at the same pace, the number of both black and white rhinos are projected to go into decline by 2015-2016 -- meaning more rhinos will be killed and die of natural causes (rhinos can live up to 50 years old, according to One Green Planet) than will be born, according to Save The Rhino.