#2 Baiji Dolphin
China’s Baiji dolphin was last spotted in 2002, and although the species is considered endangered, some scientists are 100% sure that it may be extinct. Back in 2006, some experts from the Baiji Foundation started looking for the dolphin. They were equipped with underwater microphones and optical instruments, however, they didn’t manage to detect any surviving specimen. Rumor has it that the decline of the species is attributed to a wealth of factors, such as boat traffic, overfishing, poaching, habitat loss, and pollution.