American bullfrog
This species, "O. kikuzatoi", is listed as Critically Endangered by the IUCN under criterion B1ab(iii,v)+2ab(iii,v), due to threats from capturing as bycatch, water pollution, and predation from introduced species, primarily "Lithobates catesbeianus," the American bullfrog. The American bullfrog was introduced was introduced to Kumeijima Island in 1953, and predation may provide great pressure on the population after many decades of population decline. Inbreeding within the small (and isolated) populations is becoming a significant threat also. Specimens have been observed with minor abnormalities (asymmetrical scales on the head) not recorded in the past.