The last of the Western Black rhino (Diceros bicornis longipes), a rare species of black rhino, has died and the survival of the northern white configuration hangs in the balance, according to the International Union for Conservation of Nature (IUCN).
The revelation was made as part of the IUCN's Red List, which it claims is a "true barometer for life", with stats on 61,900 species collated.
The study found that despite the best efforts of animal conservationists, one-quarter of the world's mammals are now endangered.
The western black rhino is a sub-species of Black rhino which has been poached to extinction by criminal gangs who want to trade the animals' valuable horns.
“Human beings are stewards of the earth and we are responsible for protecting the species that share our environment,” says Simon Stuart, Chair of the IUCN Species Survival Commission.
He said the fortunes of the northern white could be reversed if proposed conservation methods were put into action to manage habitats to improve breeding.
The IUCN said the Javan rhino is also "making its last stand" as the subspecies Rhinoceros sondaicus annamiticus – those outside of Java – are likely "extinct" after poachers killed what was suspected to be the last one in Vietnam in 2010.
"Although this is not the end of the Javan rhino, it does reduce the species to a single, tiny, declining population on Java," said the IUCN.
A lack of willingness among political leaders to curb the destruction of the rhinos' natural habitat and the illegal trade in rhino horn are the main threats faced by the species.
The Red List also reveals that reptiles are also under threat, with 40 per cent of Madagascar's land-loving population endangered – including chameleons, geckos and snakes.
But conservation efforts are under way that should help to safeguard some deemed at risk, including Tarzan's chameleon, the bizarre-nosed chameleon and the limbless skink.
There are success stories: fewer than 100 Southern White Rhino were in the wild at the end of the 19th century but more than 20,000 survive today, and there are more than 300 Przewalski's horses around today 15 years after the species was listed as extinct.
Powdered rhinoceros horn can sell for up to $20 a gram. ®