Rhinoceroses are universally recognized by their massive bodies, stumpy legs and either one or two dermal horns. In some species, the horns may be short or not obvious.
They are renowned for having poor eyesight, but their senses of smell and hearing are well developed.
The biggest of the five surviving species are Africa's white rhino
and Asia's greater one-horned rhinos
These two species have also seen their numbers increase significantly in recent years due to successful conservation efforts. The white rhino is now classified as near threatened, while the greater one-horned rhino has moved from endangered to vulnerable.
However, they remain at real risk from poaching, which has seen a a dramatic increase since 2008. And this poses a major threat to the survival of all rhino species, particulalry Africa's endangered black rhino
and Asia's critically endangered Javan
But there is hope. The white and greater one-horned rhinos were saved from extinction, and black rhino numbers have also increased, although they are still just a fraction of their number 50 years ago.
Although international trade in rhino horn has been banned under CITES
(Convention on International Trade in Endangered Species of Fauna and Flora) since 1977, demand remains high, particularly in Vietnam – fueling rhino poaching in both Africa and Asia.
Powdered horn is used in traditional Asian medicine as a supposed cure for a range of illnesses – from hangovers to fevers and even cancer.
There has been a huge surge in poaching since 2008, particulalry in South Africa, which has seen record numbers of rhinos poached in recent years, including 1215 in 2014 alone.
The current crisis has been primarily driven by the demand for horn by upper-middle class citizens in Vietnam. As well as its use in medicine, rhino horn is bought and consumed purely as a symbol of wealth.
Poaching gangs use increasingly sophisticated methods to evade authorities – including helicopters and night vision equipment to track rhinos, and veterinary drugs to knock them out. This means governments and conservationists need to match this level of technology to be able to tackle the problem.
Habitat loss also threatens rhinos, especially in southeast Asia and India, as human populations rise and forests are degraded or destroyed.
Important core conservation areas are increasingly isolated by logging, agricultural expansion, human settlements, road projects, and dam construction.
Asian rhinos mainly survive in isolated areas – in small populations that are at greater risk from inbreeding, natural disasters and disease.