What is the Rarest Animal in the World?

The Sumatran rhino is a critically endangered species.
The Sumatran rhino is a critically endangered species.

The Sumatran rhino, also known as the Asian two-horned rhinoceros or hairy rhinoceros, is one of the rarest big mammals in the world. It is the smallest of the five extant rhinoceros species and the only Asian rhinoceros with two horns. It is the only living species of Dicerorhinus genus and the rarest member of the Rhinocerotidae family.

Distribution and Habitat

Sumatran rhinos once inhabited the cloud forests, swamp, and rainforests in China, Indonesia, Malaysia, India, Bhutan, Myanmar, Bangladesh, Thailand, and Laos. Historically, they resided in the southwestern parts of China, but they are currently considered to be critically endangered with only five populations in the wild: one in Borneo and four in Sumatra.

Determining their population is difficult since they are solitary creatures that are widely scattered in the range, but it is estimated that there are less than one hundred rhinoceros left. The survival of the Sumatrans in Peninsular Malaysia is in doubt, and one of the populations is already extinct. A small population was discovered in 2016 in East Kalimantan; however, researchers believe that the Bornean rhinos are extinct in the northern region of Borneo. The number of Sumatran rhinoceros has reduced by over 70% in the last 20 years, and currently, they exist in protected areas.

Sumatran Rhinos in Captivity

One of the last Sumatran rhino species known as Suci lived in Cincinnati Zoo for over a decade. She was the last hope for saving her species from extinction. Cincinnati Zoo is the first facility to breed the Sumatran rhino in captivity, and they were trying to save the species from extinction through Suci since the others were too old. Her keepers wanted to mate Suci with her brother Harapan to increase their population, but she had an iron storage illness, a condition that killed her mother back in 2009. Her death on March 30, 2014, was a huge blow to the already endangered rhinoceros species.

Physical Description

Sumatran rhinos have a shoulder height of about 4.76 feet with a body length of approximately 8.2 feet. These animals weigh between 1,100 pounds and 1,760 pounds, although the heaviest individual in the zoo is known to weigh about 4,410 pounds. Just like the African rhinoceros, these animals have two horns with the larger nasal horn being near 9.8 inches long. The posterior horn is about 3.9 inches long. The horns are either black or grey, with the males having longer horns than the female. They have reddish-brown hair that is hard to see in the wild since they are usually covered with mud. The Sumatran rhino has long hair around the ears and a clump of hair on its tail.


They are solitary creatures except when pairing for mating purposes or when rearing their offspring. Individual rhinos have home ranges; with the female occupying an area of between 3.9 square miles and 5.8 square miles while the males have territories as large as 19 square miles. These creatures mark their territories by leaving excrement, bending seedlings in unique patterns, and scraping the soil using their feet. Male ranges overlap while the female territories are spaced, but there is no evidence showing that they defend their territories by fighting. These animals wallow in mud holes to protect their skin from ectoparasites while maintaining their temperatures. They usually wallow during the day for about three hours at midday.

Other Rare Animals

The Javan rhino is already extinct in many parts of Asia with less than 40 individuals left. There are only four living Yangtze giant soft-shell turtles in the world. The number of Hainan gibbon in Hainan Island has reduced to below twenty-five individuals. Other rare species which survive only in captivity include Hawaiian crow, the Guam rail, Socorro dove, and the Kihansi spray toad among others.


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