Who is the one with one horn on the nose? 
Do you know?  Not know, I suppose.
He can very well swim. But doesn’t want to stay trim.
So often he’d like to wallow. And find waters that are shallow.
Endangered! Is what the story goes. 
Lets save him, help him ease his woes.

No prizes for guessing that  the creature we are talking about in the jingle is a one horned rhinoceros.  

Rhinoceros are commonly known as rhinos.  Rhinos are mostly herbivores and love to wallow in the water. Although good swimmers they prefer not to swim. There are five known species two of them found in Africa and the rest three in Asia. Rhinos are endangered because of poaching. Their horns make excellent dagger handles and powdered horn is used to make medicines – and that is why they are hunted and killed and so that their horns can be cut off.

The African and Sumatran rhinos are two horned where as the Indian and Javan rhinos are one horned.

The one horned rhino is classified into two categories

• Greater one-horned rhinos or Indian rhinos –  They are found in the India subcontinent. In Asia this is the largest mammal next to elephant. They can weigh a maximum of 4000 kgs. There are around 2575 of these rhinos left now. Around 2000 of these are in Kaziranga National park.
• Lesser one-horned rhinos or Javan rhinos – There are very few of these left now. With a population of as few as 40 in Ujung Kulon National Park. The Javan rhino can live up to 30–45 years in the wild. They are scared of humans and attack only when they are threatened. They are almost on the verge of extinction as any natural disaster can wipe out the remaining rhinos.