Birds and animals also know obligation.
Explanation: This line has been taken from "अनपराद्ध अत्रभवती" an excerpt from "प्रतिनाहकम्" composed by the great poet Bhasa. Sumantra went to meet Lord Rama but he returned worried. Bharata asked him why he returned from half way. Sumantra replied that he didn't return half way. But when he reached the forest, he didn't find Lord Rama there. He heard that they had gone to Kishkindha: Hearing this, Bharata was worried. He said, "Monkeys are unaware of the peculiarities of men." Then Sumantra said that birds and animals also know obligation.
This statement indicates that not only human beings but the birds and animals also remain indebted. Bharata felt sad when he came to know that Rama is living in Kishkindha. Bharata argued that monkey can not distinguish between the people with noble qualities and people having vice. At that moment, Sumantra delivered the about mentioned statement. Sumantra hides the fact and in order to remove Bharat's worry for Rama, he mentions the liberal nature of monkeys.