Theory:

     In two months, the forest was back to normal. The rats disappeared, and the insects, and the smell, and the world finally went back to its familiar old self.
 
     “Well, Prem,” said the old man, “have you fallen asleep? Did my story send you off to dreamland?”
 
     I shook my head. “No, Grandfather, I was just thinking. Maybe it’s time I went back to my own village, because I have a story to tell them. But what if they don’t listen to me?”

     “We can only keep at it, my son — tell these stories again and again, to more and more people. Some of them may laugh at you or say your stories are not true. But they may remember them one day, and understand that each of us has a place in this strange, funny world of ours.”.
Explanation:
 
Finally, when all the animals came back to the forest, it only took two months to restore the normalcy in the jungle. The rotten smell was gone; the tortures of rats, frogs, insects, etc., met with an end. With this climax, the old man finished his story, narrated for Prem.

The old man questioned whether he had slept or was dreaming. Prem replied no, but, thinking to be back to the village to deliver the story to their villagers. After listening to the story, the narrator gained more confidence that it would bring in the unity effect in his village also, same as Pambupatti.

Prem enquired the old man whether his villagers will listen to the story as he was a little sceptical about it. The old man replied to his question, saying Prem should keep repeating the story to his fellow villagers even if they make fun of him. One day, they will surely understand others' need and the equal role of all in society.
Reference:
National Council of Educational Research and Training (2006). What Happened to the Reptiles - Zai Whitaker (pp. 33-42). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.