The Mercy of Prophet extended to the world of birds, deer, plants, stones, mountains besides human beings.
Once while walking outside Madinah the Prophet SallAllahu alaihi wasallam saw a Jewish man who had captured a deer. Upon seeing the Prophet SallAllahu alaihi wasallam the deer said that it was time for her to feed her young, and she would return promptly if only the Prophet SallAllahu alaihi wasallam would arrange for her freedom for a little while. The Messenger SallAllahu alaihi wasallam of Allah requested the Jewish man for some time on behalf of the deer and accepted responsibility if she did not return, and so the man released her. He was mocking the Prophet SallAllahu alaihi wasallam but was amazed when the deer returned as promised. Whereupon he immediately accepted Islam.
The Prophet not only preached to the people to show kindness to each other but also to all living souls. He forbade the practice of cutting tails and manes of horses, of branding animals at any soft spot, and of keeping horses saddled unnecessarily. [Muslim]
If he saw any animal over-loaded or ill-fed he would pull up the owner and say: “Fear Allaah in your treatment of animals.” [Abu Daawood]
A companion came to him with the young ones of a bird in his sheet and said that the mother bird had hovered over them all along. He was directed by the Prophet to replace her offspring in the same bush. [Abu Daawood]
During a journey, somebody picked up some birds eggs. The bird’s painful note and fluttering attracted the attention of the Prophet who asked the man to replace the eggs. [Al-Bukhaari]
As his army marched towards Makkah to conquer it, they passed a female dog with puppies. The Prophet not only gave orders that they should not be disturbed, but posted a man to see that this was done.